One of the most important consequences of Earth's axial tilt is the seasons.
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Fall comes when the sun's warming rays line up perpendicular to Earth's axial tilt.
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A changing axial tilt is the biggest driver of wildly varying seasons on Pluto.
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Some scientists think Mars's changing axial tilt contributed to the disappearance of its atmosphere.
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An axial tilt of 98 degrees causes the ice giant to spin on its side.
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A 2018 study suggested that Kepler-186f could have a stable axial tilt similar to Earth's.
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The fall equinox occurs when the sun's warming rays line up perpendicular to Earth's axial tilt:
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Image: Southwest Research InstituteWhen changes in axial tilt and eccentricity combine properly, Mars has an ice age.
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The earth's "axial tilt" is a jaunty 23.5 degrees, for example, while Uranus spins at 98 degrees.
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The earth's "axial tilt" is a jaunty 23.5 degrees, for example, while Uranus spins at 98 degrees, or nearly sideways.
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The earth's "axial tilt" is a jaunty 23.5 degrees, for example, while Uranus, above, spins at 98 degrees, or nearly sideways.
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Similarly, astronomers have long suspected that life would likely not survive on Earth should it have an axial tilt more akin to Uranus.
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Respectively, their research shows that Pluto features both tropic and arctic regions, and an exaggerated axial tilt that alters the dwarf planet's atmosphere over time.
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The axial tilt of Venus, for example, is so extreme — 177 degrees — that the planet is essentially flipped upside down with its South Pole pointing up.
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Beg managed to measure the duration of the year to within 25 seconds of the actual figure, and he even correctly calculated the Earth's axial tilt at 23.52 degrees.
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New Scientist says the planet would have reached a particularly hot (a relative term in the far reaches of the solar system) climate 800,000 years ago, as its axial tilt hit 103 degrees.
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The Northern Hemisphere dips toward the sun, basking in its warmth for longer than on any other day, as the chilling Southern Hemisphere swings away, all thanks to Earth's axial tilt of 23.5 degrees.
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The Northern Hemisphere dips toward the sun, basking in its warmth for longer than any other time, as the chilling Southern Hemisphere swings away, all thanks to the Earth's axial tilt of 23.5 degrees.
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The team found that the axial tilt and orbital dynamics of planets in the habitable zone around "G dwarf" stars like our own sun can lead to "snowball states," which are essentially extreme ice ages.
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The Northern Hemisphere dips toward the sun, basking in its warmth for longer than on any other day, as the chilling Southern Hemisphere swings away, all thanks to the Earth's axial tilt of 23.5 degrees.
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Both have unique characteristics—for instance, the fastest winds in the solar system are on Neptune, and Uranus appears to have been knocked onto its side at some point, making it the only planet with such an odd axial tilt.
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Over the coming century, astronomers made a number of observations that confirmed the planet's orbit, five moons, a set of rings, and its unusual orientation: unlike the rest of the planets in the solar system, it had an axial tilt of 97.77°, with one pole facing the sun.
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A celestial object's axial tilt indicates whether the object's rotation is prograde or retrograde. Axial tilt is the angle between an object's rotation axis and a line perpendicular to its orbital plane passing through the object's centre. An object with an axial tilt up to 90 degrees is rotating in the same direction as its primary. An object with an axial tilt of exactly 90 degrees has a perpendicular rotation that is neither prograde nor retrograde.
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This gives an axial tilt of about 60° in both cases.
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Jupiter's axial tilt is very small, so its seasonal variation is minimal; Uranus, on the other hand, has an axial tilt so extreme it is virtually on its side, which means that its hemispheres are either perpetually in sunlight or perpetually in darkness around the time of its solstices. Among extrasolar planets, axial tilts are not known for certain, though most hot Jupiters are believed to have negligible to no axial tilt as a result of their proximity to their stars.
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Earth's axial tilt is about 23.4°. It oscillates between 22.1° and 24.5° on a cycle and is currently decreasing.
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Earth, alone among terrestrial planets, possesses a large moon. This is thought to confer stability to Earth's axial tilt, and thus seasons and climates. The closest analogue is the Pluto-Charon system, though its axial tilt is completely different. Both our Moon and Charon are hypothesized to have formed via giant impacts.
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Milankovitch theory predicts that the planet will continue to undergo glacial periods at least until the Quaternary glaciation comes to an end. These periods are caused by the variations in eccentricity, axial tilt, and precession of the Earth's orbit. As part of the ongoing supercontinent cycle, plate tectonics will probably result in a supercontinent in 250–350 million years. Some time in the next 1.5–4.5 billion years, the axial tilt of the Earth may begin to undergo chaotic variations, with changes in the axial tilt of up to 90°.
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An object with an axial tilt between 90 degrees and 180 degrees is rotating in the opposite direction to its orbital direction. Regardless of inclination or axial tilt, the north pole of any planet or moon in the Solar System is defined as the pole that is in the same celestial hemisphere as Earth's north pole.
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For most planets, the rotation period and axial tilt (also called obliquity) are not known, but a large number of planets have been detected with very short orbits (where tidal effects are greater) that will probably have reached an equilibrium rotation that can be predicted (i.e. tidal lock, spin–orbit resonances, and non-resonant equilibria such as retrograde rotation). Gravitational tides tend to reduce the axial tilt to zero but over a longer timescale than the rotation rate reaches equilibrium. However, the presence of multiple planets in a system can cause axial tilt to be captured in a resonance called a Cassini state.
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Earth's axial tilt (obliquity) is currently about 23.4°. Earth's orbital plane is known as the ecliptic plane, and Earth's tilt is known to astronomers as the obliquity of the ecliptic, being the angle between the ecliptic and the celestial equator on the celestial sphere. It is denoted by the Greek letter ε. Earth currently has an axial tilt of about 23.44°.
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In many cases, neither the rotation period nor the axial tilt are known, limiting the predictability. The models presented here do not capture those effects.
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These rapid changes probably relate to seasonal condensation and sublimation of portions of Pluto's atmosphere, amplified by Pluto's extreme axial tilt and high orbital eccentricity.
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Illustration of the movement of the Sun north and south of the Equator, caused by axial tilt of the Earth. Illustration of the observed effect of Earth's axial tilt. This festival is currently celebrated on 14 or 15 January but due to axial precession of the earth it will continue to shift away from the actual season. The season occurs based on tropical sun (without ayanamsha).
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However, geophysical factors like Earth's orbit, its rotation, and its axial tilt cause these belts to shift gradually north and south, following the Sun's seasonal shifts.
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The axial tilt of Kepler-413b's spin axis might vary by as much as 30 degrees over 11 years, leading to rapid and erratic changes in seasons.
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As on Earth, Mars experiences Milankovitch cycles that cause its axial tilt (obliquity) and orbital eccentricity to vary over long periods of time, which has long-term effects on its climate. The variation of Mars's axial tilt is much larger than for Earth because it lacks the stabilizing influence of a large moon like Earth's moon. Mars has a 124,000-year obliquity cycle compared to 41,000 years for Earth.
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There are three parameters that affect the size and shape of the analemma—obliquity, eccentricity, and the angle between the apse line and the line of solstices. Viewed from an object with a perfectly circular orbit and no axial tilt, the Sun would always appear at the same point in the sky at the same time of day throughout the year and the analemma would be a dot. For an object with a circular orbit but significant axial tilt, the analemma would be a figure of eight with northern and southern lobes equal in size. For an object with an eccentric orbit but no axial tilt, the analemma would be a straight east–west line along the celestial equator.
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Thus, the graph of solar declination, as seen from this highly tilted Earth, would resemble a triangle wave rather than a sine wave, zigzagging between plus and minus 90°, with linear segments between the maxima and minima. If the 90° axial tilt is decreased, then the absolute maximum and minimum values of the declination would decrease, to equal the axial tilt. Also, the shapes of the maxima and minima on the graph would become less acute ("pointy"), being curved to resemble the maxima and minima of a sine wave. However, even when the axial tilt equals that of the actual Earth, the maxima and minima remain more acute than those of a sine wave.
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Earth's axial tilt (or obliquity) and its relation to the rotation axis and plane of orbit The axial tilt of Earth is approximately 23.439281° with the axis of its orbit plane, always pointing towards the Celestial Poles. Due to Earth's axial tilt, the amount of sunlight reaching any given point on the surface varies over the course of the year. This causes the seasonal change in climate, with summer in the Northern Hemisphere occurring when the Tropic of Cancer is facing the Sun, and winter taking place when the Tropic of Capricorn in the Southern Hemisphere faces the Sun. During the summer, the day lasts longer, and the Sun climbs higher in the sky.
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Why this sudden upsurge in activity should be occurring is not fully known, but it appears that Uranus's extreme axial tilt results in extreme seasonal variations in its weather.
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By measuring the location of astronomical radio sources very accurately, geodetic VLBI techniques can be used to measure things such as changes in the axial tilt of the Earth.
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Earth's axial tilt is about 23.4°. It oscillates between 22.1° and 24.5° on a 41,000-year cycle and is currently decreasing. Planets also have varying degrees of axial tilt; they lie at an angle to the plane of their stars' equators. This causes the amount of light received by each hemisphere to vary over the course of its year; when the northern hemisphere points away from its star, the southern hemisphere points towards it, and vice versa.
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Recent results have placed the age at around 4 billion years. The chance that it is tidally locked is approximately 50%. Since it is closer to its star than Earth is to the Sun, it will probably rotate much more slowly than Earth; its day could be weeks or months long (see Tidal effects on rotation rate, axial tilt and orbit). Kepler-186f's axial tilt (obliquity) is likely very small, in which case it would not have tilt- induced seasons like Earth's.
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Over thousands of years, the Earth's axial tilt and orbital eccentricity vary (see Milankovitch cycles). The equinoxes and solstices move westward relative to the stars while the perihelion and aphelion move eastward. Thus, ten thousand years from now Earth's northern winter will occur at aphelion and northern summer at perihelion. The severity of seasonal change — the average temperature difference between summer and winter in location — will also change over time because the Earth's axial tilt fluctuates between 22.1 and 24.5 degrees.
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In about 13,000 years, the north pole will be tilted toward the Sun when the Earth is at perihelion. Axial tilt and orbital eccentricity will both contribute their maximum increase in solar radiation during the northern hemisphere's summer. Axial precession will promote more extreme variation in irradiation of the northern hemisphere and less extreme variation in the south. When the Earth's axis is aligned such that aphelion and perihelion occur near the equinoxes, axial tilt will not be aligned with or against eccentricity.
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During the giant impact stage, the thickness of a protoplanetary disk is far larger than the size of planetary embryos so collisions are equally likely to come from any direction in three- dimensions. This results in the axial tilt of accreted planets ranging from 0 to 180 degrees with any direction as likely as any other with both prograde and retrograde spins equally probable. Therefore, prograde spin with a small axial tilt, common for the Solar System's terrestrial planets except Venus, is not common in general for terrestrial planets built by giant impacts. The initial axial tilt of a planet determined by giant impacts can be substantially changed by stellar tides if the planet is close to its star and by satellite tides if the planet has a large satellite.
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They are all also large enough to fully eclipse the Sun. Because Jupiter's axial tilt is minimal, and the Galilean moons all orbit in the plane of Jupiter's equator, solar eclipses are quite common.
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Lightcurve analysis indicates that Alice's pole points towards either ecliptic coordinates (β, λ) = (55°, 65°) or (β, λ) = (55°, 245°) with a 10° uncertainty. This gives an axial tilt of about 35° in both cases.
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In the Northern Hemisphere, winter solstice currently occurs around 21 December; summer solstice is near 21 June, spring equinox is around 20 March and autumnal equinox is about 22 or 23 September. In the Southern Hemisphere, the situation is reversed, with the summer and winter solstices exchanged and the spring and autumnal equinox dates swapped. The angle of Earth's axial tilt is relatively stable over long periods of time. Its axial tilt does undergo nutation; a slight, irregular motion with a main period of 18.6 years.
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At some point, perturbation effects will probably cause chaotic variations in the obliquity of the Earth, and the axial tilt may change by angles as high as 90° from the plane of the orbit. This is expected to occur between 1.5 and 4.5 billion years from now. A high obliquity would probably result in dramatic changes in the climate and may destroy the planet's habitability. When the axial tilt of the Earth exceeds 54°, the yearly insolation at the equator is less than that at the poles.
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TOTAL AXIAL TILT SENSE MAGNITUDE PHASE MAGNITUDE PHASE DEGREES DEGREES DB DB DB RATIO DEG. VOLTS/M DEGREES VOLTS/M DEGREES 90.00 .00 -999.99 9.75 9.75 .00000 90.00 LINEAR 0.00000E+00 .00 2.46922E+00 -66.00 85.00 .
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Another example is Earth's axial tilt which, due to friction raised within Earth's mantle by tidal interactions with the Moon (see below), will be rendered chaotic at some point between 1.5 and 4.5 billion years from now.
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Planets with a large axial tilt are less likely to enter snowball states and can retain liquid water further from their star. Large fluctuations of axial tilt can have even more of a warming effect than a fixed large tilt.Kelley, Peter (15 April 2014) Astronomers: 'Tilt-a-worlds' could harbor life. www.washington.edu Paradoxically, planets orbiting cooler stars, such as red dwarfs, are less likely to enter snowball states because the infrared radiation emitted by cooler stars is mostly at wavelengths that are absorbed by ice which heats it up.
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Titan's orbital tilt with respect to the sun is very close to Saturn's axial tilt (about 27°), and its axial tilt with respect to its orbit is zero. This means that the direction of incoming sunlight is driven almost entirely by Titan's day-night cycle and Saturn's year cycle. The day cycle on Titan lasts 15.9 Earth days, which is how long it takes Titan to orbit Saturn. Titan is tidally locked, so the same part of Titan always faces Saturn, and there is no separate "month" cycle.
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Lightcurve analysis indicates that Eugenia's pole most likely points towards ecliptic coordinates (β, λ) = (-30°, 124°) with a 10° uncertainty, which gives it an axial tilt of 117°. Eugenia's rotation is then retrograde, rotating backward to its orbital plane.
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Uranus has an axial tilt of 97.77°, so its axis of rotation is approximately parallel with the plane of the Solar System. The reason for Uranus's unusual axial tilt is not known with certainty, but the usual speculation is that during the formation of the Solar System, an Earth-sized protoplanet collided with Uranus, causing the skewed orientation. It is unlikely that Venus was formed with its present slow retrograde rotation, which takes 243 days. Venus probably began with a fast prograde rotation with a period of several hours much like most of the planets in the Solar System.
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The Sun appears to move northward during the northern spring, contacting the celestial equator on the March equinox. Its declination reaches a maximum equal to the angle of Earth's axial tilt (23.44°) on the June solstice, then decreases until reaching its minimum (−23.44°) on the December solstice, when its value is the negative of the axial tilt. This variation produces the seasons. A line graph of the Sun's declination during a year resembles a sine wave with an amplitude of 23.44°, but one lobe of the wave is several days longer than the other, among other differences.
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But between these hostile environments, there would be a sliver of habitability, which could support life. Kepler-186e's axial tilt (obliquity) is likely very small, in which case it would not have tilt-induced seasons as Earth and Mars do. Its orbit is probably close to circular, so it will also lack eccentricity-induced seasonal changes like those of Mars. However, the axial tilt could be larger (about 23 degrees) if another undetected nontransiting planet orbits between it and Kepler-186f; planetary formation simulations have shown that the presence of at least one additional planet in this region is likely.
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The second root race lived in Hyperborea. The second root race was colored golden yellow. Hyperborea included what is now Northern Canada, Greenland, Iceland, Scandinavia, Northern Asia and Kamchatka. The climate was tropical because Earth had not yet developed an axial tilt.
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As a result, transits of Mercury across the face of the Sun can only occur when the planet is crossing the plane of the ecliptic at the time it lies between Earth and the Sun, which is in May or November. This occurs about every seven years on average. Mercury's axial tilt is almost zero, with the best measured value as low as 0.027 degrees. This is significantly smaller than that of Jupiter, which has the second smallest axial tilt of all planets at 3.1 degrees. This means that to an observer at Mercury's poles, the center of the Sun never rises more than 2.1 arcminutes above the horizon.
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A Martian year is equal to 1.8809 Earth years, or 1 year, 320 days, and 18.2 hours. The axial tilt of Mars is 25.19° relative to its orbital plane, which is similar to the axial tilt of Earth. As a result, Mars has seasons like Earth, though on Mars they are nearly twice as long because its orbital period is that much longer. In the present day epoch, the orientation of the north pole of Mars is close to the star Deneb. Mars has a relatively pronounced orbital eccentricity of about 0.09; of the seven other planets in the Solar System, only Mercury has a larger orbital eccentricity.
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Ultraviolet light from the Sun can then break the water apart in a process called photodissociation. The hydrogen from the water molecule then escapes into space. The obliquity (axial tilt) of Mars varies considerably on geologic timescales, and has a strong impact on planetary climate conditions.
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Vesta's rotation is relatively fast for an asteroid (5.342 h) and prograde, with the north pole pointing in the direction of right ascension 20 h 32 min, declination +48° (in the constellation Cygnus) with an uncertainty of about 10°. This gives an axial tilt of 29°.
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The analysis of Rosetta images in combination with photometric light curves yielded the position of the north rotational pole of Lutetia: , . This gives an axial tilt of 96° (retrograde rotator), meaning that the axis of rotation is approximately parallel to the ecliptic, similar to the planet Uranus.
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For planets and other rotating celestial bodies, the angle of the equatorial plane relative to the orbital plane — such as the tilt of the Earth's poles toward or away from the Sun — is sometimes also called inclination, but less ambiguous terms are axial tilt or obliquity.
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On the summer solstice, Earth's maximum axial tilt toward the Sun is 23.44°. Likewise, the Sun's declination from the celestial equator is 23.44°. The summer solstice occurs during summer. This is the June solstice in the Northern Hemisphere and the December solstice in the Southern Hemisphere.
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In the 1961 disaster film The Day the Earth Caught Fire, the near-simultaneous detonation of two super-hydrogen bombs near the poles causes a change in Earth's nutation, as well as an 11° shift in the axial tilt and a change in Earth's orbit around the Sun.
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Other planets have different seasonal lags. The gas giants Jupiter, Saturn and Uranus, as well as Saturn's moon Titan, all have substantial seasonal lags corresponding to the equivalent of between two and three months in Earth terms. Mars, on the other hand, has negligible seasonal lag of no more than a few days. For the case of Venus no seasonal lag would be detected, because the planet undergoes no seasons due to very efficient heat transport in its massive atmosphere (which would obliterate the season-causing effect of axial tilt, but its axial tilt is very small anyway) and very low orbital eccentricity (almost no changes to its distance from the Sun).
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At the time of the New Horizons flyby, Nix was rotating with a period of 43.9 hours retrograde to Pluto's equator with an axial tilt of 132 degrees — it was rotating backwards in relation to its orbit around Pluto. The rotation rate of Nix had increased by 10 percent since Nix was discovered.
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For example, suppose that the Earth's orbital position is marked at the summer solstice, when the Earth's axial tilt is pointing directly toward the Sun. One full orbit later, when the Sun has returned to the same apparent position relative to the background stars, the Earth's axial tilt is not now directly toward the Sun: because of the effects of precession, it is a little way "beyond" this. In other words, the solstice occurred a little earlier in the orbit. Thus, the tropical year, measuring the cycle of seasons (for example, the time from solstice to solstice, or equinox to equinox), is about 20 minutes shorter than the sidereal year, which is measured by the Sun's apparent position relative to the stars.
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Lyshriol is the name of the homeworld of one branch of Ruby Dynasty. The Allieds call the planet Skyfall. Lyshriol is a heavy gravity world with two suns called Valdor and Aldan. It has a circular orbit and no axial tilt, so day and night are of the same length and there are no seasons.
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Ariadne is very elongate (almost twice as long as its smallest dimension) and probably bi-lobed or at least very angular. It is a retrograde rotator, although its pole points almost parallel to the ecliptic towards ecliptic coordinates (β, λ) = (−15°, 253°) with a 10° uncertainty. This gives an axial tilt of about 105°.
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She has also worked on axial tilt and precession during interglacial period. Braconnot has been involved with the Paleoclimate Modelling Intercomparison Project, which analyses climate model outputs. In 2014 Braconnot was awarded a €2.7 million grant from the BNP Paribas foundation for climate research. She was involved with the IPCC Fourth and Fifth Assessment Reports.
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Several causes have been proposed: cyclical lows in solar radiation, heightened volcanic activity, changes in the ocean circulation, variations in Earth's orbit and axial tilt (orbital forcing), inherent variability in global climate, and decreases in the human population (for example from the Black Death and the epidemics emerging in the Americas upon European contact).
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On the dividing lines between the drawings is a small globe indicating the part of the globe that is being lit by the sun at the start of the season. The differences in illumination during the year are caused by the Earth's axial tilt. The hand completes one revolution a year and shows the current season.
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The elliptical orbit of Neptune is inclined 1.77° compared to that of Earth. The axial tilt of Neptune is 28.32°, which is similar to the tilts of Earth (23°) and Mars (25°). As a result, Neptune experiences similar seasonal changes to Earth. The long orbital period of Neptune means that the seasons last for forty Earth years.
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Uranus emits the least heat, one-tenth as much as Neptune. It is suspected that this may be related to its extreme 98˚ axial tilt. This causes its seasonal patterns to be very different from those of any other planet in the Solar System. There are still no complete models explaining the atmospheric features observed in the ice giants.
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There is a pronounced mass deficit near the equator at about 90° longitude comparable to Rheasilvia basin on Vesta. There are also two additional smaller (50–70 km in diameter) crater-like depressions near the south pole. Psyche's north pole points towards the ecliptic coordinates , , with a 4° uncertainty. This gives an axial tilt of 95°.
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All known dwarf planets and dwarf planet candidates have prograde orbits around the Sun, but some have retrograde rotation. Pluto has retrograde rotation; its axial tilt is approximately 120 degrees. Pluto and its moon Charon are both tidally locked to each other. It is suspected that the Plutonian satellite system was created by a massive collision.
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It is aligned with the plane of Saturn's orbit. Saturn has an axial tilt of 27 degrees, so this ring is tilted at an angle of 27 degrees to the more visible rings orbiting above Saturn's equator. Voyager 2 view of Saturn casting a shadow across its rings. Four satellites, two of their shadows and ring spokes are visible.
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A further improvement defines a fictitious mean Sun that moves with constant speed along the celestial equator; the speed is the same as the average speed of the real Sun, but this removes the variation over a year as the Earth moves along its orbit around the Sun (due to both its velocity and its axial tilt).
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The axial tilt of the Earth results in seasons outside of the tropics. The change in the length of the day is the key signal for seasonal behavior (e.g. mating season) in non-tropical animals. The presence of light at night can result in "seasons out of time" , changing the behavior and thermoregulation of affected organisms.
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The zones are formed when rising convection cells form crystallizing ammonia that masks out these lower clouds from view. Jupiter's low axial tilt means that the poles constantly receive less solar radiation than at the planet's equatorial region. Convection within the interior of the planet transports more energy to the poles, balancing out the temperatures at the cloud layer.
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There are small oscillations around this state and in the case of Mars these axial tilt variations are chaotic. Hot Jupiters' close proximity to their host star means that their spin–orbit evolution is mostly due to the star's gravity and not the other effects. Hot Jupiters' rotation rate is not thought to be captured into spin–orbit resonance because of the way in which such a fluid-body reacts to tides; a planet like this therefore slows down into synchronous rotation if its orbit is circular, or, alternatively, it slows down into a non-synchronous rotation if its orbit is eccentric. Hot Jupiters are likely to evolve towards zero axial tilt even if they had been in a Cassini state during planetary migration when they were further from their star.
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The declination of the Sun, δ☉, is the angle between the rays of the Sun and the plane of the Earth's equator. The Earth's axial tilt (called the obliquity of the ecliptic by astronomers) is the angle between the Earth's axis and a line perpendicular to the Earth's orbit. The Earth's axial tilt changes slowly over thousands of years but its current value of about ε = 23°26' is nearly constant, so the change in solar declination during one year is nearly the same as during the next year. At the solstices, the angle between the rays of the Sun and the plane of the Earth's equator reaches its maximum value of 23°26'. Therefore, δ☉ = +23°26' at the northern summer solstice and δ☉ = −23°26' at the southern summer solstice.
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In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, or, equivalently, the angle between its equatorial plane and orbital plane. It differs from orbital inclination. At an obliquity of 0 degrees, the two axes point in the same direction; i.e., the rotational axis is perpendicular to the orbital plane.
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The stellar obliquity , i.e. the axial tilt of a star with respect to the orbital plane of one of its planets, has been determined for only a few systems. But for 49 stars as of today, the sky-projected spin- orbit misalignment has been observed, which serves as a lower limit to . Most of these measurements rely on the Rossiter–McLaughlin effect.
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The most detailed analysis indicates that it points either towards about ecliptic coordinates (β, λ) = (70°, 55°) or (40°, 255°) with a 10° uncertainty. This gives an axial tilt of about 14° or 54°, respectively. In 1988 a search for satellites or dust orbiting this asteroid was performed using the UH88 telescope at the Mauna Kea Observatories, but the effort came up empty.
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Photometry has also shown that the surface of Epsilon Eridani, like the Sun, is undergoing differential rotation i.e. the rotation period at equator differs from that at high latitude. The measured periods range from 10.8 to 12.3 days. The axial tilt of Epsilon Eridani toward the line of sight from Earth is highly uncertain: estimates range from 24° to 72°.
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The next occultation of Mercury by Venus will be on December 3, 2133. The difficulties inherent in observing Mercury mean that it has been far less studied than the other planets. In 1800, Johann Schröter made observations of surface features, claiming to have observed mountains. Friedrich Bessel used Schröter's drawings to erroneously estimate the rotation period as 24 hours and an axial tilt of 70°.
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This is unusual for a short period planet. Many short period planets show high orbital obliquity, which was taken as a sign of the scattering of the planet into this short period orbit. It can also be interpreted as the formation of a planet in an inner disk with an axial tilt. But these previous measurements of orbital obliquity were made for giant planets around mature stars.
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These changes in global temperature match with changes in orbital parameters of the Earth's orbit around the Sun. These are called Milankovitch cycles, and these are related to eccentricity, obliquity (axial tilt), and precession of Earth around its axis. These correspond to cycles with periods of 100 kyr, 40 kyr, and 20 kyr. δ18O can also be used to investigate smaller scale climate phenomena.
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Earth's climate is determined by a compilation of many things and factors. These effects include effects from the primary factors of Earth's axial tilt angle, Earth's orbital eccentricity, and the precession of solstices and equinoxes, as well as some secondary, external effects, such as meteorite/asteroid impacts on the earth's surface and solar activity from the sun, including sunspots, solar flares, and solar winds/geomagnetic storms.
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This impact hypothesis is also used in some attempts to explain the planet's axial tilt. Another hypothesis is that some form of barrier exists in Uranus's upper layers that prevents the core's heat from reaching the surface. For example, convection may take place in a set of compositionally different layers, which may inhibit the upward heat transport; perhaps double diffusive convection is a limiting factor.
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The term stadial is another word for glacial period, and interstadial is another word for interglacial period. The oscillation between glacial and interglacial periods is due to the Milankovitch cycles. These are cycles that have to do with Earth's axial tilt and orbital eccentricity. Earth is currently tilted at 23.5 degrees. Over a 41,000 year cycle, the tilt oscillates between 22.1 and 24.5 degrees.
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The current trophy is made from silver and gilt, and features a golden globe held up by three silver columns. The columns, shaped as stumps and bails, represent the three fundamental aspects of cricket: batting, bowling and fielding, while the globe characterises a cricket ball. The seam is tilted to symbolize the axial tilt of the Earth. It stands 60 centimetres high and weighs approximately 11 kilograms.
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This was revised by Johannes Kepler, yielding an elliptic orbit for Mars that more accurately fitted the observational data. The first telescopic observation of Mars was by Galileo Galilei in 1610. Within a century, astronomers discovered distinct albedo features on the planet, including the dark patch Syrtis Major Planum and polar ice caps. They were able to determine the planet's rotation period and axial tilt.
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But Saturn has an axial tilt of nearly 27°. The orbital plane of Titan only crosses the line of sight to the Sun at two points along Saturn's orbit. As the orbital period of Saturn is 29.7 years, an eclipse is only possible about every 15 years. The timing of the Jovian satellite eclipses was also used to calculate an observer's longitude upon the Earth.
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North of the Arctic Circle and south of the Antarctic Circle, an extreme case is reached in which there is no daylight at all for part of the year, and continuous daylight during the opposite time of year. This is called polar night and midnight sun, respectively. This variation in the weather (because of the direction of the Earth's axial tilt) results in the seasons.
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Lightcurve analysis indicates a somewhat angular shape and that Iris's pole points towards the ecliptic coordinates (β, λ) = (10°, 20°) with a 10° uncertainty. This gives an axial tilt of 85°, so that on almost a whole hemisphere of Iris, the sun does not set during summer, and does not rise during winter. On an airless body this gives rise to very large temperature differences.
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In 1900, it was 7 minutes of arc north of the equator. As a result of a shift in the Earth's axial tilt, it crossed over to the Southern Hemisphere in December 1923. This is an evolved A-type giant star with a stellar classification of A0 III. It has around three times the mass of the Sun and 4.5 times the Sun's radius.
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The elliptical orbit of Jupiter is inclined 1.31° compared to Earth. Because the eccentricity of its orbit is 0.048, Jupiter's distance from the Sun varies by 75 million km between its nearest approach (perihelion) and furthest distance (aphelion). The axial tilt of Jupiter is relatively small: only 3.13°. As a result, it does not experience significant seasonal changes, in contrast to, for example, Earth and Mars.
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Either way, this suggests a loose rubble pile structure. Sylvia is also a fairly fast rotator, turning about its axis every 5.18 hours (giving an equatorial rotation velocity of about 230 km/h or 145 mph). The short axis is the rotation axis. Direct images indicate that Sylvia's pole points towards ecliptic coordinates (β, λ) = (+62.6°, 72.4°) with only a 0.5° uncertainty, which gives it an axial tilt of around 29.1°.
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Perhaps one of the most apparent factors contributing to Earth climate change is the angle at which the earth is tilted. This is the angle at which Earth's axis of rotation is from the vertical, also known as Earth's obliquity. Earth's current tilt angle is approximately 23.5 degrees. The axial tilt angle affects climate largely by determining which parts of the earth get more sunlight during different stages of the year.
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The mass of Massalia is dependent on the mass of 4 Vesta and perturbation of 44 Nysa. Lightcurve analysis indicates that Massalia's pole points towards either ecliptic coordinates (β, λ) = (45°, 10°) or (β, λ) = (45°, 190°) with a 10° uncertainty. This gives an axial tilt of 45°in both cases. The shape reconstruction from lightcurves has been described as quite spherical with large planar, nonconvex parts of the surface.
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This causes a colder global climate as ice sheets start to build up. The shape of Earth's orbit around the sun affects the Earth's climate. Over a 100,000 year cycle, Earth oscillates between having a circular orbit to having a more elliptical orbit. From 2.58 million years ago to about 1.73 million ± 50,000 years ago, the degree of axial tilt was the main cause of glacial and interglacial periods.
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All eight planets in the Solar System orbit the Sun in the direction of the Sun's rotation, which is counterclockwise when viewed from above the Sun's north pole. Six of the planets also rotate about their axis in this same direction. The exceptions – the planets with retrograde rotation – are Venus and Uranus. Venus's axial tilt is 177°, which means it is rotating almost exactly in the opposite direction to its orbit.
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This may indicate the presence of an additional source of heat within the planet. One possible candidate is tidal heating from an eccentric orbit, a possibility which has not been ruled out from the available measurements. However, another planet with a significantly inflated radius, HD 209458 b, is in a circular orbit. An alternative possibility is that the planet has a high axial tilt, like Uranus in the Solar System.
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In the Northern Hemisphere summer, when the earth’s axial tilt was directed toward the sun, Laurasia would have received the most direct solar insolation. This would have yielded a broad area of warm, rising air and low surface pressure over the continent. Models have suggested that this seasonal low was positioned at 35° latitude, relatively near the Tethys Ocean.Kutzbach, J.E. and R.G. Gallimore, 1989: Pangaean climates: Megamonsoons of the megacontinent.
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Radiometric observations at Arecibo Observatory revealed that Sigurd is a contact binary, composed of two lobes in contact with each other. The more or less ellipsoidal lobes are elongated and joined on their long axis. The body has an axial tilt of 50° to 130°. The observing astronomers also note, that more than 10% of all larger (> 200 meters) near-Earth objects observed by radar are such contact binaries.
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A picture of Jupiter and its moon Io taken by Hubble. The black spot is Io's shadow. Saturn occults the Sun as seen from the Cassini–Huygens space probe The gas giant planets have many moons and thus frequently display eclipses. The most striking involve Jupiter, which has four large moons and a low axial tilt, making eclipses more frequent as these bodies pass through the shadow of the larger planet.
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The rotational axis of the Moon also undergoes precession. Since the Moon's axial tilt is only 1.5° with respect to the ecliptic (the plane of Earth's orbit around the Sun), this effect is small. Once every 18.6 years, The lunar north pole describes a small circle around a point in the constellation Draco, while correspondingly, the lunar south pole describes a small circle around a point in the constellation Dorado.
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Camilla has a very dark surface and primitive carbonaceous composition. A large number of rotational lightcurves of have been obtained from photometric observations since the 1980s. Best rated results gave a short rotation period of 4.844 hours with a brightness amplitude between 0.32 and 0.53 magnitude. Lightcurve analysis indicates that Camilla's pole most likely points towards ecliptic coordinates (β, λ) = (+51°, 72°) with a 10° uncertainty, which gives it an axial tilt of 29°.
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This could mean a body reorienting itself to put extraneous mass near the equator and regions lacking mass tend towards the poles. This is called polar wander. According to a paper released from the University of Arizona, this could be caused by masses of frozen nitrogen building up in shadowed areas of the dwarf planet. These masses would cause the body to reorient itself, leading to its unusual axial tilt of 120°.
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Circumpolar star trails captured with an extended exposure In astronomy, a circumpolar constellation is a constellation (group of stars) that never sets below the horizon, as viewed from a location on Earth. Due to Earth's rotation and axial tilt with respect to the Sun, the stars and constellations can be divided into two categories. Those stars and constellations that never rise or set are called circumpolar. The rest are divided into seasonal stars and constellations.
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Its sidereal rotation period (day) is roughly 16.11 hours. Because its axial tilt is comparable to Earth's, the variation in the length of its day over the course of its long year is not any more extreme. Because Neptune is not a solid body, its atmosphere undergoes differential rotation. The wide equatorial zone rotates with a period of about 18 hours, which is slower than the 16.1-hour rotation of the planet's magnetic field.
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It differs strongly from the thermal behaviour of the Uranian irregular moons that is comparable to classical trans-Neptunian objects. This suggests a separate origin. Artist's conception of the Sun's path in the summer sky of a major moon of Uranus (which shares Uranus's axial tilt) All major moons comprise approximately equal amounts rock and ice, except Miranda, which is made primarily of ice. The ice component may include ammonia and carbon dioxide.
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These orbital variations cause the axial tilt (the angle between rotational and orbital axes) to vary between 0 and 0.33°. Ganymede participates in orbital resonances with Europa and Io: for every orbit of Ganymede, Europa orbits twice and Io orbits four times. Conjunctions (alignment on the same side of Jupiter) between Io and Europa occur when Io is at periapsis and Europa at apoapsis. Conjunctions between Europa and Ganymede occur when Europa is at periapsis.
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However, recent geologic evidence suggests that FSDs are deposits left by glaciers, which covered portions of the volcanoes during a recent period of high obliquity. During periods of high obliquity (axial tilt) the polar regions receive higher levels of sunlight. More water from the poles enters the atmosphere and condenses as ice or snowfall in the cooler equatorial regions. Mars changes its obliquity from about 15° to 35° in cycles of 120,000 years.
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However, proving that a body is in hydrostatic equilibrium is extremely difficult, but by using a combination of shape and gravity data, the hydrostatic contributions can be deduced. Specific techniques to detect inner oceans include magnetic induction, geodesy, librations, axial tilt, tidal response, radar sounding, compositional evidence, and surface features. Artist's cut-away representation of the internal structure of Ganymede, with a liquid water ocean "sandwiched" between two ice layers. Layers drawn to scale.
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A peak of eternal light (PEL) is a hypothetical point on the surface of an astronomical body that is always in sunlight. Such a peak must have high latitude, high elevation, and be on a body with very small axial tilt. The existence of such peaks was first postulated by Beer and Mädler in 1837. The pair said about the lunar polar mountains: "...many of these peaks have (with the exception of eclipses caused by the Earth) eternal sunshine".
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This is the primary cause for the different seasons Earth experiences throughout the year, as well as the intensity of the seasons for higher latitudes. For example, in the Northern Hemisphere, if there were no axial tilt, i.e. Earth's obliquity would be zero degrees, then there would be no change in the seasons from year to year. This would be because there would be no difference in the amount of solar irradiation received, year-round, anywhere on Earth.
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Metis' direction of rotation is unknown at present, due to ambiguous data. Lightcurve analysis indicates that the Metidian pole points towards either ecliptic coordinates (β, λ) = (23°, 181°) or (9°, 359°) with a 10° uncertainty.J. Torppa et al., Shapes and rotational properties of thirty asteroids from photometric data, Icarus Vol. 164, p. 346 (2003). The equivalent equatorial coordinates are (α, δ) = (12.7 h, 21°) or (23.7 h, 8°). This gives an axial tilt of 72° or 76°, respectively.
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The Callisto was going straight up. The book offers a fictional account of life in the year 2000. It contains abundant speculation about technological invention, including descriptions of a worldwide telephone network, solar power, air travel, space travel to the planets Saturn and Jupiter, and terraforming engineering projects -- damming the Arctic Ocean, and an adjustment of the axial tilt of the Earth (Terra) by the Terrestrial Axis Straightening Company. The future United States is a multi-continental superpower.
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If the Earth were a perfect sphere, there would be no precession. This average torque is perpendicular to the direction in which the rotation axis is tilted away from the ecliptic pole, so that it does not change the axial tilt itself. The magnitude of the torque from the Sun (or the Moon) varies with the angle between the Earth's spin axis direction and that of the gravitational attraction. It approaches zero when they are perpendicular.
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This gives an axial tilt of about 33°. Astraea is physically unremarkable but notable mainly because for 38 years (after the discovery of Vesta in 1807) it had been thought that there were only four asteroids. With an apparent magnitude of 8.7 (on a favorable opposition on 15 February 2016), it is indeed only the seventeenth-brightest main-belt asteroid, and fainter than, for example, 192 Nausikaa or even 324 Bamberga (at rare near-perihelion oppositions).
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The Rocky Mountains in Canada overlook Moraine Lake. A planet that can sustain life is termed habitable, even if life did not originate there. Earth provides liquid water—an environment where complex organic molecules can assemble and interact, and sufficient energy to sustain metabolism. The distance of Earth from the Sun, as well as its orbital eccentricity, rate of rotation, axial tilt, geological history, sustaining atmosphere, and magnetic field all contribute to the current climatic conditions at the surface.
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The surface of Venus is effectively isothermal; it retains a constant temperature not only between the two hemispheres but between the equator and the poles. Venus' minute axial tilt—less than 3°, compared to 23° on Earth—also minimises seasonal temperature variation. Altitude is one of the few factors that affect Venusian temperature. The highest point on Venus, Maxwell Montes, is therefore the coolest point on Venus, with a temperature of about and an atmospheric pressure of about .
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Uranus, tipped on its side, is postulated to have seasonal effects far stronger than on Earth. Similarly, Mars is postulated to have varied its axial tilt over eons, and to a far greater extent than on Earth. This is hypothesized to have dramatically altered not only seasons but climates on Mars, for which some evidence has been observed. Venus has negligible tilt, eliminating seasons, and a slow, retrograde rotation, causing different diurnal effects than on Earth and Mars.
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It has also been translated into many languages including Arabic, Turkish, and Hebrew. Commentaries by known astronomers like Quishji have also been made. Ulugh Beg determined the length of the tropical year as 365d 5h 49m 15s, which has an error of +25s, making it more accurate than Nicolaus Copernicus' estimate which had an error of +30s. Ulugh Beg also determined the Earth's axial tilt as 23;30,17 degrees in sexagesimal notation, which in decimal notation converts to 23.5047 degrees.
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Rotation of a planar figure around a point Rotational Orbit v Spin plane of orbit and axial tilt (for Earth). Mathematically, a rotation is a rigid body movement which, unlike a translation, keeps a point fixed. This definition applies to rotations within both two and three dimensions (in a plane and in space, respectively.) All rigid body movements are rotations, translations, or combinations of the two. A rotation is simply a progressive radial orientation to a common point.
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Polar regions receive less intense solar radiation than the other parts of Earth because the sun's energy arrives at an oblique angle, spreading over a larger area, and also travels a longer distance through the Earth's atmosphere in which it may be absorbed, scattered or reflected, which is the same thing that causes winters to be colder than the rest of the year in temperate areas. The axial tilt of the Earth has a major effect on climate of the polar regions. However, since the polar regions are the farthest from the equator, they receive the weakest solar radiation and are therefore generally frigid year round due to the earth's axial tilt of 23.5° not being enough to create a high maximum midday declination to sufficiently strengthen the sun's rays even in summer, except for relatively brief periods in peripheral areas near the polar circles. The large amount of ice and snow also reflects a large part of what weak sunlight the Polar regions receive, contributing to the cold.
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World map showing the Tropic of Capricorn Relationship between Earth's axial tilt (ε) to the tropical and polar circles The Tropic of Capricorn (or the Southern Tropic) is the circle of latitude that contains the subsolar point at the December (or southern) solstice. It is thus the southernmost latitude where the Sun can be seen directly overhead. It also reaches 90 degrees below the horizon at solar midnight on the June Solstice. Its northern equivalent is the Tropic of Cancer.
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The term GMT should not thus be used for certain technical purposes requiring precision.Hilton and McCarthy 2013, pp. 231–2. Because of Earth's uneven angular velocity in its elliptical orbit and its axial tilt, noon (12:00:00) GMT is rarely the exact moment the Sun crosses the Greenwich meridian and reaches its highest point in the sky there. This event may occur up to 16 minutes before or after noon GMT, a discrepancy calculated by the equation of time.
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The purpose of the commission was to recognize the space exploration program. The plaque on the right is an equation of time table to correct for the time differences caused by the axial tilt of the Earth as well as its orbital eccentricity. As the plaque indicates with an additional correction, the equation of time table does not correct for daylight saving time. Like most of Moore's work completed after 1954, this was a modeled sculpture instead of a direct carving.
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Pluto's last passage through its perihelion was on 5 September 1989. As of 2015, it is moving away from the Sun and its overall surface illumination is decreasing. However, the situation is complicated by its big axial tilt (122.5°), which results in long polar days and nights on large parts of its surface. Shortly before the perihelion, on 16 December 1987, Pluto underwent equinox, and its north poleDue to reverse direction of axial rotation of Pluto, naming of its poles is somewhat ambiguous.
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Rapid rotation reduces the daily variation in temperature and makes photosynthesis viable.scientificamerican.com, Fact or Fiction: The Days (and Nights) Are Getting Longer, By Adam Hadhazy, 14 June 2010 The Rare Earth hypothesis further argues that the axial tilt cannot be too large or too small (relative to the orbital plane). A planet with a large tilt will experience extreme seasonal variations in climate. A planet with little or no tilt will lack the stimulus to evolution that climate variation provides.
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More recent visible-light Hubble Space Telescope images of a full rotation taken in 2003 and 2004 showed 11 recognizable surface features, the natures of which are currently unknown. One of these features corresponds to the "Piazzi" feature observed earlier. These last observations also determined that the north pole of Ceres points in the direction of right ascension 19 h 24 min (291°), declination +59°, in the constellation Draco. This means that Ceres's axial tilt is very small—about 3°.
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Another hypothesis states that when Uranus was "knocked over" by the supermassive impactor which caused its extreme axial tilt, the event also caused it to expel most of its primordial heat, leaving it with a depleted core temperature. Another hypothesis is that some form of barrier exists in Uranus's upper layers which prevents the core's heat from reaching the surface. For example, convection may take place in a set of compositionally different layers, which may inhibit the upward heat transport.
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A National Library of Romania fund, mysteriously kept under C. A. Rosetti's alias Dinu Rosetti, comprises most of the letters addressed to Românul. Even after its founder's death, the newspaper was known outside Romania: "Romanul of Bucharest" is mentioned by Jules Verne in his speculative novel of 1889, The Purchase of the North Pole. It is the only Romanian title cited among the press reports on the central event: the planned modification of the axial tilt. Jules Verne, Sans dessus dessous.
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Historically, there have been cyclical ice ages in which glacial sheets periodically covered the higher latitudes of the continents. Ice ages may occur because of changes in ocean circulation and continentality induced by plate tectonics. The Milankovitch theory predicts that glacial periods occur during ice ages because of astronomical factors in combination with climate feedback mechanisms. The primary astronomical drivers are a higher than normal orbital eccentricity, a low axial tilt (or obliquity), and the alignment of summer solstice with the aphelion.
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The name was approved by IAU's Working Group for Planetary System Nomenclature on August 6, 2012. Since Tolkien is very close to the north pole, and Mercury has almost no axial tilt, Tolkien receives very little sunlight. S band radar data from the Arecibo Observatory collected between 1999 and 2005 indicates a radar-bright area covers the entire floor of Tolkien, which is probably indicative of a water ice deposit.Chabot, N. L., D. J. Lawrence, G. A. Neumann, W. C. Feldman, and D. A. Paige, 2018.
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The Moon's axial tilt with respect to the ecliptic is only 1.5424°, much less than the 23.44° of Earth. Because of this, the Moon's solar illumination varies much less with season, and topographical details play a crucial role in seasonal effects. From images taken by Clementine in 1994, it appears that four mountainous regions on the rim of the crater Peary at the Moon's north pole may remain illuminated for the entire lunar day, creating peaks of eternal light. No such regions exist at the south pole.
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Nix is not tidally locked and tumbles chaotically similarly to all smaller moons of Pluto; the moon's axial tilt and rotation period vary greatly over short timescales. Due to the chaotic rotation of Nix, it can occasionally flip its entire rotational axis. The varying gravitational influences of Pluto and Charon as they orbit their barycenter causes the chaotic tumbling of Pluto's small moons, including Nix. The chaotic tumbling of Nix is also strengthened by its elongated shape, which creates torques that act on the object.
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The ICC Cricket World Cup trophy. The ICC Cricket World Cup Trophy is presented to the winning team of the ICC Cricket World Cup. The current trophy is 60 cm high, is made from silver and gold, and features a golden globe held up by three silver columns. The columns, shaped as stumps and bails, represents the three fundamental aspects of cricket: batting, bowling and fielding, while the globe characterises a cricket ball, with the seam that is tilted to represent Axial tilt of the Earth.
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There is a roughly 50-50 chance it is tidally locked. Since it is closer to its star than Earth is to the Sun, it will probably rotate much more slowly than Earth; its day could be weeks or months long (see Tidal effects on rotation rate, axial tilt and orbit). Planetary formation simulations have also shown that there could be one additional non-transiting low-mass planet between Kepler-186e and Kepler-186f. If this planet exists, it is likely not much more massive than Earth.
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Plot of equatorial spin velocity vs. mass for planets comparing Beta Pictoris b to the Solar System planets. In April 2014, the first measurement of a planet's rotation period was announced: the length of day for the super- Jupiter gas giant Beta Pictoris b is 8 hours (based on the assumption that the axial tilt of the planet is small.)Length of Exoplanet Day Measured for First Time. Eso.org. 30 April 2014Klotz, Irene (30 April 2014) Newly Clocked Exoplanet Spins a Whole Day in 8 Hours. Discovery.com.
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Earth's obliquity may have been reasonably accurately measured as early as 1100 BC in India and China. The ancient Greeks had good measurements of the obliquity since about 350 BC, when Pytheas of Marseilles measured the shadow of a gnomon at the summer solstice. About 830 AD, the Caliph Al-Mamun of Baghdad directed his astronomers to measure the obliquity, and the result was used in the Arab world for many years. In 1437, Ulugh Beg determined the Earth's axial tilt as 23°30′17″ (23.5047°).
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The projected rotational velocity is a relatively low 5 km/s, but the rotation rate is unknown since the axial tilt hasn't been determined. 14 Ceti shows an X-ray emission of , which is on the high side for an F5 star. Both the corona and chromosphere of this star show indications of a magnetic field, and a surface field was detected in 2009 with a strength of . This made it the only known star between classes F0 and F7 to have a Zeeman effect detected.
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The rotation period of Ceres (the Cererian day) is 9 hours and 4 minutes. It has an axial tilt of 4°. This is small enough for Ceres's polar regions to contain permanently shadowed craters that are expected to act as cold traps and accumulate water ice over time, similar to the situation on the Moon and Mercury. About 0.14% of water molecules released from the surface are expected to end up in the traps, hopping an average of 3 times before escaping or being trapped.
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The Northern Hemisphere experiences more direct sunlight during May, June, and July, as the hemisphere faces the Sun. The same is true of the Southern Hemisphere in November, December, and January. It is Earth's axial tilt that causes the Sun to be higher in the sky during the summer months, which increases the solar flux. However, due to seasonal lag, June, July, and August are the warmest months in the Northern Hemisphere while December, January, and February are the warmest months in the Southern Hemisphere.
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Tide pools resulting from tidal interaction of the Moon are said to have promoted the evolution of complex life. The Moon is unusual because the other rocky planets in the Solar System either have no satellites (Mercury and Venus), or only tiny satellites which are probably captured asteroids (Mars). The Giant-impact theory hypothesizes that the Moon resulted from the impact of a Mars-sized body, dubbed Theia, with the young Earth. This giant impact also gave the Earth its axial tilt (inclination) and velocity of rotation.
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Martian season lengths and time as compared to seasons on Earth Various schemes have been used or proposed for timekeeping on the planet Mars independently of Earth time and calendars. Mars has an axial tilt and a rotation period similar to those of Earth. Thus, it experiences seasons of spring, summer, autumn and winter much like Earth. Coincidentally, the duration of a Martian day is within a few percent of that of an Earth day, which has led to the use of analogous time units.
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The phenomenon was observed and confirmed during the summer solstice of 2015. The entire passage, which was filmed, lasts a bit over 4 minutes. Scientific literature mentions two archaeological locations in Great Britain where the "double sunset" has been observed on the solstices, but "double sunrise" is not recorded. As the axial tilt changed since then, a geospatial analysis was conducted, using the GPS, which proved that the "double sunrise" occurred at that time, too, and that it was visible from the original location of Lepenski Vir.
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Eartha's mounting at the base using a cantilever arm with two motors. The globe was built with a scale of 1:1,000,000, on which one inch represents sixteen miles. As with most globes, it is mounted at a 23.5 degree angle, the same axial tilt as the Earth itself; thus the equator is diagonal to the floor. It uses a cantilever mount with two motors, and simulates one day's revolution and rotation every 18 minutes, though it is possible for the motors to fully rotate the globe in as little as one minute.
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The probability of finding an Earth analog depends mostly on the attributes that are expected to be similar, and these vary greatly. Generally it is considered that it would be a terrestrial planet and there have been several scientific studies aimed at finding such planets. Often implied but not limited to are such criteria as planet size, surface gravity, star size and type (i.e. Solar analog), orbital distance and stability, axial tilt and rotation, similar geography, oceans, air and weather conditions, strong magnetosphere and even the presence of Earth-like complex life.
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The most characteristic of these is the seasonal cycle (caused by the consequences of the Earth's axial tilt), although wind magnitudes additionally have strong spatial components. Consequently, primary production in temperate regions such as the North Atlantic is highly seasonal, varying with both incident light at the water's surface (reduced in winter) and the degree of mixing (increased in winter). In tropical regions, such as the gyres in the middle of the major basins, light may only vary slightly across the year, and mixing may only occur episodically, such as during large storms or hurricanes.
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Thus the maximum latitudes of the tropics have the same value positive and negative. Likewise they approximate, due to the earth not being a perfect sphere, the "angle" of the Earth's axial tilt. The "angle" itself is not perfectly fixed due chiefly to the influence of the moon, but the limits of tropics are a geographic convention, being an averaged form, not least the variance is very small. In terms of climate, the tropics receive sunlight that is more direct than the rest of Earth and are generally hotter and wetter.
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At the Equator, the daytime period always lasts about 12 hours, regardless of season. As viewed from the Equator, the Sun always rises and sets vertically, following an apparent path nearly perpendicular to the horizon. Due to the axial tilt of Earth, Sun always lies within 23.44° north or south of the celestial equator, so the subsolar point always lies within the tropics. From the March equinox to the September equinox, the Sun rises within 23.44° north of due east, and sets within 23.44° north of due west.
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Like the other small moons of Pluto, Kerberos is not tidally locked and its rotation is chaotic, varying quickly over geological timescales. The varying gravitational influences of Pluto and Charon as they orbit their barycenter causes the chaotic tumbling of Pluto's small moons, including Kerberos. At the time of the New Horizons flyby, the rotational period of Kerberos was about 5.33 days and its rotational axis was tilted about 96 degrees to its orbit. The high axial tilt of Kerberos meant that it was rotating sideways relative to its orbit around the Pluto-Charon barycenter.
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Globes of Earth often display an analemma. The north–south component of the analemma results from the change in the Sun's declination due to the tilt of Earth's axis of rotation. The east–west component results from the nonuniform rate of change of the Sun's right ascension, governed by combined effects of Earth's axial tilt and orbital eccentricity. One can photograph an analemma by keeping a camera at a fixed location and orientation and taking multiple exposures throughout the year, always at the same time of day (disregarding daylight saving time, if applicable).
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The first day of each month is shown in black, and the solstices and equinoxes are shown in green. It can be seen that the equinoxes occur approximately at altitude , and the solstices occur approximately at altitudes where ε is the axial tilt of the earth, 23.4°. The analemma is plotted with its width highly exaggerated, revealing a slight asymmetry (due to the two-week misalignment between the apsides of the Earth's orbit and its solstices). The analemma is oriented with the smaller loop appearing north of the larger loop.
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Crescent Uranus as imaged by Voyager 2 while en route to Neptune In 1986, NASA's Voyager 2 interplanetary probe encountered Uranus. This flyby remains the only investigation of Uranus carried out from a short distance and no other visits are planned. Launched in 1977, Voyager 2 made its closest approach to Uranus on 24 January 1986, coming within of the cloudtops, before continuing its journey to Neptune. The spacecraft studied the structure and chemical composition of Uranus's atmosphere, including its unique weather, caused by its axial tilt of 97.77°.
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Pluto's rotation period, its day, is equal to 6.387 Earth days. Like Uranus, Pluto rotates on its "side" in its orbital plane, with an axial tilt of 120°, and so its seasonal variation is extreme; at its solstices, one-fourth of its surface is in continuous daylight, whereas another fourth is in continuous darkness. The reason for this unusual orientation has been debated. Research from the University of Arizona has suggested that it may be due to the way that a body's spin will always adjust to minimise energy.
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This gives an axial tilt of about 165°. Like other true members of the family, its surface is composed of silicates and some nickel-iron, and is quite bright. Calcium- rich pyroxenes and olivine, along with nickel-iron metal, have been detected on Eunomia's surface. Spectroscopic studies suggest that Eunomia has regions with differing compositions: A larger region dominated by olivine, which is pyroxene-poor and metal-rich, and another somewhat smaller region on one hemisphere (the less pointed end) that is noticeably richer in pyroxene, and has a generally basaltic composition.
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Milankovitch cycles. The climatic event was probably a result of predictable changes in the Earth's orbit (Milankovitch cycles) and a continuation of changes that caused the end of the last glacial period. The effect would have had maximum Northern Hemisphere heating 9,000 years ago, when the axial tilt was 24° and the nearest approach to the Sun (perihelion) was during the Northern Hemisphere's summer. The calculated Milankovitch Forcing would have provided 0.2% more solar radiation (+40 W/m2) to the Northern Hemisphere in summer, tending to cause greater heating.
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These orbital variations cause the axial tilt (the angle between rotational and orbital axes) to vary between 0.4 and 1.6°. The dynamical isolation of Callisto means that it has never been appreciably tidally heated, which has important consequences for its internal structure and evolution. Its distance from Jupiter also means that the charged-particle flux from Jupiter's magnetosphere at its surface is relatively low—about 300 times lower than, for example, that at Europa. Hence, unlike the other Galilean moons, charged-particle irradiation has had a relatively minor effect on Callisto's surface.
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During the early and middle Holocene, large lakes such as Lake Chad and Lake Ptolemy developed within the Sahara and river systems such as Wadi Howar flowed, although it is not clear if they were flowing through a still desertic landscape. The formation of these paleolakes was ultimately linked to a stronger African monsoon caused by a higher axial tilt and the perihelion of Earth coinciding with late July and thus the monsoon season. Today the eastern Sahara is among the driest locations on Earth as it is far removed from oceanic moisture sources.
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Pluto may be defined as having retrograde rotation and an axial tilt of 60 degrees, or prograde rotation and a tilt of 120 degrees. Following the latter convention (the right-hand rule), the hemisphere currently in daylight is the northern one, with much of the southern hemisphere in darkness. This is the convention used by the International Astronomical Union (IAU) and the New Horizons team, and their maps put the sunlit hemisphere on top. However, older sources may define Pluto's rotation as retrograde and therefore the sunlit side as the southern hemisphere.
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A season is a division of the year marked by changes in weather, ecology, and the amount of daylight. On Earth, seasons are the result of Earth's orbit around the Sun and Earth's axial tilt relative to the ecliptic plane. In temperate and polar regions, the seasons are marked by changes in the intensity of sunlight that reaches the Earth's surface, variations of which may cause animals to undergo hibernation or to migrate, and plants to be dormant. Various cultures define the number and nature of seasons based on regional variations.
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Compared to axial tilt, other factors contribute little to seasonal temperature changes. The seasons are not the result of the variation in Earth's distance to the Sun because of its elliptical orbit."Fundamentals of physical geography", PhysicalGeography.net, Ch. 6: Energy and Matter:(h) Earth-Sun Geometry, In fact, Earth reaches perihelion (the point in its orbit closest to the Sun) in January, and it reaches aphelion (the point farthest from the Sun) in July, so the slight contribution of orbital eccentricity opposes the temperature trends of the seasons in the Northern Hemisphere.
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The angle of the Earth's axial tilt with respect to the orbital plane (the obliquity of the ecliptic) varies between 22.1° and 24.5°, over a cycle of about 41,000 years. The current tilt is 23.44°, roughly halfway between its extreme values. The tilt last reached its maximum in 8,700 BCE. It is now in the decreasing phase of its cycle, and will reach its minimum around the year 11,800 CE. Increased tilt increases the amplitude of the seasonal cycle in insolation, providing more solar radiation in each hemisphere's summer and less in winter.
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If they move clockwise, the sun will be in the south at midday, and if they move anticlockwise, then the sun will be in the north at midday. Because of the Earth's axial tilt, no matter what the location of the viewer, there are only two days each year when the sun rises precisely due east. These days are the equinoxes. On all other days, depending on the time of year, the sun rises either north or south of true east (and sets north or south of true west).
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The opposite phenomenon, polar night, occurs in winter, when the Sun stays below the horizon throughout the day. Since the axial tilt of the Earth is considerable (23 degrees, 26 minutes, 21.41196 seconds), the Sun does not set at high latitudes in local summer. The Sun remains continuously visible for one day during the summer solstice at the polar circle, for several weeks only closer to the pole, and for six months at the pole. At extreme latitudes, the midnight sun is usually referred to as polar day.
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This gives an axial tilt of 42°. It has a bright surface and, if its identification as the parent body of the H chondrites is correct, a surface composition of silicate chondritic rocks mixed with pieces of iron–nickel. A likely scenario for the formation of the surface metal is as follows: # Large impacts caused local melting of the iron rich H chondrite surface. The metals, being heavier, would have settled to the bottom of the magma lake, forming a metallic layer buried by a relatively shallow layer of silicates.
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Owing to the Earth's axial tilt, winter in the Northern Hemisphere lasts from the December solstice (typically December 21 UTC) to the March equinox (typically March 20 UTC), while summer lasts from the June solstice through to the September equinox (typically on 23 September UTC). The dates vary each year due to the difference between the calendar year and the astronomical year. Within the northern hemisphere, oceanic currents can change the weather patterns that affect many factors within the north coast. Such events include ENSO (El Niño southern oscillation).
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An analemma illustrates the changing position of the Sun over the course of a year, as seen at a fixed time of day. A year is the orbital period of a planetary body, for example, the Earth, moving in its orbit around the Sun. Due to the Earth's axial tilt, the course of a year sees the passing of the seasons, marked by change in weather, the hours of daylight, and, consequently, vegetation and soil fertility. In temperate and subpolar regions around the planet, four seasons are generally recognized: spring, summer, autumn and winter.
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The planet is 1.52 times as far from the Sun as Earth, resulting in just 43% of the amount of sunlight. If Mars had an Earth-like orbit, its seasons would be similar to Earth's because its axial tilt is similar to Earth's. The comparatively large eccentricity of the Martian orbit has a significant effect. Mars is near perihelion when it is summer in the southern hemisphere and winter in the north, and near aphelion when it is winter in the southern hemisphere and summer in the north.
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However, because the 18.6-year cycle of standstills is so much longer than the Moon's orbital period (about 27.3 days), the change in the declination range over periods as short as half an orbit is very small. The period of the lunar nodes precessing in space is slightly shorter than the lunar standstill interval due to Earth's axial precession, altering Earth's axial tilt over a very long period relative to the direction of lunar nodal precession. Simply, the standstill cycle results from the combination of the two inclinations.
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There have been numerous supernovae in a region, meaning that planets in the area are rich in valuable radioactive ores, but Pyrrus is the only even marginally habitable one, and thus the only one that can support sustained mining operations. Pyrrus is no paradise. It has a gravity of 2 g; its 42° axial tilt creates severe weather; it has frequent earthquakes and volcanic eruptions; two large moons generate tides of up to 30 meters; and finally, there are high levels of radiation. Everything on the planet is deadly to humans.
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The various cycles of earth's climate seem to be explained by the eccentricity, axial tilt, and precession of the Earth's orbit as well as cycles in the amount of solar radiation. Ruddiman primarily relies on the groundwork by Milutin Milankovitch to explain the effects of solar radiation and earth's orbit on the climate. By examining ice cores from around the world scientists have been able to link levels of greenhouse gases such as carbon dioxide and methane to the various cycles of earth's climate history. The discovery of carbon dating aided a great deal in developing this understanding.
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Since the asteroid is likely to be a rubble pile, accounting for a possible porosity of 20–40% leads to the material density of 4.2–5.8 g/cm3, which means that Kalliope is probably made of a mixture of metal with silicates. Spectroscopic studies have shown, however, evidence of hydrated minerals and silicates, which indicate rather a stony surface composition. Kalliope also has a low radar albedo, which is inconsistent with a purely metallic surface. Lightcurve analysis indicates that Kalliope's pole most likely points towards ecliptic coordinates (β, λ) = (−23°, 20°) with a 10° uncertainty, which gives Kalliope an axial tilt of 103°.
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From this distance, the Sun's angular diameter is reduced to one and a quarter arcminutes across. Here are the angular diameters of the moons that are large enough to fully eclipse the Sun: Naiad, 7–13'; Thalassa, 8–14'; Despina, 14–22'; Galatea, 13–18'; Larissa, 10–14'; Proteus, 13–16'; Triton, 26–28'. Just because the moons are large enough to fully eclipse the Sun does not necessarily mean that they will do so. Eclipses of the Sun from Neptune are rare due to the planet's long orbital period and large axial tilt of 28 degrees.
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World map showing the Tropic of Cancer Relationship between Earth's axial tilt (ε) to the tropical and polar circles The Tropic of Cancer, which is also referred to as the Northern Tropic, is the most northerly circle of latitude on Earth at which the Sun can be directly overhead. This occurs on the June solstice, when the Northern Hemisphere is tilted toward the Sun to its maximum extent. It also reaches 90 degrees below the horizon at solar midnight on the December Solstice. Using a continuously updated formula, the circle is currently north of the Equator.
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Gonggong is known from the late Warring States period (before 221 BCE). Gonggong appears in the ancient "Heavenly Questions" (Tianwen) poem of the Chu Ci, where he is blamed for knocking the earth's axis off center, causing it to tilt to the southeast and the sky to tilt to the northwest. This axial tilt is used to explain why the rivers of China generally flow to the southeast, especially the Yangzi River and the Yellow River, and why the sun, moon, and stars move towards the northwest. Literature from the Han dynasty becomes much more detailed regarding Gonggong.
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The orbit of 8 Flora compared with the orbits of Earth, Mars and Jupiter Lightcurve analysis indicates that Flora's pole points towards ecliptic coordinates (β, λ) = (16°, 160°) with a 10° uncertainty. This gives an axial tilt of 78°, plus or minus ten degrees. Flora is the parent body of the Flora family of asteroids, and by far the largest member, comprising about 80% of the total mass of this family. Nevertheless, Flora was almost certainly disrupted by the impact(s) that formed the family, and is probably a gravitational aggregate of most of the pieces.
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The relative "hot spot" is due to Neptune's axial tilt, which has exposed the south pole to the Sun for the last quarter of Neptune's year, or roughly 40 Earth years. As Neptune slowly moves towards the opposite side of the Sun, the south pole will be darkened and the north pole illuminated, causing the methane release to shift to the north pole. Because of seasonal changes, the cloud bands in the southern hemisphere of Neptune have been observed to increase in size and albedo. This trend was first seen in 1980 and is expected to last until about 2020.
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Within icehouse states, there are "glacial" and "interglacial" periods that cause ice sheets to build up or retreat. The causes for these glacial and interglacial periods are mainly variations in the movement of the earth around the Sun. The astronomical components, discovered by the Serbian geophysicist Milutin Milanković and now known as Milankovitch cycles, include the axial tilt of the Earth, the orbital eccentricity (or shape of the orbit) and the precession (or wobble) of the Earth's rotation. The tilt of the axis tends to fluctuate between 21.5° to 24.5° and back every 41,000 years on the vertical axis.
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At this time in the late 19th century, astronomical observations were made without photography. Astronomers had to stare for hours through their telescopes, waiting for a moment of still air when the image was clear, and then draw a picture of what they had seen. Astronomers believed at the time that Mars had a relatively substantial atmosphere. They knew that the rotation period of Mars (the length of its day) was almost the same as Earth's, and they knew that Mars' axial tilt was also almost the same as Earth's, which meant it had seasons in the astronomical and meteorological sense.
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In addition to the steady progressive motion (resulting in a full circle in about 25,700 years) the Sun and Moon also cause small periodic variations, due to their changing positions. These oscillations, in both precessional speed and axial tilt, are known as the nutation. The most important term has a period of 18.6 years and an amplitude of 9.2 arcseconds. In addition to lunisolar precession, the actions of the other planets of the Solar System cause the whole ecliptic to rotate slowly around an axis which has an ecliptic longitude of about 174° measured on the instantaneous ecliptic.
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For instance, Titania was shown to possess no atmosphere at a pressure larger than 10–20 nanobar. The path of the Sun in the local sky over the course of a local day during Uranus's and its major moons' summer solstice is quite different from that seen on most other Solar System worlds. The major moons have almost exactly the same rotational axial tilt as Uranus (their axes are parallel to that of Uranus). The Sun would appear to follow a circular path around Uranus's celestial pole in the sky, at the closest about 7 degrees from it.
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Mars' polar ice caps were discovered in the mid-17th century. In the late 18th century, William Herschel proved they grow and shrink alternately, in the summer and winter of each hemisphere. By the mid-19th century, astronomers knew that Mars had certain other similarities to Earth, for example that the length of a day on Mars was almost the same as a day on Earth. They also knew that its axial tilt was similar to Earth's, which meant it experienced seasons just as Earth does—but of nearly double the length owing to its much longer year.
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By 1784, the southern cap appeared much smaller, thereby suggesting that the caps vary with the planet's seasons and thus were made of ice. In 1781, he estimated the rotation period of Mars as 24h 39m 21.67s and measured the axial tilt of the planet's poles to the orbital plane as 28.5°. He noted that Mars had a "considerable but moderate atmosphere, so that its inhabitants probably enjoy a situation in many respects similar to ours". Between 1796 and 1809, the French astronomer Honoré Flaugergues noticed obscurations of Mars, suggesting "ochre-colored veils" covered the surface.
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For Earth's current orbital eccentricity, incoming solar radiation varies by about 6.8%, while the distance from the Sun currently varies by only 3.4% (). Perihelion presently occurs around January 3, while aphelion is around July 4. When the orbit is at its most eccentric, the amount of solar radiation at perihelion will be about 23% more than at aphelion. However, the Earth's eccentricity is always so small that the variation in solar irradiation is a minor factor in seasonal climate variation, compared to axial tilt and even compared to the relative ease of heating the larger land masses of the northern hemisphere.
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In winter, the climate becomes cooler and the days shorter. Above the Arctic Circle and below the Antarctic Circle there is no daylight at all for part of the year, causing a polar night, and this night extends for several months at the poles themselves. These same latitudes also experience a midnight sun, where the sun remains visible all day. By astronomical convention, the four seasons can be determined by the solstices—the points in the orbit of maximum axial tilt toward or away from the Sun—and the equinoxes, when Earth's rotational axis is aligned with its orbital axis.
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The changing Earth–Sun distance causes an increase of about 6.9% in solar energy reaching Earth at perihelion relative to aphelion. Because the Southern Hemisphere is tilted toward the Sun at about the same time that Earth reaches the closest approach to the Sun, the Southern Hemisphere receives slightly more energy from the Sun than does the northern over the course of a year. This effect is much less significant than the total energy change due to the axial tilt, and most of the excess energy is absorbed by the higher proportion of water in the Southern Hemisphere.
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Because of Earth's axial tilt (often known as the obliquity of the ecliptic), the inclination of the Sun's trajectory in the sky (as seen by an observer on Earth's surface) varies over the course of the year. For an observer at a northern latitude, when the north pole is tilted toward the Sun the day lasts longer and the Sun appears higher in the sky. This results in warmer average temperatures, as additional solar radiation reaches the surface. When the north pole is tilted away from the Sun, the reverse is true and the weather is generally cooler.
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The rotation period of Siarnaq was measured by the Cassini spacecraft to be 10.19 hours; this is the shortest rotation period of all prograde irregular moons of Saturn. Siarnaq displays a light curve with three maxima and minima over a full rotation, implying a roughly triangular shape. From Cassini observations of Siarnaq at different phase angles, the orientation of its north rotational pole has been determined to be pointing toward 98° ecliptic latitude and −23° ecliptic longitude. This corresponds to a sideways axial tilt, indicating that Siarnaq experiences long, extreme seasons similar to the planet Uranus.
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The planets rotate around invisible axes through their centres. A planet's rotation period is known as a stellar day. Most of the planets in the Solar System rotate in the same direction as they orbit the Sun, which is counter-clockwise as seen from above the Sun's north pole, the exceptions being Venus and Uranus, which rotate clockwise, though Uranus's extreme axial tilt means there are differing conventions on which of its poles is "north", and therefore whether it is rotating clockwise or anti-clockwise. Regardless of which convention is used, Uranus has a retrograde rotation relative to its orbit.
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Helliconia is 1.28 Earth masses in size, making it somewhat larger than Earth and with a bigger axial tilt of 35 degrees. This means that small-year seasons are harsher, but the planet still has huge polar ice caps, capable of surviving even the great summer, and the human-habitable surface area is comparable to that of Earth. There are three continents, a tropical continent (Campannlat), a northern continent (Sibornal) and a southern continent (Hespagorat). Helliconia Spring and Helliconia Summer mainly take place in Campannlat, with its rich vitality; Helliconia Winter focuses on Sibornal, where the harsher environment encourages technological progress.
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Copernicus' version of trepidation combined the oscillation of the equinoxes (now known to be a spurious motion) with a change in the obliquity of the ecliptic (axial tilt), acknowledged today as an authentic motion of the Earth's axis. Trepidation was a feature of Hindu astronomy and was used to compute ayanamsha for converting sidereal to tropical longitudes. The third chapter of the Suryasiddhanta, verses 9-10, provides the method for computing it, which E. Burgess interprets as 27 degree trepidation in either direction over a full period of 7200 years, at an annual rate of 54 seconds.
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James D. Hays is a professor of Earth and environmental sciences at Columbia University's Lamont-Doherty Earth Observatory. Hays founded and led the CLIMAP project, which collected sea floor sediment data to study surface sea temperatures and paleoclimatological conditions 18,000 years ago. Hays is probably best known as a co-author of the 1976 paper in Science, "Variations in the Earth's orbit: Pacemaker of the ice ages." Using ocean sediment cores, the Science paper verified the theories of Milutin Milanković that oscillations in climate can be correlated with Earth's orbital variations of eccentricity, axial tilt, and precession around the Sun (see Milankovitch cycles).
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It is rotating rapidly, with a projected rotational velocity of 254 km/s along the equator, which causes the star to take the pronounced shape of an oblate spheroid like Altair. Because the inclination of the star's axial tilt is unknown, this means that the azimuthal equatorial velocity is at least this amount and possibly higher. By comparison, the Sun is a slow rotator with an equatorial azimuthal velocity of 2 km/s. The doppler shift from the rapid rotation results in very diffuse absorption lines in the star's spectrum, as indicated by the 'nn' in the classification.
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The permanent diurnal zone covers 22 percent of the total areas of the dwarf planet. The region experiences a continuous sunrise and sunset for each and every Pluto rotation period of 6.4 days over a time period of 10 million years. The present-day diurnal climate zone of Pluto spans from 30°N to 30°S, encompassing 50% of the total surface area, due to the current axial tilt of 120°. As obliquity changes to rise from this value, the diurnal zone will expand to the maximum from 37°N to 37°S (covering a total area of 60%), which will be reached in roughly 600,000 years.
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These factors include the angle of Earth's axial tilt (also known as Earth's obliquity), the eccentricity of Earth's orbit (how circular/elliptical Earth's orbit is), and Earth's position in time in the precession of the solstices and equinoxes (with different Earth-Sun distances during any given season).Ruddiman, William F. "Earth's Climate Past and Future, 2nd Edition." Although these are the primary three factors in shaping Earths climate, there are other, external, factors that can help shape Earth's climate. These external factors usually affect Earth climate on a very different time scale than the other three, and include factors such as meteors striking Earth and geomagnetic storms.
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On the other hand, if Earth's axial tilt angle was great (45+ degrees), the seasonality of each hemisphere, individually, would be highly exaggerated. Summers would be extremely hot, with substantially more hours of daylight than night each day. Winters would be extremely cold, with substantially more hours of night than daylight each day. This is because, during summer for the northern hemisphere, if the earth is tilted more (pointed towards the sun more), there would be more available hours in which the suns rays can strike any certain place, thereby increasing the number of daylight hours at any given place, with more and more daylight hours at higher latitudes.
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World map with the intertropical zone highlighted in crimson Areas of the world with tropical climates The tropics are the region of Earth surrounding the Equator. They are delimited in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S; these latitudes correspond to the axial tilt of the Earth. The tropics are also referred to as the tropical zone and the torrid zone (see geographical zone). The tropics include all zones on Earth where the Sun contacts a point directly overhead at least once during the solar year (which is a subsolar point).
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Its orbit is probably close to circular, so it will also lack eccentricity-induced seasonal changes like those of Mars. However, the axial tilt could be larger (about 23 degrees) if another undetected nontransiting planet orbits between it and Kepler-186e; planetary formation simulations have shown that the presence of at least one additional planet in this region is likely. If such a planet exists, it cannot be much more massive than Earth as it would then cause orbital instabilities. One review essay in 2015 concluded that Kepler-186f, along with the exoplanets Kepler-442b and Kepler-62f, were likely the best candidates for being potentially habitable planets.
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This is especially true of red dwarf systems, where comparatively high gravitational forces and low luminosities leave the habitable zone in an area where tidal locking would occur. If tidally locked, one rotation about the axis may take a long time relative to a planet (for example, ignoring the slight axial tilt of Earth's moon and topographical shadowing, any given point on it has two weeks – in Earth time – of sunshine and two weeks of night in its lunar day) but these long periods of light and darkness are not as challenging for habitability as the eternal days and eternal nights on a planet tidally locked to its star.
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Two dark features had circular shapes and were presumed to be craters; one of them was observed to have a bright central region, whereas another was identified as the "Piazzi" feature. Visible-light Hubble Space Telescope images of a full rotation taken in 2003 and 2004 showed eleven recognizable surface features, the natures of which were then undetermined. One of these features corresponds to the "Piazzi" feature observed earlier. These last observations indicated that the north pole of Ceres pointed in the direction of right ascension 19 h 24 min (291°), declination +59°, in the constellation Draco, resulting in an axial tilt of approximately 3°.
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One benefit of such predictions, particularly those of satellite eclipses by Jupiter since they were subject to less observer error, would be determining an observer's longitude on Earth with respect to the prime meridian. By observing an eclipse of a Jovian satellite, an observer could determine the current time at the prime meridian by looking up the eclipse in an ephemeris table. Io was particularly useful for this purpose since its shorter orbital period and closer distance to Jupiter made eclipses more frequent and less affected by Jupiter's axial tilt. Knowing the time at the prime meridian and the local time, the observer's longitude could then be calculated.
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Cassini spacecraft photographs the Earth and Moon (bottom-right) from Saturn (July 19, 2013) The sky in the upper reaches of Saturn's atmosphere is blue (from imagery of the Cassini mission at the time of its September 2017 demise), but the predominant color of its cloud decks suggests that it may be yellowish further down. Observations from spacecraft show that seasonal smog develops in Saturn's southern hemisphere at its perihelion due to its axial tilt. This could cause the sky to become yellowish at times. As the northern hemisphere is pointed towards the sun only at aphelion, the sky there would likely remain blue.
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Because of a phenomenon known as the precession of the equinoxes, the poles trace out circles on the celestial sphere, with a period of about 25,700 years. The Earth's axis is also subject to other complex motions which cause the celestial poles to shift slightly over cycles of varying lengths (see nutation, polar motion and axial tilt). Finally, over very long periods the positions of the stars themselves change, because of the stars' proper motions. An analogous concept applies to other planets: a planet's celestial poles are the points in the sky where the projection of the planet's axis of rotation intersects the celestial sphere.
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Industrialized societies usually follow a clock-based schedule for daily activities that do not change throughout the course of the year. The time of day that individuals begin and end work or school, and the coordination of mass transit, for example, usually remain constant year-round. In contrast, an agrarian society's daily routines for work and personal conduct are more likely governed by the length of daylight hours and by solar time, which change seasonally because of the Earth's axial tilt. North and south of the tropics daylight lasts longer in summer and shorter in winter, with the effect becoming greater the further one moves away from the tropics.
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This means that solar radiation due to (1) axial tilt inclining the southern hemisphere toward the Sun and (2) the Earth's proximity to the Sun, both reach maximum during the southern summer and both reach minimum during the southern winter. Their effects on heating are thus additive, which means that seasonal variation in irradiation of the southern hemisphere is more extreme. In the northern hemisphere, these two factors reach maximum at opposite times of the year: The north is tilted toward the Sun when the Earth is furthest from the Sun. The two effects work in opposite directions, resulting in less extreme variations in insolation.
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The possibility of life on moons of gas giants (such as Jupiter's moon Europa, or Saturn's moon Titan) adds further uncertainty to this figure. The authors of the rare Earth hypothesis propose a number of additional constraints on habitability for planets, including being in galactic zones with suitably low radiation, high star metallicity, and low enough density to avoid excessive asteroid bombardment. They also propose that it is necessary to have a planetary system with large gas giants which provide bombardment protection without a hot Jupiter; and a planet with plate tectonics, a large moon that creates tidal pools, and moderate axial tilt to generate seasonal variation.
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Viking Orbiter 1, 1976) Mars' temperature and circulation vary every Martian year (as expected for any planet with an atmosphere and axial tilt). Mars lacks oceans, a source of much interannual variation on Earth. Mars Orbiter Camera data beginning in March 1999 and covering 2.5 Martian years show that Martian weather tends to be more repeatable and hence more predictable than that of Earth. If an event occurs at a particular time of year in one year, the available data (sparse as it is) indicates that it is fairly likely to repeat the next year at nearly the same location, give or take a week.
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According to their model, if the polar regions had a subsurface lake perhaps formed originally through friction as a subglacial lake at times of favourable axial tilt, then supplied by accumulating layers of snow on top as the ice sheets thickened, they suggest that it could still be there. If so, it could be occupied by similar life forms to those that could survive in Lake Vostok. Ground penetrating radar could detect these lakes because of the high radar contrast between water and ice or rock. MARSIS, the ground penetrating radar on ESA's Mars Express detected a subglacial lake in Mars near the south pole.
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The sculpture is an outdoor circular concrete pad in diameter circumscribed by eight walls high by wide. Four of the walls are in the cardinal directions, with four adjacent walls situated at angular distances of 23.4 degrees (corresponding with the axial tilt of the Earth) north and south of the east and west walls. The cardinal East and West walls have square windows, the four adjacent walls have isosceles trapezoid windows. Summer Solstice Sunset Autumnal Equinox Sunset Summer Solstice sunset seen through southeastern and northwestern walls At sunrise of any given day, the sunlight hitting the eastern walls will cast shadows across the circle, as light passes through the windows.
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50 in (12.7 mm) AN/M2 "light-barrel" M2 Browning machine guns, the standard heavy-calibre machine gun used throughout the American air services of World War II, bringing the total to six. The inner pair of machine guns had 400 rounds per gun, and the others had 270 rpg, for a total of 1,880.AN 01-60JE-2 1944, p. 386B. The B/C subtypes' M2 guns were mounted with an inboard axial tilt, this angled mounting had caused problems with the ammunition feed and with spent casings and links failing to clear the gun- chutes, leading to frequent complaints that the guns jammed during combat maneuvers.
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There are five climate zones on Pluto which are defined by the sub-solar latitude, each with specific boundaries. However, the latitude ranges of the climate zones expand and shrink in response to the obliquity range of Pluto from a minimum of 103° to a maximum of 127° over the 2.8 million year oscillation period. That means some of the zones have permanent latitude ranges, whereas other zones change their boundaries based on the variation of the axial tilt on a multi-million-year time scale. Permanent boundaries refer to the latitude zones that experience certain characteristics at all times, regardless of the obliquity variation of the dwarf planet over the obliquity oscillation period.
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Hydra is not tidally locked and rotates chaotically; its rotational period and axial tilt vary quickly over astronomical timescales, to the point that its rotational axis regularly flips over. Hydra's chaotic tumbling is largely caused by the varying gravitational influences of Pluto and Charon as they orbit around their barycenter. Hydra's chaotic tumbling is also strengthened by its irregular shape, which creates torques that act on the object. At the time of the New Horizons flyby of Pluto and its moons, Hydra's rotation period was approximately 10 hours and its rotational axis was tilted about 110 degrees to its orbit — it was rotating sideways at the time of the New Horizons flyby.
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Ocean tides are converted to heat by frictional losses in the oceans and their interaction with the solid bottom and with the top ice crust. In late 2008, it was suggested Jupiter may keep Europa's oceans warm by generating large planetary tidal waves on Europa because of its small but non-zero obliquity. This generates so-called Rossby waves that travel quite slowly, at just a few kilometers per day, but can generate significant kinetic energy. For the current axial tilt estimate of 0.1 degree, the resonance from Rossby waves would contain 7.3 J of kinetic energy, which is two thousand times larger than that of the flow excited by the dominant tidal forces.
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Provided gravitational interaction of a moon with other satellites can be neglected, moons tend to be tidally locked with their planets. In addition to the rotational locking mentioned above, there will also be a process termed 'tilt erosion', which has originally been coined for the tidal erosion of planetary obliquity against a planet's orbit around its host star. The final spin state of a moon then consists of a rotational period equal to its orbital period around the planet and a rotational axis that is perpendicular to the orbital plane. If the moon's mass is not too low compared to the planet, it may in turn stabilize the planet's axial tilt, i.e.
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Saturn's axial tilt is 26.7°, meaning that widely varying views of the rings, which occupy its equatorial plane, are obtained from Earth at different times. Earth makes passes through the ring plane every 13 to 15 years, about every half Saturn year, and there are about equal chances of either a single or three crossings occurring in each such occasion. The most recent ring plane crossings were on 22 May 1995, 10 August 1995, 11 February 1996 and 4 September 2009; upcoming events will occur on 23 March 2025, 15 October 2038, 1 April 2039 and 9 July 2039. Favorable ring plane crossing viewing opportunities (with Saturn not close to the Sun) only come during triple crossings.
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Uranus' southern hemisphere in approximate natural colour (left) and in higher wavelengths (right), showing its faint cloud bands and atmospheric "hood" as seen by Voyager 2 The climate of Uranus is heavily influenced by both its lack of internal heat, which limits atmospheric activity, and by its extreme axial tilt, which induces intense seasonal variation. Uranus' atmosphere is remarkably bland in comparison to the other giant planets which it otherwise closely resembles. When Voyager 2 flew by Uranus in 1986, it observed a total of ten cloud features across the entire planet. Later observations from the ground or by the Hubble Space Telescope made in the 1990s and the 2000s revealed bright clouds in the northern (winter) hemisphere.
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Atlas V, proposed for OCEANUS, shown here launching a lunar probe into space Ice giant sized planets are the most common type of planet according to Kepler data. The little data available on Uranus, an ice giant planet, come from ground-based observations and the single flyby of the Voyager 2 spacecraft, so its exact composition and structure are essentially unknown, as internal heat flux, and cause of its unique magnetic fields and extreme axial tilt or obliquity, making it a compelling target for exploration according to the Planetary Science Decadal Survey. The primary science objectives of OCEANUS are to study Uranus' interior structure, magnetosphere, and the Uranian atmosphere. The required mission budget is estimated at $1.2 billion.
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The polar circle is located at a latitude between these two areas, at the latitude of approximately 66.5 degrees. In the northernmost city of Sweden, Kiruna, at 67°51'N, the polar night lasts for around 28 twenty-four-hour periods, while the midnight sun lasts around 50 twenty-four-hour periods. While it is day in the Arctic Circle, it is night in the Antarctic Circle, and vice versa. Any planet or moon with a sufficient axial tilt that rotates with respect to its star significantly more frequently than it orbits the star (no tidal locking between the two) will experience the same phenomenon (a nighttime lasting more than one rotation period).
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On 23 August 2006, researchers at the Space Science Institute (Boulder, Colorado) and the University of Wisconsin observed a dark spot on Uranus's surface, giving scientists more insight into Uranus atmospheric activity. Why this sudden upsurge in activity occurred is not fully known, but it appears that Uranus's extreme axial tilt results in extreme seasonal variations in its weather. Determining the nature of this seasonal variation is difficult because good data on Uranus's atmosphere have existed for less than 84 years, or one full Uranian year. Photometry over the course of half a Uranian year (beginning in the 1950s) has shown regular variation in the brightness in two spectral bands, with maxima occurring at the solstices and minima occurring at the equinoxes.
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They include mapping the surface at per pixel, observations of Pluto's smaller satellites, observations of how Pluto changes as it rotates on its axis, and topographic mapping of Pluto's regions that are covered in long-term darkness due to its axial tilt. The last objective could be accomplished using laser pulses to generate a complete topographic map of Pluto. New Horizons principal investigator Alan Stern has advocated for a Cassini-style orbiter that would launch around 2030 (the 100th anniversary of Pluto's discovery) and use Charon's gravity to adjust its orbit as needed to fulfill science objectives after arriving at the Pluto system. The orbiter could then use Charon's gravity to leave the Pluto system and study more KBOs after all Pluto science objectives are completed.
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Pallas has a high eccentricity and a highly inclined orbit Pallas has unusual dynamic parameters for such a large body. Its orbit is highly inclined and moderately eccentric, despite being at the same distance from the Sun as the central part of the asteroid belt. Furthermore, Pallas has a very high axial tilt of 84°, with its north pole pointing towards ecliptic coordinates (β, λ) = (30°, −16°) with a 5° uncertainty in the Ecliptic J2000.0 reference frame. This means that every Palladian summer and winter, large parts of the surface are in constant sunlight or constant darkness for a time on the order of an Earth year, with areas near the poles experiencing continuous sunlight for as long as two years.
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Nine years later, they arrive and discover that Earth II is sub-optimal: its high axial tilt creates temperature extremes on either side of its equator, making very little land livable. It is also poor in minerals, presumably exhausted by a previous civilisation which has left ruined buildings behind. The crew are of three minds over what to do next: Wilson, Holle, and Grace join a majority deciding to push on to "Earth III", which is 30 years' travel away in the constellation of Lepus. Kelly leads a group returning to Earth, while a minority colonise Earth II. Once the colonists land, the remaining passengers split up the ship's two hulls and the warp drive to go their separate ways, losing simulated gravity in the process.
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Yearly changes in the location of the Tropic of Cancer near a highway in Mexico Nutation subtly changes the axial tilt of Earth with respect to the ecliptic plane, shifting the major circles of latitude that are defined by the Earth's tilt (the tropical circles and the polar circles). In the case of Earth, the principal sources of tidal force are the Sun and Moon, which continuously change location relative to each other and thus cause nutation in Earth's axis. The largest component of Earth's nutation has a period of 18.6 years, the same as that of the precession of the Moon's orbital nodes. However, there are other significant periodic terms that must be accounted for depending upon the desired accuracy of the result.
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The Tropic of Capricorn is the dividing line between the Southern Temperate Zone to the south and the tropics to the north. The Northern Hemisphere equivalent of the Tropic of Capricorn is the Tropic of Cancer. The Tropic of Capricorn's position is not fixed, but constantly changes because of a slight wobble in the Earth's longitudinal alignment relative to its orbit around the Sun. Earth's axial tilt varies over a 41,000 year period from 22.1 to 24.5 degrees and currently resides at about 23.4 degrees. This wobble means that the Tropic of Capricorn is currently drifting northward at a rate of almost half an arcsecond (0.468″) of latitude, or 15 metres, per year (it was at exactly 23° 27′S in 1917 and will be at 23° 26'S in 2045).
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Five million years of glacial cycles are shown, based on oxygen isotope ratio believed to be a good proxy of global ice volume. The MPT is the transition between the periodicities shown in green. The Mid-Pleistocene Transition (MPT), also known as the Mid-Pleistocene Revolution (MPR)Mark A. Maslin and Andy J. Ridgwell (2005): Mid-Pleistocene revolution and the ‘eccentricity myth’, Geological Society, London, Special Publications, 247, 19-34, 1 January 2005, is a fundamental change in the behaviour of glacial cycles during the Quaternary glaciations. The transition happened approximately 1.25–0.7 million years ago, in the Pleistocene epoch. Before the MPT, the glacial cycles were dominated by a 41,000 year periodicity with low-amplitude, thin ice sheets and a linear relationship to the Milankovitch forcing from axial tilt.
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The Earth is not a perfect sphere but an oblate spheroid, with an equatorial diameter about 43 kilometers larger than its polar diameter. Because of the Earth's axial tilt, during most of the year the half of this bulge that is closest to the Sun is off-center, either to the north or to the south, and the far half is off-center on the opposite side. The gravitational pull on the closer half is stronger, since gravity decreases with the square of distance, so this creates a small torque on the Earth as the Sun pulls harder on one side of the Earth than the other. The axis of this torque is roughly perpendicular to the axis of the Earth's rotation so the axis of rotation precesses.
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At first, he is confused and initially believes they might have come to the wrong system because it has changed considerably; the Sun has apparently evolved into a red giant and what might be Earth is in orbit around a super-hot Jupiter. Having followed a message clearly from humans (warning not to visit other human-occupied star systems), and being too old to survive going anywhere else, Corbell puts the ship into orbit around what is surely the Earth. The Earth's climate has changed, especially its surface temperature; the poles are now temperate, while the former temperate zones reach temperatures of over 50 degrees Celsius (120+ degrees Fahrenheit). The Earth's axial tilt is still 23.5 degrees so the poles experience 6 years of night and 6 years of day.
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No follow-up missions to New Horizons have been formally planned, but at least two mission concepts have been studied. In April 2017, a workshop met in Houston, Texas to discuss ideas for a follow-up mission. Possible objectives discussed by the group for a follow-up mission include mapping the surface at 30 feet per pixel, observations of Pluto's smaller satellites, observations of how Pluto changes as it rotates on its axis, and topographic mapping of Pluto's regions that are covered in long-term darkness due to its axial tilt. The last objective could be accomplished using infrared laser pulses. According to New Horizons principal investigator Alan Stern, “If we send an orbiter, we can map 100 percent of the planet, even terrains that are in total shadow.
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In 2007 there was direct observational confirmation of the YORP effect on the small asteroids 54509 YORP (then designated ) and 1862 Apollo. The spin rate of 54509 YORP will double in just 600,000 years, and the YORP effect can also alter the axial tilt and precession rate, so that the entire suite of YORP phenomena can send asteroids into interesting resonant spin states, and helps explain the existence of binary asteroids. Observations show that asteroids larger than 125 km in diameter have rotation rates that follow a Maxwellian frequency distribution, while smaller asteroids (in the 50 to 125 km size range) show a small excess of fast rotators. The smallest asteroids (size less than 50 km) show a clear excess of very fast and slow rotators, and this becomes even more pronounced as smaller-sized populations are measured.
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VSOP model • Graphic shows variations in five orbital elements: • Precession index and obliquity control insolation at each latitude: • Ocean sediment and Antarctic ice strata record ancient sea levels and temperatures: • Vertical gray line shows present (2000 CE) Milankovitch cycles describe the collective effects of changes in the Earth's movements on its climate over thousands of years. The term is named for Serbian geophysicist and astronomer Milutin Milanković. In the 1920s, he hypothesized that variations in eccentricity, axial tilt, and precession resulted in cyclical variation in the solar radiation reaching the Earth, and that this orbital forcing strongly influenced the Earth's climatic patterns. Similar astronomical hypotheses had been advanced in the 19th century by Joseph Adhemar, James Croll and others, but verification was difficult because there was no reliably dated evidence, and because it was unclear which periods were important.
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How Mars might have looked during an ice age between 2.1 million and 400,000 years ago, when Mars' axial tilt is thought to have been larger than today. HiRISE view of Olympia Rupes in Planum Boreum, one of many exposed water ice layers found in the polar regions of Mars. Depicted width: 1.3 km (0.8 miles) HiRISE image of "dark dune spots" and fans formed by eruptions of CO2 gas geysers on Mars' south polar ice sheet. Mars has ice caps at its north pole and south pole, which mainly consist of water ice; however, there is frozen carbon dioxide (dry ice) present on their surfaces. Dry ice accumulates in the north polar region (Planum Boreum) in winter only, subliming completely in summer, while the south polar region additionally has a permanent dry ice cover up to eight meters (25 feet) thick.
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He is one of the pioneers who participated in the renaissance of the astronomical theory of paleoclimate (also known as the Milankovitch theory) in the 1970s, and to its promotion and development in the following decades. He has renewed this theory and improved the accuracy of the long term variations of the astronomical parameters used for the calculation of the incoming solar radiation (insolation) over the last and next millions of years. He became known in 1977 for his paper in Nature and later in the Journal of Atmospheric Physics (1978) delivering all the spectral components of the long term variations of eccentricity, obliquity (axial tilt) and climatic precession. His contributions have played a key role in the time scale calibration and interpretation of the paleoclimate records and in the modelling of the glacial-interglacial cycles.
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The movement of daylight between the northern and southern hemispheres happens because of the axial tilt of the Earth. The imaginary line around which the Earth spins, which goes between the North Pole and South Pole, is tilted about 23° from the oval that describes its orbit around the Sun. The Earth always points in the same direction as it moves around the Sun, so for half the year (summer in the Northern Hemisphere), the North Pole is pointed slightly toward the Sun, keeping it in daylight all the time because the Sun lights up the half of the Earth that is facing it (and the North Pole is always in that half due to the tilt). For the other half of the orbit, the South Pole is tilted slightly toward the Sun, and it is winter in the Northern Hemisphere.
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An illustration of what Mars may have looked like during an ice age about 400,000 years ago caused by a large axial tilt As on Earth, the effect of precession causes the north and south celestial poles to move in a very large circle, but on Mars the cycle is 175,000 Earth years rather than 26,000 years as on Earth. As on Earth, there is a second form of precession: the point of perihelion in Mars's orbit changes slowly, causing the anomalistic year to differ from the sidereal year. However, on Mars, this cycle is 83,600 years rather than 112,000 years as on Earth. On both Earth and Mars, these two precessions are in opposite directions, and therefore add, to make the precession cycle between the tropical and anomalistic years 21,000 years on Earth and 56,600 years on Mars.
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By definition, the positions of the Tropic of Cancer, Tropic of Capricorn, Arctic Circle and Antarctic Circle all depend on the tilt of the Earth's axis relative to the plane of its orbit around the sun (the "obliquity of the ecliptic"). If the Earth were "upright" (its axis at right angles to the orbital plane) there would be no Arctic, Antarctic, or Tropical circles: at the poles the sun would always circle along the horizon, and at the equator the sun would always rise due east, pass directly overhead, and set due west. The positions of the Tropical and Polar Circles are not fixed because the axial tilt changes slowly – a complex motion determined by the superimposition of many different cycles (some of which are described below) with short to very long periods. In the year 2000 AD the mean value of the tilt was about 23° 26′ 21″.
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Solar radiation would normally strip any free water or water ice from the lunar surface, splitting it into its constituent elements, hydrogen and oxygen, which then escape to space. However, because of the only very slight axial tilt of the Moon's spin axis to the ecliptic plane (1.5 °), some deep craters near the poles never receive any sunlight, and are permanently shadowed (see, for example, Shackleton crater, and Whipple crater). The temperature in these regions never rises above about 100 K (about −170 ° Celsius),Ice on the Moon, NASA and any water that eventually ended up in these craters could remain frozen and stable for extremely long periods of time — perhaps billions of years, depending on the stability of the orientation of the Moon's axis. While the ice deposits may be thick, they are most likely mixed with the regolith, possibly in a layered formation.
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While the original study addresses the first reason for increased volcanism (reduced confining pressure), scientists have more recently shown that these lavas have unusually high trace element concentrations, indicative of increased melting in the mantle. This work in Iceland has been corroborated by a study in California, in which scientists found a strong correlation between volcanism and periods of global deglaciation. The effects of current sea level rise could include increased crustal stress at the base of coastal volcanoes from a rise in the volcano's water table (and the associated saltwater intrusion), while the mass from extra water could activate dormant seismic faults around volcanoes. In addition, the wide-scale displacement of water from melting in places such as West Antarctica is likely to slightly alter the Earth's rotational period and may shift its axial tilt on the scale of hundreds of metres, inducing further crustal stress changes.
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Eclipses of the Sun from Jupiter are not particularly rare, since Jupiter is very large and its axial tilt (which is related to the plane of the orbits of its satellites) is relatively small—indeed, the vast majority of the orbits of all five of the objects capable of occulting the Sun will result in a solar occultation visible from somewhere on Jupiter. The related phenomenon of satellite eclipses in the shadow of Jupiter has been observed since the time of Giovanni Cassini and Ole Rømer in the mid Seventeenth Century. It was soon noticed that predicted times differed from observed times in a regular way, varying from up to ten minutes early to up to ten minutes late. Rømer used these errors to make the first accurate determination of the speed of light, correctly realizing that the variations were caused by the varying distance between Earth and Jupiter as the two planets moved in their orbits around the Sun.
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The closest approach to Uranus occurred on January 24, 1986, when Voyager 2 came within of the planet's cloudtops."Uranus Approach" NASA Jet Propulsion Laboratory, California Institute of Technology. Accessed December 11, 2018. Voyager 2 also discovered 11 previously unknown moons: Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, Belinda, Puck and Perdita. The mission also studied the planet's unique atmosphere, caused by its axial tilt of 97.8°; and examined the Uranian ring system. The length of a day on Uranus as measured by Voyager 2 is 17 hours, 14 minutes. Uranus was shown to have a magnetic field that was misaligned with its rotational axis, unlike other planets that had been visited to that point, and a helix-shaped magnetic tail stretching 10 million kilometers (6 million miles) away from the Sun. When Voyager 2 visited Uranus, much of its cloud features were hidden by a layer of haze; however, false- color and contrast-enhanced images show bands of concentric clouds around its south pole.
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Relationship between Earth's axial tilt (ε) to the tropical and polar circles Excluding cooler highland regions in China, the climate at the Tropic of Cancer is generally hot and dry except for easterly coastal areas where orographic rainfall can be very heavy, in some places reaching annually. Most regions on the Tropic of Cancer experience two distinct seasons: an extremely hot summer with temperatures often reaching and a warm winter with maxima around . Much land on or near the Tropic of Cancer is part of the Sahara Desert, while to the east the climate is torrid monsoonal with a short wet season from June to September and very little rainfall for the rest of the year. The highest mountain on or adjacent to the Tropic of Cancer is Yu Shan in Taiwan; though it had glaciers descending as low as during the Last Glacial Maximum, none survive and at present no glaciers exist within of the Tropic of Cancer; the nearest currently surviving are the Minyong and Baishui in the Himalayas to the north and on Iztaccíhuatl to the south.
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Near the equator, this means the variation in strength of solar radiation is different relative to the time of year than it is at higher latitudes: Maximum solar radiation is received during the equinoxes, when a place at the equator is under the subsolar point at high noon, and the intermediate seasons of spring and autumn occur at higher latitudes, and the minimum occurs during both solstices, when either pole is tilted towards or away from the sun, resulting in either summer or winter in both hemispheres. This also results in a corresponding movement of the equator away from the subsolar point, which is then situated over or near the relevant tropic circle. Nevertheless, temperatures are high year round due to the earth's axial tilt of 23.5° not being enough to create a low minimum midday declination to sufficiently weaken the sun's rays even during the solstices. Near the equator there is little temperature change throughout the year, though there may be dramatic differences in rainfall and humidity.
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In theory, the exact year when this will begin to occur depends on uncertainties in the future tidal slowing of the Earth rotation rate, and on the accuracy of predictions of precession and Earth axial tilt. The seriousness of the spring equinox drift is widely discounted on the grounds that Passover will remain in the spring season for many millennia, and the text of the Torah is generally not interpreted as having specified tight calendrical limits. The Hebrew calendar also drifts with respect to the autumn equinox, and at least part of the harvest festival of Sukkot is already more than a month after the equinox in years 1, 9, and 12 of each 19-year cycle; beginning in AM 5818 (2057 CE), this will also be the case in year 4. (These are the same year numbers as were mentioned for the spring season in the previous paragraph, except that they get incremented at Rosh Hashanah.) This progressively increases the probability that Sukkot will be cold and wet, making it uncomfortable or impractical to dwell in the traditional succah during Sukkot.
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