query: what is the shape of earth 's orbit around the sun

pos: Earth's orbit orbit. The orbital ellipse goes through each of the six Earth images, which are sequentially the perihelion (periapsis — nearest point to the Sun) on anywhere from January 2 to January 5, the point of March equinox on March 19, 20, or 21, the point of June solstice on June 20, 21, or 22, the aphelion (apoapsis — farthest point from the Sun) on anywhere from July 3 to July 5, the September equinox on September 22, 23, or 24, and the December solstice on December 21, 22, or 23. The diagram shows an exaggerated shape of Earth's orbit; the

pos: Equation of time one year. If the Earth orbited the Sun with a constant speed, in a circular orbit in a plane perpendicular to the Earth's axis, then the Sun would culminate every day at exactly the same time, and be a perfect time keeper (except for the very small effect of the slowing rotation of the Earth). But the orbit of the Earth is an ellipse not centered on the Sun, and its speed varies between 30.287 and 29.291 km/s, according to Kepler's laws of planetary motion, and its angular speed also varies, and thus the Sun appears to move faster (relative

pos: Earth's orbit orbit. The orbital ellipse goes through each of the six Earth images, which are sequentially the perihelion (periapsis — nearest point to the Sun) on anywhere from January 2 to January 5, the point of March equinox on March 19, 20, or 21, the point of June solstice on June 20, 21, or 22, the aphelion (apoapsis — farthest point from the Sun) on anywhere from July 3 to July 5, the September equinox on September 22, 23, or 24, and the December solstice on December 21, 22, or 23. The diagram shows an exaggerated shape of Earth's orbit; the

neg: Horseshoe orbit no repeated looping: each one traces a full horseshoe with respect to the other). The following explanation relates to an asteroid which is in such an orbit around the Sun, and is also affected by the Earth. The asteroid is in almost the same solar orbit as Earth. Both take approximately one year to orbit the Sun. It is also necessary to grasp two rules of orbit dynamics: The horseshoe orbit arises because the gravitational attraction of the Earth changes the shape of the elliptical orbit of the asteroid. The shape changes are very small but result in significant changes

neg: 2002 AA29 a point moving with the Earth around the Sun (the reference frame of the Earth–Sun system), it describes over the course of 95 years an arc of almost 360°, which during the next 95 years it retraces in reverse. The shape of this arc is reminiscent of a horseshoe, from which comes the name “horseshoe orbit”. As it moves along the Earth's orbit, it winds in a spiral about it, in which each loop of the spiral takes one year. This spiral motion (in the Earth–Sun reference frame) arises from the slightly lower eccentricity and the tilt of the orbit:

neg: Apache Point Observatory Lunar Laser-ranging Operation this effect.) If the Moon just revolved around the Earth, there would be no way to tell what fraction of the Moon's or the Earth's gravity was caused by each form of mass, since only the total can be measured. However, the orbit of the Moon is also strongly affected by the gravity of the Sun—in essence, Earth and Moon are in free fall around the Sun. If the energy portion of mass behaves differently from the conventional portion, then the Earth and the Moon will fall differently toward the Sun, and the orbit of the Moon around the Earth

neg: Inclined orbit Inclined orbit A satellite is said to occupy an inclined orbit around Earth if the orbit exhibits an angle other than 0° to the equatorial plane. This angle is called the orbit's inclination. A planet is said to have an inclined orbit around the Sun if it has an angle other than 0° to the ecliptic plane. A geosynchronous orbit is an inclined orbit with an altitude of that completes one revolution every sidereal day tracing out a small figure-eight shape in the sky. A geostationary orbit is a special case of geosynchronous orbit with no inclination, and therefore no

neg: Orbital station-keeping Global Geoscience WIND satellite—each have annual station-keeping propellant requirements of approximately 1 m/s or less. Earth-Sun —approximately 1.5 million kilometers from Earth in the anti-sun direction—is another important Lagrangian point, and the ESA Herschel space observatory operated there in a Lissajous orbit during 2009–2013, at which time it ran out of coolant for the space telescope. Small station-keeping orbital maneuvers were executed approximately monthly to maintain the spacecraft in the station-keeping orbit. The James Webb Space Telescope needs to use propellant to maintain its halo orbit around the Earth-Sun L2, which provides an upper limit to its designed lifetime: it

neg: Horseshoe orbit viewed relative to the Earth. Its orbit around the Sun still takes only slightly more than one Earth year. Given enough time, the Earth and the satellite will be on opposite sides of the Sun. Eventually the satellite comes around to point D where Earth's gravity is now reducing the satellite's orbital velocity. This causes it to fall into a lower orbit, which actually increases the angular speed of the satellite around the Sun. This continues until point E where the satellite's orbit is now lower and faster than Earth's orbit, and it begins moving out ahead of Earth. Over

neg: Earth's orbit Earth's orbit All celestial bodies in the Solar System, including planets such as our own, orbit around the Solar System's centre of mass. The sun makes up 99.76% of this mass which is why the centre of mass is extremely close to the sun. Earth's orbit is the trajectory along which Earth travels around the Sun. The average distance between the Earth and the Sun is 149.60 million km (92.96 million mi), and one complete orbit takes days (1 sidereal year), during which time Earth has traveled 940 million km (584 million mi). Earth's orbit has an eccentricity of 0.0167.

neg: Earth move to an orbit from the Sun when the star reaches its maximum radius. Most, if not all, remaining life will be destroyed by the Sun's increased luminosity (peaking at about 5,000 times its present level). A 2008 simulation indicates that Earth's orbit will eventually decay due to tidal effects and drag, causing it to enter the Sun's atmosphere and be vaporized. The shape of Earth is approximately oblate spheroidal. Due to rotation, the Earth is flattened at the poles and bulging around the equator. The diameter of the Earth at the equator is larger than the pole-to-pole diameter. Thus

neg: 3753 Cruithne 3753 Cruithne 3753 Cruithne ( , ) is a Q-type, Aten asteroid in orbit around the Sun in 1:1 orbital resonance with Earth, making it a co-orbital object. It is an asteroid that, relative to Earth, orbits the Sun in a bean-shaped orbit that effectively describes a horseshoe, and that can change into a quasi-satellite orbit. Cruithne does not orbit Earth and at times it is on the other side of the Sun, placing Cruithne well outside of Earth's Hill sphere. Its orbit takes it inside the orbit of Mercury and outside the orbit of Mars. Cruithne orbits the Sun

neg: Orbit of the Moon Moon and Earth rotate on their own axes. In representations of the Solar System, it is common to draw the trajectory of Earth from the point of view of the Sun, and the trajectory of the Moon from the point of view of Earth. This could give the impression that the Moon orbits Earth in such a way that sometimes it goes backwards when viewed from the Sun's perspective. Because the orbital velocity of the Moon around Earth (1 km/s) is small compared to the orbital velocity of Earth about the Sun (30 km/s), this never happens. There are no

neg: Interplanetary spaceflight it must change its speed by another 2.3 km/s in order to match Mars' orbital speed around the Sun and enter an orbit around it. For comparison, launching a spacecraft into low Earth orbit requires a change in speed of about 9.5 km/s. For many years economical interplanetary travel meant using the Hohmann transfer orbit. Hohmann demonstrated that the lowest energy route between any two orbits is an elliptical "orbit" which forms a tangent to the starting and destination orbits. Once the spacecraft arrives, a second application of thrust will re-circularize the orbit at the new location. In the case

neg: Lunar phase Lunar phase The lunar phase or phase of the Moon is the shape of the directly sunlit portion of the Moon as viewed from Earth. The lunar phases gradually and cyclically change over the period of a synodic month (about 29.53 days), as the orbital positions of the Moon around Earth and of Earth around the Sun shift. The Moon's rotation is tidally locked by Earth's gravity; therefore, most of the same lunar side always faces Earth. This near side is variously sunlit, depending on the position of the Moon in its orbit. Thus, the sunlit portion of this face

neg: Apache Point Observatory Lunar Laser-ranging Operation Furthermore, both are in orbit around the Sun, meaning they are both falling towards the Sun at all times, even as they revolve around each other. If the Earth and the Moon were affected differently by the gravity of the Sun, this would directly affect the orbit of the Moon around the Earth. But as closely as scientists can measure, the orbit of the Moon is just as predicted from assuming that gravity acts the same on each — to within 1 part in , the Earth and the Moon fall towards the Sun in exactly the same way, despite

neg: Eclipse happen during an "eclipse season", the two times of each year when the plane of the Earth's orbit around the Sun crosses with the plane of the Moon's orbit around the Earth. The type of solar eclipse that happens during each season (whether total, annular, hybrid, or partial) depends on apparent sizes of the Sun and Moon. If the orbit of the Earth around the Sun, and the Moon's orbit around the Earth were both in the same plane with each other, then eclipses would happen each and every month. There would be a lunar eclipse at every full moon,

neg: 2003 YN107 2003 YN107 was discovered by the Lincoln Near Earth Asteroid Research (LINEAR) system in orbit around the Sun on 20 December 2003. Its diameter is approximately 10 to 30 metres. The object is on NASA's Earth Close Approach list, and is estimated to miss Earth by 0.01 AU. It revolves around the Sun on an Earth-like, almost circular, orbit. Its orbital period of 363.846 days also is very close to the sidereal year. From approximately 1997 to 2006, the asteroid remained within ) of Earth and it appeared to slowly orbit Earth. However, is no second moon, as it is

neg: Orbit of the Moon associated with the lunar orbit. The sidereal month is the time it takes to make one complete orbit around Earth with respect to the fixed stars. It is about 27.32 days. The synodic month is the time it takes the Moon to reach the same visual phase. This varies notably throughout the year, but averages around 29.53 days. The synodic period is longer than the sidereal period because the Earth–Moon system moves in its orbit around the Sun during each sidereal month, hence a longer period is required to achieve a similar alignment of Earth, the Sun, and the Moon.

neg: Spherical Earth energy can also move water, rock, and soil to make the Earth slightly out of round. Earth undulates as the shape of its lowest potential energy changes daily due to the gravity of the Sun and Moon as they move around with respect to the Earth. This is what causes tides in the oceans' water, which can flow freely along the changing potential. The IAU definitions of planet and dwarf planet require that a Sun-orbiting body has undergone the rounding process to reach a roughly spherical shape, an achievement known as hydrostatic equilibrium. The same spheroidal shape can be seen

neg: Hohmann transfer orbit planet. The delta-"v" needed is only 3.6 km/s, only about 0.4 km/s more than needed to escape Earth, even though this results in the spacecraft going 2.9 km/s faster than the Earth as it heads off for Mars (see table below). At the other end, the spacecraft will need a certain velocity to orbit Mars, which will actually be less than the velocity needed to continue orbiting the Sun in the transfer orbit, let alone attempting to orbit the Sun in a Mars-like orbit. Therefore, the spacecraft will have to decelerate in order for the gravity of Mars to capture

neg: TRAPPIST-1 and "g") are similar in size to Earth, and two ("d" and "h") are intermediate in size between Mars and Earth. Three of the planets ("e", "f" and "g") orbit within the habitable zone. The system is very flat and compact. All seven of TRAPPIST-1's planets orbit much closer than Mercury orbits the Sun. Except for TRAPPIST-1b, they orbit farther than the Galilean satellites do around Jupiter, but closer than most of the other moons of Jupiter. The distance between the orbits of TRAPPIST-1b and TRAPPIST-1c is only 1.6 times the distance between the Earth and the Moon. The planets

neg: Kolob Bruce R. McConkie came to a different conclusion, arguing that during the first "day" of creation (not necessarily a 1000-year "day" in Kolob time; with a "day" referring to a phase of creation), Earth was formed and placed in orbit around the Sun. The idea that the Earth was formed elsewhere and then migrated to orbit around the Sun differs from the scientific explanation of the Earth's formation. According to scientific consensus, the Earth formed in orbit around the Sun about 4.5 billion years ago by accretion from a protoplanetary disk, and has remained near its original orbit until the

neg: Near-Earth Object Camera by the Spitzer Space Telescope. The spacecraft would operate in a halo orbit around the Sun–Earth , and employ a Sun shield. This orbit would allow fast data downlink speeds to Earth, allowing full-frame images to be downloaded from the telescope. Near-Earth Object Camera The Near-Earth Object Camera (NEOCam) is a proposed space-based infrared telescope designed to survey the Solar System for potentially hazardous asteroids. NEOCam would survey from the Sun–Earth Lagrange point, allowing it to look close to the Sun and see objects inside Earth's orbit. NEOCam would be a successor to the WISE mission; the principal investigator is

neg: Spherical Earth 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. This means that at the

neg: Characteristic energy infinity – entered an elliptical orbit around the Sun. But the maximal velocity on the new orbit could be approximated to 33.5 km/s by assuming that it reached practical "infinity" at 3.5 km/s and that such Earth-bound "infinity" also moves with Earth's orbital velocity of about 30 km/s. The InSight mission to Mars launched with a maximum C of 14.3 km/s. The Parker Solar Probe (via Venus) plans a maximum C of 154 km/s. C3 (km/s) from earth to get to various planets : Mars 12, Jupiter 80, Saturn or Uranus 147. To Pluto (with its orbital inclination) needs about

neg: Eclipse cycle Sun, Moon, and Earth has changed. As seen from the Earth, the time it takes for the Moon to return to a node, the draconic month, is less than the time it takes for the Moon to return to the same ecliptic longitude as the Sun: the synodic month. The main reason is that during the time that the Moon has completed an orbit around the Earth, the Earth (and Moon) have completed about of their orbit around the Sun: the Moon has to make up for this in order to come again into conjunction or opposition with the Sun.

neg: Polar orbit time. To keep the same local time on a given pass, the time period of the orbit must be kept as short as possible, this is achieved by keeping the orbit lower around Earth. However, very low orbits of a few hundred kilometers rapidly decay due to drag from the atmosphere. Commonly used altitudes are between 700 and 800 km, producing an orbital period of about 100 minutes. The half-orbit on the Sun side then takes only 50 minutes, during which local time of day does not vary greatly. To retain the Sun-synchronous orbit as Earth revolves around the Sun

neg: Lunar theory P1 and P2, of the Moon in its orbit around the Earth, the respective vectors LS1 and LS2 for the perturbing acceleration due to the Sun. The Moon's position at P1 is fairly close to what it was at P in Newton's diagram; corresponding perturbation LS1 is like Newton's LS in size and direction. At another position P2, the Moon is farther away from the Sun than the Earth is, the Sun's attraction LQ2 on the Moon is weaker than the Sun's attraction SQ=SQ2 on the Earth, and then the resulting perturbation LS2 points obliquely away from the Sun. Constructions

neg: Sidereal time the moment when the Sun is exactly due south or north (depending on the observer's latitude and the season). A mean solar day (what we normally measure as a "day") is the average time between local solar noons ("average" since this varies slightly over the year). Earth makes one rotation around its axis in a sidereal day; during that time it moves a short distance (about 1°) along its orbit around the Sun. So after a sidereal day has passed, Earth still needs to rotate slightly more before the Sun reaches local noon according to solar time. A mean solar

neg: Sun-synchronous orbit rate. The plane of the orbit is not fixed in space relative to the distant stars, but rotates slowly about the Earth's axis. Typical Sun-synchronous orbits around Earth are about 600–800 km in altitude, with periods in the 96–100-minute range, and inclinations of around 98°. This is slightly retrograde compared to the direction of Earth's rotation: 0° represents an equatorial orbit, and 90° represents a polar orbit. Sun-synchronous orbits can happen around other oblate planets, such as Mars. A satellite around the almost spherical Venus, for example, will need an outside push to maintain a Sun-synchronous orbit. The angular precession

neg: Earth's orbit As seen from Earth, the planet's orbital prograde motion makes the Sun appear to move with respect to other stars at a rate of about 1° (or a Sun or Moon diameter every 12 hours) eastward per solar day. Earth's orbital speed averages about 30 km/s (108,000 km/h; 67,000 mph), which is fast enough to cover the planet's diameter in 7 minutes and the distance to the Moon in 4 hours. From a vantage point above the north pole of either the Sun or Earth, Earth would appear to revolve in a counterclockwise direction around the Sun. From the same

neg: 2003 YN107 not bound to Earth. It is the first discovered member of a postulated group of coorbital objects, or quasi-satellites, which show these path characteristics. Other members of this group include 10563 Izhdubar, 54509 YORP, , , and . Before 1996, the asteroid had been on a so-called horseshoe orbit around the Sun, along the Earth's orbit. After 2006, it had regained such an orbit. This makes it very similar to , which will become a quasi-satellite of Earth in approximately 600 years. 2003 YN107 was discovered by the Lincoln Near Earth Asteroid Research (LINEAR) system in orbit around the Sun

neg: Lunar month respect to the Sun as seen from the Earth. While the Moon is orbiting the Earth, the Earth is progressing in its orbit around the Sun. After completing a sidereal month, the Moon must move a little further to reach the new position having the same angular distance from the Sun, appearing to move with respect to the stars since the previous month. Therefore, the synodic month takes 2.2 days longer than the sidereal month. Thus, about 13.37 sidereal months, but about 12.37 synodic months, occur in a Gregorian year. Since Earth's orbit around the Sun is elliptical and not

neg: Delta-v budget propulsion and the Oberth effect. According to Marsden and Ross, "The energy levels of the Sun–Earth and points differ from those of the Earth–Moon system by only 50 m/s (as measured by maneuver velocity)." We may apply the formula (where μ = GM is the standard gravitational parameter of the sun, see Hohmann transfer orbit) to calculate the Δ"v" in km/s needed to arrive at various destinations from Earth (assuming circular orbits for the planets, and using perihelion distance for Pluto). In this table, the column labeled "Δ"v" to enter Hohmann orbit from Earth's orbit" gives the change from Earth's

neg: STEREO and Spacecraft B will take 387 days. The A spacecraft/Sun/Earth angle will increase at 21.650 degree/year. The B spacecraft/Sun/Earth angle will change −21.999 degrees per year. Given that the length of Earth's orbit is around 940 million kilometres, both craft have an average speed, in a rotating geocentric frame of reference in which the sun is always in the same direction, of about 1.8 km/s, but the speed varies considerably depending on how close they are to their respective aphelion or perihelion (as well as on the position of Earth). Their current locations are shown here. Over time, the STEREO

neg: Lagrangian point station keeping keeps a spacecraft in a desired Lissajous orbit for a long time. Also, for Sun–Earth- missions, it is preferable for the spacecraft to be in a large-amplitude () Lissajous orbit around than to stay at , because the line between Sun and Earth has increased solar interference on Earth–spacecraft communications. Similarly, a large-amplitude Lissajous orbit around keeps a probe out of Earth's shadow and therefore ensures continuous illumination of its solar panels. The and points are stable provided that the mass of the primary body (e.g. the Earth) is at least 25 times the mass of the secondary

neg: Claimed moons of Earth Sun (not Earth) on the same orbital path as Earth, and appear to lead or follow Earth along the same orbital path. Other small natural objects in orbit around the Sun may enter orbit around Earth for a short amount of time, becoming temporary natural satellites. , the only confirmed example has been in Earth orbit during 2006 and 2007, though further instances are already predicted. The first major claim of another moon of Earth was made by French astronomer Frédéric Petit, director of the Toulouse Observatory, who in 1846 announced that he had discovered a second moon in an

neg: 2010 TK7 the asteroid orbited the Sun with a period of 365.389 days, close to Earth's 365.256 days. As long as it remains in 1:1 resonance with Earth, its average period over long time intervals will exactly equal that of Earth. On its eccentric (e = 0.191) orbit, 's distance from the Sun varies annually from 0.81 AU to 1.19 AU. It orbits in a plane inclined about 21 degrees to the plane of the ecliptic. Trojans do not orbit right at Lagrangian points but oscillate in tadpole-shaped loops around them (as viewed in a corotating reference frame in which the planet

neg: Claimed moons of Earth the Earth–Moon system, whereas the orbit of a quasi-satellite would negligibly change if Earth and the Moon were suddenly removed because a quasi-satellite is orbiting the Sun on an Earth-like orbit in the vicinity of Earth. Earth possesses one known trojan, a small Solar System body caught in the planet's gravitationally stable Lagrangian point. This object, is roughly 300 metres across. Like quasi-satellites, it orbits the Sun in a 1:1 resonance with Earth, rather than Earth itself. On 14 September 2006, an object estimated at 5 meters in diameter was discovered in near-polar orbit around Earth. Originally thought to be

neg: Longitude by chronometer moment in time at which the sun passes through the sight tube on its descent from Zenith between a half-hour and hour later, the two times can be averaged to obtain a longitude sufficiently accurate for navigation (within 2nmi). Unfortunately, the Earth does not make a perfect circular orbit around the Sun. Due to the elliptical nature of the Earth’s orbit around the Sun, the speed of the Sun’s apparent orbit around the Earth varies throughout the year and that causes it to appear to speed up and slow down very slightly. Consequently, noon at the Prime Meridian is rarely

neg: Horseshoe orbit relative to the Earth. The horseshoe becomes apparent only when mapping the movement of the asteroid relative to both the Sun and the Earth. The asteroid always orbits the Sun in the same direction. However, it goes through a cycle of catching up with the Earth and falling behind, so that its movement relative to both the Sun and the Earth traces a shape like the outline of a horseshoe. Starting at point A, on the inner ring between and Earth, the satellite is orbiting faster than the Earth and is on its way toward passing between the Earth and

neg: Eclipse season seen from the sublunar point) depends on the apparent sizes of the Sun and Moon, which is a function of the elliptical distance of Earth from the Sun and of the Moon from Earth, respectively, as seen from Earth's surface. If the Earth had a perfectly circular orbit centered around the Sun, if the Moon's orbit was also perfectly circular and centered around the Earth, and if both orbits were coplanar (on the same plane) with each other, then two eclipses would happen every lunar month (29.53 days). A lunar eclipse would occur at every full moon, a solar eclipse

neg: Orbit of the Moon moves in its orbit around the common centre of gravity. The Sun's gravitational effect on the Moon is more than twice that of Earth's on the Moon; consequently, the Moon's trajectory is always convex (as seen when looking Sunward at the entire Sun–Earth–Moon system from a great distance outside Earth–Moon solar orbit), and is nowhere concave (from the same perspective) or looped. That is, the region enclosed by the Moon's orbit of the Sun is a convex set. Orbit of the Moon The Moon orbits Earth in the prograde direction and completes one revolution relative to the stars in about

neg: Hohmann transfer orbit on the earth) when 300 km above the Earth's surface. This is obtained by adding to the specific kinetic energy the square of the speed (7.73 km/s) of this low Earth orbit (that is, the depth of Earth's gravity well at this LEO). The column "Δv from LEO" is simply the previous speed minus 7.73 km/s. Note that in most cases, Δ"v" from LEO is less than the Δ"v" to enter Hohmann orbit from Earth's orbit. To get to the Sun, it is actually not necessary to use a Δ"v" of 24 km/s. One can use 8.8 km/s to go

neg: Interglacial interglacials and glacials coincide with cyclic changes in the Earth's orbit. Three orbital variations contribute to interglacials. The first is a change in the Earth's orbit around the sun, or eccentricity. The second is a shift in the tilt of the Earth's axis, the obliquity. The third is precession, or wobbling motion of Earth's axis. Warm summers in the Southern hemisphere occur when that hemisphere is tilted toward the sun and the Earth is nearest the sun in its elliptical orbit. Cool summers occur when the Earth is farthest from the sun during that season. These effects are more pronounced

neg: Adhik Maas AD) it would occur once, in 1963 AD. The Moon takes about 27.3 days to make one complete orbit around the earth. The earth orbits around the sun once every 365.2422 days (= earth’s orbital speed of 29.79 km per second). The earth and the moon in 27.3 days have moved as a system about 1/12 of the way around the sun. This means that from one full moon to the next full moon, the moon must travel 2.2 extra days before it appears again as a full moon, due to the curve of the earth’s orbit around the sun.

neg: Solar and Heliospheric Observatory on-board emergency in 1998 that nearly resulted in the loss of the spacecraft. The three main scientific objectives of "SOHO" are: The "SOHO" spacecraft is in a halo orbit around the Sun–Earth L1 point, the point between the Earth and the Sun where the balance of the (larger) Sun's gravity and the (smaller) Earth's gravity is equal to the centripetal force needed for an object to have the same orbital period in its orbit around the Sun as the Earth, with the result that the object will stay in that relative position. Although sometimes described as being at L1, the

neg: J002E3 an approximately 40-year cycle between heliocentric and geocentric orbit. When it was first discovered, it was quickly found that the object was in an orbit around Earth. Astronomers were surprised at this, as the Moon is the only large object in orbit around the Earth, and anything else would have been ejected long ago due to perturbations with the Earth, the Moon and the Sun. Therefore, it probably entered into Earth orbit very recently, yet there was no recently launched spacecraft that matched the orbit of J002E3. One explanation could have been that it was a 30-meter-wide piece of rock,

neg: Geostationary ring Geostationary ring The geostationary ring is a volume segment around the geostationary orbit defined by variations in altitude and declination that can occur for uncontrolled objects left in the geostationary orbit. The geostationary orbit is subject to orbit perturbations caused by anomalies in the gravitational field of the Earth, by the gravitational effects of Sun and Moon, and by solar radiation pressure. A precessional motion of the orbit plane is caused by the oblatedness of the Earth (formula_1), and the gravitational effects of Sun and Moon. This motion has a period of about 53 years. The two parameters describing the

neg: Geostationary ring km below GEO to 75 km above GEO and from -15 degrees to 15 degrees declination. Geostationary ring The geostationary ring is a volume segment around the geostationary orbit defined by variations in altitude and declination that can occur for uncontrolled objects left in the geostationary orbit. The geostationary orbit is subject to orbit perturbations caused by anomalies in the gravitational field of the Earth, by the gravitational effects of Sun and Moon, and by solar radiation pressure. A precessional motion of the orbit plane is caused by the oblatedness of the Earth (formula_1), and the gravitational effects of Sun

neg: Venus disc and "quarter phase" at its maximum elongations from the Sun, and appears its brightest in the night sky. The planet presents a much larger thin "crescent" in telescopic views as it passes along the near side between Earth and the Sun. Venus displays its largest size and "new phase" when it is between Earth and the Sun (at inferior conjunction). Its atmosphere is visible through telescopes by the halo of sunlight refracted around it. The Venusian orbit is slightly inclined relative to Earth's orbit; thus, when the planet passes between Earth and the Sun, it usually does not cross

neg: Solar eclipse Apollo 12 observed the in 1969 and when the Cassini probe observed in 2006. The Moon's orbit around the Earth is slightly elliptical, as is the Earth's orbit around the Sun. The apparent sizes of the Sun and Moon therefore vary. The magnitude of an eclipse is the ratio of the apparent size of the Moon to the apparent size of the Sun during an eclipse. An eclipse that occurs when the Moon is near its closest distance to Earth ("i.e.," near its perigee) can be a total eclipse because the Moon will appear to be large enough to completely

neg: Sun-synchronous orbit causes. Earth observation satellites, in particular, prefer orbits with constant altitude when passing over the same spot. Careful selection of eccentricity and location of perigee reveals specific combinations where the perturbations largely cancel and hence the orbit is relatively stable – a frozen orbit. The ERS-1, ERS-2 and Envisat of European Space Agency, as well as the MetOp spacecraft of EUMETSAT, are all operated in such Sun-synchronous frozen orbits. Sun-synchronous orbit A Sun-synchronous orbit (SSO, also called a heliosynchronous orbit) is a nearly polar orbit around a planet, in which the satellite passes over any given point of the planet's

neg: Low Earth orbit orbit is about 7.8 km/s, but reduces with increased orbital altitude. Calculated for circular orbit of 200 km it is 7.79 km/s and for 1500 km it is 7.12 km/s. The delta-v needed to achieve low Earth orbit starts around 9.4 km/s. Atmospheric and gravity drag associated with launch typically adds 1.3–1.8 km/s to the launch vehicle delta-v required to reach normal LEO orbital velocity of around . The pull of gravity in LEO is only slightly less than on the earth's surface. This is because the distance to LEO from the earth's surface is far less than the earth's

neg: King tide around the Sun in an elliptic orbit that takes a little over 365 days to complete. Its gravitational force is greatest when the Earth is at perihelion — closest to the Sun in early January — and least when the Earth is at aphelion — farthest from the Sun in early July. The king tides occur when the Earth, Moon and Sun are aligned at perigee and perihelion, resulting in the largest tidal range seen over the course of a year. So, tides are enhanced when the Earth is closest to the Sun around January 2 of each year. They

neg: Orbit of the Moon Orbit of the Moon The Moon orbits Earth in the prograde direction and completes one revolution relative to the stars in about 27.32 days (a sidereal month) and one revolution relative to the Sun in about 29.53 days (a synodic month). Earth and the Moon orbit about their barycenter (common center of mass), which lies about from Earth's center (about of the radius of Earth). On average, the distance to the Moon is about from Earth's center, which corresponds to about 60 Earth radii. With a mean orbital velocity of 1.022 km/s (0.635 miles/s), the Moon covers a distance approximately

neg: Kepler orbit the two body case can be completely solved mathematically and the resulting orbit which follows Kepler's laws of planetary motion is called a "Kepler orbit". The orbits of all planets are to high accuracy Kepler orbits around the Sun. The small deviations are due to the much weaker gravitational attractions between the planets, and in the case of Mercury, due to general relativity. The orbits of the artificial satellites around the Earth are, with a fair approximation, Kepler orbits with small perturbations due to the gravitational attraction of the sun, the moon and the oblateness of the Earth. In high

neg: Tidal acceleration planet with a satellite. The plane of the Moon's orbit around Earth lies close to the plane of Earth's orbit around the Sun (the ecliptic), rather than in the plane perpendicular to the axis of rotation of Earth (the equator) as is usually the case with planetary satellites. The mass of the Moon is sufficiently large, and it is sufficiently close, to raise tides in the matter of Earth. In particular, the water of the oceans bulges out towards and away from the Moon. The average tidal bulge is synchronized with the Moon's orbit, and Earth rotates under this tidal

neg: Tropical year Tropical year A tropical year (also known as a solar year) is the time that the Sun takes to return to the same position in the cycle of seasons, as seen from Earth; for example, the time from vernal equinox to vernal equinox, or from summer solstice to summer solstice. Because of the precession of the equinoxes, the seasonal cycle does not remain exactly synchronized with the position of the Earth in its orbit around the Sun. As a consequence, the tropical year is about 20 minutes shorter than the time it takes Earth to complete one full orbit around

neg: Lunar phase the times of lunar phases. It might be expected that once every month, when the Moon passes between Earth and the Sun during a new moon, its shadow would fall on Earth causing a solar eclipse, but this does not happen every month. Nor is it true that during every full moon, the Earth's shadow falls on the Moon, causing a lunar eclipse. Solar and lunar eclipses are not observed "every" month because the plane of the Moon's orbit around the Earth is tilted by about 5° with respect to the plane of Earth's orbit around the Sun (the plane

neg: Sun-synchronous orbit per orbit for an orbit around an oblate planet is (equation 24 of the article Orbital perturbation analysis (spacecraft)) given by where An orbit will be Sun-synchronous when the precession rate equals the mean motion of the Earth about the Sun, which is 360° per sidereal year (), so we must set , where is the orbital period. As the orbital period of a spacecraft is (where is the semi-major axis of the orbit), and as for a circular or almost circular orbit, it follows that or when is 360° per year, As an example, for = (the spacecraft about

neg: Late Cenozoic Ice Age 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. When the tilt is greater (high obliquity), the seasons are more extreme. During times when the tilt is less (low obliquity), the seasons are less extreme. Less tilt also means that the polar regions receive less light from the sun. This causes a colder global climate as ice sheets start to build up. The shape of Earth's orbit around the sun affects

neg: Orbital effects on climate how elliptical something is. In the case of climate, eccentricity is applied to the shape of Earth's orbit. In a similar fashion to Earth's obliquity, the more uniform Earth's orbit is (more like a perfect circle), the less difference there is in climate change throughout the year. Unlike obliquity, eccentricity affects the entire planet approximately the same, instead of primarily changing polar climate. The base idea with eccentricity is this: “How far away is the earth as a whole from the sun?” If there is no eccentricity to Earth's orbit, then Earth will remain at the same distance from the

neg: Moon of millions of years ago, the Moon would always completely cover the Sun on solar eclipses, and no annular eclipses were possible. Likewise, hundreds of millions of years in the future, the Moon will no longer cover the Sun completely, and total solar eclipses will not occur. Because the Moon's orbit around Earth is inclined by about 5.145° (5° 9') to the orbit of Earth around the Sun, eclipses do not occur at every full and new moon. For an eclipse to occur, the Moon must be near the intersection of the two orbital planes. The periodicity and recurrence of

neg: Frozen orbit for the benefit of the mission. For these missions, a near-circular orbit with an altitude of 600–900 km is used. An appropriate inclination (97.8-99.0 degrees) is selected so that the precession of the orbital plane is equal to the rate of movement of the Earth around the sun, about 1 degree per day. As a result, the spacecraft will pass over points on the Earth that have the same time of day during every orbit. For instance, if the orbit is "square to the sun", the vehicle will always pass over points at which it is 6 a.m. on the

neg: Orbital plane (astronomy) and the phase of the orbit are more easily changed by propulsion systems. Orbital planes of satellites are perturbed by the non-spherical nature of the Earth's gravity. This causes the orbital plane of the satellite's orbit to slowly rotate around the Earth, depending on the angle the plane makes with the Earth's equator. For planes that are at a critical angle this can mean that the plane will track the Sun around the Earth, forming a Sun-synchronous orbit. A launch vehicle's launch window is usually determined by the times when the target orbital plane intersects the launch site. Orbital plane

neg: Elon Musk's Tesla Roadster publishes solutions for the trajectory as target body "-143205". The Roadster is in a heliocentric orbit that crosses the orbit of Mars and reaches a distance of from the Sun. With an inclination of roughly 1 degree to the ecliptic plane, compared to Mars' 1.85° inclination, this trajectory by design cannot intercept Mars, so the car will neither fly by Mars nor enter an orbit around Mars. This was the second object launched by SpaceX to leave Earth orbit, after the DSCOVR mission to the Earth–Sun Lagrangian point. Nine months after launch, the Tesla had travelled beyond the orbit of

neg: Saturn the Sun is over 1.4 billion kilometers (9 AU). With an average orbital speed of 9.68 km/s, it takes Saturn 10,759 Earth days (or about years) to finish one revolution around the Sun. As a consequence, it forms a near 5:2 mean-motion resonance with Jupiter. The elliptical orbit of Saturn is inclined 2.48° relative to the orbital plane of the Earth. The perihelion and aphelion distances are, respectively, 9.195 and 9.957 AU, on average. The visible features on Saturn rotate at different rates depending on latitude and multiple rotation periods have been assigned to various regions (as in Jupiter's case).

neg: Ocean power in New Zealand Zealand's tides are semi-diurnal. The primary cause, the lunar tide, is labelled the M2. The M stands for the moon and the 2 stands for twice a day. A fourth influence occurs because the orbit of the moon around the earth and the orbit of the earth around the sun are elliptical rather than circular. The effect of this is that the time between high tides changes a little from day to day. The moon takes about 24.8 hours to orbit around the earth, so it takes half this time, 12.4 hours, for the M2 tides to occur. The tides

neg: Center of mass orbit each other. When a moon orbits a planet, or a planet orbits a star, both bodies are actually orbiting around a point that lies away from the center of the primary (larger) body. For example, the Moon does not orbit the exact center of the Earth, but a point on a line between the center of the Earth and the Moon, approximately 1,710 km (1,062 miles) below the surface of the Earth, where their respective masses balance. This is the point about which the Earth and Moon orbit as they travel around the Sun. If the masses are more

neg: 2010 GZ60 approach to the Sun) is estimated to have occurred around September 2010. Aphelion (furthest distance from the Sun) is estimated to have occurred around February 2016. , the asteroid is estimated to be from Earth. Perihelion (closest approach to the Sun) may not occur again until August 2021. Orbits computed with only a handful of observations can be unreliable. Short observation arcs can result in computer generated orbits rejecting some data unnecessarily. The 2018 JPL orbit determination shows a semi-major axis of 4.9 AU (albeit with a large 20 AU uncertainty) which would be near Jupiter's orbit. Such an orbit

neg: Greenhouse and icehouse Earth million years ago. 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 spin. The tilt of the axis tends to fluctuate between 21.5° to 24.5° and back every 41,000 years on the

neg: Orbital effects on climate 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). 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. These external forces usually contribute to climate change on a time scale, as meteorites strike the earth, on

neg: (469219) 2016 HO3 the best and most stable example to date of a near-Earth companion, or quasi-satellite. "Since loops around our planet, but never ventures very far away as we both go around the Sun, we refer to it as a quasi-satellite of Earth", said Paul Chodas, manager of NASA's Center for Near-Earth Object (NEO) Studies at the Jet Propulsion Laboratory in Pasadena, California. In its yearly trek around the Sun, asteroid spends about half of the time closer to the Sun than Earth is (that is, the asteroid is inside the Earth's orbit) and passes ahead of our planet, and about half

neg: Earth hours. Due to this motion, on average it takes 24 hours—a solar day—for Earth to complete a full rotation about its axis so that the Sun returns to the meridian. The orbital speed of Earth averages about , which is fast enough to travel a distance equal to Earth's diameter, about , in seven minutes, and the distance to the Moon, , in about 3.5 hours. The Moon and Earth orbit a common barycenter every 27.32 days relative to the background stars. When combined with the Earth–Moon system's common orbit around the Sun, the period of the synodic month, from

neg: 2001 GO2 2001 GO2 With an orbital period of 368.95 days, is in a near 1:1 orbital resonance with Earth, and also has about the same orbit around the Sun as Earth. Unlike most near-Earth asteroids that simply fly by when they approach Earth, the Earth catches up with this asteroid from behind so that the asteroid then pauses in the vicinity of Earth. While in the vicinity of Earth, the asteroid moves in a helical (corkscrew) pattern that resembles an orbit around the Earth, like the Earth has a new moon. But it is not really a moon, because the asteroid

neg: 2002 AA29 this time it is lifted onto a slower orbit, further from the Sun. On this orbit it can no longer keep pace with the Earth, and it falls behind until in 95 years it is once again approaching the Earth from in front. The Earth and chase each other in turn around the Sun, but do not get close enough to break the pattern. On 8 January 2003, the asteroid approached the Earth from in front to a distance of , its closest approach for nearly a century. Since that date, it has been hurrying ahead (with a semi-major axis

neg: Delta-v budget table only give the Δv needed to get to the orbital distance of the planet. The speed relative to the planet will still be considerable, and in order to go into orbit around the planet either aerocapture is needed using the planet's atmosphere, or more Δv is needed. The New Horizons space probe to Pluto achieved a near-Earth speed of over 16 km/s which was enough to escape from the sun. (It also got a boost from a fly-by of Jupiter.) To get to the sun, it is actually not necessary to use a Δ"v" of 24 km/s. One can

neg: Ecliptic the movement of Earth around the Earth–Moon center of mass, the apparent path of the Sun wobbles slightly, with a period of about one month. Due to further perturbations by the other planets of the Solar System, the Earth–Moon barycenter wobbles slightly around a mean position in a complex fashion. The ecliptic is actually the apparent path of the Sun throughout the course of a year. Because Earth takes one year to orbit the Sun, the apparent position of the Sun takes one year to make a complete circuit of the ecliptic. With slightly more than 365 days in one

neg: Frozen orbit propellant. For most spacecraft, changes to orbits are caused by the oblateness of the Earth, gravitational attraction from the sun and moon, solar radiation pressure, and air drag. These are called "perturbing forces". They must be counteracted by maneuvers to keep the spacecraft in the desired orbit. For a geostationary spacecraft, correction maneuvers on the order of 40–50 m/s per year are required to counteract the gravitational forces from the sun and moon which move the orbital plane away from the equatorial plane of the Earth. For sun-synchronous spacecraft, intentional shifting of the orbit plane (called "precession") can be used

neg: Motion (physics) and their moons move with the sun. Thus, the solar system is moving. The Earth is rotating or spinning around its axis. This is evidenced by day and night, at the equator the earth has an eastward velocity of . The Earth is also orbiting around the Sun in an orbital revolution. A complete orbit around the sun takes one year, or about 365 days; it averages a speed of about . The Theory of Plate tectonics tells us that the continents are drifting on convection currents within the mantle causing them to move across the surface of the planet

neg: Molniya orbit However, the perigee needs to be high enough to keep the satellite above the atmosphere to avoid drag, and the orbital period needs to be approximately half a sidereal day. These two factors constrain the eccentricity, which becomes approximately 0.737. To track satellites using Molniya orbits, scientists use the SDP4 simplified perturbations model, which calculates the location of a satellite based on orbital shape, drag, radiation, gravitation effects from the sun and moon, and earth resonance terms. Molniya orbit A Molniya orbit (, "Lightning") is a type of satellite orbit. It is a highly elliptical orbit with an inclination of

neg: Earth that it formed from the collision of a Mars-size protoplanet called Theia with the early Earth. This hypothesis explains (among other things) the Moon's relative lack of iron and volatile elements and the fact that its composition is nearly identical to that of Earth's crust. Earth has at least five co-orbital asteroids, including 3753 Cruithne and . A trojan asteroid companion, , is librating around the leading Lagrange triangular point, L4, in the Earth's orbit around the Sun. The tiny near-Earth asteroid makes close approaches to the Earth–Moon system roughly every twenty years. During these approaches, it can orbit Earth

neg: Sun-synchronous orbit Earth. The dawn/dusk orbit has been used for solar-observing scientific satellites such as Yohkoh, TRACE, Hinode and PROBA2, affording them a nearly continuous view of the Sun. A Sun-synchronous orbit is achieved by having the osculating orbital plane precess (rotate) approximately one degree eastward each day with respect to the celestial sphere to keep pace with the Earth's movement around the Sun. This precession is achieved by tuning the inclination to the altitude of the orbit (see Technical details) such that Earth's equatorial bulge, which perturbs inclined orbits, causes the orbital plane of the spacecraft to precess with the desired

neg: Galileo Galilei Moon. The heliocentric model of the solar system developed by Nicolaus Copernicus predicted that all phases would be visible since the orbit of Venus around the Sun would cause its illuminated hemisphere to face the Earth when it was on the opposite side of the Sun and to face away from the Earth when it was on the Earth-side of the Sun. On the other hand, in Ptolemy's geocentric model it was impossible for any of the planets' orbits to intersect the spherical shell carrying the Sun. Traditionally, the orbit of Venus was placed entirely on the near side of

neg: Solar eclipse the Earth is inclined at an angle of just over 5 degrees to the plane of the Earth's orbit around the Sun (the ecliptic). Because of this, at the time of a new moon, the Moon will usually pass to the north or south of the Sun. A solar eclipse can occur only when new moon occurs close to one of the points (known as nodes) where the Moon's orbit crosses the ecliptic. As noted above, the Moon's orbit is also elliptical. The Moon's distance from the Earth can vary by about 6% from its average value. Therefore, the Moon's

neg: Methods of detecting exoplanets due to the Doppler effect. The radial-velocity method measures these variations in order to confirm the presence of the planet using the binary mass function. The speed of the star around the system's center of mass is much smaller than that of the planet, because the radius of its orbit around the center of mass is so small. (For example, the Sun moves by about 13 m/s due to Jupiter, but only about 9 cm/s due to Earth). However, velocity variations down to 1 m/s or even somewhat less can be detected with modern spectrometers, such as the HARPS (High

neg: Rotation Moons revolve around their planet, planets revolve about their star (such as the Earth around the Sun); and stars slowly revolve about their galaxial center. The motion of the components of galaxies is complex, but it usually includes a rotation component. Most planets in our solar system, including Earth, spin in the same direction as they orbit the Sun. The exceptions are Venus and Uranus. Uranus rotates nearly on its side relative to its orbit. Current speculation is that Uranus started off with a typical prograde orientation and was knocked on its side by a large impact early in its

neg: Lagrangian point with regard to its orbit around the larger mass. The triangular points ( and ) are stable equilibria, provided that the ratio of is greater than 24.96. This is the case for the Sun–Earth system, the Sun–Jupiter system, and, by a smaller margin, the Earth–Moon system. When a body at these points is perturbed, it moves away from the point, but the factor opposite of that which is increased or decreased by the perturbation (either gravity or angular momentum-induced speed) will also increase or decrease, bending the object's path into a stable, kidney bean-shaped orbit around the point (as seen

neg: Perigean spring tide Perigean spring tide A proxigean spring tide (also known as a perigean spring tide) is a tide that occurs three or four times per year when the Moon's perigee (its closest point to Earth during its 29.5-day elliptical orbit) coincides with a spring tide (when the Earth, Sun and Moon are nearly aligned every two weeks). This tide usually adds only a couple of inches to normal spring tides. The Moon's orbit around Earth is elliptical, which causes the Moon to be closer to Earth and farther away at different times. The Moon and the Sun are aligned every two

neg: Lunar standstill completes one orbit around the Sun in 365.25636 days, slightly longer than one year due to precession altering the direction of Earth's inclination. The Moon's orbit around Earth (shown dotted) is inclined at an angle of "i" = 5.14° relative to the ecliptic. The Moon completes one orbit around the Earth in 27.32166 days. The two points at which Moon crosses the ecliptic are known as its orbital nodes, shown as "N1" and "N2" (ascending node and descending node, respectively), and the line connecting them is known as the "line of nodes". Due to precession of the Moon's orbital inclination,

neg: Milankovitch cycles (its eccentricity varies). When the orbit is more elongated, there is more variation in the distance between the Earth and the Sun, and in the amount of solar radiation, at different times in the year. In addition, the rotational tilt of the Earth (its obliquity) changes slightly. A greater tilt makes the seasons more extreme. Finally, the direction in the fixed stars pointed to by the Earth's axis changes (axial precession), while the Earth's elliptical orbit around the Sun rotates (apsidal precession). The combined effect is that proximity to the Sun occurs during different astronomical seasons. Milankovitch studied changes in

neg: (6491) 1991 OA (6491) 1991 OA The S-type body is an Amor asteroid – a subgroup of near-Earth asteroids that approach the orbit of Earth from beyond, but do not cross it. It orbits the Sun at a distance of 1.0–4.0 AU once every 3 years and 11 months (1,444 days). Its orbit has an eccentricity of 0.59 and an inclination of 6° with respect to the ecliptic. Its "minimum orbit intersection distance" (MOID) with Earth is 0.0420 AU, and on 1 August 2086, it will make a close approach and pass by Earth at a distance of . A first precovery was

neg: Orbit of the Moon rearward loops in the Moon's solar orbit. Considering the Earth–Moon system as a binary planet, its centre of gravity is within Earth, about or 72.6% of the Earth's radius from the centre of the Earth. This centre of gravity remains on the line between the centres of the Earth and Moon as the Earth completes its diurnal rotation. The path of the Earth–Moon system in its solar orbit is defined as the movement of this mutual centre of gravity around the sun. Consequently, Earth's centre veers inside and outside the solar orbital path during each synodic month as the Moon

neg: Apollo 11 involved separating "Columbia" from the spent S-IVB stage, turning around, and docking with "Eagle" still attached to the stage. After the LM was extracted, the combined spacecraft headed for the Moon, while the rocket stage flew on a trajectory past the Moon. This was done to avoid colliding with the spacecraft, the Earth, or the Moon. A slingshot effect from passing around the Moon threw it into an orbit around the Sun. On July 19 at 17:21:50 UTC, Apollo 11 passed behind the Moon and fired its service propulsion engine to enter lunar orbit. In the thirty orbits that followed,

neg: Counter-Earth L3" Lagrangian point (see diagram), would mean the combined gravitational pull of the two large masses of Earth and Sun would provide "precisely the centripetal force required to orbit with them". But a small planet would be even more influenced by the orbit of Venus, Mars and Jupiter, making it even more unstable. Any planetary sized body 180 degrees from Earth should also have been visible to some space probes, such as NASA's STEREO coronagraph probes (two spacecraft launched into orbits around the Sun in 2006, one farther ahead of and one behind the Earth's orbit) which would have seen

neg: Edward W. Morley of the year, as the Earth revolved in its orbit around the Sun. These careful measurements were created to measure the differences in the speed of light in different directions. Michelson and Morley always found that the speed of light did not vary at all depending on the direction of measurement, or the position of the Earth in its orbit, deducing what we call a "null result" for their speed-of-light experiments. Neither he nor Michelson ever considered that these null results disproved the hypothesis of the existence of "luminiferous aether", in which electromagnetic waves were thought to be propagated. Their

neg: Retrograde and prograde motion than asteroids to be retrograde. Halley's Comet has a retrograde orbit around the Sun. Most Kuiper belt objects have prograde orbits around the Sun. The first Kuiper belt object discovered to have a retrograde orbit was . Other Kuiper belt objects with retrograde orbits are (471325) 2011 KT, , and 2011 MM. All of these orbits are highly tilted, with inclinations in the 100° - 125° range. Meteoroids in a retrograde orbit around the Sun hit the Earth with a faster relative speed than prograde meteoroids and tend to burn up in the atmosphere and are more likely to hit

neg: Coronal loop March 2007 due to its resounding success, allowing SOHO to observe a complete 11-year solar cycle. SOHO continually faces the Sun holding a slow orbit around the First Lagrangian Point (L1), where the gravitational balance between the Sun and Earth provides a stable position for SOHO to orbit. SOHO is continually eclipsing the Sun from the Earth at a distance of approximately 1.5 million kilometres. SOHO is managed by scientists from the European Space Agency (ESA) and NASA. Containing more instruments than both TRACE and Yohkoh, this large solar mission was designed to look at the chain from the solar

neg: Apache Point Observatory Lunar Laser-ranging Operation radius of by the contribution to the Earth’s mass from the self-energy to yield 75 meters. The signature of an EP violation is very simple, depending only on the distance of the Moon from the Sun. This repeats about every 29.5 days, somewhat longer than the time the Moon takes to go around the Earth once, which is 27.3 days. (This difference arises since the Earth moves along its orbit as the Moon goes around, so the Moon has to make a little more than one orbit to get back to the same position relative to the Sun.) This makes