Rotation
Earth's rotation period relative to the Sun—its mean solar day—is 86,400 seconds of mean solar time (86,400.0025 SI seconds). As the Earth's solar day is now slightly longer than it was during the 19th century due to tidal acceleration, each day varies between 0 and 2 SI ms longer.
Earth's rotation period relative to the fixed stars, called its stellar day by the International Earth Rotation and Reference Systems Service (IERS), is 86,164.098903691 seconds of mean solar time (UT1), or 23h 56m 4.098903691s.[2][n 12] Earth's rotation period relative to the precessing or moving mean vernal equinox, misnamed its sidereal day, is 86,164.09053083288 seconds of mean solar time (UT1) (23h 56m 4.09053083288s) as of 1982.[2] Thus the sidereal day is shorter than the stellar day by about 8.4 ms.[129] The length of the mean solar day in SI seconds is available from the IERS for the periods 1623–2005[130] and 1962–2005.
Apart from meteors
within the atmosphere and low-orbiting satellites, the main apparent
motion of celestial bodies in the Earth's sky is to the west at a rate
of 15°/h = 15'/min. For bodies near the celestial equator,
this is equivalent to an apparent diameter of the Sun or Moon every two
minutes; from the planet's surface, the apparent sizes of the Sun and
the Moon are approximately the same.
Orbit
Main article: Earth's orbit
Earth orbits the Sun at an average distance of about 150 million kilometers every 365.2564 mean solar days, or one sidereal year.
From Earth, this gives an apparent movement of the Sun eastward with
respect to the stars at a rate of about 1°/day, which is one apparent
Sun or Moon diameter every 12 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 the Earth averages about 29.8 km/s (107,000 km/h),
which is fast enough to travel a distance equal to the planet's
diameter, about 12,742 km, in seven minutes, and the distance to the
Moon, 384,000 km, in about 3.5 hours.
The Moon revolves with the Earth around a common barycenter
every 27.32 days relative to the background stars. When combined with
the Earth–Moon system's common revolution around the Sun, the period of
the synodic month, from new moon to new moon, is 29.53 days. Viewed from the celestial north pole, the motion of Earth, the Moon and their axial rotations are all counterclockwise.
Viewed from a vantage point above the north poles of both the Sun and
the Earth, the Earth revolves in a counterclockwise direction about the
Sun. The orbital and axial planes are not precisely aligned: Earth's axis is tilted some 23.4 degrees from the perpendicular to the Earth–Sun plane (the ecliptic),
and the Earth–Moon plane is tilted up to ±5.1 degrees against the
Earth–Sun plane. Without this tilt, there would be an eclipse every two
weeks, alternating between lunar eclipses and solar eclipses.
The Hill sphere, or gravitational sphere of influence, of the Earth is about 1.5 Gm or 1,500,000 km in radius.[135][n 13]
This is the maximum distance at which the Earth's gravitational
influence is stronger than the more distant Sun and planets. Objects
must orbit the Earth within this radius, or they can become unbound by
the gravitational perturbation of the Sun.
Earth, along with the Solar System, is situated in the Milky Way galaxy and orbits about 28,000 light years from the center of the galaxy. It is about 20 light years above the galactic plane in the Orion spiral arm.
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