Anonymous
Anonymous asked in Science & MathematicsAstronomy & Space · 1 decade ago

Earth's revolution and rotation?

What is the Earth's revolution - other names, length, shape, cuase, etc?

what is the Earth's rotation - other names, length, effects, direction, etc?

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  • 1 decade ago
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    The revolution of the Earth is its motion around the sun. You could call it Earth's orbit if you like.

    Its shape is a nearly circular ellipse. Length in time is 1 year; length in distance is pi x 186 million miles. It's caused by the inherent motion of the Earth and the Sun's gravity. The Sun is pulling the Earth towards it, but the Earth is moving fast enough that it goes around the sun instead of towards it.

    The rotation of the the Earth is its spin on its axis. It's what causes day and night. The Earth spins towards the East, which is why the sun rises from that direction.

    Length depends on whether you count the Synodic or Sidereal rotation. Sidereal rotation is the amount of time it takes for the same star to be directly overhead again, which is 23 hours and 56 minutes. But it takes longer for the Sun to be directly overhead again, because in that time the Earth has moved forwards in its orbit (see revolution, above). So the Synodic rotation (the time for the Sun to return to the same spot in the sky) is 24 hours, or 1 day.

  • 1 decade ago

    revolution - a.k.a.: translation, orbit.

    almost circular, mean radius is called 1 Astronomical Unit (AU) and is a unit of measurement within the solar system.

    1 AU = 149,597,871.5 km (most of us use 150 million km)

    = 93,498, 670 mi (we use 93.5 million miles).

    More accurate model is an ellipse with an eccentricity of 0.01675 (0 would be a perfect circle, 1 would be a straight line segment).

    Real shape of orbit is an ellipse with a slight (2000 km) zig-zag each month: it is the mass centre of the Earth-Moon system that orbits the Sun, and the Earth wobbles around that centre of mass.

    In 2008, perihelion (closest to the sun) was on Jan. 2 at 147,096,448 km; aphelion will be on July 4 at 152,104,136 km.

    All distances are centre to centre.

    Duration of orbit (in relation to fixed stars): 365.256363 days of 86,400 seconds. This is the duration to use in orbital mechanics.

    Average orbital speed = 29.786 km/s (107,230 km/h = 67,000 mph)

    -----

    rotation - a.k.a. spin. The original scale of 24 hours per day was based on rotation in relation to Sun (averaged over the year); 1 day = 86,400 seconds.

    The Earth's surface is moving eastward (which makes the sun appear to go westward).

    Rotation causes winds to spiral (counterclockwise in the northern hemisphere) into low pressure centres, instead of flowing directly to the centre. (Coriolis effect)

    Rotation causes Earth to act like a gyro when the gravitational attraction of the Sun and Moon pull on the equatorial bulge: a precession period of 25,800 years as the orientation of the spin axis "wobbles". (precession of the equinoxe)

    Tidal effect of the Moon causes Earth's rotation to slow down (however, we do not see any difference over a lifetime). (Tidal braking)

    Rotation in relation to fixed stars: 86,164.1 seconds (23h 56m04.1s) This is the rotation period to use when comparing satellite rates (e.g., a geostationary satellite -- which keeps above the same point all the time -- must have this period).

    If you take the Earth's circumference to be 40,000 km, then a person standing at the equator at sea level is taken eastward at 1671.2 km/h (1.044.5 mph).

    At other latitudes, the speed is 1671.2*Cos(LAT)

  • 1 decade ago

    You can name the phenomenas with some words.

    The earth rotate around the sun once each year, that could be named translation and rotate around its own axis once per day it could be named rotation, this motion creates a precession force like a giroscope which keeps its angular position which causes the 4 stations in the year.

  • 6 years ago

    The shape of the Earth is almost sphere. The revolution takes a little over 365 days. The day or spin takes almost 24 hours.

    Source(s): This is Winston.
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  • Anonymous
    1 decade ago

    earth revolves around the sun

    at 30km/second

  • 1 decade ago

    revolution: goes round the sun

    rotation:Goes round on it axis

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