Earths Rotation
Earth’s Rotation
Earth 's rotation is the rotation of the solid Earth around its own axis. The Earth rotates from the west towards the east. As viewed from the North Star or polestar Polaris, the Earth turns counter-clockwise.
The North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is the point in the Northern Hemisphere where the Earth 's axis of rotation meets its surface. This point is distinct from the Earth 's North Magnetic Pole. The South Pole is the other point where the Earth 's axis of rotation intersects its surface, in Antarctica.
The Earth rotates once in about 24 hours with respect to the sun and once every 23 hours 56 minutes and 4 seconds with respect to the stars (see below). Earth 's rotation is slowing slightly with time; thus, a day was shorter in the past. This is due to the tidal effects the Moon has on Earth 's rotation. Atomic clocks show that a modern day is longer by about 1.7 milliseconds than a century ago,[2] slowly increasing the rate at which UTC is adjusted by leap seconds.
Contents
[hide]
1 History
1.1 Empirical tests
2 Rotation period
2.1 True solar day
2.2 Mean solar day
2.3 Stellar and sidereal day
2.4 Angular speed
3 Changes in rotation
3.1 Measurement
4 Origin
5 See also
6 Notes
7 References
8 External links
History[edit]
Among the ancient Greeks, several of the Pythagorean school believed in the rotation of the earth rather than the apparent diurnal rotation of the heavens. The first was Philolaus (470-385 BCE) though his system was complicated, including a counter-earth rotating daily about a central fire.[3]
A more conventional picture was that supported by Hicetas, Heraclides and Ecphantus in the fourth century BCE who assumed that the earth rotated but did not suggest that the earth revolved about the sun. In the third century, Aristarchus of Samos suggested the sun 's central place.
However, Aristotle in the fourth century criticized the ideas of Philolaus as being based on theory rather
Earth 's rotation is the rotation of the solid Earth around its own axis. The Earth rotates from the west towards the east. As viewed from the North Star or polestar Polaris, the Earth turns counter-clockwise.
The North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is the point in the Northern Hemisphere where the Earth 's axis of rotation meets its surface. This point is distinct from the Earth 's North Magnetic Pole. The South Pole is the other point where the Earth 's axis of rotation intersects its surface, in Antarctica.
The Earth rotates once in about 24 hours with respect to the sun and once every 23 hours 56 minutes and 4 seconds with respect to the stars (see below). Earth 's rotation is slowing slightly with time; thus, a day was shorter in the past. This is due to the tidal effects the Moon has on Earth 's rotation. Atomic clocks show that a modern day is longer by about 1.7 milliseconds than a century ago,[2] slowly increasing the rate at which UTC is adjusted by leap seconds.
Contents
[hide]
1 History
1.1 Empirical tests
2 Rotation period
2.1 True solar day
2.2 Mean solar day
2.3 Stellar and sidereal day
2.4 Angular speed
3 Changes in rotation
3.1 Measurement
4 Origin
5 See also
6 Notes
7 References
8 External links
History[edit]
Among the ancient Greeks, several of the Pythagorean school believed in the rotation of the earth rather than the apparent diurnal rotation of the heavens. The first was Philolaus (470-385 BCE) though his system was complicated, including a counter-earth rotating daily about a central fire.[3]
A more conventional picture was that supported by Hicetas, Heraclides and Ecphantus in the fourth century BCE who assumed that the earth rotated but did not suggest that the earth revolved about the sun. In the third century, Aristarchus of Samos suggested the sun 's central place.
However, Aristotle in the fourth century criticized the ideas of Philolaus as being based on theory rather
References: Deviation of day length from SI based day, 1962–2010 The Earth 's rotation axis moves with respect to the fixed stars (inertial space); the components of this motion are precession and nutation