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Earth's rotation axis moves with respect to the fixed stars (inertial space); the components of this motion are precession and nutation. It also moves with respect to Earth's crust; this is called polar motion. Precession is a rotation of Earth's rotation axis, caused primarily by external torques from the gravity of the Sun, Moon and other bodies.
The Earth's rotation rate is still slowing down, though gradually, by about two thousandths of a second per rotation every 100 years. [1] Estimates of how fast the Earth was rotating in the past vary, because it is not known exactly how the moon was formed. Estimates of the Earth's rotation 500 million years ago are around 20 modern hours per ...
Eartha is the world's largest rotating and revolving globe, located within the former headquarters of the DeLorme mapping corporation in Yarmouth, Maine. [1] Garmin purchased the company and the building in 2016. [2] The globe weighs approximately 5,600 pounds (2,500 kg), and has a diameter of over 41 feet (12.5 m).
Quizlet was founded in October 2005 by Andrew Sutherland, who at the time was a 15-year old student, [2] and released to the public in January 2007. [3] Quizlet's primary products include digital flash cards, matching games, practice electronic assessments, and live quizzes. In 2017, 1 in 2 high school students used Quizlet. [4]
The Earth rotation angle (ERA) measures the rotation of the Earth from an origin on the celestial equator, the Celestial Intermediate Origin, also termed the Celestial Ephemeris Origin, [9] that has no instantaneous motion along the equator; it was originally referred to as the non-rotating origin. This point is very close to the equinox of J2000.
[2] Relative to Earth's surface, the geographic poles move by a few metres over periods of a few years. [ 3 ] This is a combination of Chandler wobble , a free oscillation with a period of about 433 days; an annual motion responding to seasonal movements of air and water masses; and an irregular drift towards the 80th west meridian . [ 4 ]
One complete orbit takes 365.256 days (1 sidereal year), during which time Earth has traveled 940 million km (584 million mi). [2] Ignoring the influence of other Solar System bodies, Earth's orbit, also called Earth's revolution, is an ellipse with the Earth–Sun barycenter as one focus with a current eccentricity of 0.0167. Since this value ...
In a geocentric coordinate system, this is the axis of rotation of the celestial sphere. Consequently, in ancient Greco-Roman astronomy , the axis mundi [ 1 ] is the axis of rotation of the planetary spheres within the classical geocentric model of the cosmos.