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Estimates of the Earth's rotation 500 million years ago are around 20 modern hours per "day". The Earth's rate of rotation is slowing down mainly because of tidal interactions with the Moon and the Sun. Since the solid parts of the Earth are ductile, the Earth's equatorial bulge has been decreasing in step with the decrease in the rate of rotation.
The usual effect of the declining pressure of the atmosphere with height (vertical pressure variation) is to bend radio waves down towards the surface of the Earth. This results in an effective Earth radius, [3] increased by a factor around 4 ⁄ 3. [4] This k-factor can change from its average value depending on weather.
Lunisolar precession is caused by the gravitational forces of the Moon and Sun on Earth's equatorial bulge, causing Earth's axis to move with respect to inertial space. Planetary precession (an advance) is due to the small angle between the gravitational force of the other planets on Earth and its orbital plane (the ecliptic), causing the plane ...
A diagram of the Earth–Moon system showing how the tidal bulge is pushed ahead by Earth's rotation. This offset bulge exerts a net torque on the Moon, boosting it while slowing Earth's rotation. 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 of the ...
The precession of Earth's axis was later explained by Newtonian physics. Being an oblate spheroid, Earth has a non-spherical shape, bulging outward at the equator. The gravitational tidal forces of the Moon and Sun apply torque to the equator, attempting to pull the equatorial bulge into the plane of the ecliptic, but
This bulge creates a gravitational effect that causes orbits to precess around the rotational axis of the primary body. The direction of precession is opposite the direction of revolution. For a typical prograde orbit around Earth (that is, in the direction of primary body's rotation), the longitude of the ascending node decreases, that is the ...
It's Advent calendar season, and if you haven't picked up your treat for the year, you may have missed your window. Many of the year's best Advent calendars have sold out already, like the Bonne ...
The oscillation periods of the Earth as a whole are not near the astronomical periods, so its flexing is due to the forces of the moment. The tide components with a period near twelve hours have a lunar amplitude (Earth bulge/depression distances) that are a little more than twice the height of the solar amplitudes, as tabulated below.