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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 point towards which the Earth in its solar orbit is directed at any given instant is known as the "apex of the Earth's way". [4] [5] From a vantage point above the north pole of either the Sun or Earth, Earth would appear to revolve in a counterclockwise direction around the Sun. From the same vantage point, both the Earth and the Sun would ...
In the United Kingdom, railroads gradually switched to Greenwich Mean Time (set from local time at the Greenwich observatory in London), followed by public clocks across the country generally, forming a single time zone. In the United States, railroads published schedules based on local time, then later based on standard time for that railroad ...
When the disk undergoes a full clockwise revolution, the bicycle wheel will not return to its original position, but will have undergone a net rotation of 2π sin φ. Foucault-like precession is observed in a virtual system wherein a massless particle is constrained to remain on a rotating plane that is inclined with respect to the axis of ...
The rotation has caused the planet to settle on a spheroid shape, such that the normal force, the gravitational force and the centrifugal force exactly balance each other on a "horizontal" surface. (See equatorial bulge.) The Coriolis effect caused by the rotation of the Earth can be seen indirectly through the motion of a Foucault pendulum.
A sphere is the only stable shape for a non-rotating, gravitationally self-attracting liquid. The outward acceleration caused by Earth's rotation is greater at the equator than at the poles (where is it zero), so the sphere gets deformed into an ellipsoid, which represents the shape having the lowest potential energy for a rotating, fluid body ...
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 ...
The x-axis is permanently fixed in a direction relative to the celestial sphere, which does not rotate as Earth does. The z-axis lies at a 90° angle to the equatorial plane and extends through the North Pole. Due to forces that the Sun and Moon exert, Earth's equatorial plane moves with respect to the celestial sphere.