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The Earth-centered, Earth-fixed coordinate system (acronym ECEF), also known as the geocentric coordinate system, is a cartesian spatial reference system that represents locations in the vicinity of the Earth (including its surface, interior, atmosphere, and surrounding outer space) as X, Y, and Z measurements from its center of mass.
Universal time tracks the Earth's rotation in time, which performs one revolution in about 24 hours. The Earth's rotation is uneven, so UT is not linear with respect to atomic time. It is practically proportional to the sidereal time, which is also a direct measure of Earth rotation. The excess revolution time is called length of day (LOD).
The gravitational attraction of the Sun and Moon on the Earth's equatorial bulge cause the rotational axis of the Earth to precess in space similar to the action of a top. This is called precession. Nutation is the smaller amplitude shorter-period (< 18.6 years) wobble that is superposed on the precessional motion of the Celestial pole. It is ...
Alignment with the Earth's axis is the only direction for which the gyroscope's spinning axis can be stationary with respect to the Earth and not be required to change direction with respect to inertial space. After being spun up, a gyrocompass can reach the direction of alignment with the Earth's axis in as little as a quarter of an hour. [55]
When you brush your teeth can make a big difference in your oral health.
GRB 221009A came from the constellation of Sagitta and occurred an estimated 1.9 billion years ago, [14] however its source is now 2.4 billion light-years away from Earth due to the expansion of the universe during the time-of-flight to Earth. [15]
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 ...
Regardless of the time of day (i.e. Earth's rotation on its axis), the North Pole will be dark, and the South Pole will be illuminated; see also arctic winter. Figure 3 shows the angle of sunlight striking Earth in the Northern and Southern Hemispheres when Earth's northern axis is tilted away from the Sun, when it is winter in the north and ...