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[nb 1] Earth's orbital speed averages 29.78 km/s (19 mi/s; 107,208 km/h; 66,616 mph), which is fast enough to cover the planet's diameter in 7 minutes and the distance to the Moon in 4 hours. [3] 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".
Time zones of the world. A time zone is an area which observes a uniform standard time for legal, commercial and social purposes. Time zones tend to follow the boundaries between countries and their subdivisions instead of strictly following longitude, because it is convenient for areas in frequent communication to keep the same time.
Standard time zones of the world. The number at the bottom of each zone specifies the number of hours to add to UTC to convert it to the local time. As international commerce increased, the need for an international standard of time measurement emerged. Several authors proposed a "universal" or "cosmic" time (see Time zone § Worldwide time zones).
The time when the Sun transits the observer's meridian depends on the geographic longitude. To find the Sun's position for a given location at a given time, one may therefore proceed in three steps as follows: [1] [2] calculate the Sun's position in the ecliptic coordinate system, convert to the equatorial coordinate system, and
Average distance from the Sun — Earth: 1.00 — Average distance of Earth's orbit from the Sun (sunlight travels for 8 minutes and 19 seconds before reaching Earth) — Mars: 1.52 — Average distance from the Sun — Jupiter: 5.2 — Average distance from the Sun — Light-hour: 7.2 — Distance light travels in one hour — Saturn: 9.5 ...
The United States Naval Observatory states "the Equation of Time is the difference apparent solar time minus mean solar time", i.e. if the sun is ahead of the clock the sign is positive, and if the clock is ahead of the sun the sign is negative. [6] [7] The equation of time is shown in the upper graph above for a period of slightly more than a ...
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The sidereal year differs from the solar year, "the period of time required for the ecliptic longitude of the Sun to increase 360 degrees", [2] due to the precession of the equinoxes. The sidereal year is 20 min 24.5 s longer than the mean tropical year at J2000.0 (365.242 190 402 ephemeris days) .