Rotation period (length of day in Earth days)
0.72 (17.9 Earth hours)(retrograde)
Revolution period (length of year in Earth days) ...
Tablets dating back to the Old Babylonian period document the application of mathematics to the variation in the length of daylight over a solar year.
The daily eastward progression in the sky is slow around the equinoxes (that is the shift in the length of daylight vs darkness is foreshortened and rise and set times for the sun change very little from one day to the next).
Length of Day on Mercury
Length of Year on Mercury
Mercury Number of Moons
Mercury Diagram
Mercury Fact Sheet
Mercury's Density
Who Discovered the Planet Mercury?
Mercury's Symbol
Mercury's Size
What is Mercury Named After?
* The monk Bede (c.672 â€" 735) wrote in his influential treatise on computus, The Reckoning of Time, that the Earth was round, explaining the unequal length of daylight from "the roundness of the Earth, ...
One of the divisions of the year, marked by alternations in the length of day and night, or by distinct conditions of temperature, moisture, etc., caused mainly by the relative position of the earth with respect to the sun.
Why is the length of daylight in the northern hemisphere so short on December 21?
When will the Sun be at its highest altitude in the year in Los Angeles or Seattle? How about Singapore (on the Equator)? Why?
seasons Changes in average temperature and length of day that result from the tilt of Earth's (or any planet's) axis with respect to the plane of its orbit.
Within the Solar System, the approximate length of day on each planet (measured relative to an Earth day of 24 hours) is:
Planet
Mercury ...
At the Earth's equator, the Sun's declination has no effect on the length of daylight. There, you pretty much have 12 hours of daylight and 12 hours of night all year long. The Rite of Spring ...
Variations in the Earth's orientation and length of day.
Maintenance of the terrestrial reference frame
Measurement of gravitational forces of the Sun and Moon on the Earth and the deep structure of the Earth
Improvement of atmospheric models.
Because its orbital eccentricity is greater than that of Earth, the length of day varies from the average by a greater amount than that of Earth, and hence its equation of time shows greater variation than that of Earth: on Mars, ...
relative orbital positions of Earth and Mars and on the rotation of Mars, in particular the secular precession of the longitude of the node, the short period nutation of the obliquity and the node, seasonal and tidal variations in the length of day ...
Photoperiodicity is the physiological reaction of organisms to the length of day or night. It occurs in plants and animals....
, germination
Germination ...
the Northern Hemisphere, the vernal equinox occurs around March 21st, and in the fall the autumnal equinox happens around September 21st (although the specific dates vary slightly from year to year.) At the time of the equinoxes, the length of day ...
Table of Contents Click on an underlined topic to go there.
If you are looking for information about a topic not listed here, try the illustrated Astronomy Dictionary.
The Planets
Mercury
-Mercury Map
-Inside Mercury
-Length of Day, Year ...
He tried to measure latitude by utilizing the ratio of the longest to the shortest day at a particular place instead of following the customary method of the Babylonians of measuring the difference in length of day as one travels northward.
In 1980 and 1981 the Voyager spacecraft measured Saturn's day as ten hours, 39 minutes and 24 seconds. But when the Cassini spacecraft arrived in 2004, it measured the length of day as ten hours, 47 minutes and six seconds.
Scrollable database information on Jupiter included its current position, magnitude, rise and set time, mass, apparent diameter, actual diameter, distance from earth, length of day, orbital period, surface gravity, temperature range, number of moons, ...
 See also: Earth, Sun, Year, Orbit, Day
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