All in a day's work
* In our Solar System, Mercury is the closest planet to the Sun. Because of this proximity it is not easy to see except at twilight. Mercury also orbits the Sun so quickly, early astronomers believed it was actually two different stars -- one which appeared in the morning and another in the evening.
* A year on Mercury is only 88 days. (This is the time it takes Mercury to circle the Sun once.) Mercury rotates once on its axis every 58.6 Earth days. This would normally meet the definition of a "day" on Mercury, but because everything is in motion -- the Sun, Mercury, the Earth, etc., it takes 176 Earth days for Mercury to go from sunrise to sunrise.
* Obviously, Mercury spins very, very slowly. It completes three rotations on its axis for every two orbits of the Sun. In other words and in one sense, three "days" on Mercury takes two "years." (This is the one orbit on its axis sense.) In another sense, Mercury's "day" lasts two years. One year is spent in daylight, the other in darkness. (This is the "sunrise to sunrise" sense.)
* Mercury is almost tidally locked to the Sun. This means over time, the gravity of the Sun has slowed the rotation of the planet to almost match its time in orbit around the Sun. (This is phenomenon is also known as a gravitational lock.) This keeps the same area of the planet exposed to the Sun for a very long time, and until 1965 scientists believed the same side of Mercury constantly faced the Sun.
There are other dimensions to Mercury.
Basic Stuff About Mercury in Astrology
More about Mercury in Science
Some facts & history
* For now, Mercury is considered the smallest planet in our Solar System. That honor used to belong to Pluto, but since science is messing around over whether or not to call Pluto a planet (currently designated a "dwarf planet"), Mercury is technically the smallest.
* Mercury is about 3,000 miles at its equator, compared to Earth at about 8,000 miles. So, the Earth is about 2 1/2 times the size of Mercury. (Or Mercury is about 38% the size of the Earth, however you want to envision it.)
* Mercury is one of five planets visible to the naked eye. The others are Venus, Mars, Jupiter and Saturn. Beyond that, you need a telescope, which is why it took so long to "discover" the outer planets.
* Who discovered Mercury and when it happened is unknown -- and impossible to calculate. Because it is visible to the eye, many ancient cultures knew about it. One of the earliest recorded mentions of Mercury was by the Sumerians around 3,000 BC.
* Mercury also has the highest orbital eccentricity of all the planets. Its distance from the Sun ranges from 24.9 million miles to 43,5 million miles. Its orbit is elliptical rather than circular -- and the least circular orbit of all the planets at that.
Here's how Mercury is used & respected elsewhere.
Quick Notes on Mercury in Astrology
Mercury in Astrology
Light Reading & Open Articles
Learn more about Mercury in Astrology
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Mercury in Astrology -- Articles Index
Mercury Retrograde -- Articles Index