Mercury
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Mercury is the smallest planet in the Solar System, and it is the closest to the Sun. It orbits the Sun in 88 days. It rotates on its axis every 58.6 days,[1] which is 3 rotations for every two orbits (called "3:2 resonance"). It can be seen from Earth only at sunrise and sunset. It is named for the Roman messenger god who was known as Hermes in Greek.
It was the study of this planet's orbit that Albert Einstein used to help confirm the theory of General Relativity.[cite reference]
Mercury is also an element, number 80 in the periodic table. It is the only metal that is commonly found in liquid form.
- ↑ "The theory that Mercury is in synchronous rotation with its orbital motion was shattered in 1965. Astronomers Gordon Pettengill and Rolf Dyce used a radio telescope to make radar observations of Mercury’s spin rate. They found that Mercury’s rotation period is only 58.6 Earth days, not the 88 days accepted for nearly a century." [1]