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  Being closest to the Sun, Mercury   travels fastest in its orbit. Mercury: The Speedy Planet

People began observing Mercury thousands of years ago. The Greeks called the planet Hermes, after the swift messenger of the gods in Greek mythology. The Romans called him Mercury. Planet Mercury is difficult to see because it is always close to the Sun when we view it from the Earth. This means that at sunrise or sunset, it is never far above the horizon. And it is never seen in a dark sky. But under ideal conditions, it outshines all the stars, even the brightest one, Sirius.

∆ The symbol for Mercury.

∆ A carved relief showing Mercury.

Traveling at speed Mercury travels faster in its path, or orbit , around the Sun than any other planet. It takes just under 88 days to circle the Sun, at an average speed of nearly 107,500 miles (173,000 km) an hour. Most planets travel around the Sun in a nearly circular orbit. But Mercury travels in a more oval, or elliptical orbit. This means that it is much closer to the Sun at some times than at others. This causes its speed to change. It gets faster when it nears the Sun and slower when it goes farther away. If you lived on Mercury, you would find this change in speed would cause some odd effects. At certain times the Sun would appear to move backwards in the sky. At others the Sun would rise, set, then rise again on the same day.

∆ Mercury is the planet that is closest to the Sun.

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