How Long is a Day on Mercury
Using radio waves to calculate Mercury's orbit. Image credit: NASA
Mercury has very very long days. How long is one day on Mercury? Each day on Mercury lasts as long as 58 days, 15 hours on Earth. This is quite a feat, considering a whole year on Mercury is only 88 days.
I recommend you to read these amazing books for more information about the planet Mercury.
It gets even stranger, though. Because the orbit of Mercury is very eccentric, it reaches a point in its orbit when the speed of its orbital velocity matches its angular rotational velocity. When this happens, the Sun will appear to go backwards in the sky before it resumes its regular direction.
Astronomers used to think that Mercury was tidally locked to the Sun. In other words, its period of rotation matched its orbital period. In this situation, Mercury would always show the same side to the Sun. But in the 1960s, this was shown to be incorrect.
Recent Posts
Earth’s Old Trees Keep A Record of Powerful Solar Storms
Most of the time the Sun is pretty well-mannered, but occasionally it's downright unruly. It…
New Supercomputer Simulation Explains How Mars Got Its Moons
One mystery in planetary science is a satisfying origin story for Mars's moons, Phobos and…
The Early Universe May Have Had Giant Batteries of Dust
The largest magnetic fields in the universe may have found themselves charged up when the…
The First Close-Up Picture of Star Outside the Milky Way
Like a performer preparing for their big finale, a distant star is shedding its outer…
Here’s What We Know About Earth’s Temporary Mini-Moon
For a little over a month now, the Earth has been joined by a new…
New Study Suggests Black Holes Get their “Hair” from their Mothers
Despite decades of study, black holes are still one of the most puzzling objects in…