It’s tidally locked to earth. Earth isn’t tidally locked to it. Happens slowly due to gravity and differential mass. Relatively stable satellites end up tidally locked given the time. Pretty sure lack of water/liquids/atmosphere hastens the process.
Mercury orbits the sun every 88 earth days. It spins on its axis every 59 earth days, relative to an outside observer (sidereal day.) That makes the solar day (from sunrise to sunrise) 179 earth days long.
No. I rounded off the numbers. A Mercury day is exactly 2 Mercury years. Which is why it’s “in resonance”. That means that gravity will speed up or slow down the rotation to keep the ratio stable over time.
It’s tidally locked to earth. Earth isn’t tidally locked to it. Happens slowly due to gravity and differential mass. Relatively stable satellites end up tidally locked given the time. Pretty sure lack of water/liquids/atmosphere hastens the process.
Yeah, Earth’s moon isn’t the only satellite to tidally lock to its planet. In fact, several are.
Photos and Deimos are tidally locked to Mars. 8 of Jupiter’s moons and 15 of Saturn’s. Pluto and Charon.
Mercury is tidally locked to the sun, but it’s in 3:2 resonance rather than 1:1.
Now those are some fun facts.
Can you ELI5 that last one?
Mercury orbits the sun every 88 earth days. It spins on its axis every 59 earth days, relative to an outside observer (sidereal day.) That makes the solar day (from sunrise to sunrise) 179 earth days long.
So in a certain sense, a ‘day’ on Mercury is 2.034090909090 ‘years’ long? (Solar day divided by orbiting the sun, lol)
No. I rounded off the numbers. A Mercury day is exactly 2 Mercury years. Which is why it’s “in resonance”. That means that gravity will speed up or slow down the rotation to keep the ratio stable over time.
Oh that’s really neat!
Guys please upvote we all need an eli5