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uncomfortable levels of eye contact (mander.xyz)

submitted 10 months ago by fossilesque@mander.xyz to c/science_memes@mander.xyz

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[-] uphillbothways@kbin.social 20 points 10 months ago* (last edited 10 months ago)

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.

[-] Bassman1805@lemmy.world 32 points 10 months ago* (last edited 10 months ago)

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.

[-] Zombiepirate@lemmy.world 16 points 10 months ago

Now those are some fun facts.

[-] DharmaCurious@startrek.website 11 points 10 months ago

Can you ELI5 that last one?

[-] brianorca@lemmy.world 5 points 10 months ago

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.

[-] Kase@lemmy.world 2 points 10 months ago

So in a certain sense, a 'day' on Mercury is 2.034090909090 'years' long? (Solar day divided by orbiting the sun, lol)

[-] brianorca@lemmy.world 5 points 10 months ago* (last edited 10 months ago)

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.