What would happen? I would imagine the side facing the sun would get very hot. Would it reflect more light/heat to us at night?
It sort of already has, it’s tidally locked to the Earth.
Besides, the direction the moon faces the sun is determined by its orbit around the Earth, not rotation on its own axis.
Stopped rotating relative to what? The Earth? The Sun? The centre of the galaxy? It can’t stop rotating relative to more than one of them.
What does that mean?
Ok then. If the moon rotated in such a way that it just had 1 side facing the sun all the time. Would we notice anything I mentioned in the OP.
Also I thought the moon was still rotating on it’s own axis?
Then yeah, the side facing the sun would get very hot. Depending how the extreme temperatures affected the chemistry of the rock, it might produce marginally more light or marginally less. It would never provide any measurable amount of heat
It is still rotating on its own axis, relative to everything but the Earth. It is tidally locked to the Earth, so it rotates at exactly the same speed as its orbit around the Earth. The upshot is that it always has one side facing the Earth all the time.
Imagine someone walking around a building, while at the same time always facing the building. The person will have to spin 360o around their own axis, but they won’t rotate at all relative to the building.
No, the Moon is tidally locked to the Earth so that one face always faces us. The Moon rotates around the Earth’s axis each 28 days. The Moon does not rotate about its own axis.
I think you are asking what would happen if the Moon was tidally locked to the Sun ie. one face always pointed at the Sun. The Moon would rotate in that case.
Nothing dramatic. The sunny surface would heat up a little and gases would be released. We might see frost on the dark side - that would be interesting.
Maybe you should take a moment to think about it. It makes perfectly good sense to me.
I daresay it is possible to invent an uncharitable interpretation of Alessan’s comment under which it it becomes false or incoherent, but why would you insist on doing so?
(Oh, you’re Blake. Nevermind.)
Care to explain how that is even possible? How can Object A always *face *Object B, *rotate *around Object B, *orbit *Object B, yet never rotate around it’s *own *axis? That would seem to be impossible in 3 dimensional space.
Look at this time series
A A A A
| / \ |
| / \ |
B B B------ A B B B A------B B B
\ | /
\ | /
A A A
A has orbited B, and it has done that without rotating on its own axis. But it can;t possibly do that while always having the same face to Object B. In order to that it A is going to have to rotate on its own axis.
Correct?
Here’s a trickish question:
How many times does the Earth rotate on its axis in one year?
I’m guessing there is some semantic trick here, but the obvious answer is ~365.25.
If one grants that “rotating on one’s axis” is ambiguous, then we can at least hope for self-consistency. Your answer here is inconsistent with your response #9.
Google “sidereal day”.
:dubious:
The sidereal day is shorter than the stellar day by about 8.4 ms
So 365.24999999999999 is not approximately ~365.25?
The moon currently does rotate around its own axis, completing one rotation every 27.3 days.
The moon also orbits around the earth, completing one orbit every 27.3 days.
It rotates in the same direction as its orbit, with the net result being that it always has the same side facing toward the earth.
If the moon somehow became tidally locked to the sun, it would still be orbiting the earth (with an orbital period of 27.3 days), but it would now only complete one rotation every 365.25 days.
The length of a regular day (noon-noon) is a solar day, a stellar day is something quite different. A sidereal day (one 360[sup]o[/sup] rotation) is ~3m56s shorter than a solar day. The solar day is longer because the earth is also rotating around the sun, and it takes the extra ~3.56 for the earth to rotate relative to the sun.
Which works out to ~24 hours a year.
So still ~365.25 rotations in a year.
I’m sure there is some gotcha moment coming up, but I still don’t see it.
Sounds like you missed at least three point(s).
First of all, neither the “sidereal day” nor the “stellar day” is the solar day. From the very same Wiki paragraph where you find the irrelevant factoid you could also have learned that the stellar day (close enough to the sidereal day for our purpose) is “23h 56m 4.090 530 832 88s, 0.997 269 566 329 08 mean solar days.” If you type “365.2422/0.997269” into Google you get 366.2424.
That’s right! The Earth rotates 366¼ times per year, not 365¼ times.
BTW, there are 365.2422 solar days in a year (not “365.24999999999999” 
), just as there are zero Earth-referenced lunar days in a month. It is weird. Should one count the extra rotation or not? Either way seems OK, as long as you keep track which way you’re doing it and retain consistency. You insisted (in #9) on counting the extra rotation of the Moon around the Earth (making it 1 per month instead of zero), so you should count the extra Earth rotation as well, making it 366¼ rotations, not 365¼.
Does this help?
Not in the least. It’s the sort of pointless nitpickery that the Dope does so well.
Claiming that 366.2424 is not approximately 365.25? Seriously?
Claiming that “the extra rotation of the Moon around the Earth” is the same as if the moon had"rotated on its own axis"? Really?
Come on, have we really been reduced to this? What next? Arguing about what the definition of is, is?
The simple fact is that the moon does rotate about its own axis abut once a month and the Earth also rotates about its own axis about 365 times a year.
Clear as (a solar) day, septimus. I vote for “the moon does not rotate about its axis,” not because of the definition of rotate, but the definition of axis. If I swing a pocket watch around by its chain, nobody would claim that the watch was rotating about the timepiece’s hands’ center point, but rather rotating around my hand. The moon surely rotates, just as the watch does, but around the Earth’s axis, not an axis through the center of the moon.
~366.25 rotations.
The ‘gotcha’ bit is the fact that the earth is revolving around the sun - remember, a ‘day’ is slightly more than one actual rotation because of this. So the earth will rotate once more than the number of apparent days, the ‘missing’ day is used up by those extra 3.56 minutes.