# If the moon stopped orbiting the earth

I know this is impossible, but theoretically speaking what would happen if the moon was stopped, so that it stopped orbiting the earth and "stood still"? Would it hit earth or what impact would it have on earth?

diazona
Homework Helper
If the moon momentarily stopped moving with respect to the Earth, then the Earth's gravity would pull the moon toward it. After a short time they would crash together. (It's likely that tidal forces would start pulling both the Earth and moon apart before they actually hit)

It's similar to if a plane somehow stopped mid-flight, it would just fall.

Thank you!
But since it gains speed as it falls closer to earth wouldn't it again go into a stable orbit? Or doesn't it work that way?:S

diazona
Homework Helper
No. Think about which direction the moon would be moving. It would be gaining speed toward the earth, which would just cause it to keep coming. In order to go into a stable orbit, it would need to change direction and start moving parallel to the Earth's surface.

Okey! But if the moon fell shouldnt the moon's force of gravity have an impact on earth as well, so that they both were attracted towards each other and the earth would "move"?

diazona
Homework Helper
Yep, that's exactly what would happen.

Is there anyway to calculate with what force the moon would hit earth and/or how long it would take? Or would such calculations be too complicated..? Is there in that case any simpler way to estimate the force and time?

russ_watters
Mentor
You can use Newton's laws, plugged into a spreadsheet. It isn't too difficult. It would take several days for the moon to hit the earth.

Could you show me more precisely how i could do that? What kind of equations would i use etc?
Thanks!