Originally posted by zeeblebot
google: flashlight on the moon
Could I see a flashlight beam from Earth on the moon?
Can you shine a flashlight on the moon?ua
Of course you can shine a flashlight on the moon. Doesn't mean anyone will see it
Actually, there has been laser light flashing the moon for decades, since the Apollo dudes dropped a corner reflector on the moon, they use the timing of the returned photons (only a few photons ever get back to the scopes watching) to tell the distance to the moon within a cm or so to figure out more about gravity and such. There is also a Russian probe from the '70's, Lunikod, that also has a corner reflector they just pinned down the location so now that rover, now dead, is also used as part of the system which gives them another angle to add to the data which refines the final distance data.
As to would the sky be clear or overcast, obviously if it were overcast you wouldn't see much, just like you wouldn't see much of a movie if it was say, a drive in, looking through a fog bank. You sure would see the projection beam though....
Since there are a few photons that make it back to the scopes on Earth from the laser fire, and the retro-reflectors are only a few square cm in size, I suppose you could work up how many photons you need to have coming in to be visible to the naked eye on Earth, of course depending on atmospheric conditions and Lunar conditions (lit by the sun, dark, in between) So you could just figure out how many photons would get back to Earth from a laser on the moon. No idea how many that would be for say 100 watts delivered though, not sure exactly just how many photons are in 100 watts of laser light and how many photons the eye needs to get to register as light, also how many more photons the eye needs to register color.