My son wants to know what would happen if the moon got much closer to the earth.
Also, if it got much farther away.
i told him if it were farhter, there would be no tides, and that would-what? kill a lot of marine life?
You’re pretty much on the right track. The tides are the major physical contribution that the moon has on the Earth. The moon getting closer would probably cause, on average, higher tides and more of a headache for Earth-based observational astronomers.
Also the moon getting farther away would make Earth based astronomy a whole lot easier. It’s a pretty bright beacon.
Altering the distance of the moon would certainly alter the strength of the tides. If the moon was brought in close enough, some nasty consequences would occur. The tides will get larger at an exponential rate as the moon gets closer. I can’t comment on what it would do to marine life if the moon was pushed further away, but I wouldn’t think it would be super drastic off the cuff.
What would happen to the moon if it was brought close enough is interesting as well. Look up roche limit in google to get some info on that
Odd thing to be contributing, but there might be (human)commercial impact from a reduction in tidal activity; some ports rely on channels being clear at high tide for ships to pass.
Southampton (my home city) has a ‘double tide’ due to the presence of the Isle of Wight; this is considered an advantage.
(Here is a tidal graph for Southampton Water - not the best example I’ve seen - sometimes the ‘shoulders’ are much more pronounced)
Like JS Princeton mentioned, proximity should have a direct effect on the amount of reflected light from the sun.
I’ve heard that back when the materials that would eventually become the moon were beginning to coalesce into a single mass, the moon was much larger than it was today and, therefore, much brighter. I can’t help but think this would have had an effect on nightime predatory hunters and their prey.
Tidal pools. Many a creature owe their existence to tidal pools.
Also, it may show up as a mass extinction event when all is said and done. So much of the food chain would be disruoted.
Additionally, it’s hard to account for everything from local climate changes, to algae formations, changes in breeding grounds/habits - sea life would take a big hit, as well as coatal life…
If I could bet, I’d say that in the end, it would go down in history as a mass extinction event.
Yahbut, the tidal effect of the Sun is just about half that of the moon. When they are aligned, you get 1 1/2 tide, the spring tide, and when they are at 90 degrees to each other (I forget what that’s called 
), you get (1 - 1/2) tide, the neap tide.
If the lunar tide were reduced to half, then the neap tide would be virtually zero, but the spring tide would be 1. If the moon were to disappear, we’d still have a tide on the order of a neap tide–but the semidiurnal high tide would always occur near noon and midnight.