would it effect our earth if the moon was 15,700 miles nearer to earth? how about 70,000 miles closer? why?

Much closer than that, dont forget the moon was formed as a result if a colliision. The oldest fossils are recods of sinlge celled about a billion years old. By looking at thekr life cycles, almost like looking at tree rings, scientists have learned some cool things.

There were many more days in a year then, more than 400, which means the days were much shorter at about 18 hours.

Tides were instead a few fet betwen high and low, as much as 50 feet high. These much more pwerful tides would sweep much further inland acause great erosion that may have created the siuo of elements that allowed life to form.

the fact that we have gold and other rare elements close to the surface is a result of the collision too.

So a pretty good thing we had the moon closer.

The Moon is receding at 4 cm per year. That is 0.04 m per year

4 m per hundred years

4 km per 100,000 years

40 km per million years.

15,700 miles is 25,120 km

That would be approx. 650 million years ago.

There was already life on Earth at the time, although it was mostly unicellular life.

70,000 mi (112,000 km) would have been 2.8 billion years ago. Difficult to say if there was life around that time. Some people say yes.

The biggest influence of the Moon would have been tidal. The tidal "force" (it is actually a "gradient" which is a derivative of the force), varies as the inverse of the CUBE of the distance.

The present average distance is 384,000 km.

If we reduce this distance by 25,120 km (15,700 miles), then the tidal force caused by the Moon would have been (384,400 / 359,280)^3 = 1.225 times what it is today (22.5 % stronger). Enough of course to have much stronger tides back then. But not enough to actually destroy things.

If we reduce the distance by 112,000 km (70,000 miles) the tidal force increases by a factor of

(384,400 / 272,400)^3 = 2.81

The Moon's contribution to the total tidal force would have been almost three times what it is today (the Sun's contribution would not change and, in that respect, would represent a very small portion, way back then).

This is certainly big enough to prevent life to get a foothold "on the margin" (the tidal zone between low and high water). This may explain why unicellular life did not evolve into multi-cellular life 2.8 billion years ago, but why it began to do so 650 million years ago.

There could be life on earth, but much of it would exist away from the shores and in the oceans. If the moon was closer to the earth, it would have greater gravitational impact on the earth. The moon causes the tides, and so the tides would rise and fall by a greater distance, traveling much father inland. Places close to the ocean would be periodically flooded. Therefore, the cities that exist along the ocean today would may be flooded periodically if the moon was that much closer to the earth.

Well at one time the moon was very close to the earth. It has been moving away from the Earth at about a rate of 1&1/2 inches per year, or something close to that. According to what I watch on TV something collided with the earth and threw up enough rock to form the moon. If it was closer the tides would be more pronounced, if it were farther they would be much less. It may also have some affect on the stability of our rotation but you will have to check on that as I am going from memory. There would still be life on earth but who knows how it may be different.