Two questions...?

Question

Since gravity attracts two massive bodies, why is it then that the Moon is actually moving further and further away from us and why doesn't it just plummet towards the Earth?

If everything in the Universe is moving away from each other why is it that the Andromeda galaxy and our own galaxy are moving towards each other?

Answer 1

There are points of gravitational balance and the moon has passed beyond that point so it is slowly moving away from the earth. I can't say the exact forces that moved it beyond the point of no return but after billions of years of collisions from comets and meteors, the tug of Jupiter and Saturn and the fact that the earth's orbit isn't perfect all those forces put a little energy into moving the moon.

When the big bang exploded it sent the contents of the universe moving in random directions and expanding. The Milky Way has the misfortune to be on the same path that the Andromeda galaxy is cruising on. Eventually the gravity of the two will force a collision. Since the super massive black hole in the Andromeda Galaxy is larger than the one in our galaxy Andromeda will gobble us up.

Due to the nature of the universe there is no center it just expanded in random directions and at random speeds. The galaxies and intergalactic objects are expanding the galaxies themselves will be stable since they are organized around a gravitational center. We don’t know the exact course of all the interstellar objects and in the past they may have influenced the movement of others; changing their path or even speed or slowing them down. It is also possible that our local galactic group could be orbiting around a larger structure. The Magellanic clouds seem to deny this; but they may just be cruising by because they are moving faster.

The sun will not have gone into its red giant phase by the time of the collision so there is a small chance that we might actually survive and the earth could be a witness to the collision. Of course few stars will actually collide, instead the force of gravity will have its say moving and shifting the planets and stars around.

Answer 2

The universe is expanding on a large scale, but that doesn't mean EVERYTHING is moving apart. The atoms of your body aren't getting further apart, for example, even though people are spreading further apart. Even on the scale of galaxy clusters, gravity still acts to keep the galaxies bound to each other.

Some of the galaxies will pass each other and continue on a slightly different path. Others, which happen by chance to pass closer, will pass through and distort each other several times before settling down into a larger single galaxy.

The moon doesn't fall to Earth because it is moving at just the right speed to balance the attraction of gravity.

Answer 3

the moon's velocity is fast enough to fight the pull of gravity, yet not fast enough to completely break free.
http://science.howstuffworks.com/satellite3.htm

we're still "uncertain" HOW the universe is truly expanding.

"Although we see galaxies moving away from us in all directions, this does not mean that our galaxy is in the center of some sort of explosion; observers in other galaxies would see the same thing. It only means that the space between all galaxies is growing larger."
http://hubblesite.org/reference_desk/faq/answer.php.id=49&cat=cosmology

the gravity of galaxies could alter the courses of other galaxies over time as they pass and/or "hit" others.

our milky way has already been hit by another galaxy (an elliptically looped shaped satellite galaxy, called the Sagittarius Dwarf galaxy) (if not more) and we have "joined with it"
http://en.wikipedia.org/wiki/Sagittarius_Dwarf_Elliptical_Galaxy

That could have changed our angle of trajectory when we connected, sending us in a direction other than "forward". The same could go for the Andromeda galaxy.

thumb me down if you want, but you asked for reasons and I gave them to you.