To get an understanding of what causes gravity you need to start by understanding what 'energy' actually is, and luckily, we can see(1) it and we can touch(2) it, however, we can also feel(3) its effect on the bottom of our feet.
http://www.simplegravity.com/
gravity causes objects to fall
Matter causes gravity in the first place.
Gravity causes the ships iron anchor to sink to the ocean.
Earth is hafly big, so it has gravity. Larger, it has more gravity. Smaller, it has less gravity.
Gravity.
Gravity
Gravity
Gravity
gravity?
Gravity.
No. The earth has its own gravity. The lunar gravity causes tides on earth, but does not control earth's gravity.
It depends on how much gravity that causes stars to form. It depends on how big the star in the galaxies is.