I could prove that there is gravity.
!. Everything is being pulled down. FACT
2.All falling objects fall at a specific acceleration dependent on it's height from sea level. FACT(was gonna say from center of earth, but.......)

1. Everything's weight is determined by it's mass times the gravitational acceleration, at sea level about 32 ft. per second.

There is gravity, but gravity is an effect, not a cause. No one knows the cause of gravity. Newtons laws are correct and have been used by engineers and architects for nearly 400 hundred. Skyscrapers, airplanes bridges, etc. wouldn't be possible without them.