What if gravity reversed?

Answer 1

We would be in really big trouble. Celestial bodies such as the Sun, but also the Earth and Moon are kept intact due to gravity. If gravity would reverse, that is, if matter started to repel each other, our planet would be blown up.

A planet simply could not exist, it would be like trying to build a planet using positively charged particles. They repel each other and you would need some additional (powerful!) force to overcome it.

Luckily it can be shown that any force originating from coordinate invariance, which means that the laws of physics are the same for every observer, which is the case for general relativity, that such a force must be attractive. It simply cannot be repulsive.

Answer 2

If gravity were to reverse, everything on Earth would be pulled away from the surface and into the sky. This would lead to chaos and destruction as buildings, vehicles, and people are lifted into the air. Survival would be extremely challenging in a world where gravity is reversed.