In one of the first classes I’ve taken in graduate school, a peer asked whether we thought gravity pushes or pulls. I was stuck between the two, but since everyone else agreed that gravity pulls, I didn’t say much and have been mulling it over ever since.
I finally figured out why I couldn’t settle for one or the other: relativity.
The reason we jump to the conclusion that gravity “pulls” is because that is how we experience gravity. We feel the gravitational force of the earth pulling us toward its surface – we call it falling. However, imagine you are at some fixed point in space looking at the interactions between the earth and the moon. This is where relativity comes in – you are able to observe Earth and its moon interacting from a fixed point not on the surface of either planetary object being observed. In essence you have never experienced gravity and can only draw conclusions based on what you see. The two objects seem to move towards each other, a phenomena we tend to describe as attraction. But what if that’s not what’s occurring? Just because we describe it as “pulling” doesn’t mean the gravitational force isn’t “pushing”.
What if, in the galactic scale, gravity behaves otherwise? Of course, I’m not in a position to test this hypothesis, but I think it is worth considering. Physicists must be in the practice of considering what reality would be like if the opposite of every scientific law and theory were true. Otherwise, scientific developments such as Quantum Mechanics never would have occurred!
I’d be interested to hear your thoughts!