Grant Sanderson, of the excellent 3Blue1Brown math YouTube channel, has set up a contest for new creators to make math videos, called the Summer of Math Exposition. Well, this isn’t my first math video, but in the spirit of the contest, I did take the opportunity to try something new. This is the first video I’ve made with the Manim Python library (a version of Sanderson’s code to help make cool animations) and the first that I’ve done with a serious effort at video editing.

For my entry, I chose a topic that’s been on my to-do list for a while: negative mass. Negative mass appears in some theories of exotic physics. (For example, it’s needed to make warp drives work.) However, it doesn’t seem to be in any rigorous way. The actual scientific theories seem to be mostly of the “assume a particle with negative mass” variety.

But the bigger problem, as I explain in the video, is that I’ve never seen negative mass explained in a way that made sense. If you try to work out how it works, you always seem to end up with objects passing through each other. So, for this video, I went back to the most basic level. I plugged negative numbers into the equations of motion to see what happened, and it turns out, I didn’t get objects passing through each other. I got objects exerting negative forces instead. Watch the video to find out what I found.

There is more to come. It’s going to take at least one more video to fully address how negative mass ought to work, since I only had time to do basic collisions in this one. Stay tuned for the next installment.