What Does Negative Mass Mean? Part 1 #SoME1

Negative mass sometimes appears in theories of exotic physics, but it's never explained in a way that makes sense to me. So, I went back to basics and looked at how negative mass would behave in Physics 101. Weird stuff starts to happen like objects spontaneously accelerating, moving in the wrong direction, and more.

This is my entry for 3blue1brown's Summer of Math Exposition contest. Part 2 with spring forces and friction still to come.

[rascal]

I didn't understand most of the stuff in this video but I really liked when the blocks went "Clack" and then magically started changing directions

[Seethenhagen]

"How can you have less than zero stuff?"

Credit card debt is one way

[khoda]

Something interesting to think about is that stationary objects with negative mass actually have potential energy relative to when they're moving, so you can extract energy from them with accelerating them.

[NStripleseven]

Imagine you get a block of negative mass object and you walk into it and fall over backwards.

[IgroSome]

"If physics starts throwing 'divide by 0' errors, then there's a good chance you're doing something wrong."
Well said

[karicowo]

I just really like the idea of a real life div/0 error popping up if somebody ever were to collide two opposite masses in the future

[splitframe]

8:00 So the universe devs just said "Well we ain't gonna fix this division by 0 bug here with negative masses because the chance of it happening is too low"?
I wouldn't trust my universe with such slackers.

[azu]

Imagine making a piece of clothing like a belt out of negative mass and it gives you a boost to your real life speed stat

[Name_Pendingg]

the modle: 7:32
me: oh the bottom one just moves two cubes move twice as fast
the cubes: *deletes them selves*
me:

[TheGundeck]

7:30 It seems when + and - masses collide inelastically, the masses cancel, leaving only the sum of the mass remaining. So if + and - masses were exactly equal, you would have 0 mass remaining to go infinite (or light) speed, which is fine.

[lespiderweb]

Mass:*flees*
Antimatter:get your ass back here

[ValentineC]

I now want to see someone punching a negative mass punching bag and seeing how they react when it punches back

[rzu]

My expression during the 5kg Vs -5kg collision.

Oh... Oh no...

[tristanc]

Criminally undersubbed. You took a concept that is inherently complex and reduced it to a level that everyone can access. A mark of a great teacher to be sure!

[aaabbb]

At 9:58, you say that they're identical, but that's only because you assumed that the negative mass block would change direction upon hitting the infinite mass block.

Nothing in the equations of conservation of momentum and energy says which way the blocks have to move after the collision (a solution where the blocks pass through each other is equally valid under these equations). This is fine with regular physics, since there's obviously only one direction that prevents the blocks from going through each other, but when that's literally the question we're asking, all we've done is assume our conclusion.

[petergilliam]

Great video! the Nuclear explosion made me laugh out loud. Please continue making these videos

[invalidmember]

I feel like a 3D first person puzzle game with this kind of this would be such a cool idea

[kuserosu]

Finally some interesting shit to watch at 3 am

[Scrogan]

Ooh I love this! Another interesting thing to think about is if inertial mass and gravitational mass are not intrinsically equal to one another. Such a notion isn’t compatible with GR as it violates the equivalence principle, but hey we can dive into the world of science fiction whenever we please. If you define that exotic matter has a normal inertial mass but an inverted gravitational mass, you get normal conservation of momentum and a rather nice coulomb-like negative gravitational force. Normal inertial mass with small perturbations from its normal gravitational mass on the other hand would give you a hard time noticing the difference in the first place, and an even harder time trying to seperate them since centrifuges won’t do anything.

Also I want to see plausible physics behind gravitational flux expulsion, because that could give some much more interesting antigravity.

[syllabusgames]

The clicky sound returns!
Thank you for showing the math for every collision. Your explanations were good enough that I didn’t have to read them, but if I was ever confused by an interaction, having the Physics 1 math available is a good second chance to understand what’s happening.
I’ve been going through the SoME1 submissions, giving people feedback, and honestly, your video didn’t have any problems I noticed. It’s well paced, everything is clear, and if someone started talking to me about negative mass interactions, I think I could explain the main points of the video to them. You stuck to 3B1B’s video format rather closely, but he uses it for a reason. It works well.