What Does Negative Mass Mean? Part 2

Negative mass appears in some exotic theories of physics, but it's never been clear to me how it would work, so I tried to break down in Physics 101 terms.

Here, I discuss continuous forces on hypothetical negative-mass objects, following up on the previous discussion of collisions. It turns out that they don't always punch backwards through the thing that's pushing them. It's the total mass of the system that matters.

[like]

-2 kg: *Hits 5 kg*
5 kg: COME HERE YOU LITTLE SH*T!!!

[FinetalPies]

I think I will introduce objects of negative mass as a cursed item in my D&D campaign to confuse my players, thanks for the inspiration!

[L.Mandrake]

Since we don't have a definition for how forces act on a negative mass, maybe it would be best to use Lagrangian mechanics: no forces, only energy.

[Badspot]

Wrapping around infinity like that is a good indicator that you're missing some theory or using the wrong coordinate system. For example, imagine you're studying lines and angles but only know about y=mx+b. As a line goes vertical, the slope approaches infinity and then wraps around - it doesn't make any sense. But with the knowledge of polar coordinates or trig functions, it's much easier to work with.

It's the same with negative mass, negative energy, black holes and other seemingly intractable math problems - we're just missing some key insight that puts the problem into a manageable state.

[Scrogan]

Considering that particles frequently scatter off one another elastically just due to their electric charges, if you had a positive mass electron and a negative mass electron, their equal and opposite masses would give you that awful error as soon as they’re close enough for their electric fields to influence one another. Which is infinitely far away. Whoever thought that antimatter could have negative mass is really pushing it.

I wonder what negative mass means to other particle things, like E^2 = (mc^2)^2 + (pc)^2, the debroglie wavelength and the wave nature of a negative mass particle in general, the uncertainty principle, maybe even GR. Might be funny to calculate the momentum-neutral reference frame between the collision of a positive and negative mass.

Considering a mass-based sinusoid turned into an exponential, I wonder if other mass-based exponentials will turn into sinusoids? Like linear friction, or newton’s cooling law, etc. Or if some sinusoids turn into exponential decays instead of increases. It all reminds me of quantum tunnelling, where the boundary conditions are such that the sinusoid smoothly transitions into an exponential because the energy is negative, then back into a sinusoid on the other side. Guess maybe you’d store a negative mass particle in a box with a repulsive force instead. Trying to imagine electron orbitals like that will get strange quickly, no doubt.

[matthewparker]

Fron what I can tell, not having given it any deep thought, the microphysics of negative mass are conceptually easier to understand than the macrophysics of negative mass and contact forces.

Can't wait for a part 3.

[piolix]

Really enjoying this, looking forward to see more.
Also appreciate the use of 3B1B's Python engine :D

[MrCheeze]

My man really came up with a research paper's worth of material and then animated it for us to watch online for free :D

[congruentcrib]

Can I just say this guy has been handed gold from YouTube for making his video appear in the recommended. Typically view count is 100-300… negative mass videos 100-150k views. Along with that he breaks down the fundamentals and explains it well. Happy to subscribe! Love to hear more.

[GusCraft]

My favorite is that friction causes negative mass to accelerate, so if left alone it will speed up.

[trevorclinton]

In the band theory of conductors, it is possible for an electron to have negative effective mass. This is quite common in semiconductors. The negative effective mass of the electrons causes the “holes” to have positive effective mass.

[eufalesio]

I really like this series, it's a very interesting and yet unintuitive concept, yet you explain it intuitively.

[Mitch_Rogoff]

It makes some intuitive sense that a negative mass would pull an object with it away from the direction of force, because that would let you put it on a scale and have it read a negative number

[ismaelbrowne]

I found your other video 4 days ago, and seeing you hadn't posted part 2 in months, I tought it would never come, but here it is!! Excited to watch this

[robheusd]

Part of the weird behaviour of negative masses in Newtonian physics is due to the fact that the direction of force would be opposite to the direction of the acceleration. But this is not the only option, we could relax this by making the assumption that the equaivalence of inertial mass and gravitational mass is not strictly true, only the square of the inertial mass and the square of the gravitational mass are equal. That would leave us with 4 options, two signs for two different types of masses. If for example it is assumed that inertial mass is always positive, this would get rid of the weird behaviour in which the direction of force applied to a mass is opposite to the direction of acceleration of the mass.
In that case only the gravitational mass can be positve or negative, and the weird effect of a negative mass chasing an equal but opposite positive mass would also disappear - same sign masses would simply attract, and opposite sign masses would repel each other.

[benG]

I really hope you do that part 3, I'd like to see a physicist tackle what kind of structure a negative mass particle could form and how to handle it's interactions with normal matter.

[chirpter]

You are really smart and I really enjoy the way you ruthlessly simplify complex topics to first principles and straightforward models to mechanistically and more easily understand them. Great stuff

[kusyalxix]

Again, some interesting shit to watch at 3 am. thank you

[Law-gnome]

In the book Timemaster, Robert Forward explores a lot of what negative matter could be used for (light speed travel, warp gates, etc.) His interpretation of negative matter and positive matter physically interacting was that the two objects would nullify each other - essentially cancelling each other out of existence. 1-1=0 and all that.

[MrRyanroberson]

This was uploaded only a couple days after i watched the prior video and this is very satisfying to have available