Empty space is not empty: The mind-blowing idea of virtual prticles | Don Lincoln and Lex Fridman

Added: 2026-06-04

[00:00:02]Since we brought up antimatter, we have to talk about it. Uh you've talked about in several of your lectures from different angles including uh the dark energy crisis and including uh empty space and vacuum and so on. So let's look at the empty space angle. So uh you know turns out that empty space is not empty.

[00:00:25]>> It's true which is kind of bizarre. Can you can you speak about what do we know about what makes up empty space?

[00:00:32]>> That's a hard hard question because we don't know what space is. But let's start out.

[00:00:38]>> Let's just start out with something simple. We'll assume that space is not quantized. Okay. Now, it probably is. I don't know. But, you know, we got to start with somewhere. So, let's start out with sort of the space of calculus.

[00:00:52]The space that you can divide forever.

[00:00:55]The modern version of quantum mechanics is called quantum field theory. And it postulates that a space exists. Then it postulates that within space there exist fields for every known subatomic particle. So there is a photon field, there's an electron field, there's an up quark field, there's a down quark field, there's a all the fields.

[00:01:20]And those fields can vibrate. And when they vibrate, those are the subatomic particles. So an electron field vibrating in a characteristic way is an electron. Now, it's also possible for the electron field to vibrate not in the characteristic way, but in a way that's still vibrating, but it's not an exact electron. So this is what we call virtual particles. Now, virtual particles, there are lots of ways to talk about them. And the way I'm talking about now is the most correct and the most sophisticated way that we can talk about them. I will talk about them briefly in a in a simpler way to help.

[00:02:07]But right now that's the important thing is that there are these fields specific vibrations are the known particles.

[00:02:14]Vibrations that are a little different are are these virtual particles. They're particles that don't truly exist.

[00:02:22]And so that is what we think space is. There is all of these these these fields they are all vibrating a little. If you insert the right amount of energy you can get it to vibrate in the characteristic way and make that subatomic particle but even when you don't there is um the particles I mean the fields are there and they are vibrating. So those vibrating vibrations are what we called virtual particles.

[00:02:50]Now your viewers may have heard of virtual particles in other ways in which case it says that space is just empty and what happens is matter and antimatter particles briefly appear for a very short period of time before they coalesce back again and disappear and and reemerge back into the field. And so that these are both correct. So what happens is is that's what quantum field theory says is it says that these ripples are hearing or these particles are appearing and disappearing. And so that just sounds nuts. You look at empty space, you're not seeing anything happening, but they're happening fast enough that they can't be seen. But they do have consequences. And there are two experimental measurements that I can think of that validate that this thing that sounds crazy is really happening.

[00:03:42]And one is called the Casemir effect. So in the casemir effect you take two metal plates that parallel plates and you put them near one another very very close.

[00:03:54]Now if this is the case if if these virtual particles exist then in between the plates these particles appearing and disappearing and outside the plates the particles are disappear appearing and disappearing. However, because these plates are close to one another, this puts a constraint on the wavelength of the particles that can occur between the two plates because they the particles cannot extend outside the plates. So the shortwavelength particles can exist inside the between the plates, but the longer ones cannot. However, outside the plates there is no constraint. So short wavelength and long wavelength particles can exist there. And the net effect is there are more particle virtual particles outside and less particles inside. And therefore you have a net pressure which would then push those two plates together. That is a prediction we've been talking about. And guess what? It happens. Those plates push together. So that is a validation for the existence of these particles in empty space. Now there is another measurement and this changes the magnetic properties of particles like the electron the muon and and so forth and so this was uh discovered in 1948.

[00:05:13]So if you take old school standard quantum mechanics um you know the spin of an electron you know its charge you can calculate its magnetic moment and it comes out to a number. If you do the measurement, what you find is the measurement disagrees with the quantum mechanics, the 1930s quantum mechanical prediction by 0.1%. And that was measured 1948 and people went, "Huh?" So this happened at the Shelter Island conference in New York. And on the way home, someone who saw the this measurement thought about it and they invented what we now call quantum electronamics. So old quantum mechanics quantizes matter. The second quantization quantizes both matter and the fields. In this case, quantized the electric fields. And so in this quantized um field, it predicts that surrounding a bare say electron which is spinning and has a has a charge, there is this this bath of particles, virtual particles appearing and disappearing all around it. And the ensemble of all of those particles appearing and disappearing will alter the magnetic properties that you can measure for the subatomic particle. and it changes it by 0.1%. And we have measured this and we have not measured this imprecisely. We have measured the magnetic properties of both the electron and the muon to 12 count them 12 significant figures. And the theory and the data agree number for number for 10 places. And then once you get out to the very end where both the theory and the data have some imprecision, they then disagree. And so maybe there's some interesting stuff going on there. But 10 figures, it's just staggering. So virtual particles refer to matter and antimatter particles coming to life.

[00:07:23]>> Correct.