Transcription
If you trust physicists, then you're surrounded by virtual particles that constantly pop into existence and then immediately disappear. That sounds crazy, I know. And yet, a new experiment just proved that virtual particles are real. That's a big deal for our understanding of empty space and just what quantum physics actually means. Let's have a look.
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And now back to the science news. The question of what virtual particles are is symptomatic of the current problems in the foundations of physics. One perspective you can take is that it's just a weird name we give to some parts of the mathematics. It doesn't mean anything. Shut up and calculate. On the other hand, that math certainly looks very much like the things we call real particles, though with the caveat that they don't obey Einstein's E=mc². Albert doesn't like this at all. For what the math is concerned, we know that it checks out. The presence of virtual particles, for example, very slightly changes the electric field around an atomic nucleus. It's a tiny change, yet it can and has been measured. But does that mean that there are really particles there popping in and out of existence? How would you even test that?
This is where the new result comes in. It's a paper from the STAR collaboration at the Relativistic Heavy Ion Collider, RHIC for short, at Brookhaven Lab in the United States. For particle colliders are concerned, this one is in the medium to high range. For this experiment, they use proton-proton collisions at a center of mass energy of about 200 GeV. That's about 10 times less than what the Large Hadron Collider can achieve. In this experiment, they test a specific picture of virtual particles. You see, the strong nuclear force that keeps atomic nuclei together has a strange property. It gets stronger the larger the distance between particles. For the electric and magnetic interaction and gravity, it's the opposite. They get weaker the larger the distance. A simple way to understand the strong nuclear force is to imagine that the two particles are connected by a string that can stretch. The more you stretch it, the more energy you need and the harder it gets to stretch it further. This is loosely speaking where string theory originally came from. And this string is full of virtual particles and antiparticles.
Now, in this experiment, they slam protons into each other. The protons are made of quarks. Some of these quarks get torn apart and between them, you get this highly energetic string of virtual particles. But if you pump enough energy into the string to push the particles, the quarks further apart, you'll never succeed in getting a single quark. Instead, the energy becomes so high that the string breaks and creates a new particle and antiparticle pair. Then each of the new particles is bound again with other quarks. It's a consequence of what's called confinement. The reason why we can never see quarks in isolation. But this breaking of the string converts a virtual quark-antiquark pair into a real quark-antiquark pair. And that pair of quarks is now contained in two separate composite particles.
In the paper, they look specifically at so-called lambda particles. These then decay and from the decay products, they can reconstruct the spin of the lambdas. And now here's the thing. The spin of the lambda pairs correlated, which means that their constituents share a common origin. So this proves that the virtual particles were there and then became real. And yes, this process is very similar to how Hawking envisioned the particle production near black holes works, except that in this part, the pulling is done by gravity. You can still argue about the interpretation. You can say the correlation came from the quantum state rather than from virtual particles. You can say the language of virtual particles is just a convenient way to describe that quantum state. The virtual particles aren't really there. But I think this is nonsense because you could use the same logic to argue that real particles aren't really there. They're just convenient math that we use to describe observations. For I'm concerned, if the math describes observations correctly, that is what it means for something to be real. If not, I'd like to reinterpret my text slip, please.
So, this isn't just philosophy. I think that the question of what the vacuum is matters for the question of what space is. Is there really anything more than virtual particles around us? Or is the relation between the virtual particles themselves what creates space? I think physicists don't spend enough time thinking about nothing. The Relativistic Heavy Ion Collider, by the way, ceased operations in February, and Brookhaven is now building a new partner accelerator called the Electron-Ion Collider. It's remarkable for almost for how little you've heard of it. Good thing you have me to keep you informed, though, so don't forget to subscribe. Thanks for watching. See you tomorrow.