A Milky Way Size Particle Collider? | Bullaki Science Podcast Clips with Sabine Hossenfelder

Why would we need a particle collider of the size of the Milky Way or a detector of the size of Jupiter orbiting a neutron star and?
Sabine Hossenfelder is an author and theoretical physicist working on the foundations of physics. To be more precise she describes herself as a phenomenologist rather than a theorist. She is a Research Fellow at the Frankfurt Institute for Advanced Studies where she leads the Superfluid Dark Matter group. She is the author of ‘Lost in Math: How Beauty Leads Physics Astray’, which explores the concept of elegance in fundamental physics and cosmology. More importantly she’s an outstanding science communicator, who has attracted a huge audience on her CZcams channel, where she publishes explanatory videos on topics related to physics.
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SH. So if you naively try to estimate at which energy scale in a particle collision, the effects of quantum gravity would become as strong as the effects of the other interactions, then you get something, that’s called the Planck energy, which is like ~10^15 TeV. The Large Hadron Collider reaches around 14 or something TeV. So there’s like this 14 orders of magnitude gap between what we can presently do in an experiment and the energy scale that you would need to reach to produce an appreciable number of gravitons, say, so that you could actually measure them.
Then that’s the question like, what would it take to actually build a particle collider that could reach this energy and this is when you get this estimate with the size of the Milky Way. This is assuming you use the technology that we currently use for the Large Hadron Collider.
So you just scale this up. And the story with the detector the size of Jupiter is what size would a detector need to have to detect individual gravitons. You can do that if you have a detector to the size of planet Jupiter, if you put it in orbit around a neutron star, and then you wait for 10 years, something like this. So you get all these completely ridiculous numbers.
But as I was just trying to say, I think that these estimates are very misleading, because they are entirely different effects of quantum gravity that are much easier to observe. So you don’t necessarily need to actually produce or measure gravitons. To find evidence for the quantization of gravity, it’s like you don’t actually need to detect single photons to find evidence for the quantization of the electromagnetic interaction. You can see this, for example, in the spectral lines in atoms, or just by the existence of atoms, basically, you need electromagnetism to be quantized. Otherwise, it just doesn’t work.