John Carlos Baez on Nostr: In this thread I'm talking about the Great Stagnation in fundamental physics and how ...
In this thread I'm talking about the Great Stagnation in fundamental physics and how to get out of it. I want to get into some details without using any equations, so forgive me for being either too technical or not precise enough.
Why did people want so badly for quantum gravity to be renormalizable? Why was that the wrong thing to want? And what should we want instead?
This is a long story but let's start.
Renormalization started out as a trick to avoid infinities in quantum field theory. But in 1982 Kenneth Wilson won the Nobel prize for a better understanding of what renormalization is really about. The idea is that colliding particles at higher energies probes the laws of nature at shorter distance scales - and some physical 'constants' are actually different then!
Renormalization is the study of how this works.
For example, the charge of the electron is observed to be larger when we measure it by colliding electrons at very high energies:
https://www.sciencedirect.com/science/article/abs/pii/S0370269300001222
The reason is that around each electron there's a cloud of virtual particle-antiparticle pairs. The positively charged virtual particles are attracted to the electron while the negatively charged ones are repelled, as shown in the ludicrously oversimplified cartoon below. This cloud 'shields' some of the electron's charge and makes the charge seem smaller when measured at greater distances. As we collide electrons with more energy, we penetrate more of this cloud and the observed charge goes up!
So far, the measurements match our theories very well. But what would happen if we could collide electrons with arbitrarily high energy? Of course we don't know. But what do our theories predict?
(3/n)
Why did people want so badly for quantum gravity to be renormalizable? Why was that the wrong thing to want? And what should we want instead?
This is a long story but let's start.
Renormalization started out as a trick to avoid infinities in quantum field theory. But in 1982 Kenneth Wilson won the Nobel prize for a better understanding of what renormalization is really about. The idea is that colliding particles at higher energies probes the laws of nature at shorter distance scales - and some physical 'constants' are actually different then!
Renormalization is the study of how this works.
For example, the charge of the electron is observed to be larger when we measure it by colliding electrons at very high energies:
https://www.sciencedirect.com/science/article/abs/pii/S0370269300001222
The reason is that around each electron there's a cloud of virtual particle-antiparticle pairs. The positively charged virtual particles are attracted to the electron while the negatively charged ones are repelled, as shown in the ludicrously oversimplified cartoon below. This cloud 'shields' some of the electron's charge and makes the charge seem smaller when measured at greater distances. As we collide electrons with more energy, we penetrate more of this cloud and the observed charge goes up!
So far, the measurements match our theories very well. But what would happen if we could collide electrons with arbitrarily high energy? Of course we don't know. But what do our theories predict?
(3/n)