Hornbein said:
According to Sabine Hossenfelder in the extremely early Universe nothing had mass because the electroweak symmetry was not yet broken so there was no Higgs field. Am I correct in thinking this is not controversial?
https://youtu.be/9-jIplX6Wjw?t=638
Some of the previous discussion got very technical for a B-level thread. I'm going to attempt to boil it down more simply.
At high energies, which can be calculated to quite a bit of precision in the Standard Model, all of the particles in the Standard Model (i.e. quarks and leptons and W bosons and Z bosons) cease to get rest mass from the Higgs field.
At energies quite a bit lower than that, temperatures are still too hot for composite particles made of quarks and gluons (which carry the strong force) to hold together.
Instead, these particles form what is called a "quark gluon plasma" which is a big mush of quarks and gluons.
In contrast, at lower energies quarks and gluons "confined" in small lumps called "hadrons" that are bound by the strong force with only a few primary quarks each (called valence quarks). Hadrons also have a "sea" of other short-lived or "virtual" particles that pop into and out of existence, however, which is how things which aren't primary components of a proton, for example, can pop out of a proton-proton collision at high energies.
Sabine is oversimplifying (or being oversimplified in paraphrase) in saying that nothing had mass.
No fundamental particles had "rest mass" but the universe still would have had vast amounts of mass-energy at that point (mass is equivalent to energy for gravitational purposes) with sources other than particle rest masses. Also, some particles have a trivial portion of their mass that is due not to its Higgs field interactions, but to other sources (such as the strong force component of the W boson mass).
A bunch of quark-gluon plasma, for example, would have a finite, well defined gravitational mass and would require the application of force to move in space-time with change in velocity (a.k.a. acceleration) equal to the amount of force divided by the mass to be moved.
Figuring out how all this would have played out, however, is not easy.
This is because all of the Standard Model laws of physics are affected by energy scale, not just the Higgs field. For example, the strength of the strong force, the weak force, and electromagnetic force are all different at very high energies than they are a energies comparable to the part of the universe in which we live now, which has been at this low energy state for the vast majority of the 13.8 billion years of the universe.
Between the energy scale of our era and the energy scale of electroweak symmetry breaking, electromagnetism gets stronger, while the strong force gets weaker.
It also isn't just a matter of tweaking the strength of forces and other constants of the Standard Model. Electroweak symmetry breaking involves a phase-like change in the set of allowed particles that exist in the universe, at least on the force carrying fundamental boson side. The familiar set of particles (to physicists) of W bosons, Z bosons, photons, and the Higgs boson are replaced by a different pre-electroweak symmetry breaking set of possible particles. The predominant assumption is that the Standard Model fermions had come into existence via baryogenesis and leptongenesis
before electroweak symmetry breaking, and that before that point there were
the three W vector bosons and one B vector boson, none of which had rest mass. These different carrier bosons also jumble the version concepts of electromagnetism and the weak force, in addition to the Higgs field, as the distinct forces we know them to be in our era.
In the history of the universe, this is believed to have happened shortly after the Big Bang, when the universe was at a temperature 159.5±1.5 GeV a.k.a. approximately 10
15 Kelvin (assuming the Standard Model of particle physics).
This is all taking place starting
a billionth of a second before the Big Bang and ending a 100,000th of a second after the Big Bang, when the observable universe (assuming spherical symmetry) had a radius similar in order of magnitude to the size of the inner solar system. It is close to the boundary between solid scientific prediction and educated scientific guesswork and speculation.
Anyway, that's what should happen if the universe behaves at high energies as a straight extrapolation of the laws of physics we have devised that at tested experimentally up to the energy scales of the Large Hadron Collider.
We don't have any particularly good reason for something different that what the laws of physics predict should happen at that scale to occur. But we also have no direct empirical evidence that can confirm that this is what happens either. The temperatures at this point are many orders of magnitude higher than anything we have directly observed.
We also don't have a consensus theory about how quarks, electrons, muons, tau leptons, and neutrinos (collectively the "Standard Model fermions"), came into being in the first place. The process by which this happened is called baryogenesis (for quarks) and leptogenesis (for electrons, muons, tau leptons, and neutrinos), and we don't know how, when, or why any of these things happened, although we can narrow down the "when" part to an extremely small window of time at or after the Big Bang.