What Was It Like When We First Made Protons And Neutrons?
“But at this stage, the biggest new thing that occurs is that particles are no longer individual-and-free on all scales. Instead, for the first time, the Universe has created a stable, bound state of multiple particles. A proton is two up and one down quark, bound by gluons, while a neutron is one up and two down quarks, bound by gluons. Only because we created more matter than antimatter do we have a Universe that has protons and neutrons left over; only because the Higgs gave rest mass to the fundamental particles do we get these bound, atomic nuclei.
Owing to the nature of the strong force, and the tremendous binding energy that occurs in these stretched-spring-like interactions between the quarks, the masses of the proton and neutron are some 100 times heavier than the quarks that make them up. The Higgs gave mass to the Universe, but confinement is what gives us 99% of our mass. Without protons and neutrons, our Universe would never be the same.”
The very early Universe looks nothing like our Universe today. Not only are there no stars or galaxies, but there weren’t any atoms or atomic nuclei. If we go back early enough, there weren’t even protons or neutrons, but free quarks (and antiquarks) instead. This era lasted for just 10-to-20 microseconds in the early Universe, but the story of how we went from a quark-gluon plasma to a Universe filled with protons and neutrons is a fascinating true part of our shared cosmic history.