system
Given the following post, respond as if you're commenting on Reddit:
human
What does it really mean that the electromagnetic force and weak force converge at high energies?

I did my undergrad in physics at MIT, so I'm pretty solid on quantum mechanics and E&M, but I've never had a good intuitive understanding of what it means that the electromagnetic force and weak force converge at high energies (the eletroweak force). I've encountered this idea in pop-science books and it was touched on in classes, but I'm hoping someone here can explain it more. (and if possible, explain symmetry breaking and the role that photons and quarks play in these two forces)
gpt
Yeah hard to explain without maths thought. There is some tool called gauge transformation, when you input a symmetry and do the transformation you can deduce the equations of motion of a particle and the fields associated. 

For example: we know the group of symmetry related to  the equations of electromagnetism (mathematically we call it U(1) ). When we use U(1) we deduce all laws of electromagnetism.

Now we can try higher symmetry groups (based on the reaction symmetries of the experiments in nature). When we input U(1)xSU(2)l (related to weak processes) we get four bosonic fields with zero mass. Yet the experiment tells us weak bosons have mass.

To fix this we use the Higgs mechanism to "break the symmetry". Now the theory predicts that at ground state (low T) there are two charged boson and a neutral boson with mass that correspond with the W^(+/-) and the Z boson that we find experimentally. The fourth particle has no mass and corresponds to the photon. 

At high T however all the W,Z and photon must mix  to give the real 4 bosons predicted originally of one unified force called electroweak force.

Hope it helps.