# Why can increasing energy, the weak force and the EM-force become a similar force?

When the heat of the universe was much higher it seems that the weak force and the EM-force was combined into the electro weak force.

For a layman the EM-force and the weak force look quite different, doing different things. In a simplified example:

EM-force When two electrons approach each other they emit a (virtual) photon, repelling the two electrons. Or an electron and proton approach each other, they are attracted to each other, probably also by emitting a photon (?).

Weak force An down quark emits a W boson and turns into a up quark. The W-boson decays in a electron and neutrino.

In short, in the first force is a repelling or attracting force but in the second is a decay force changing a particle into another one.

I know there are more sorts of reactions, but for simplicity I use these ones.

The question is now how can these to very different looking reactions be one and the same when the heat of the energy was much higher? It would be nice if this could be explained in a bit of layman terms also.

• It's not that they become similar, it's that the hidden symmetries of the are no longer hidden. The (unbroken) weak isospin and weak hypercharge interactions are attractive/repulsive interactions as well as (for the charged W bosons), flavor changing interactions. Nov 6, 2017 at 0:56

• To be sure, the unbroken gauge bosons are three SU(2) bosons $(W^+, W^-, W^0)$ and one U(1) boson $(B)$. The $Z$ boson is a certain mixture of the $W^0$ and $B$ bosons and the photon is the orthogonal mixture. Nov 6, 2017 at 0:59