[Physics] Was everything in the Universe “created” from light

big-bangcosmologyuniverse

Is the following true?

The only matter existing directly after the big bang was electromagnetic radiation.

Best Answer

No.

We don't know what happened in the very early stages of the Big Bang because we have no experimentally tested theory that takes us back that far. However, courtesy of the LHC we have an experimentally tested theory that takes us back to a time called the electroweak epoch, and we can use this theory to answer your question in the negative.

Electromagnetism is a low energy effective theory. It works below energies of somewhere around a teraelectron volt, but above that energy it has to be replaced by a unified theory of the electromagnetic and weak forces called (somewhat obviously) the electroweak theory. The discovery that proved this (not that anyone seriously doubted it) was the discovery of the Higgs boson at the LHC in 2013.

Anyhow, the electroweak theory tells us that during the electroweak epoch there were four massless vector bosons. At low energies these become the Z, W$^+$, W$^-$ and the photon, but above the electroweak transition the four bosons were indistinguishable.

I confess I don't know how to calculate the particle content during the electroweak epoch, so I shall say nothing further on the subject. Nevertheless we can be confident that whatever was floating around at those energies was not just photons.

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