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“A period of rapid expansion, ‘cosmic inflation’, likely happened before the hot Big Bang”

COSMOLOGY

Could dark matter have existed before the Big Bang?

Depends on what is meant by the Big Bang. If it refers to a hypothetical ‘Big Bang singularity’ where time began, then no. If it refers to the ‘hot Big Bang’, then the answer can be yes.

What cosmologists mean by the term is the state in which the universe was 13.8 billion years ago. At that point the universe was compressed into a tiny volume, hence its matter content – the matter that today comprises galaxies, stars, planets and us – was very dense and hot. This ‘hot Big Bang’ state left behind an afterglow that cosmologists now call ‘cosmic microwave background radiation’. By measuring it we can directly see an image of the Big Bang and deduce what happened during it.

However, it is possible that there were epochs that preceded the hot Big Bang era. For example, a period of rapid expansion dubbed ‘cosmic inflation’ likely happened before the hot Big Bang. That