A second big bang? The radical idea rewriting dark matter’s origins

POP the kettle on. Sit down and listen closely to the bubbles of water vapour as they expand, collapse and collide. You have just run an experiment simulating the big bang – the very origin of the universe – and you may also have solved the mystery of how the cosmos got its dark matter.

Well, sort of. Because by mulling over colliding bubbles on a cosmological scale, physicists are finding cause for speculation about fresh sparks of cosmic creation. It is possible, they say, that in the weeks after the big bang there was a second, similarly profound moment of transformation. This one may have spawned monstrous shadow particles trillions of times the mass of those that make up normal matter and could make sense of the mysterious, invisible matter that seems to hold galaxies together.

As outlandish as it might sound, the concept of a “dark” big bang is broadly in line with a quiet revolution that is already under way, as cosmologists rewrite what we think of as the standard big bang to account for multiple distinct “phase transitions”, each leaving its mark on the cosmos. What’s more, we now have the tools to test this idea by peering into the universe’s earliest moments and untangling the faint ripples produced by these profound primordial shifts.

If we find evidence for the dark big bang among them, it would not only transform our view of the early universe, but also offer fresh clues about the nature of dark matter and how we might finally unmask its identity.

We think that dark matter exists because it solves several astronomical headaches. …