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. Archive link: https://archive.li/YH6tl