Drops from a leaky faucet beat a clear rhythm. A similar rhythm, only on the scale of the universe, has been found by astrophysicists: the formation of primordial black holes — tiny objects born in the first moments after the Big Bang — also proceeds not chaotically, but in a strictly measured way. The mass of such a hole grows not smoothly, but in jumps, as if repeating the same pattern over and over, but each time on a smaller scale.
Previously, this "rhythmicity" was known only for an idealized, non-expanding universe. New modeling on the expanding universe — which is what our universe was like in the beginning — has confirmed that the stepped rhythm persists. This is critically important because primordial black holes are considered one of the main candidates for dark matter — the invisible framework holding galaxies together.
Because of the rhythmicity, future detectors of gravitational waves — ripples in spacetime — will be able to pick up not random noise, but an ordered "melody" played by merging holes. And here's an unexpected twist: these holes could be so small that, flying through Earth, they wouldn't touch a single atom, even though each one weighs as much as a mountain.
Primordial black holes, if they exist, can be the size of an atom but weigh as much as a mountain.