If you squeeze a handful of sand, it gets denser, but at some point the grains press against each other: there's no more room to compress. Some theorists think space behaves similarly at ultra-small distances: it has a limit to divisibility, a kind of 'grain.' In this new study, that principle was applied to the birth of black holes in the early universe — the very ones that might explain what dark matter is made of.
The authors took equations similar to those describing the universe's expansion and added a regulator — a parameter ℓ that prevents density from becoming infinite. It turns out this regulator creates a clear mass threshold: a black hole lighter than about 10¹⁸ kg (the mass of a large asteroid) simply cannot collapse. The reason is that space's 'grains' prevent matter from compressing enough, like trying to pack a snowball from large ice crystals rather than soft snow.
This changes the picture of primordial black hole formation. Previously, it was thought they could be arbitrarily light, but now it turns out: below the threshold — silence. Such a mass gap could explain why astronomers don't see microlensing from a swarm of tiny black holes. And although the regulator ℓ is still hypothetical, the idea itself links the quantum nature of space to the large-scale structure of the cosmos, like ripples on water revealing an unseen fish.
If a primordial black hole with the mass of an asteroid passed through your room, its gravity would stretch air atoms like taffy, but it would be the size of a proton and wouldn't hit a single molecule.
In Dan Simmons' novel 'Hyperion,' there are the Time Tombs, where space is warped so that ordinary geometry breaks down — similar to how space's 'graininess' breaks the usual rules of collapse.