In the first moments after the Big Bang, the universe inflated at an unimaginable rate. This inflation left behind ripples — tiny overdensities in the hot radiation and plasma. As the universe cooled, these clumps began to live their own lives: some dispersed, while others, the densest ones, collapsed into black holes.
The authors recreated this process on a computer using Einstein's equations in their full, unsimplified form. They did not set the scenario by hand but let matter and spacetime dictate the course of events themselves. It turned out that a clump's fate depends on a single number: if the initial overdensity exceeds a threshold of about 0.8 (in arbitrary units of density contrast), there is no turning back — a black hole is born.
This result does not merely repeat old estimates but provides independent confirmation. It is like a second measurement with a different instrument: if two different methods show the same thing, we really do understand something about the birth of the first black holes. And they, in turn, may explain where the universe's missing mass is hiding: that very dark matter.
The clump from which a black hole is born can be smaller than an atom, yet its mass is that of a mountain.
In Stanisław Lem's novel 'Solaris', the sentient ocean can control gravity — much like the early universe 'sculpts' black holes from quantum ripples.