Submitted by **Durable_me** t3_10bwcjy
in **askscience**

I know that when you squeeze the earth to a size of an orange it will become a black hole.

And when you squeeze an orange-sized metal sphere to the size of a virus, it will become a black hole.

But can you squeeze together 50 neutrons and make a black hole? (let's assume you have unlimited energy available)

and next ... can you squeeze 2 neutrons together to form a black hole?

but next.... can you squeeze 1 neutron together (the quarks in it) to become a black hole?

and even next..... if the previous is true, than in fact a quark is a black hole on itself... Or a quark is composed of even smaller particles that can be squeezed together to form yet another even smaller black hole....

But if that is true, these smaller particles are black holes on their own, and that is not possible...

So where is the flaw in this all?

mfb-t1_j4d0j5h wroteElementary particles don't have a size in the way classical objects do, but their wave function is never perfectly localized - they have a non-zero volume in that sense (for electrons in atoms it would be the volume of their orbitals, for example). The larger the center-of-mass energy the smaller the radius of that volume can be. As you increase the energy of e.g. a collision process you can make the system "smaller" and the Schwarzschild radius grows. The two get to a similar length at the Planck energy (2GJ) which corresponds to the Planck mass (~20 microgram) and the corresponding Schwarzschild radius is the Planck length. It's expected that the smallest black hole is somewhere around that. These are order of magnitude estimates, the precise numbers will depend on a quantum theory of gravity which we don't have yet (at least not in a way that we would be able to calculate this).

If there are microscopic extra dimensions and if gravity extends into them then gravity could be much stronger at very small distances. This would effectively mean the Schwarzschild radius is larger and you need less energy to produce a black hole. The energy might be so low that we can reach it with accelerators, so we look for possible black hole signatures at the LHC. Nothing found so far. It's pretty much an all-or-nothing search: If you have enough energy then you expect to produce tons of them and it's obvious within weeks, so we are pretty sure the LHC energy is not enough to make black holes.