A LHC question on black holes who's answer I probably won't understand

So I was reading some stuff on sub atomic particles for fun and saw something that peaked my curiosity. From what I read any fundamental particle is a singularity. So electrons and quarks which pretty much make up matter are all sizeless, IE infinitely small. There’s even a theory that electrons might actually be black holes but that theory has problems. However the main thing is even if these particles are in some regards a black hole they obviously don’t suck up everything around them. So should the same thing be true of “black holes” generated by the LHC? I mean that they might have some of the features of a black hole (like being a singularity) but like quarks and electrons not actually be dangerous.

Search on some of the many threads here on black holes. What they will all say is that black holes don’t suck. That’s a total, if unfortunately common, misunderstanding of them. They have exactly as much gravity as anything else of the same mass. The mass of a black hole created by the LHC - assuming such a thing is even possible - will be of sub-atomic size. So it will have the same amount of gravity as any other sub-atomic particle. Which is so small as to be utterly meaningless. That’s why they can’t be dangerous. In addition, most theories say that such a black hole will disappear in a tiny amount of time due to Hawking radiation. The whole LHC thing is crackpot science.

So what IS the mass of a black hole?

The minimum mass of a black hole created purely by gravitational collapse is 3-4 times the mass of the sun. They can be bigger of course – much, much bigger – if you keep throwing stuff into them.

Lighter black holes can be created in high-energy conditions – during the Big Bang, for example, or inside the LHC.

It’s not really true that fundamental particles are singularities. Instead, they are objects with no known lower bound on their size.

To expand a bit, you can have a black hole of basically any mass. Black holes come from density, not mass. If you take any amount of mass and squeeze it into a small enough volume, you end up with a black hole with that mass.

Now, squeezing anything down that much is very hard to do. As The Hamster King says, two ways it can happen are to have so much mass, as in a large star, that gravity overwhelms all the other forces, or to have a high-energy collision of particles, as in the LHC.

Anything between a very small value and very large value. The sorts of black holes that might just possibly be created by the LHC would be the mass of an atom or two, the sorts of black holes believed to exist at the core of galaxies would be the equivalent mass of billions of stars.

If I’m reading the OP’s question correctly, he was really asking: “If electrons and black holes are both singularities, why would an electron ‘bounce’ off of another particle, while the black hole would ‘consume’ it?”

And the answer is basically as Pleonast says: so-called “point particles” are not singularities in the same sense as a black hole. They are just so small that we can’t determine how small and so small that equations describing their interactions don’t need to take size into account in order to be accurate.

This is actually one difference between electrons and black holes. If we want to answer the question “Will an electron hit object x?” we only need to know how big object X is. If we want to answer “Will a black hole hit object x?” then we want to know both the size of the black hole’s event horizon and the size of the object.

Cool. Thanks. Now back to your regularly scheduled OP.

Additionally, it’s hard to speak of black holes of very low mass because quantum physics gets into the act. At that point a view of black holes based solely on general relativity becomes inaccurate. The mass at which the two theories bump heads is called the Planck mass, about 22 micrograms (or rather larger than an average human cell!)

Yes, that’s pretty much my question. I guess I was confused since the Wiki entry on electrons (and quarks for that matter) describes them as “point-like” particles without a spatial extend which sounded to me as though it was also a singularity. Just curious when you say we can’t determine how small they are do you mean we currently can’t or that the laws of quantum mechanics actually prevent us from ever knowing that?

We speak of electrons as being point particles, because we’ve never managed to measure a radius for them, only upper bounds on the radius. But that doesn’t mean that they’re black holes. According to classical (that is to say, non-quantum) theories of black holes (which are almost certainly pathetically wrong in this regime, but let’s roll with it anyway), for an electron to become a black hole it would need a radius of 10[sup]-57[/sup] meters. By contrast, the best bound we can experimentally put on the size of the electron is that it’s less than about 10[sup]-22[/sup] m, which leaves plenty of room for it to still be larger than its Schwarzschild radius.