A scientist at CERN LHC (Large Hadron Collider) was asked during an interview about the possible results and consequences of operating the LHC at full power of collision in the near future, one of the results he literally said :

One of the theories that predicts the consequences of operating the LHC at full power collision is that mini black holes might form, but do not be afraid of those black holes, they will not start expanding and destroy the earth, they will instantaneously disappear.

I know that black holes create disturbance in space-time. And they actually appear when matter massively gets pressurized into a small size of volume in space which causes gravity to increase insanely which in turn initialize a black hole that even light its self can not escape away from.

So how can a mini black hole disappear anyway? What in the world would cause a small size, a mini size, a tiny little black hole to vanish or disappear?

  • $\begingroup$ What would happen if the pressure in a system is more powerful than the attractive force of gravity on it? $\endgroup$ – Mitch Goshorn May 13 '15 at 3:12
  • $\begingroup$ @MitchGoshorn Is this answering a question with a question? If so, I need more clarifications on your question. $\endgroup$ – Bilal Sulaiman May 13 '15 at 3:15
  • 1
    $\begingroup$ Normally a planet or stellar body reaches the volume it does as the result of reaching equilibrium between internal pressure and gravity. If the force of gravity were greater, the body would compress until the pressure grew great enough that it stabilized. If the pressure were to increase, the body would expand, lowering pressure until the body stabilized. An ordinary black hole is the result of stellar amounts of matter compressing as internal pressure suddenly drops. But these micro blackholes are not the result of gravity, rather they result from a collision. So how will the body equalize? $\endgroup$ – Mitch Goshorn May 13 '15 at 4:31
  • $\begingroup$ @MitchGoshorn this specific question you asked, maybe the key for the answer. They are recreating the "Big Bang" circumstances in the LHC at CERN, as a result they put many theories of consequences of such an experiment and the mini black hole theory was one of them. $\endgroup$ – Bilal Sulaiman May 13 '15 at 4:38
  • $\begingroup$ It's fascinating really. Sometimes the result of such systems can be counter-intuitive. In some circumstances, adding matter to a body will decrease its volume. Other times, removing matter could increase its volume. If you stuck the whole universe in a singularity and then found a way to give pressure the upper hand in the way gravity gets it during supernova events, the result might look a lot like the Big Bang. A MBH is certainly not a universe of matter, but it gives scientists a glimpse into what it might have been like. $\endgroup$ – Mitch Goshorn May 13 '15 at 4:50

This result is due to Hawking radiation.

Due to random quantum fluctuations, particles are radiated from a black hole.

When the black hole has a mass less than the Moon, it will evaporate.


I should add that any black holes created can only have the mass of the particles involved in the collision - two protons. So it's not going to do any harm before it evaporates. However, we would learn a lot from the event.

  • $\begingroup$ The mass of the black hole would be the mass of the two protons plus the energy of their collision. $\endgroup$ – Keith Thompson Nov 2 '15 at 19:58
  • $\begingroup$ @Keith Yes, that's correct. Of course, the black hole would still evaporate. $\endgroup$ – andy256 Nov 2 '15 at 20:44

Mini black holes are thought not to exist, so it's an unlikely idea anyway, and Hawking Radiation is largely accepted (but I think, not proven) . . . so maybe, "what if" concerns very unlikely but slightly valid, but there's also this:

We get particle collisions faster than Cern can produce in our upper atmosphere every day. If there was any danger of high energy collisions, We'd have likely observed it already either in our atmosphere or by Hubble. The fact that high energy collisions happen every day on every planet, every good sized moon and every star in the galaxy suggests that high energy collisions don't form into matter eating strangelets or tiny but hungry black holes. If they did, we'd have seen some evidence of that.

So we have both very strong observational evidence as well as theoretical evidence. CERN isn't playing with particle energy that doesn't happen - it happens all the time in space.

Just for fun - the Oh-my-god particle, way more energy energy than anything that happens in CERN: http://en.wikipedia.org/wiki/Oh-My-God_particle


Small mass black holes are extremely small and, if Hawking Radiation is real, extremely short-lived. (I cannot over-emphasise how extremely!) Even a one hundred ton black hole would be smaller than an electron and evaporate in the blink of an eye (and in a multi-million megaton explosion).

According to http://en.wikipedia.org/wiki/Large_Hadron_Collider, the LHC is achieving 328 TeV per ion in its heavy ion collisions. 328 TeV is about 5x10-24kg.

A black hole of that mass would be about 10-50m in diameter and would live for about 10-70s. (Both of these are much less than planck length and planck time (10-35m and 10-44s) so such a small black hole is arguably impossible for that reason if not for others.) If it were possible it would be soo many orders of magnitude too small and too short-lived to be able to acquire any extra mass before it disappeared.

The process of evaporation (Hawking radiation) is virtual particle pairs forming on the event horizon and one falling in and one escaping. The one that escapes becomes a real particle with mass and that mass is taken from the black hole. (In effect the other virtual particle becomes a real negative mass falling into it). That's very simplistic and I don't understand enough myself to explain it in significantly greater detail. It is not proven to exist as UserLTK says and I doubt if it could happen at the lengths and timescales of this sub-planck-scale black hole if such a thing were possible anyway.


I asked myself the question at the time of the experiment.

1. Nothing stops a fast black hole
The 1st point of reassurance was that nothing stops a black hole, and the energies involved in the collider are so high that the tiny black hole produced would leave the planet within 200 uS as the 11 Km/s escape velocity is trivial compared to even 30,000 km/s which is 10 % of the speed of light. The collider produces particles within 1% of the speed of light.

2. High energy collisions are natural, and we are still here
The 2nd and more reassuring point was that the experiments were not unusual in the natural sense. Cosmic rays repeat them on average about 14,000 times a day around the planet.

http://home.cern/about/physics/cosmic-rays-particles-outer-space - explains that very high energy cosmic rays hit each of the 510 million $Km^2$ of the earths surface once per century (about 36,500 days).

BTW. I do have a degree in physics, and some of my professors were CERN researchers. last century though.

  • $\begingroup$ The question is asking about black hole evaporation, not formation. Also, what do you mean by "nothing stops a black hole"? It isn't true. $\endgroup$ – HDE 226868 Nov 1 '15 at 20:04

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.