On hadron colliders, dark matter and black holes

**RPMiller** · 09-05-2008, 12:14 PM

Originally Posted by Morshwan

I am living not so far from the Hadron collider. When they will launch the first test, I will try to post here to tell you how dark is the black hole ;-)

Something tells me that the Internet access may be an issue.

LOL

**Redrobes** · 09-02-2008, 04:16 PM

From daily mail article...

Within four years, one of these 'celestial vacuums' could have swollen to such a size that it is capable of sucking the Earth inside-out.

Four years ??? That's a pretty slow exponential growth then. So if you have a while, then if you discover one of these holes in the middle of your machine infinitesimally small but growing, can you just hold it there and wait for the Hawking radiation to evaporate it ? Would you need to be able to control its position ? Does that imply a need for a graviton/gravity wave generator to move it or do you move bits of mass about to position it.

**jfrazierjr** · 09-02-2008, 09:09 PM

Originally Posted by torstan

Not yet, but then they just* sent a small bunch of protons a hop skip and a jump around the ring - 3km of a possible 27km. No collisions yet. The test was done to see whether the little ring (the SPS) could throw a bunch of protons into the bigger ring without the bigger ring fumbling the catch. Now think how much difficulty the American relay teams had doing this stuff last week (yes, the Brits screwed it up too, but I can't say I expected much more...) and this one has to be done with sub-microsecond precision. That was definitely a non-trivial manoeuvre and they deserve a lot of credit for managing it first time.

It'll be interesting to track the large number of 'End of the World!' stories as a function of how close we get to the LHC start next week (note that there will be no collisions for a while, and they will be low energy when they start).

Here's my first contribution:
http://www.dailymail.co.uk/sciencete...d-halt-it.html

If you get any, post them here.

*For a given value of 'just'

Hmmm... 8/8/8 sounds like a triple digit date that would be a great day for the world to end.

**torstan** · 09-03-2008, 04:15 AM

Unfortunately you can discredit people all you like but they can still call themselves scientists as long as they can produce evidence of a PhD, unlike doctors who can have their status stripped by the medical council (I believe). So nutters who really think that we'll destroy the world can take it to a paper and get equal say to the scientists and because everyone loves an underdog almost as much as they love a disaster story it gets printed.

Redrobes: You are right, black holes form slowly due to the capture of matter. They also lose mass through Hawking radiation. For a large one, the accretion of matter is much faster than the decay but for a small one the decay is much faster than the accretion and a microscopic black hole should never become a large black hole. For something other than this to happen, the laws of physics would have to be very different from what we think they are. As the CERN report pointed out, if you change the laws of physics you usually see an effect of it somewhere else first - in this case through cosmic rays hitting earth, or any other nearby large object. Essentially, these collisions are happening on all objects in space and none of the nearby celestial bodies have been swallowed by a celestial void or black hole yet so we are fine.

RPMiller: If a black hole formed and did not dissipate then it would be affected by gravity, so it would gravitate to the center of the earth (like any massive object). It would not be very heavy, so it would take a bit of time to do this. It would cause damage at the atomic scale (though very little in reality) as it travelled. Once at the center of the earth it would slowly accumulate matter (hundreds of years is a number I've heard thrown about but I haven't done the calculation myself) until it became large enough to be an issue. Again, if it were to happen here, it would already have happened all over the universe, and especially in our solar system. We don't see objects being eaten from the inside by black holes, so it is safe. But the short answer to your question is that the black hole only sucks matter in by gravitational force, and it only has the mass of the objects that created it. Now two hydrogen nuclei are pretty light so the gravitational force is fantastically small. Therefore the experiment would be able to occur around it without feeling any effect from the gravity of the black hole. Only when it got large would it start to affect the experiment, and by that time it will have moved outside the area of the detector.

**Valarian** · 09-03-2008, 05:04 AM

Originally Posted by torstan

For something other than this to happen, the laws of physics would have to be very different from what we think they are.

It'd be a hell of a time to go "Oops" though. I can just see red-faced scientists trying to explain why Switzerland is sinking.

Originally Posted by torstan

Therefore the experiment would be able to occur around it without feeling any effect from the gravity of the black hole. Only when it got large would it start to affect the experiment, and by that time it will have moved outside the area of the detector.

So what you're saying is that, even if a black hole is created, we won't know about it until it eats the Earth because it's travelled outside the detector range. Comforting

**RPMiller** · 09-02-2008, 04:20 PM

I just realized something. If a black hole forms inside the collider, wouldn't that stop all future experiments since the black hole would then suck in any future particles that go near it? I think that would be a good indicator that there might be a black hole forming.

**Valarian** · 09-02-2008, 05:26 PM

Just have to quote Babylon 5 here ....

Originally Posted by Susan Ivanova

No boom today... boom tomorrow. There's always a boom tomorrow.

**Valarian** · 09-05-2008, 08:39 AM

There's a perverse part of me that really wants all the scientists to be wrong and they have to go "Oops". Then again, it'd mean that the doomsayers are right and I'd hate that.