LHC Doomsday Scenarios: Questions & Answers

[hammertime]

I'm not sure how much this has been covered on this board, but I have a few questions regarding the hypothetical doomsday scenarios involving the LHC.

1) I've heard that mini-black holes could be created at LHC, but that they are supposed to evaporate. How can we be sure that they will? Is it because there are numerous mathematical independent derivations of Hawking radiation? Is it because they are virtually demanded to be unstable by the laws of thermodynamics and QM? Is there any difference between the ones created in the lab and the ones created by cosmic rays?

2) Is there any evidence for strange matter in the universe?

3) Is the metastability of the vacuum speculative? Is there any evidence for or against it? People have argued that, because cosmic rays have been colliding for billions of years, they would have already triggered a transition to a true vacuum, and we wouldn't be here. Does this mean that the vacuum is not metastable? Could mankind ever trigger such a disaster, perhaps by making collisions more powerful than those found in nature?

It's just that these scenarios have got me a little worried. Not necessarily because I'm afraid they will happen, but simply because they are possible. Please keep in mind that I know very little about theoretical physics or QM in your response.

Thanks.

 

[yenchin]

1) I've heard that mini-black holes could be created at LHC, but that they are supposed to evaporate. How can we be sure that they will? Is it because there are numerous mathematical independent derivations of Hawking radiation? Is it because they are virtually demanded to be unstable by the laws of thermodynamics and QM? Is there any difference between the ones created in the lab and the ones created by cosmic rays?

It doesn't matter. Even if Hawking radiation does not happen, the black holes are far too small to be of any threat; they are much much smaller than proton. So they will take very long to eat up the Earth, we would have died of other things like the Sun expanding into red giant or all that.

 

[hammertime]

1) I've heard HR is incorrect because Hawking's derivation makes some dubious assumptions.

2) I've also heard that there are numerous independent derivations for HR (all of which reach the same conclusion), some experimental evidence for it (in analog models ie acoustic), and that HR is virtually demanded by the laws of thermodynamics.

So which is it? Does it exist or no? Is (1) or (2) correct?

 

[william donnelly]

The argument of (1) doesn't follow logically. Hawking's derivation might be incorrect (it might have incorrect assumptions), but that doesn't make the conclusion wrong. The fact that different derivations lead to the same conclusion suggest that Hawking's conclusion was correct.

To the best of my knowledge (2) is correct.

 

[kharranger]

Nothing disastrous can possibly happen at LHC. This is because cosmic rays with energies equal to and far larger than LHC particle energies are hitting the Earth's atmosphere all the time, so if any doomsday type thing could happen, it already would have happened.

 

[Voltage]

I found the penultimate paragraph of this article somewhat alarming:

http://www.space.com/scienceastronomy/mystery_monday_040524.html

 

[arivero]

The most ancient tale about doomsday is, afaik, the one about Bethe calculation of the (lack of) chain reaction in atmosphere following the explosion of the atomic bomb.