Wednesday, April 22, 2015

Why the LHC will (probably) not destroy the universe

11 comments:

Uncle Al said...

1) Physics Today 68(4) 46 (2015), Figure 6.
doi: 10.1063/PT.3.2749 (view online, download pdf)
2)"Disappearing stars" Supernova 1987 from B3 supergiant Sandeluk -69° 202 - no remnant.
3) The Nine Billion Names of God (1953) Arthur C. Clarke
"Overhead, without any fuss, the stars were going out."

Rrun the LHC pedal to the metal, throttle to the firewall, flat out, full sail, flank speed. Terminate theoretic curve-fittings - observation is the only way to know.

Robb Lutton said...

One question. How does vacuum decay affect the multiverse? If it happens I wouldn't think that it would be constrained to one "bubble". And by definition everything has happened somewhere in the multiverse so it must have already been destroyed...or am I missing something?

Sabine Hossenfelder said...

Robb,

Depends on what you mean with multiverse. The vacuum decay spreads to all causally connected regions with the same potential for the vacuum. In most multiverses, this is not very far. Of course many parts of the multiverse are uninhabitable to begin with for this reason. Best,

B.

nicolas poupart said...

Everything depends on the coefficient L of the Drake Equation, to achieve zero risk we should rather wait for a good approximation by the SETI :-)

David said...

Wouldn't the proliferation of the vacuum decay move no faster than the speed of light? If so, then we would not immediately see (nor experience) any vacuum decay which started from a miniscule black hole many millions or billions of light years from us, correct? And if that is correct then that would not preclude the LHC creating one right here on Earth and starting the destruction of the Universe at our doorstep?

Sabine Hossenfelder said...

That's right, very good point. Most of the universe might already be destroyed, we just haven't noticed yet.

David said...

A related question...
There have been calculations made of the time it would take a black hole to evaporate. It seems that the smaller they are, the faster they evaporate. A figure given by Wikipedia says that it is estimated that a black hole with roughly 2.28 × 10^5 kg mass would evaporate in about 1 second. Since any black holes created by the LHC would be on the order of 2-3 protons in mass, I would expect that the evaporation would be for all practical purposes instantaneous.
My question: Has anyone estimated the time it would take for the vacuum decay to get started from a nucleation event, and compared that to the lifetime of a miniscule black hole with the mass of an atom, and then speculated as to who would win (the start of the nucleation event, or the complete evaporation of the miniscule black hole)?
Another question (apologies for my rambling posts): As far as we know, what is the smallest increment of time that our universe can experience (assuming it is not a continuous scale)? Assuming there is a smallest time increment, I would think this would put a lower limit on the smallest black hole that could be created (if the theoretical evaporation time was less than the smallest allowed time increment then a black hole would not have time to form before it would evaporate).

Sabine Hossenfelder said...

David,

The black hole either decays itself (evaporates) or it triggers vacuum decay. The question is what is more likely to happen. The answer is: it depends on the mass of the black hole. If they are very small, it's more likely to trigger vacuum decay instead of evaporating. Best,

B.

mr chang said...

Sabine I note your comments and the video. Given the above posters points, do you think it is likely / possible this will happen next month at the LHC? And how likely is it that this could have happened elsewhere in the universe and we just haven't seen if

mr chang said...

Sabine I note your comments and the video above. Taking into consideration the comments above, do you think it is likely to happen at the LHC? And what is the likelihood that this has already happened in the universe and we haven't seen it? I'm really starting to worry

Sabine Hossenfelder said...

Mr Chang,

Estimating probabilities for speculative theories is extremely difficult and not something I am qualified to do. Risk assessment is a complicated business.

As I said in my video, if it has happened elsewhere in the universe, we cannot miss it. David pointed out correctly, that since the signal takes some time to reach us this only accounts for what's in our backwards lightcone. The same is the case of course for black holes "only" eating up stars. If a star was eaten up right now at the other end of the Milky way, we wouldn't see it for the next 100,000 years or so.

So all I can say is that basically the probability that the LHC produces a black hole that destroys the universe is small than that it produces a black hole that destroys the Earth.

Best,

B.