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## Black Holes From the LHC Could Last For Minutes672

Posted by kdawson
from the becoming-greyer dept.
KentuckyFC writes "There is absolutely, positively, definitely no chance of the LHC destroying the planet (or this way either) when it eventually switches on some time later this year. And yet a few niggling doubts are persuading some scientists to run through their figures again. One potential method of destruction is that the LHC will create tiny black holes that could swallow everything in their path, including the planet. Various scientists have said this will not happen because the black holes would decay before they could do any damage. But physicists who have re-run the calculations now say that the mini black holes produced by the LHC could last for seconds, possibly minutes. Of course, the real question is whether they decay faster than they can grow. The new calculations suggest that the decay mechanism should win over and that the catastrophic growth of a black hole from the LHC 'does not seem possible' (abstract). But shouldn't we require better assurance than that?"
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## Black Holes From the LHC Could Last For Minutes

• #### Assurances (Score:5, Informative)

on Friday January 23, 2009 @12:10PM (#26575387) Homepage Journal

But shouldn't we require better assurance than that?

What better assurance can we get than mathematical formulas? Unfortunately the only other way to find out is to run an experiment, right? I just hope their formulas and the assumptions they are based on are correct.

• #### Assurances (Score:2, Informative)

on Friday January 23, 2009 @12:11PM (#26575411)
What about the assurances in the fact that protons with energies on the order of the energy in the LHC, and several orders of magnitude larger, have been bombarding the planet for billions of years without any stable black hole forming, ever? I'm sure that for almost any event you can find some incredibly unlikely scenario of it triggering a sequence of events that will doom humanity. But it's not generally seen as a reason to stop doing things. Because it's never happened despite things going on for quite some time now.
• #### Bogus (Score:5, Informative)

on Friday January 23, 2009 @12:17PM (#26575485)

Groups of high energy particles striking each other is not rare in nature. It happens all the time, right in our own atmosphere, on the surface of the moon.

This is all Chicken-Little nonsense.

• #### Re:What could possibly go wrong? (Score:5, Informative)

on Friday January 23, 2009 @12:25PM (#26575631) Homepage
Teller did. According to this article [wikipedia.org], he showed that igniting the atmosphere was possible, but unlikely. He just didn't cover up the data fast enough, and it got out.

Teller also raised the speculative possibility that an atomic bomb might "ignite" the atmosphere, because of a hypothetical fusion reaction of nitrogen nuclei.[citation needed] Bethe calculated, according to Serber, that it could not happen. However, a report co-authored by Teller showed that ignition of the atmosphere was not impossible, just unlikely.[6] In Serber's account, Oppenheimer mentioned it to Arthur Compton, who "didn't have enough sense to shut up about it. It somehow got into a document that went to Washington" which led to the question being "never laid to rest".[7]

• #### Can't Grow Fast Enough To Matter (Score:3, Informative)

on Friday January 23, 2009 @12:26PM (#26575659) Homepage

> Various scientists have said this will not happen because the black holes would decay
> before they could do any damage.

The argument is stronger than that. Even if the holes don't decay at all their collision cross-sections are so small that they cannot get big enough to matter before the sun turns into a red giant and swallows the Earth.

An even stronger argument is that if the LHC can create such holes so can cosmic rays and yet we are still here.

• #### Re:cosmic rays (Score:5, Informative)

on Friday January 23, 2009 @12:28PM (#26575689) Journal
That's what I thought, too, and in the comment section you'll find a comment from Geoffrey A. Landis [geoffreylandis.com], scientist at the NASA John Glenn Research Center, stating:

Jeez - read the abstract. Its a calculation based on a theoretical model using some very speculative physics for which there is NO EVIDENCE WHATSOEVER. Really. Ignore it.
The main thing to keep in mind is, cosmic rays have energies vastly higher than the LHC. If the LHC could produce black holes, then there would be black holes floating around everywhere.

• #### Cite the original paper (Score:4, Informative)

on Friday January 23, 2009 @12:30PM (#26575715) Homepage Journal

If you bothered to go past the Slashdot summary of the arXiv blog summary of the paper's abstract summary, and actually RTFA by Casadio et al. [arxiv.org], you would find the following:

We can conclude that black holes created at the LHC under the warped brane-world scenario and described according to Ref. [4] would always remain microscopically small in mass and radius when traversing through the Earth.

and also this:

We conclude that, for the RS scenario and black holes described by the metric (6), the growth of black holes to catastrophic size does not seem possible. Nonetheless, it remains true that the expected decay times are much longer (and possibly â 1 sec) than is typically predicted by other models, as was first shown in Ref.[4].

Possibly, potentially, maybe, under certain conditions, they might be longer lived than expected. They still can't grow.

• #### Re:Folks I don't want to hear say oops (Score:5, Informative)

on Friday January 23, 2009 @12:31PM (#26575737) Homepage
I wonder if they are taking any bets on the probability of an "oops" incident.

Source: July 16, 1945: Trinity Blast Opens Atomic Age @ Wired [wired.com]
"The Trinity test, as it was known, was the culmination of the American effort to win the race against Germany (and, ultimately, the Soviet Union) in building an atomic bomb. A mere three weeks after the test, the United States used atomic bombs to destroy the Japanese cities of Hiroshima and Nagasaki.
But prior to the 16th, none of those involved in the project knew if they had built a devastating new weapon or a spectacular dud.
With gallows humor, the Los Alamos physicists got up a betting pool on the possible yield of the bomb. Estimates ranged from zero to as high as 45,000 tons of TNT. Enrico Fermi, who won the Nobel Prize for Physics in 1938 for his work on nuclear fission, offered side odds on the bomb destroying all life on the planet."

• #### Relax (Score:2, Informative)

on Friday January 23, 2009 @12:34PM (#26575781)

maximum LHC center-of-mass energy (in a Pb-Pb collision): ~1.14e15 eV

cosmic ray flux at Earth's upper atmosphere: ~1 per km^2 per year with energy > 10^19 eV

Collisions 10,000 times more energetic occur multiple times every day over your head, and you're still here. Except now, we can finally reproduce them for study in the lab.

• #### Re:Its all okay. Nothing to see here. (Score:4, Informative)

on Friday January 23, 2009 @12:42PM (#26575953)

Even if the black holes lasted indefinately, their cross sectional area is too small to pick up any significant amount of matter. The Earth would be swallowed up by the sun long before the black hole began to threaten Earth in any way.

• #### Even if it does so what? (Score:5, Informative)

on Friday January 23, 2009 @12:45PM (#26576001)

If the LHC manages to create mini blck holes, let's be clear here, tese will be very very mini. A black hole weighing what? Same as a couple atoms of carbon?

Consider that even if matter collapses to a singularity, its gravitational effect is still just proportional to its mass. Given that the LHC is a vacuum where the collisions are occuring, the blackhole could only ever mass the sum total of the mass of the particles used in the collision. From a casual outside observer you wouldn't even notice, and the black hole would decay before it could acquire more mass.

• #### Cosmic Rays anyone? (Score:4, Informative)

<serpent11@[ ]mail.com ['hot' in gap]> on Friday January 23, 2009 @12:51PM (#26576145) Homepage

The most energetic particle that the LHC can create is 574 TeV/particle lead nuclei. Nature has been bombarding our solar system with a significant flux of particles as powerful as 100 million TeV for as long as it's been around. If it was possible to spawn a black hole capable of consuming a planet from a collision with a particle a mere thousand TeV in energy, then it is all but certain that we would have seen every large body in our solar system converted from billions of years of bombardment from cosmics ray 100,000 times more energetic (caveat: much more energy is available for consumption into a black hole should two particles collide "head-on" with opposing momenta versus a fast particle with a stationary target).

Though, the above reasoning does not exclude the possibility that black holes that may last minutes but yet not consume planets.

~Ben

• #### Re:Folks I don't want to hear say oops (Score:3, Informative)

on Friday January 23, 2009 @01:06PM (#26576503) Journal

I doubt you're awake during brain surgery, but I'd rather hear a urologist say "oops" than a brain surgeon. After all, they can sew your penis back on, but there's no fixing a torn or cut brain.

Actually it's pretty standard to be conscious during brain surgery. The reason being that once they start poking around in your brain they don't really have much feedback on what's going on unless you're able to tell them what your experiencing, so if you suddenly say something like "I taste blue" they may know they're in the right ballpark area or not.

• #### Re:What could possibly go wrong? (Score:4, Informative)

<<moc.liamg> <ta> <avadnaP.amihB>> on Friday January 23, 2009 @01:11PM (#26576587) Journal

Not as much fallout as what is created by burning coal to create electricity.

• #### Same process happens in upper atmosphere (Score:3, Informative)

on Friday January 23, 2009 @01:12PM (#26576601)
The LHC black holes are not new. Physicists have seen super-heavy particles hitting the upper atmosphere for some time. These particles are huge (something like half the plank mass, but memory is a bit fuzzy ), and moving very fast. It is not known where these particles originate from, but the idea of the black holes in the LHC is based on the same mechanism. The LHC black holes would get generated very similarly to the mechanism that these super heavy particles possibly generate black holes in the upper atmosphere. See http://www.college.ucla.edu/news/07/ultra-high-energy-particles.html [ucla.edu] and http://news.bbc.co.uk/2/hi/uk_news/7598996.stm [bbc.co.uk] for more info
• #### Re:cosmic rays (Score:4, Informative)

on Friday January 23, 2009 @01:12PM (#26576607)

Actually cosmic rays don't fully replicate the black hole problem. Keep in mind that a black hole in the LHC would be fed for some bit of time by the stream of high energy particles in the LHC before it leaves the beam path and that black holes apparently have a relatively large cross section compared to subatomic particles. In theory, if you can feed a black hole more mass than it loses, you'll eventually grow it large enough to cause a problem, if you drop it into the Earth.

Having said that, neutron stars are a better case study. They have densities far above that of Earth. For example, the average density of Earth is somewhere around 5.5*10^3 kg/m^3, presumably a little more in the core and around 2.5-3 kg/m^3 near the surface (I guess). The surface of a neutron star [wikipedia.org] can have densities around 10^9 kg/m^3. That's almost a million times as dense. The interior can be far higher, somewhere above 10^17 kg/m^3. That's a factor of 10^14 more. Glancing at wikipedia [wikipedia.org], the power output of a black hole is proportional to the inverse square of the mass. The cross-section area is proportional to the 2/3 power of the mass (mass is proportional to volume which is proportional to 3/2 the power of the cross-sectional area). That leads to the tricky observation that the ratio of mass sucked to mass lost is proportional to 8/3 power power of mass. So a black hole formed by such a cosmic ray immediately interacts with mass roughly 10^6 denser than the surface of the Earth. Neutron stars obviously have a massively greater acceleration (10^12 stronger roughly), so velocities will be a lot faster. Let's suppose that means that a black hole on a neutron star intercepts 10^18 (=10^12 * 10^6) times as much mass as it would on Earth. For a black hole on a neutron star to have the same ratio of mass in to out as one in Earth would have, it'd need a mass almost 10^7 times smaller.

Some natural cosmic rays are known to have energies above 10^20 eV. In comparison, the energy of lead ions (the highest energy particles mentioned in the wikipedia article) in the LHC will be somewhere around 10^15 eV. At a stab, that means black holes in neutron stars ought to form with initial masses of around 10^20 eV and dissipate, else the neutron star would rapidly go away. So to generate black holes with equivalent mass in/out ratios to those on a neutron star generated by the most powerful cosmic rays we've observed, we'd need around 10^12 lead ion particles crammed into the black hole to duplicate a black hole we know dissipates on the surface of a neutron star. While there's probably that many in the beam, it doesn't strike me that the black hole will intercept many of them before it is knocked out of the beam path. The black hole might even escape Earth's gravity altogether since it is likely to start with a velocity that is a significant fraction of the speed of light. I ignore the initial velocity in the above calculation because the speed has to slow to below escape velocity before there is a problem of black hole growth.

• #### Re:I say "go for it!" (Score:3, Informative)

on Friday January 23, 2009 @01:36PM (#26577037)
heard of gambler's ruin? (http://en.wikipedia.org/wiki/Gambler%27s_ruin)
• #### Re:Its all okay. Nothing to see here. (Score:5, Informative)

by Anonymous Coward on Friday January 23, 2009 @01:41PM (#26577145)
No. The fact is that the mass of the particles is going to be negligible compared to your arm, and the size is going to be negligible compared to atoms. The Shwarzchild radius for a 1kg black hole is ~1.5 x 10^-27 m, or 12 orders of magnitude smaller than radius of the nucleus of an atom.

These black holes aren't going to have appreciable gravitational pull, and they aren't going to have appreciable cross section to actually absorb matter.

The truth is, we already know darn well what is going to happen macroscopically. We know physics pretty darn well. Its the very fine details that we aren't sure about.
• #### Re:Folks I don't want to hear say oops (Score:1, Informative)

by Anonymous Coward on Friday January 23, 2009 @01:50PM (#26577365)

At the LHC's first collisions, a black hole forms....

scientist: Oops... OMFG! Call the President!
evil voice from inside the black hole: What good is a phone call if you are unable to speak?

Scientist: OMFG! Call the president!
evil voice from inside the black hole: The EU does not HAVE a president, shitkicker!

Fixed that for y'all

• #### Re:Gravity still applies (Score:1, Informative)

by Anonymous Coward on Friday January 23, 2009 @02:06PM (#26577647)

But, see here's the thing: the black hole may have very little mass, and therefore attract very little nearby matter.

However, it is also affected by the Earth's gravity.

The black hole will fall downward, like all objects that have mass, drawntoward the center of the earth.

Every bit of matter between the black hole and the center of the earth will fall into the black hole, adding to its mass like a snowball rolling down a hill.

When the black hole hits the bottom of Earth's gravity well, the pressure of all the material above it will press downard into it, putting more and more Earth material past the black hole's event horizon. With nothing to stop the inward falling mass of the planet's mass into the hole, the hole will swallow the entire planet...those calculations are apparently not as precisely calibrated as previously thought.

No.

• #### Agreed, this is silly. (Score:5, Informative)

on Friday January 23, 2009 @02:36PM (#26578221) Homepage Journal
People have this amazing misunderstanding of black holes generated by Hollywood. If you take the moon, and crush it into a black hole, it will still follow the same orbital path, and have the same effect on the tides as it does currently. It will just occupy a much smaller space. Its event horizon with be incredibly small, and the amount of mass that would be added to annually would be about the same as it gains now through occasional collisions of small objects in space (i.e.,just about 0)

Since they will not have immense mass to apply to the particles, they will have to apply truly immense amounts of energy (E=mc^2). Should they actually achieve a 'black hole', it will have the same amount of gravitational attraction as it did before.

I think I will spend my time worrying about more likely problems, like cholesterol and cancer.
• #### Re:Bogus (Score:3, Informative)

on Friday January 23, 2009 @04:00PM (#26579591) Homepage

The question is whether the beams can supply a black hole with enough mass that it passes the turning point and is able to grow further from the mass absorbed by falling through Earth's crust.

Atoms are about 1e-10 m apart, and the Schwartzchild radius is 1.48e-27 m/kg. So unless the LHC boffins plan to accelerate over a million billion tonnes of matter through the collider, the answer is no.

• #### Re:Bogus (Score:4, Informative)

on Friday January 23, 2009 @06:19PM (#26581937) Homepage

A nitpick, you misjudged the head-on situation vs the stationary target situation. Via Relativity you can always translate the collision into an equal head-on collision frame of reference. The only thing that matters is the total collision velocity (aka total energy). Two head-on particles is equal to one particle with twice the energy at a stationary target. The double energy of a head-on collision is nowhere near comparable to the hundreds-of-thousands of times higher energy of a cosmic ray.

The only difference shows up when the collision products spray against the surrounding earth-reference-frame matter. Both collisions would spray a spherical fireball in the collision reference frame, but in the earth frame the stationary target collision would look like a sharply directional cone spray of products.

-

• #### Figure it out... (Score:3, Informative)

<mariet' at' `got.net'> on Friday January 23, 2009 @06:34PM (#26582223) Journal

As others have said many times, nature dramatically exceeds any test we've ever done on an almost daily basis. If microscopic black holes were going to gobble up the earth, it would have happened long ago, in fact, all the stars and planets in the universe would now be black holes. You may have noticed, this hasn't happened. ergo...

Think about it... the sun, 186,000 miles across reduces to a black hole, and the radius of the event horizon would be measured in mere dozens of miles. Now squish an atomic nucleus (even carrying the mass of all that acceleration), the resulting black hole and it's event horizon would vanish down to dimensions comparable to the Plank Length. At that dimension, the distance between any particles is beyond imagining. With a lifespan of even hours the best such an object could hope to do is gravitationally disrupt a few atomic nuclii.

This simply isn't a threat to anyone or anything.

• #### Re:Bogus (Score:3, Informative)

on Friday January 23, 2009 @07:02PM (#26582617)
Check your numbers. If a 10^20 eV cosmic ray collides with a ~stationary proton in the atmosphere (proton mass is ~10^9 eV), the available energy in the collision is \sqrt{2mE} which will be about 4.5 x 10^14 eV. The top energy of the LHC is 1.4 x 10^13 eV. So, the cosmic ray collision still has 30 times as much energy available as the LHC collision.

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