Artificial Black Holes, again

Jake
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Wikipedia http://en.wikipedia.org/wiki/Micro_black_hole" that hawking radiation is a controversial theory which very well may not be true. Correct me if I'm wrong, but doesn't this mean that if we are able to create micro black holes at the Large Hadron Collider, and if Hawking radiation is wrong, we are effectivly destroying all of humanity and this entire solar system? Won't scientists at the collider try and create micro black holes? Isn't this a bit reckless on the part of the scientists to endanger all of human existence based on very theoretical science? All of this just to possibly learn a bit more about black holes. Doesn't make too much sense if you ask me...

I'm just trying to understand the thinking in all of this, thanks.
 
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Jake said:
Wikipedia http://en.wikipedia.org/wiki/Micro_black_hole" that hawking radiation is a controversial theory which very well may not be true. Correct me if I'm wrong, but doesn't this mean that if we are able to create micro black holes at the Large Hadron Collider, and if Hawking radiation is wrong, we are effectivly destroying all of humanity and this entire solar system?

This argument comes back sometimes. Of course, each time something new is tried, there can always be some imaginary (or real) catastrophe anticipated. But the aim of the LHC is not to create black holes, and probably won't.
There have been more catastrophic scenarios, one being that the vacuum state of the universe is an unstable one, and that a collision of high enough energy might "trigger" the sudden phase transition to another vacuum state (like the sudden freezing of an undercooled liquid). That would not only destroy the Earth and the solar system, but the entire visible universe. The advantage is that death in this case is totally painless.
 
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Wikipedia dodges another blow!
 
Jake said:
Wikipedia http://en.wikipedia.org/wiki/Micro_black_hole" that hawking radiation is a controversial theory which very well may not be true. Correct me if I'm wrong, but doesn't this mean that if we are able to create micro black holes at the Large Hadron Collider, and if Hawking radiation is wrong, we are effectivly destroying all of humanity and this entire solar system?

No, even if it formed and didn't evaporate, a micro black hole would not destroy the solar system, humanity, or even the laboratory. The interaction cross section (if approximated by the horizon area) of a micro black hole is absolutely miniscule (at least in the theories I've seen).
 
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vanesch said:
There have been more catastrophic scenarios, one being that the vacuum state of the universe is an unstable one, and that a collision of high enough energy might "trigger" the sudden phase transition to another vacuum state (like the sudden freezing of an undercooled liquid). That would not only destroy the Earth and the solar system, but the entire visible universe. The advantage is that death in this case is totally painless.

As much fun as it must be to "play" with the LHC, the energies it's capable of reaching don't come close to what occurs naturally in the universe. Since the universe has been round for awhile, and since it's still here, I suspect the notion of existence being torn assunder by the experiments we puny humans do as a tad unjustified.
 
Jake said:
we are effectivly destroying all of humanity and this entire solar system?
Even if it didn't evaporate and it did manage to interact with matter enough to suck in the entire planet (that's two enormous if's which go against GR and interacting quantum field theories) then it wouldn't destroy the Sun, it would form a black hole the mass of the Earth orbiting the Sun. Even the Moon wouldn't really notice any change, because all it notices is the Earth's gravity and the black hole would just fall to the centre of the Earth and absorb it all. The Moon would continue orbitting because the gravity wouldn't change.

As already said though, that's almost certainly not going to happen anyway. It's just too many people hear "black hole" and think "Giant, unstoppable cosmic vacuum cleaner that devours everything around it".
 
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SpaceTiger said:
No, even if it formed and didn't evaporate, a micro black hole would not destroy the solar system, humanity, or even the laboratory. The interaction cross section (if approximated by the horizon area) of a micro black hole is absolutely miniscule (at least in the theories I've seen).

Yes, as long as it escapes with sufficient momentum. But if it is produced at low enough momentum, so that it falls down, right through the earth, and back, it is supposed to slowly eat out what it finds on its way, no ?
So like each time eating out a very very thin needle of "earth" along a diameter, wouldn't this end up (I have no idea how long it would take, it's maybe only 5 protons eaten up per voyage) eating up all of Earth ?
 
Considering there are particles that are hitting the Earth's atmosphere with several orders of magnitude more energy than what will be produced at the LHC, and also considering that we're not all dead yet, I'd say we're pretty safe.
 
So the argument for "this is safe" are as follows:

1.) That even if we produce black holes, and they don't evaporate, they won't interact with matter and get any bigger.

This is wrong because eventually it will absorb matter, grow bigger and absorb it faster until it consume all of earth.

2.) That we won't have enough energy to produce black holes anyway.

Too risky because it is theorized that if string theory is correct, we will in fact have enough energy to create a micro black hole in our accellerator.

3.) It is safe because particles hitting our atmosphere from space have more energy than particles will have in the accellerator, so the accellerator experiments must be safe.

Who's to say this is true, do we know this for sure? And couldn't the different aspects of the matter and energy be different in the experiment from the interacations that happen naturally in our atmosphere, such that our experiments would create black holes?

In other words, none of the arguments for why this whole black hole experiments are safe are so rock solid definite that it is safe to jepordize everything just for the sake of some science experiment.
 
  • #10
Well, we have large amounts of evidence that it is indeed happening in the atmosphere. I'll just link to the Wiki article, but you can Google for it and get all sorts of results:
http://en.wikipedia.org/wiki/Oh-My-God_particle

These lines in particular:
"It was most likely a proton traveling with velocity almost equal to the speed of light..."
"Since the first observation, by the University of Utah's Fly's Eye Cosmic Ray Detector, at least fifteen similar events have been recorded, confirming the phenomenon."

And the LHC will be accelerating hadrons (protons and heavy ions). The max energy for a proton in the LHC will be around 10^10 eV, whereas the Oh-My-God particles peak at around 10^20 eV. That's 10 orders of magnitude.

Another quote from a different source:
http://www.srl.caltech.edu/personnel/dick/cos_encyc.html
"The frequency of air showers ranges from about 100 per m^2 per year for energies >10^15 eV to only about 1 per km^2 per century for energies beyond 10^20 eV."

So, there are about 100 events per year on every square meter of the Earth with 10,000 times as much energy as the events that will occur in the LHC. That works out to about 5x10^16 events over the whole Earth per year. 2.5x10^26 events over the lifetime of the Earth.

So, therefore, if the LHC kills us, it would be an event that happens in only 1 out of every >10^26 interactions. I think we can take our chances... :)
 
  • #11
Also: The most energetic particles produce "showers" of particles (MANY particles, ~10^11), many of which are still much greater in energy than what the LHC could possibly produce.
 
  • #12
Jake said:
So the argument for "this is safe" are as follows:

1.) That even if we produce black holes, and they don't evaporate, they won't interact with matter and get any bigger.

This is wrong because eventually it will absorb matter, grow bigger and absorb it faster until it consume all of earth.

I think you may be missing the timescale involved here. The sun will turn into a red giant long before such a tiny black hole could eat the Earth.

See for example

http://curious.astro.cornell.edu/question.php?number=572

That was worked out for a billion ton black hole that did not evaporate, much larger than anything a particle accelerator could create.

3.) It is safe because particles hitting our atmosphere from space have more energy than particles will have in the accellerator, so the accellerator experiments must be safe.

Who's to say this is true, do we know this for sure?

Yes, another poster has already posted some references to a MUCH more energetic events that already occur in nature.

Worry about getting struck by a meteorite on the way to work, or if you like global destruction, the next "Dinosaur killer" impact, it's more logical than worrying about creating a black hole in a particle accelerator.

(It would be even more logical, of course, to worry about getting in a traffic accident, or slipping on your bathtub, or choking on your food).
 
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  • #13
We are safe IF the current hypotheses are true. We can't know that they are true without performing the experiment, and if they aren't true, then... well... you know.

The conserved momentum of naturally ocurring impacts would send a subsequently formed black hole clean through the Earth before it could accrue any meaningful mass. Therefore the argument that the Earth is constantly being bombarded anyway, is rather meaningless.

The CERN created black holes will have little (if any) relative momentum to the earth. They'll just hang around, causing what damage they might.

Should these things fall into the Earth's core, they will be in an environment where the average densisty is 811.6 pounds per square foot, the pressure is about 52 milliion pounds per square inch and it's about 11,000 degrees farenheit!

Imagine all of that crushing pressure just looking for an escape route! The real concern then isn't what might "fall" into the nano black hole, but rather what might be pushed in.

As far as planetary destruction is concernd, how do we know that the asteroid belt wasn't the result of a black hole orbiting the center of mass of a former planet?

It has been supposed under GR that we'd need about 620 orders of magnitude more energy than CERN to create nano black holes. It can only work if string theory is correct and the energy required comes from other dimensions.

Unfortunately, it's looking like the energy requirements aren't as high as originally supposed. In fact, they think they've already created one at another collider (reference).

Side note: Did you know that if the sun became a black hole its event horizon would be like 1.9 kilometers wide, but if Earth became a black hole its event horizon would only be around a centimeter wide?

You might doubt black hole formation at CERN, but the way they are talking about it, they have little doubt. They are expecting to make thousands of 'em at a time (reference).

Personally, I agree that the risk here is seemingly small. However since we are literally risking everyone and everything, I think the risk is too great. Just ask yourself: What if they're wrong?

I say let's wait to do these experiments off-world, safely away from our only earth.

ubavontuba
 
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  • #14
pervect said:
I think you may be missing the timescale involved here. The sun will turn into a red giant long before such a tiny black hole could eat the Earth.

See for example

http://curious.astro.cornell.edu/question.php?number=572

That was worked out for a billion ton black hole that did not evaporate, much larger than anything a particle accelerator could create.

Although I agree with you, we should be cautious here. To even produce black holes at TeV energies, we need compactified extra dimensions, and this can greatly increase the Schwarzschild radius of a micro black hole. If the Planck scale is ~1 TeV, the Schwarzschild radius of a Planck mass black hole works out to:

r_h\sim\frac{c^2m_{pl0}}{1~TeV}l_{pl0}

where the "pl0" subscript refers to the standard Planck quantities. This works out to around 10-19 m -- still smaller than the billion ton black hole, but not by much. The timescale would be very long, much longer than that estimated in your link. While in 4-D the horizon size scales as the mass, higher-dimensional spaces have a scaling that goes less dramatically with mass (M2/7 in 10-D). More info here:

http://xxx.arxiv.org/abs/hep-ph/0106219"

Anyway, I otherwise agree with you completely. It's true that, if the Earth existed eternally and the black hole remained bound, it would eventually "swallow" the earth, but the timescales are so long that it's not even worth thinking about. Other things will get us (and even the earth) before then.
 
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  • #15
That's what I was getting at: all the hypotheses that "prove" that these black hole experiments are safe are simply to weak and newly hypothosized to risk our entire future for some discretionary science experiements. In other words, no matter what explanation anyone has for why micro black hole experiments are safe, it's not good enough because it's not proven. The only thing that is known is that black holes here on Earth can end our entire existence, so I think it's safe to say we need quite a bit of undeniable, undebatable proof that these experiements are safe before we can resonably justify the risks involved. I'm sorry but just saying that "Hawking radiation theory is probably right" isn't good enough for me, not when the entire world's existence hangs in the balance.

In simple mechanical engineering, any unknown factor like material strength or long term strain is treated with caution to ensure it is not a danger and safety threat. But here, we are dealing with the most unproven, theoretical physics, often based just on hypothesese, and yet these people expect to mess around with this stuff as if it's no big deal, and not as if it has a chance of ending our entire existence. The whole thing just seems ludacris.
 
  • #16
I have to say I'm uncomfortable about the LHC. Particularly when I read Michiu Kaku saying energies seen not since the Big Bang.
 
  • #17
pervect said:
See for example

http://curious.astro.cornell.edu/question.php?number=572

Hey, thanks, that was exactly my question in my previous post...
 
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  • #18
vanesch said:
and that a collision of high enough energy might "trigger" the sudden phase transition to another vacuum state (like the sudden freezing of an undercooled liquid). That would not only destroy the Earth and the solar system, but the entire visible universe.


...Or maybe not to cause destruction, but a "flip" of time. (I'm laughing right now, so you might too...) :smile:

So, in some weird kind of way all the physical processes, all the chemical reactions go backwards - a crazy, crazy, crazy world.
Now imagine that there are only few civilisations in the Universe (maybe 6-7), so when some of them researches technology to such level that they can try it (make such experiment) - they "filp" the time for the whole Universe, and for all of the rest of the civilisations in existence! Maybe some of those civilisations function in the other "flip" of the time - so it seems as a normal logic of things for them (like some other culture would see some other numeric system as logical and use it (instead of decade system like us)). Maybe some of them can function in both directions of time (or they developed a technology to overcome such problem). Maybe not. Maybe we all play a weird intergalactic game of ping-pong. Switching it backward and forward, and so on... Until some of them figure this out (SOMEHOW!), so they must make an intergalactic quantum telescope just to figure-out where the punny little imbeciles actually are; and then they must make a quantum telecomunication device, and a quantum device that can manipulate matter at predetermined distance, so they could finaly make a pohone call in the nick of time yelling in their native thongue: "STOP it! You idiots! What a heck do you think you're doing??! You'll have us all FLIPPED!". ...And if some of them decide to make phisical contact with those which function in other direction of time, someone suddenly realize that they might be made of anti-matter, and so he says "Don't touch them! They might explode!"
Oops... to late... a few teratons of explosion force... nothing really...
-------------------

Heh... Highly unprobable, but makes a good story for "a comedy movie of cathaclismical proportions".
(if somebody uses this idea without my prior consent I'LL SUE! :smile: )
 
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  • #19
Don't you hate when it happens... I thought I've lost the original post so I've wrote it all over agen up there, but then I've found it after all...

vanesch said:
...and that a collision of high enough energy might "trigger" the sudden phase transition to another vacuum state...

Or, maybe not cause a destruction, but a reversal of time (in some way we are still ignorant of, because we (let's be objective) still have a whole load of missconceptions (not being aware of it (BELIEVING differently) is a part of the concept of "missconception")))? (I'm laughing on this, so you might too)

...Imagine: all the physical laws being wierdly reversed (but somehow normal for some other type of logic (like some other culture could have another numeric system (insted of decade like us))), all the chemical reactions (by some weird logic) going backwards - a crazy crazy world - world where there is no process of decission for our type ("flip") of inteligence, because first there are ideas, and then they aren't (instead of normaly). So - imagine that totaly crazy concept in context of this: that there are a few civilisations (6-7) in whole of Universe, so they (in a way) play an intergalactic game of ping-pong: first one of them who see all of that crazy reversed as normal and live in those reversed conditions flip the time in Universe, then the other do it and set them straight (asrev eciv <-) a perplexed mix-up of different out-comes for all of them in that "crazy game". (all that until some of them (!SOMEHOW!) realize this and then make a quantum comunication machine which can also manipulate matter on a predermined distance (so you must first have a gigantic "quantum telescope" to first see where the punny little far away imbeciles which are in our "filip" actualy are)) - and finaly make a phone call in the nick of time - yelling on it in their native languge "You idiots! What the **** are you doing?? Do you want us all FLIPPED!"

(Then you find those other beings in other "flip" state of the Universe - some of them functioning in that different logic, some of them being victimes of it (some of them being able to go both ways?); and you find-out that some of them are made of anti-matter - so you must say "Stop! Don't touch them! They'll explode!")

(A good material for a comedy... totaly unprobable, but makes a good story...)

(where "****" = "heck")
 
  • #20
Jake said:
That's what I was getting at: all the hypotheses that "prove" that these black hole experiments are safe are simply to weak and newly hypothosized to risk our entire future for some discretionary science experiements.

I strongly disagree. While realistic prudence is necessary, timidity beyond reason is unwarranted and foolish. By that logic, Columbus should not have set sail, lest he anger the sea monsters that lived near the edge of the world so they would destroy all ships on the sea. Nor should we do research on biological mutations, lest we create a superbug that will infect everyone and wipe out all mammals. Hey, we probably shouldn't be broadcasting radio waves out to the universe, since that might alert the hostile K'zini to our presence and invite all the extraterrestrials to come and conquer us. After all, those are all possibilities that we cannot preclude (well, except for the sea dragons maybe, but there's still a lot of unexplored territory under the oceans). We just don't know enough to take such risks when the whole world is at stake, right?
 
  • #21
By the way, you all should stop using incadescent light bulbs, because one out of every 10^100 photons will have energy in excess of 10^10 eV. This is an unacceptable risk.
 
  • #22
Haha, I just went through the blackbody equation to try and find the true probability of getting a photon of 10^10 eV out of an Incadescent bulb...

Turns out it's roughly 1 out of every 10^100000000000 photons... :)
 
  • #23
That's what I was getting at: all the hypotheses that "prove" that these black hole experiments are safe are simply to weak and newly hypothosized to risk our entire future for some discretionary science experiements.
Of course, you need to believe these very hypotheses to even come to the conclusion that black holes would get formed!
 
  • #24
Bob3141592 said:
I strongly disagree. While realistic prudence is necessary, timidity beyond reason is unwarranted and foolish. By that logic, Columbus should not have set sail, lest he anger the sea monsters that lived near the edge of the world so they would destroy all ships on the sea.

When the stakes are this high, and the likely hood unknown, it is not foolish at all, in fact the only thing foolish is not being this cautions. You're analagous examples aren't relevant either, because each one of them is easier to analyze and understand then this almost entirely hypothetical explanation as to why these micro black hole experiments would be safe.

Hurkyl: The concept of black holes has been around for a lot longer time than hawking radiation, and by that standard alone I would believe in black holes more solidly than hawking radiation. In the very least, all theories are equally possible, in which case my previous arguments are not changed.
 
  • #25
Jake said:
Hurkyl: The concept of black holes has been around for a lot longer time than hawking radiation, and by that standard alone I would believe in black holes more solidly than hawking radiation. In the very least, all theories are equally possible, in which case my previous arguments are not changed.

As has been said several times already, our safety is not dependent on the existence of hawking radiation -- micro black holes are too small to interact noticably with the Earth on short timescales. In addition, traditional black hole theory predicts that no black holes will be formed at the LHC -- it is only some "extra dimensions" theories that predict micro black holes at TeV energies. Even if these "extra dimensions" theories are correct, none that I'm aware of predict black holes that interact enough to have any noticable impact on the earth. I think Bob's analogies are perfectly appropriate.
 
  • #26
SpaceTiger said:
As has been said several times already, our safety is not dependent on the existence of hawking radiation -- micro black holes are too small to interact noticably with the Earth on short timescales. In addition, traditional black hole theory predicts that no black holes will be formed at the LHC -- it is only some "extra dimensions" theories that predict micro black holes at TeV energies. Even if these "extra dimensions" theories are correct, none that I'm aware of predict black holes that interact enough to have any noticable impact on the earth. I think Bob's analogies are perfectly appropriate.

Bob's analogies: No, all of them had a lot more testable predictions and claims, and most importantly a knowledge of previous tests and outcomes, than does this micro black hole issue. But that's beside the point.

Now, will micro black holes, if created, not sink to the middle of the earth, where the pressure is very high and matter dense as stated on this thread? And if so, what equations predict how long it will take for the micro black holes to grow to a size that will consume the earth?
 
  • #27
These are not new ideas, they've been thoroughly dismissed before.

"Review of Speculative "Disaster Scenarios" at RHIC
W. Busza, R.L. Jaffe, J. Sandweiss and F. Wilczek"

http://www.bnl.gov/rhic/docs/rhicreport.pdf#search='Review%20of%20speculative%20disaster%20scenarios%20at%20RHIC
 
  • #28
Jake said:
Bob's analogies: No, all of them had a lot more testable predictions and claims, and most importantly a knowledge of previous tests and outcomes, than does this micro black hole issue. But that's beside the point.

On the contrary, I would say our understanding of the possibilities here is much more reliable than our understanding of mutant viruses or extraterrestrials. I'm not concerned about those things either, but I couldn't present you with an equation or OOM calculation that would refute the existence of hostile aliens.


Now, will micro black holes, if created, not sink to the middle of the earth, where the pressure is very high and matter dense as stated on this thread?

It depends on the velocity at production. A black hole created at low energy will indeed become bound to the Earth and oscillate back and forth through its interior. The density at the center of the Earth is only about five times higher than at the surface, so it won't make a big difference to the calculation. Very crudely, the time it will take the black hole to interact with a single particle is

\tau\sim\frac{1}{n\sigma v}

where n is the number density of particles, \sigma is the interaction cross section, and v is the black hole's velocity. Using the horizon radius to estimate the cross section, the average density of the Earth to estimate n, and escape velocity to estimate the black hole's velocity, I get that it takes about a year for the black hole to interact with only one particle. If we're very liberal and add a nucleon's worth of mass (~1 GeV) to the micro black hole, then it will take of order 1000 years to double its mass (from 1 TeV to 2 TeV). For comparison, the energy equivalent mass of the Earth is of order 1048 TeV.

In classical black hole theory, the rate of interaction (and therefore accretion) would increase quadratically as the mass increased; that is, until it became Eddington limited. A black hole can't accrete too quickly or else the radiation pressure will blow away the surrounding matter. This results in a mass accretion rate that goes linearly with mass, leading to exponential growth of the black hole. The e-folding time for this accretion should be of order tens of millions of years. To accrete the earth, the black hole needs to undergo about 115 e-foldings -- that'll take several billion years.

And the above analysis is extremely liberal. For starters, micro black holes at the LHC, if made, would not be classical ones, they would have a cross section that increased much more slowly with mass. This would dramatically slow the growth of the black hole, particularly in the initial stages. Secondly, it's not obvious to me what would happen if a micro black hole of this size collided with a nucleon. The most it could do is take the nucleon's entire mass, but realistically, it would probably only take a fraction of the total mass energy -- perhaps a quark or gluon. Finally, the Eddington limit is only the maximum rate at which it can accrete. It could very well end up accreting at a much slower rate after interactions damp its motion through the earth.
 
  • #29
Just for curiosity sake.

Lets say we had the technology to rapidly produce Top Quarks at a phenominal rate far exceeding the decay rate speed of the Top Quark per femtosecond or much faster.

If we could ball up Top Quarks very fast how big would the Ball of Top Quarks have to be before it was so Gravitationaly strong that it would appear to have the Properties of a Black Hole.

Is there anyone who can check out the Math to find out how big of a Top Quark Ball we'd need?

I have been thinking maybe the size of a Beach Ball but I really am just guessing.

I know this isn't possible now or maybe not for a very long time from now or maybe not at all but let's just assume we had the means to do it.
 
  • #30
Quarks aren't free. You'd get hadrons (protons, neutrons, etc.) These would fly apart. Even if you forced them into nuclei, they'd fission apart. Crazy speculation isn't useful.
 
  • #31
Rach3 said:
Quarks aren't free. You'd get hadrons (protons, neutrons, etc.) These would fly apart. Even if you forced them into nuclei, they'd fission apart. Crazy speculation isn't useful.

Actually it was a question, not a speculation.

The Question was a hypothetical one.

If no one knows the Math then I guess I'll figure out how big the Ball would have to be myself then.

Sorry to interrupt this discussion, bye.
 
  • #32
Okay, so let's say that it'd take 10 billion years for one nano black hole to eat the earth. How much time for 1,000 nano black holes? How about 100,000? A million?

Their plan isn't to make just one or two, but rather thousands at a time.

Another issue; what's in it for us? Other than a "looky what we did", what value is this science to humanity?

It seems to me that any effect that might be created at these energies is wholly impracticable for utilitarian applications. Or, if there might be a way to use these effects at lower energy levels, why not just build the lower energy technology and see if it works?

Lots of valuable resources expended, little likelyhood of benefit, possibility of doomsday destruction. Yeah... that sounds like a good plan!
 
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  • #33
ubavontuba said:
Okay, so let's say that it'd take 10 billion years for one nano black hole to eat the earth.
10 billion? Make that 10 billion billion billion and you have a worst case scenario for one "nano black hole" eating the earth.
 
  • #34
Jake said:
In the very least, all theories are equally possible
Really? Is a theory that says that all terrestrial objects should spontaneuosly fly off the Earth as "possible" as a theory that says the previous theory is wrong.
 
  • #35
I think it would be cool to see an array of nanoholes eating the Earth.
 
  • #36
ubavontuba said:
Their plan isn't to make just one or two, but rather thousands at a time.

The "plan" is not to make any black holes at all. Idle theorists have been looking for all kinds of weird speculations (because it's their job, and they don't have much experimental data on their hands for which there's no explanation yet) in the vague hope that they might be on something. Give them 30 more years and they'll come up with potential strawberry production in 42 dimensions :-p
The only thing that the LHC will do is to smack protons together at about 10 times more energy than what has been done at the Tevatron at Fermilab for about 10 years or so.
In the most probable scenario, the only thing that will happen is Higgs production. In the next most probable scenario, supersymmetric particles might be found (and even this is totally speculative). All the rest is a wild guess.

Another issue; what's in it for us? Other than a "looky what we did", what value is this science to humanity?

It's a further test of some fundamental theories. Apart from the tremendeous technological spinoff resulting from the applied research by the experimentalists to make the machine and detectors up and running, there's not more utilitarian return than, say, a telescope or an astrophysics department or a visit to the moon. Nevertheless, don't underestimate the technological return by the experimentalists. It's big.

It seems to me that any effect that might be created at these energies is wholly impracticable for utilitarian applications. Or, if there might be a way to use these effects at lower energy levels, why not just build the lower energy technology and see if it works?

Lots of valuable resources expended, little likelyhood of benefit, possibility of doomsday destruction. Yeah... that sounds like a good plan!

Well MOST of the expended resources do not go to the PhD students looking at the data on their PC, but go into the applied R&D to build machine and detector. And *that* research has a lot of practical returns.

Let's for example not forget (as a VERY SMALL investment of some computer scientists thinking about a practical way to organize information dissemination within a collaboration) that it was at CERN that the WWW was invented (not "internet" as some erroneously claim). Talk about some return on investment !
 
  • #37
I feel like I'm being ignored by the doomsday people here: Can the people who think the LHC is potentially dangerous explain to me why cosmic rays, which hit the atmosphere constantly at higher energies and with much greater frequency than the particles that will be produced at the LHC, haven't devoured the Earth yet?

Why is the Earth still here after 5 billion years of cosmic ray bombardment?
 
  • #38
vanesch said:
Hey, thanks, that was exactly my question in my previous post...

Sorry for not responding to you directly, vanesch. Pervect had pretty much made all the points I was going to bring up.
ubavontuba said:
Okay, so let's say that it'd take 10 billion years for one nano black hole to eat the earth.

10 billion years is near the physical lower limit of what's possible (by the Eddington limit), but I wouldn't say it's probable.
How much time for 1,000 nano black holes? How about 100,000? A million?

Not much shorter. Remember, we're talking about exponential growth in the limiting case, so the limiting timescale will shrink only logarithmically with the number of black holes created.

It's also good to keep in mind all of the qualifications that go into these limiting calculations:

1. The black holes don't Hawking radiate away -- Given that a similar effect (the Casimir effect) has been experimentally confirmed, I don't think there's a great deal of skepticism about Hawking radiation in the physics community. Hawking radiation also lies within a regime in which most folks trust both GR and QFT.
2. The LHC would have to actually create black holes -- It's only a couple very exotic theories that predict any black hole creation at these laboratories. Mainstream theory predicts that we are a long way from the energy scale needed to create black holes (~1019 GeV).
3. The black holes would have to remain bound to the Earth -- This should only be the case with those created right at threshold, a small fraction of the total.
4. The black holes don't disappear upon interaction with other particles- - Since we don't have a reliable theory of quantum gravity, there's no reason to assume that micro black holes will stick around after creation.
5. The micro black holes will accrete rapidly -- Again, there's little we can do to address this question without QG.

If this is your idea of dangerous, then I think I should invest in your insurance provider.
 
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  • #39
Gokul43201 said:
Really? Is a theory that says that all terrestrial objects should spontaneuosly fly off the Earth as "possible" as a theory that says the previous theory is wrong.


Err, you seemed to have misunderstood me entirely. I was giving Hawking radiation more credence than it deserves, seeing that its been around for a lot less time than black hole theories in general, and therefore has had less time to be proven wrong. I was comparing specific theories not any theory. How you came to that conclusion is beyond me :)

And please explain to me where you came up with the numbers that it will take "10 billion billion billion" for a micro black hole to eat earth?
 
  • #40
Guillochon said:
I feel like I'm being ignored by the doomsday people here: Can the people who think the LHC is potentially dangerous explain to me why cosmic rays, which hit the atmosphere constantly at higher energies and with much greater frequency than the particles that will be produced at the LHC, haven't devoured the Earth yet?

Why is the Earth still here after 5 billion years of cosmic ray bombardment?

It was stated earlier in this thread that those black holes, because they are so high energy and based on how they would be created, would be flung into space far away from earth.
 
  • #41
The sky is falling!

vanesch said:
The "plan" is not to make any black holes at all.

Apparently, you didn't read my http://www.cerncourier.com/main/article/44/9/22", straight from the CERN Courier.


It's a further test of some fundamental theories. Apart from the tremendeous technological spinoff resulting from the applied research by the experimentalists to make the machine and detectors up and running, there's not more utilitarian return than, say, a telescope or an astrophysics department or a visit to the moon. Nevertheless, don't underestimate the technological return by the experimentalists. It's big.

That's one heck of an expensive microscope! Anyway, the experimentalists aren't really doing anything new, just bigger.

Well MOST of the expended resources do not go to the PhD students looking at the data on their PC, but go into the applied R&D to build machine and detector. And *that* research has a lot of practical returns.

Sorry, I just don't see it. The hardware is already well understood and has been duplicated (albeit at smaller scales) numerous times before.

Let's for example not forget (as a VERY SMALL investment of some computer scientists thinking about a practical way to organize information dissemination within a collaboration) that it was at CERN that the WWW was invented (not "internet" as some erroneously claim). Talk about some return on investment !

No, Al Gore invented the internet, haven't you heard? :-p
 
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  • #42
Run! Run for your lives! The sky is falling!

Guillochon said:
I feel like I'm being ignored by the doomsday people here: Can the people who think the LHC is potentially dangerous explain to me why cosmic rays, which hit the atmosphere constantly at higher energies and with much greater frequency than the particles that will be produced at the LHC, haven't devoured the Earth yet?

It's a matter of conservation of momentum. How fast are these particles moving relative to the earth? When they strike a particle, say of equal mass, how fast is the resulting mass moving? If the resulting mass is a nano black hole, what might stop it from passing clean through the earth?

If you want to state that subsequent collisions will stop it, I think you'd be quite frightened by how much mass it must then accrue in a very, very short time. They certainly ought to be detectable, as they pop up through the ground.

Why is the Earth still here after 5 billion years of cosmic ray bombardment?

Why is the fifth planetary orbit (the asteroid belt) a pile of loose rubble?
 
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  • #43
Jake said:
It was stated earlier in this thread that those black holes, because they are so high energy and based on how they would be created, would be flung into space far away from earth.

Point taken.

Here's a question for you: Almost all cosmic rays have interacted with many many particles before they hit our atmosphere. If creating black holes is so easy, why do we see cosmic rays at all? Shouldn't most of these high energy particles become black holes?
 
  • #44
ubavontuba said:
It's a matter of conservation of momentum. How fast are these particles moving relative to the earth? When they strike a particle, say of equal mass, how fast is the resulting mass moving? If the resulting mass is a nano black hole, what might stop it from passing clean through the earth?

Well, the same argument can probably be applied to potential BH produced at LHC: they will have considerable momentum wrt the earth, because it is highly unlikely that the momentum balance of the remnants of the collision is perfect.

Why is the fifth planetary orbit (the asteroid belt) a pile of loose rubble?

I thought that the explanation was that the pull of nearby Jupiter disrupted planet formation... I didn't know it was due to an ancient civilisation having fired up their brand new particle accelerator :smile:
 
  • #45
ubavontuba said:
Apparently, you didn't read my http://www.cerncourier.com/main/article/44/9/22", straight from the CERN Courier.

Yes, but that's highly hypothetical, no ? We already have to live in 10 dimensions...


Sorry, I just don't see it. The hardware is already well understood and has been duplicated (albeit at smaller scales) numerous times before.


The scaling up in itself needs a lot of R&D. You don't see this as spectacular breakthroughs, it are many many small improvements in the reliability of the production process and so on which make up the bulk of this research.

For instance, at PSI I remember having heard a talk about research on back-to-back connections between arrays of photodiodes on silicon and the ASIC that does the data selectioning and compression before sending it on an optical fibre. The industrially available techniques didn't have a high enough density of connection points to do this. So a lot of research was done to improve this, and the density was increased 16 fold.
Now that these back-to-back connections are available, the whole sandwich of photodiodes + electronics is used for high resolution medical X-ray imaging. It took 6-7 years of a 10 person R&D group to devellop this.

There are many such examples.
 
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  • #46
Jake said:
Wikipedia http://en.wikipedia.org/wiki/Micro_black_hole" that hawking radiation is a controversial theory which very well may not be true. Correct me if I'm wrong, but doesn't this mean that if we are able to create micro black holes at the Large Hadron Collider, and if Hawking radiation is wrong, we are effectivly destroying all of humanity and this entire solar system? Won't scientists at the collider try and create micro black holes? Isn't this a bit reckless on the part of the scientists to endanger all of human existence based on very theoretical science? All of this just to possibly learn a bit more about black holes. Doesn't make too much sense if you ask me...

I'm just trying to understand the thinking in all of this, thanks.
You don't have to try :smile:
That text seems like Star trek script writters' wild imagination gets out of control again :smile:
 
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  • #47
ubavontuba said:
It's a matter of conservation of momentum. How fast are these particles moving relative to the earth? When they strike a particle, say of equal mass, how fast is the resulting mass moving? If the resulting mass is a nano black hole, what might stop it from passing clean through the earth?
An electron hitting the upper atmosphere with energy E will have the same momentum as an electron in the LHC which has the same energy. The relative motion is taken into account when calculating collision energies, hence such concepts as "centre of momentum frame" or "centre of mass frame". Your point is zoid.
ubavontuba said:
Why is the fifth planetary orbit (the asteroid belt) a pile of loose rubble?
Because of Jupiters gravity. If it was from a black hole, we wouldn't see most of the asteroids, they'd have been absorbed by the black hole.
 
  • #48
Jake said:
Err, you seemed to have misunderstood me entirely. I was giving Hawking radiation more credence than it deserves, seeing that its been around for a lot less time than black hole theories in general, and therefore has had less time to be proven wrong. I was comparing specific theories not any theory. How you came to that conclusion is beyond me :)
I was responding to what I perceived as a sweeping statement.

And please explain to me where you came up with the numbers that it will take "10 billion billion billion" for a micro black hole to eat earth?
The Cornell-Astronomy link provided by Pervect has an estimate of 10^28 years.
 
  • #49
vanesch said:
Well, the same argument can probably be applied to potential BH produced at LHC: they will have considerable momentum wrt the earth, because it is highly unlikely that the momentum balance of the remnants of the collision is perfect.

In order for black holes to form (generally speaking) all of the energy must be expended in the collisions. Glancing blows, that allow for continued momentum of the particles, will not deliver enough energy to compress the particles into black holes. This is why they expect/hope only a small percentage of each run to form black holes.

I thought that the explanation was that the pull of nearby Jupiter disrupted planet formation... I didn't know it was due to an ancient civilisation having fired up their brand new particle accelerator :smile:

Jupiter wasn't always where it is. Besides, Jupiter's moons suffer more tidal forces than the asteroids, and yet there they are.
 
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  • #50
AlphaNumeric said:
An electron hitting the upper atmosphere with energy E will have the same momentum as an electron in the LHC which has the same energy. The relative motion is taken into account when calculating collision energies, hence such concepts as "centre of momentum frame" or "centre of mass frame". Your point is zoid.

Sure, but the relative motion frame of the two colliding particles is not the same as the relative motion frame of the earth, in this instance.

Because of Jupiters gravity. If it was from a black hole, we wouldn't see most of the asteroids, they'd have been absorbed by the black hole.

Not true, a rotating body eaten from within would collapse both outwardly and inward. It's a function of angular momentum (like Hawking radiation).
 
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