Could the Large Hadron Collider Create a Black Hole That Threatens Earth?

[enmerkar]

Of course it is worth entertaining...

 

[malawi_glenn]

enmerkar: The thing is that LHC is not more dangeorus than the tevatron, nuclear power plants or atomic bombs, LHC it in fact not danger at all. LHC is not even complex, it is just a very powerful proton accelerator.

Zz's point that there exists answers, written in elegant reports, but if "we" refer to the reports, we are arrogant.

There are better things to be afraid of then a small proton accelerator.

 

[Hurkyl]

Of course it is worth entertaining...

Why do you think that?

 

[enmerkar]

It's not the machinery I am "affraid" of. In weeks the proton accelerator will be impacting protons with incredible momentum. I see the disingenuous compairisons to high energy gama ray interactions at our upper atmosphere. Please compair apples to apples not apples to acorns. when up to par the LHC will be colliding protons in opposite directions to reveal in theory quark-quark interactions. to make an analogy we have to have honest compairisons with confident susceptibility. should MBH be produced don't just speak of one as though it has no possible interaction with the many other MBH that may be produced simultaneously. there may be correlations that quantum mechanics has not uncovered yet. I am certain that there will be correlations existent with multiple singularities in the these Fields. There are of course other concerns all of which give concern.

 

[enmerkar]

Quantum correlations between multiple singularities originating from a single event (collision) must be considered. There is currently no way of knowing how correlated MBH will behave not to mention "Strangelets" or Strange matter. matter composed of numbers of up, down, or strange quarks and quantum mechanics... there are no texts illuminating our way. this is all cross your fingers and hope we're OK.

 

[malawi_glenn]

It's not the machinery I am "affraid" of. In weeks the proton accelerator will be impacting protons with incredible momentum. I see the disingenuous compairisons to high energy gama ray interactions at our upper atmosphere. Please compair apples to apples not apples to acorns. when up to par the LHC will be colliding protons in opposite directions to reveal in theory quark-quark interactions. to make an analogy we have to have honest compairisons with confident susceptibility. should MBH be produced don't just speak of one as though it has no possible interaction with the many other MBH that may be produced simultaneously. there may be correlations that quantum mechanics has not uncovered yet. I am certain that there will be correlations existent with multiple singularities in the these Fields. There are of course other concerns all of which give concern.

You must be the biggest goof I've ever encountered that think that cosmic rays are high energy gamma rays.. cosmic rays consists of protons, electrons and ions which interact with nuclei in atmosopheric atoms at HIGHER CM-energy than LHC. It doesn't matter who and where you collide partiles, what matters is CM-energy. It doesent matter if you have two collding beams or a fixed target experimet such as the Earth beeing hit by protons acclerated from an AGN or SN. Also, what is moving and standing still are relative concepts, you can always find a frame where the Earth and the cosmic ray protons are hitting each other with equal velocity, momenta etc. I thought you was a scientist? well, you are not a physicsist for sure.

And how many times must we explain this? This is 3rd or 2nd time I have to tell someone in this tread how transformations work..

 

[SorinK]

Hi.
"Any microscopic black holes produced at the LHC are expected to decay by
Hawking radiation before they reach the detector walls."
Expected does not mean WILL decay.
What if does not decay?!

 

[gendou2]

Motion to lock or move this thread. There's no convincing people who aren't open to listening. This debate is polarized such that neither group cares to listen. There is no scientific reason for the LHC supporters to acknowledge the critics irrational viewpoint. Similarly, there is no logical argument that the LHC supporters can present to satisfy the critics. Te arguing is pointless.

 

[malawi_glenn]

Motion to lock or move this thread. There's no convincing people who aren't open to listening.

Can you adress those people?

 

[gendou2]

Hi.
"Any microscopic black holes produced at the LHC are expected to decay by
Hawking radiation before they reach the detector walls."
Expected does not mean WILL decay.
What if does not decay?!

What if gravity turns off an we all fly into space? It could happen. After all, gravity is just a theory. I find both about equally likely.

 

[humanino]

Expected does not mean WILL decay.

The Sun is expected to rise tomorrow morning. Nothing is certain in this world (c.f. Einstein quotation on being certain of the infinitude of the Universe).

 

[vanesch]

Yes, I think that article is excellent and I think that is the type of point-by-point analysis that should be employed to determine beyond all doubt that there are no safety concerns.

To answer your first question, I'll give a small list, even though I think my point should be self-evident:
1) Many "scientists" said global warming was baloney. We all now know better.

do we ? I'd say the jury is still out for that one for at least 50 years. How can you "know better" otherwise ?

2) Many "scientists" said nuclear winter was baloney. Carl Sagan managed to convince us otherwise thank heavens.

Have we observed a nuclear winter ? So how do you know ?

3) Many "scientists" said it was safe for soldiers to observe above-ground nuclear tests, or to have above-ground tests period.

Did MOST of them die ?

4) Many "scientists" at drug companies and at the FDA have countless times told us drugs are safe for us to later find out they're not

Did MOST people who took them, die ?

6) "Scientists" used to believe in bleeding people to keep them alive

Did they ? Or did they just call themselves "barbers" ?

7) "Scientists" used to tell us smoking was safe

Any published papers about that ?

8) "Scientists" used to tell pregnant women to drink wine

Any published papers about that ?

 

[gendou2]

Can you adress those people?

I certainly prefer not to name names.
The lion's share of the debate is about the trustworthiness of scientists as a group.
This is a silly thing to argue about.
Black holes are interesting, to me.
Radically skeptical arguments are not.

 

[malawi_glenn]

What if gravity turns off an we all fly into space? It could happen. After all, gravity is just a theory. I find both about equally likely.

That was the lamest answer I've ever seen.

http://library.thinkquest.org/C007571/english/advance/core8.htm

So it will acquire mass by eating on the detector, getting longer and longer lifetime and then eventually eat the Earth :-)

But maybe an expert on black holes should answer, I have only done introductory courses on general relativity.

 

[gendou2]

That was the lamest answer I've ever seen.

http://library.thinkquest.org/C007571/english/advance/core8.htm

So it will acquire mass by eating on the detector, getting longer and longer lifetime and then eventually eat the Earth :-)

But maybe an expert on black holes should answer, I have only done introductory courses on general relativity.

I was being ironic. Didn't you notice?
My intention is to expose how silly the radical skepticism is.

 

[malawi_glenn]

I certainly prefer not to name names.
The lion's share of the debate is about the trustworthiness of scientists as a group.
This is a silly thing to argue about.
Black holes are interesting, to me.
Radically skeptical arguments are not.

So what is a radicall skeptical argument?

 

[gendou2]

So what is a radicall skeptical argument?

When someone obsesses over "what if" scenarios, they are being radically skeptical of the safety we all take for granted, for example.

 

[malawi_glenn]

I was being ironic. Didn't you notice?
My intention is to expose how silly the radical skeptics are.

It is your own behaviour that makes this thread flip out. You are self contributing to the nonsense beeing posted here. So if you know a lot of black holes, write about it, if not, be quite.

 

[malawi_glenn]

When someone obsesses over "what if" scenarios, they are being radically skeptical of the safety we all take for granted, for example.

He was not obsessed, he simply asked what will happen if a MBH reaches the detector, I tried to answer hom from my small knowledge about BH lifetimes. Also since we have not observe BH-hawking radiation yet, it is a well founded question.

My ultimate answer would anyway be that it can't do no harm since if they are created in very high energy collisions, such as at the LHC or in the atmosphere beeing hit by cosmic ray protons and ions, they have not killed the Earth during the millions of years the "Large Cosmic ray collider" have been under operation.

 

[gendou2]

It is your own behaviour that makes this thread flip out. You are self contributing to the nonsense beeing posted here. So if you know a lot of black holes, write about it, if not, be quite.

What the hell, man?
I apologize if my point was not made clearly, and if my point was not helpful.
The nonsense bothers me, too.
I understand if you're frustrated, too.
Give me a break, though. Seriously.

 

[gendou2]

He was not obsessed, he simply asked what will happen if a MBH reaches the detector, I tried to answer hom from my small knowledge about BH lifetimes.

"He" who? I wasn't naming names. Read my posts before accusing me, next time, please.

 

[malawi_glenn]

What the hell, man?
I apologize if my point was not made clearly, and if my point was not helpful.
The nonsense bothers me, too.
I understand if you're frustrated, too.
Give me a break, though. Seriously.

I'm just telling you that irony and sarcasm is hard to differ on forums, exspecially when smileys are not beeing used. This thread is already very tense and loaded, if one tries to answer the questions without beeing ironic or sarcastic, things will work better.

I am not telling that Iam a good example on this, you assume that people are reading the thread which they are posting in so you don't have to post things 2,3,4 times! Like that enmerkar-guy, who is a "scientist" and uses physics language and thinks he know something.. THAT is very anoying.

 

[malawi_glenn]

"He" who? I wasn't naming names. Read my posts before accusing me, next time, please.

The guy "SorinK" (post #265) which you answered 5minutes ago, he was adressing a "what if question". It is quite reasonable that you was partly referring to this post.

 

[gendou2]

I'm just telling you that irony and sarcasm is hard to differ on forums, exspecially when smileys are not beeing used.

Got it. It would have been more helpful for me to mention that micro black holes evaporate quickly. So quickly, in fact, that their lifetime is well shorter than the time it takes to move an angstrom.

http://en.wikipedia.org/wiki/Hawking_Radiation
http://en.wikipedia.org/wiki/Micro_black_hole

h = 6.62e-34
c = 3e8
G = 6.67e-11
M = 2 * 2.176e-8
t = (5120 * pi * G^2 * M^3) / (h * c^4)
t:1.1e-39

1*10^-39 seconds is far less time than it takes light to travel one angstrom.
I feel safe in saying that the a micro black hole of 2 Planck masses would evaporate before it could gobble any nearby atoms.

 

[humanino]

I don't need those ugly formulas to think.

Mechanical intuition does a very poor job at the quantum level. How do you define temperature for a single particle ? Only energy matters here.

 

[cristo]

Let's all please try and remember that PF has rules, which must be adhered to at all times, even in threads such as this one. Furthermore, if anyone sees a questionable post, please us the "report" button to bring it to the moderators' attention.

 

[tiny-tim]

danger of white holes

Why is everyone keeping so quiet about the danger of creating white holes?

I read somewhere that when protons and anti-protons collide, there is a theoretical possibility of creating floppions, which will decay to produce a white hole that is effectively a portal from another universe.

Far from sucking the Earth in, a white hole would drain matter from an already existing universe and pour it onto the earth.

Even if we escaped the 50% danger of this being anti-matter, thus turning central Europe white-hot, the huge added mass would considerably lengthen the day, and disturb the present earth-moon equilibrium, perhaps with the obvious catastrophic result.

Even if a benign, neutral, wormhole were established, we would still be open to invasion by unfamiliar life-forms, which depending on the maximum size of the wormhole capable of being created by the LHC could be anything in size from viruses to white rabbits.

Such species would multiply exponentially, and destroy life as we know it … and please don't tell me that couldn't happen!

And does the official "safety" report deal with these dangers?

I don't think so!​

 

[gendou2]

I read somewhere that when protons and anti-protons collide, there is a theoretical possibility of creating floppions, which will decay to produce a white hole that is effectively a portal from another universe.

Where did you read this? Please cite your source. I tried looking for myself but google was no help.

As far as the white hole is concerned, I can recommend some reading:
http://curious.astro.cornell.edu/question.php?number=108

 

[SorinK]

@tiny-tim they want only formulas.
They have the impression that all that is calculated is good, and if even they don't know what will happen, they know that is not dangerous because was made at a smaller scale.
If you think that a white hole will be formed you need to give them some formulas because they don't like theories with no formulas.
I was warned because I had a theory with no formulas and wrote it here.

 

[malawi_glenn]

@tiny-tim they want only formulas.
They have the impression that all that is calculated is good, and if even they don't know what will happen, they know that is not dangerous because was made at a smaller scale.
If you think that a white hole will be formed you need to give them some formulas because they don't like theories with no formulas.
I was warned because I had a theory with no formulas and wrote it here.

If you don't have a rigour theory that can back up your statements about physical things, then I can as well say "a pink hole will eat my grandma next week". If you want to make physical statements, then you must play the game physicsists play, and that is by doing the hard math, which is the language of physics.

 

[malawi_glenn]

Why is everyone keeping so quiet about the danger of creating white holes?

I read somewhere that when protons and anti-protons collide, there is a theoretical possibility of creating floppions, which will decay to produce a white hole that is effectively a portal from another universe.

Far from sucking the Earth in, a white hole would drain matter from an already existing universe and pour it onto the earth.

Even if we escaped the 50% danger of this being anti-matter, thus turning central Europe white-hot, the huge added mass would considerably lengthen the day, and disturb the present earth-moon equilibrium, perhaps with the obvious catastrophic result.

Even if a benign, neutral, wormhole were established, we would still be open to invasion by unfamiliar life-forms, which depending on the maximum size of the wormhole capable of being created by the LHC could be anything in size from viruses to white rabbits.

Such species would multiply exponentially, and destroy life as we know it … and please don't tell me that couldn't happen!

And does the official "safety" report deal with these dangers?

I don't think so!​

LOL that was even more speculative than MBH's traveling and growing large ;-)

Maybe I'll use the report button now.

 

[gendou2]

I found this:

http://books.google.com/books?id=DG...&hl=en&sa=X&oi=book_result&resnum=2&ct=result

Looks like this idea appears in a book about religion, and is not a scientific theory at all.

 

[malawi_glenn]

I found this:

http://books.google.com/books?id=DG...&hl=en&sa=X&oi=book_result&resnum=2&ct=result

Looks like this idea appears in a book about religion, and is not a scientific theory at all.

man I go to church twice a week and it's such a shame that people writes that kind of ******** in religions (Gods) name =(

 

[malty]

I found this:

http://books.google.com/books?id=DG...&hl=en&sa=X&oi=book_result&resnum=2&ct=result

Looks like this idea appears in a book about religion, and is not a scientific theory at all.

Well it's written by a physicist . . .

 

[cristo]

To try and get this thread back on a serious track, here's a live webcam of the inside of the LHC that some of you may enjoy.

 

[malawi_glenn]

Well it's written by a physicist . . .

I am a physicist and can also write such crap if I want to.. I mean what is an "electrical antiproton"? LOL watch out so that the gauge meson don't decays into a white drawf that can explode and create a new universe in your kitchen.

 

[malty]

To try and get this thread back on a serious track, here's a live webcam of the inside of the LHC that some of you may enjoy.

Spoiler

Why is the accretion disk (or whatever it is) purple??

 

[malawi_glenn]

Spoiler

because it is a nice colour? No seriuos, it is related to wiens displacement law. Matters get hotter and well, you surley know the rest of the story.

 

[malty]

Spoiler

because it is a nice colour? No seriuos, it is related to wiens displacement law. Matters get hotter and well, you surley know the rest of the story.

Spoiler

Yeah, but greens my fav colour, I mean if we're going to create one of these things I'd rather go out with a green one! So I think that's what I'll research how to it's colour

 

[SorinK]

@malawi_glenn, the people that believe that a black hole will be formed are also physicist; they have more than High School info related to black holes and quantum physics.
If such thing can't happen, how is that in there math the results differ?!
All of them don't know math and the others do it in the right way?
The good way would be to meet and to show to the small group where they are wrong.
Are formulas that all of them understand and even if Otto is wrong, the other ones will understand where Otto is wrong and will not support him anymore.
But they don't do that, they prefer to say that the small group is wrong and that is all.
Hawkins theory is not proven.
I want to see a black hole that disappear or at least become smaller so I can agree with Hawkings.

 

[malty]

@malawi_glenn, the people that believe that a black hole will be formed are also physicist; they have more than High School info related to black holes and quantum physicist.
If such thing can't happen, how is that in there math the results differ?!
All of them don't know math and the others do it in the right way?
The good way would be to meet and to show to the small group where they are wrong.
Are formulas that all of them understand and even if Otto is wrong, the other ones will understand where Otto is wrong and will not support him anymore.
But they don't do that, they prefer to say that the small group is wrong and that is all.
Hawkins theory is not proven.
I want to see a black hole that disappear or at least become smaller so I can agree with Hawkings.

Sorin,

The trouble here is that as physicist we know that there is a definite possibility of such an event occurring, but as Zapper already said it is as possible as you smashing a vase and the vase reassembling itself without your intervention. In physics this is a possibility so we cannot say the vase will definitely be destroyed, likewise we definitely cannot say that there is no chance of a black hole (or white hole [I'm sure there's some minute possibility of that too :)]) but we are incredibily more likely to be destroyed by something other than CERN, yes it could happen but there's a million other dangers in this world that are far more likely!

Anyways if you haven't already I suggest that you read this
http://physics.aps.org/articles/v1/14

The article assesses the risk even with many of our more accepted assumptions such as Hawkins being incorrect. You don't really think that we wouldn't do worse case scenario assessments??

 

[gendou2]

SorinK, please watch this: http://cdspages.web.cern.ch/cdspages/1120625.htm

 

[ZapperZ]

@tiny-tim they want only formulas.
They have the impression that all that is calculated is good, and if even they don't know what will happen, they know that is not dangerous because was made at a smaller scale.
If you think that a white hole will be formed you need to give them some formulas because they don't like theories with no formulas.
I was warned because I had a theory with no formulas and wrote it here.

This is because you have an incomplete understand of what physics is. Physics is MORE than just saying "What goes up must come down". Physics must also say "When and Where it comes down". Both of these means that there must be QUALITATIVE and QUANTITATIVE agreements with observation! Without the latter, it is merely a hand-waving argument.

Please note that the PF Guidelines is strictly applied throughout PF, and certainly in the physics sub-forums.

Zz.

 

[Orion1]

Interesting video listed in reference of what is predicted to happen when the LHC reaches full intensity!
[/Color]
Reference:
http://www.youtube.com/watch?v=moEzECvJDas&feature=related"

 

[vanesch]

The trouble here is that as physicist we know that there is a definite possibility of such an event occurring, but as Zapper already said it is as possible as you smashing a vase and the vase reassembling itself without your intervention. In physics this is a possibility so we cannot say the vase will definitely be destroyed, likewise we definitely cannot say that there is no chance of a black hole (or white hole [I'm sure there's some minute possibility of that too :)]) but we are incredibily more likely to be destroyed by something other than CERN, yes it could happen but there's a million other dangers in this world that are far more likely!

I would again want to point out that there is NO *definite probability* that the LHC will create earth-eating things. Contrary to the probability of the vase re-assembling itself, which has a tiny but genuine probability of happening (that is, if you would do an inimaginable number of times the experiment, in some cases the vase WOULD re-assemble), we have in fact no indication at all that the LHC *could* produce an earth-gobbling thing - even if we were to build a gazillion LHCs on a gazillion Earth's.

So what can we do ? We can say that according to most of our theoretical understanding, it is physically impossible to create such an earth-gobbling thing. That would be it.

Or, we can go a step further, and say: LET US SUPPOSE, against all of what we think to know, that we are fundamentally wrong concerning our basic knowledge, and ASSUME that - despite all of what we know telling us that it is physically impossible - it is nevertheless possible. In that case, it has a hypothetical probability of happening. How high could this probability eventually be in order for it not to be in contradiction with observation ?

Now, the last point is important: it means that we have to find ways that would give us observable consequences of our hypothesis that this "theoretically impossible thing" occurs nevertheless. So it depends on our ability to do so, that we can derive UPPER BOUNDS for this probability. If we just stay in our armchair, the upper bound is something around 100%. Indeed, sitting in our armchair is not *incompatible* with our strange thing happening at 100% probability. But it could still be 0%. We simply don't know. So it is not because we sit in our armchair that the probability of creating black holes that eat up the Earth got a probability of 100% ! It's that we didn't do much work to find a better upper boundary. It's like me saying that I don't know how much money you have in the bank, but an upper boundary must be something like 1000 000 times Bill Gates' fortune. It's just because I don't know any better that I can only say something of the kind. If I would have done some better job, I'd find a better upper boundary. In no way this implies that you are so rich.

So the more work I can put into restricting the upper boundary, the lower it can become. In fact, if the actual phenomenon doesn't physically exist (as is suggested by about all of our theories), then with enough work and observation, I can put that boundary as low as I want.

Now, people did a limited amount of work, and they considered only a certain class of observable phenomena, such as planets like Jupiter, or neutron stars, that are exposed for millions of years to LHC-like collisions. From that, they could derive an upper boundary of the eventual probability for our hypothetical event to happen. It DOESN'T MEAN AT ALL, that this is an ESTIMATE for that probability. Only, we don't know any better. If we would like to get a lower boundary, we should do more observations, we should do more clever deductions, etc...

Again, there's a big difference between an *upper boundary* on an eventual probability of an event happening, which should theoretically actually not happen (but we are modest and recon that all of our theoretical knowledge could be wrong), and an *estimate* of the probability of a genuine phenomenon happening, like an estimate for a smoker to devellop cancer due to smoking.

So it is not because some or other scientist writes that "black holes have a probability smaller than 1/500 to eat up the earth" that this means that once out of 500, a black hole will eat up the earth. It simply means that with the limited set of observations, the scientist couldn't find a stronger upper boundary on the probability (which might - and most probably is - zero if we have any reason to believe current theory) starting from the set of observations he decided to start with, and considering the kind of reasoning and approximations he made.

 

[gendou2]

Interesting video listed in reference of what is predicted to happen when the LHC reaches full intensity!
[/Color]
Reference:
http://www.youtube.com/watch?v=moEzECvJDas&feature=related"

I don't see how a flashy animation of the Earth being swallowed by a black hole contributes to the discussion one bit.
You obviously need to watch this, too: http://cdspages.web.cern.ch/cdspages/1120625.htm

 

[Almanzo]

What's wrong with the following syllogism?

1. Lord Martin Rees would not be trying to scare people, unless he himself were scared.
2. Lord Martin Rees is trying to scare people.
3. Therefore: Lord Martin Rees is scared.

And, by the way, I would like to suggest that if cosmic rays hitting atoms in the Earth's atmosphere are producing black holes, these holes will pass just once through the planet, and then disappear into the great unknown. Their velocity would be way beyond escape velocity.

 

[vanesch]

What's wrong with the following syllogism?

1. Lord Martin Rees would not be trying to scare people, unless he himself were scared.
2. Lord Martin Rees is trying to scare people.
3. Therefore: Lord Martin Rees is scared.

Sure. Or:

1. Lord Martin Rees would not be trying to scare people, unless he knew that makes his book sell.
2. Lord Martin Rees is trying to scare people.
3. Lord Martin Rees knows that fearmongering makes a good sales argument.

Or:

1. LMR would not be trying to scare people, unless blah blah
2. LMR is not trying to scare people
3. anything

Or:
...

And, by the way, I would like to suggest that if cosmic rays hitting atoms in the Earth's atmosphere are producing black holes, these holes will pass just once through the planet, and then disappear into the great unknown. Their velocity would be way beyond escape velocity.

Ooops. Didn't think of that

There are two points here:
1) if ever the LHC produces earth-gobbling BH, they will ALSO pass with high momentum through the detector, the Earth and disappear in the great unknown.
2) cosmic-ray BH might eventually "zap through" the earth, but they won't zap through a neutron star without a few interactions. A few interactions is what it takes to slow them down because of conservation of momentum.
Let us not forget that the LHC has at most 14 TeV at its disposal (but actually much less for the elementary collisions of the partons) which corresponds to at most the weight of 10 000 protons. That's very tiny for a BH ! Much much much smaller than the size of a proton. So IF these things interact with a proton, they won't eat up all of the proton, but just maybe one quark of it... and hence liberate a pion. In doing so, there will be a release of energy, comparable to the binding energy of the quark in the proton (grossly, the difference in mass between a proton and a pion). So they will get random kicks. Very very soon, they'll acquire enough speed to escape the very very low Earth attraction... *unless* they eat up much faster much more mass. But if that's the case, they will be stopped by a neutron star too even if they started out very fast, and eat it up very quickly.

You can give your BH a certain set of properties, but then you have to stick to them. Once you stick to a certain set of properties, you should find out how such a BH would behave if produced in the LHC, and how it would behave if produced by a cosmic ray at the surface of a neutron star. In both cases, you have to find out whether your neutron star could have survived, and not earth. That's what has been analysed.

 

[mal4mac]

man I go to church twice a week and it's such a shame that people writes that kind of ******** in religions (Gods) name =(

Yeah. Why don't they stick to the sensible stuff like ghosts descending the Earth and having it away with virgins?

 

[ZapperZ]

I would again want to point out that there is NO *definite probability* that the LHC will create earth-eating things. Contrary to the probability of the vase re-assembling itself, which has a tiny but genuine probability of happening (that is, if you would do an inimaginable number of times the experiment, in some cases the vase WOULD re-assemble), we have in fact no indication at all that the LHC *could* produce an earth-gobbling thing - even if we were to build a gazillion LHCs on a gazillion Earth's.

So what can we do ? We can say that according to most of our theoretical understanding, it is physically impossible to create such an earth-gobbling thing. That would be it.

Or, we can go a step further, and say: LET US SUPPOSE, against all of what we think to know, that we are fundamentally wrong concerning our basic knowledge, and ASSUME that - despite all of what we know telling us that it is physically impossible - it is nevertheless possible. In that case, it has a hypothetical probability of happening. How high could this probability eventually be in order for it not to be in contradiction with observation ?

Now, the last point is important: it means that we have to find ways that would give us observable consequences of our hypothesis that this "theoretically impossible thing" occurs nevertheless. So it depends on our ability to do so, that we can derive UPPER BOUNDS for this probability. If we just stay in our armchair, the upper bound is something around 100%. Indeed, sitting in our armchair is not *incompatible* with our strange thing happening at 100% probability. But it could still be 0%. We simply don't know. So it is not because we sit in our armchair that the probability of creating black holes that eat up the Earth got a probability of 100% ! It's that we didn't do much work to find a better upper boundary. It's like me saying that I don't know how much money you have in the bank, but an upper boundary must be something like 1000 000 times Bill Gates' fortune. It's just because I don't know any better that I can only say something of the kind. If I would have done some better job, I'd find a better upper boundary. In no way this implies that you are so rich.

So the more work I can put into restricting the upper boundary, the lower it can become. In fact, if the actual phenomenon doesn't physically exist (as is suggested by about all of our theories), then with enough work and observation, I can put that boundary as low as I want.

Now, people did a limited amount of work, and they considered only a certain class of observable phenomena, such as planets like Jupiter, or neutron stars, that are exposed for millions of years to LHC-like collisions. From that, they could derive an upper boundary of the eventual probability for our hypothetical event to happen. It DOESN'T MEAN AT ALL, that this is an ESTIMATE for that probability. Only, we don't know any better. If we would like to get a lower boundary, we should do more observations, we should do more clever deductions, etc...

Again, there's a big difference between an *upper boundary* on an eventual probability of an event happening, which should theoretically actually not happen (but we are modest and recon that all of our theoretical knowledge could be wrong), and an *estimate* of the probability of a genuine phenomenon happening, like an estimate for a smoker to devellop cancer due to smoking.

So it is not because some or other scientist writes that "black holes have a probability smaller than 1/500 to eat up the earth" that this means that once out of 500, a black hole will eat up the earth. It simply means that with the limited set of observations, the scientist couldn't find a stronger upper boundary on the probability (which might - and most probably is - zero if we have any reason to believe current theory) starting from the set of observations he decided to start with, and considering the kind of reasoning and approximations he made.

vanesch: I think this post of yours should be framed and stickied for everyone to read before they write anything about "black holes" at the LHC!

:)

Do you mind if I copy it for my blog? :)

Zz.