Artificial Black Holes, again...


by Jake
Tags: artificial, black, holes
vanesch
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#91
Jun16-06, 01:53 AM
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Quote Quote by MelissaSweet
Hi guys. Just a few quick questions:
Your calculations seem to be based on a constant rate of absorption, is this right? Wouldn't the absorption rate increase exponentially?
Yes, that is correct, but it won't change the conclusion very much (it will change the result by a few orders of magnitude).
As has been exposed (see link by pervect), even a billion ton black hole would need 10^28 years to eat the earth. But first, our nano 10^(-24) kg black hole needs to grow to a billion ton black hole and will thus have to eat about ~10^38 atoms. It is still smaller than the size of a proton during all that time.
The more pessimistic calculation by Orion (using more dimensions, and hence a higher effective G constant for the nano black hole) would become rather complicated, because this effective G constant would SHRINK as the nano black hole grows, and leaves its "quantum domain" to become more and more a classical black hole. So although its mass would increase, its effective cross section wouldn't rise proportionally.

In your cross section, are you looking only at the Schwarzschild radius? Doesn't gravity extend far beyond?
Yes, but the "cross section" is the quantified probability of ABSORPTION, not simply of interaction. The moon interacts gravitationally with the earth, but isn't ABSORBED by the earth. So anything much farther away from the BH than the Schwarzschild radius will simply undergo a deflection (talking classically). This interaction is extremely small: don't forget that outside of the Schwarzschild radius, the gravitational effect of a BH is the same as any other mass. So you'd get the gravitational attraction of a mass of 10^(-24) kg, which is normally utterly neglegible.

Also, there has been made a crude assumption: that is, when a nano black hole encounters an iron nucleus, that it eats the ENTIRE nucleus, even though the nano BH is much much much smaller than the nucleus. But this is probably entirely wrong: it would only eat at most a gluon or a quark, meaning that it would leave most of the mass of the nucleus behind (which would probably undergo a desintegration into another nucleus and a few pions or so).


Someone mentioned that the scientists failed to mention the effect that conservation of momentum has on nanoblackholes. Is that right? If they missed this very basic concept what else might they be missing?
No, the point was something different. Some people argued that eventual nano black holes produced in cosmic rays (of much higher energy than the LHC accelerator will produce) have high momentum wrt the earth, and hence will just fly once through the earth, so the fact that these collisions are regularly happening is no proof that nano black holes aren't dangerous.
That reasoning is correct: indeed, even if we underwent showers of nanoblack holes, they would at most eat one or two iron atoms before having travelled through the earth and fly off in the blackness of space.
So the observation that cosmic rays exist, is no proof of the "safety" of nanoblack holes, is entirely correct.

However, the reasoning ALSO applies to the eventual nanoblack holes produced at the LHC. It is only in the case that they are produced in the exact center of gravity of the two colliding particles that they don't have any momentum left and hence fall to the earth. But this is a highly exceptional case, because colliding protons, at these energies, must rather be seen as the collision of two bags of potatoes, the real interactions being between the potatoes (quarks and gluons), and not between the entire bags. So normally, such collisions produce a lot of "debris" together with an interesting interaction (such as the production of a nano BH). It is what renders the experimental observation a pain in the a**: between miriads of uninteresting tracks in one and the same event, you have to find those three or four tracks which indicate something interesting. There is a priori no reason for any correlation between the debris, and the interesting interaction (this has already been established for many years in lower-energy interactions ; I did my PhD on part of the problem for instance). So there is no reason to assume that this interaction happens in the center of gravity of the bag of potatoes, it is rather in the center of gravity of the two potatoes who do the interaction. Now, this center of interaction usually has high momentum wrt the center of gravity of the interacting protons, so the resultant product (in casu a nano BH) also.
In that case, it flies right off the reaction event, through the earth, or through the sky, into outer space.

And, honestly, the possibility that all these exotic processes happen (only predicted by very exotic and speculative theories) is way more dubious than the (also speculative, but way more down to earth) prediction that Hawking radiation really happens. In fact, all these speculative theories which open the possibility of the production of nano BH, ALSO predict Hawking radiation.

And if this is true, a nano black hole will go POOF even before leaving the detector.

So the entire reasoning is flawed. Current established physics says that NO black holes will be produced at the LHC. One needs to switch to speculative theories to open up even their possibility. And those same speculative theories (just as well as a small extrapolation of currently established physics) foresee Hawking radiation. So it is a bit aberrant to speculate on the production of nano BH using these theories, and refute them at the same time when considering Hawking radiation, no ?
Quaoar
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Jun16-06, 01:20 PM
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Quote Quote by vanesch
No, the point was something different. Some people argued that eventual nano black holes produced in cosmic rays (of much higher energy than the LHC accelerator will produce) have high momentum wrt the earth, and hence will just fly once through the earth, so the fact that these collisions are regularly happening is no proof that nano black holes aren't dangerous.
I'm gonna have to disagree on this point. True, most of the black holes produced by cosmic rays would escape, but you must realize that every time there is an event, many many many particles are produced in the shower (~10^11, from what I've read). I would imagine that since these events happen millions of time a year across the globe, at least one black hole would come out of a collision with a small enough kinetic energy as to not escape the Earth's gravitational pull. So, coupled with the fact that a black hole takes so long to become the size of a single proton, it's POSSIBLE that there are some floating in and out of the Earth right now, as we speak.
MelissaSweet
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#93
Jun21-06, 02:17 AM
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Hi again, my friends and I came up with a few more questions. We hope they're not too naive:

Quote Quote by Vanesch
Yes, but the "cross section" is the quantified probability of ABSORPTION, not simply of interaction. The moon interacts gravitationally with the earth, but isn't ABSORBED by the earth. So anything much farther away from the BH than the Schwarzschild radius will simply undergo a deflection (talking classically). This interaction is extremely small: don't forget that outside of the Schwarzschild radius, the gravitational effect of a BH is the same as any other mass. So you'd get the gravitational attraction of a mass of 10^(-24) kg, which is normally utterly neglegible.
Isn't your angular momentum effect limited by the earth's own angular momentum? Therefore wouldn't classical gravity work to grow the nanoblackhole because mass falls to the center of the earth in a classical way?

No, the point was something different. Some people argued that eventual nano black holes produced in cosmic rays (of much higher energy than the LHC accelerator will produce) have high momentum wrt the earth, and hence will just fly once through the earth, so the fact that these collisions are regularly happening is no proof that nano black holes aren't dangerous.
That reasoning is correct: indeed, even if we underwent showers of nanoblack holes, they would at most eat one or two iron atoms before having travelled through the earth and fly off in the blackness of space.
So the observation that cosmic rays exist, is no proof of the "safety" of nanoblack holes, is entirely correct.
So that snubabooba guy was right? Isn't that scary by itself?

However, the reasoning ALSO applies to the eventual nanoblack holes produced at the LHC. It is only in the case that they are produced in the exact center of gravity of the two colliding particles that they don't have any momentum left and hence fall to the earth. But this is a highly exceptional case, because colliding protons, at these energies, must rather be seen as the collision of two bags of potatoes, the real interactions being between the potatoes (quarks and gluons), and not between the entire bags. So normally, such collisions produce a lot of "debris" together with an interesting interaction (such as the production of a nano BH). It is what renders the experimental observation a pain in the a**: between miriads of uninteresting tracks in one and the same event, you have to find those three or four tracks which indicate something interesting. There is a priori no reason for any correlation between the debris, and the interesting interaction (this has already been established for many years in lower-energy interactions ; I did my PhD on part of the problem for instance). So there is no reason to assume that this interaction happens in the center of gravity of the bag of potatoes, it is rather in the center of gravity of the two potatoes who do the interaction. Now, this center of interaction usually has high momentum wrt the center of gravity of the interacting protons, so the resultant product (in casu a nano BH) also.
In that case, it flies right off the reaction event, through the earth, or through the sky, into outer space.
We seem to agree that colliding bags of potatoes might be very messy but the largest mess would occur at the center of the interaction. Are you saying this isn't right?

And, honestly, the possibility that all these exotic processes happen (only predicted by very exotic and speculative theories) is way more dubious than the (also speculative, but way more down to earth) prediction that Hawking radiation really happens. In fact, all these speculative theories which open the possibility of the production of nano BH, ALSO predict Hawking radiation.

And if this is true, a nano black hole will go POOF even before leaving the detector.
That's reassurring but isn't it also speculative? We read the article about the possible nanoblackhole at the RHIC. Do you have more information on it? Was it observed to completely evaporate? Did it leave the detector?

So the entire reasoning is flawed. Current established physics says that NO black holes will be produced at the LHC. One needs to switch to speculative theories to open up even their possibility. And those same speculative theories (just as well as a small extrapolation of currently established physics) foresee Hawking radiation. So it is a bit aberrant to speculate on the production of nano BH using these theories, and refute them at the same time when considering Hawking radiation, no ?
We don't know we're just college students. We think ignoring problems is stupid but we don't know enough to think about this critically. We're wondering if the scientists are similarly handicapped. Snubbabubba apparently found a weakness in their arguments. Can we safely assume they're right otherwise?
ZapperZ
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Jun21-06, 04:44 AM
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Quote Quote by MelissaSweet
That's reassurring but isn't it also speculative? We read the article about the possible nanoblackhole at the RHIC. Do you have more information on it? Was it observed to completely evaporate? Did it leave the detector?
Which article?

Most people only read Wilczek's first essay on this and that's all they get, while ignoring a second paper that analyzed this in detail and came to the conclusion that "...The authors estimate the parameters relevant to black-hole production and find that they are absurdly small..."[1] So what blackhole? How could it leave a detector when it doesn't even have any appreciable chance of being formed in the first place? And the fact that RHIC's stuctural integrity hasn't changed since Day 1 is ample proof that these black holes never occured.

Zz.

1. R.L. Jaffe et al., Rev. Mod. Phys. v.72, 1125 (2000).
vanesch
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Jun21-06, 05:48 AM
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Quote Quote by Guillochon
I'm gonna have to disagree on this point. True, most of the black holes produced by cosmic rays would escape, but you must realize that every time there is an event, many many many particles are produced in the shower (~10^11, from what I've read). I would imagine that since these events happen millions of time a year across the globe, at least one black hole would come out of a collision with a small enough kinetic energy as to not escape the Earth's gravitational pull. So, coupled with the fact that a black hole takes so long to become the size of a single proton, it's POSSIBLE that there are some floating in and out of the Earth right now, as we speak.
True. One should indeed compare the "integrated luminosity" of 4 billion years of cosmic rays with 10 years of LHC operation.
vanesch
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Jun21-06, 06:01 AM
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Quote Quote by MelissaSweet
Isn't your angular momentum effect limited by the earth's own angular momentum? Therefore wouldn't classical gravity work to grow the nanoblackhole because mass falls to the center of the earth in a classical way?
I don't understand a word if what you're saying

So that snubabooba guy was right? Isn't that scary by itself?
No, he wasn't right, because that's by far not the entire argument.
In fact, the argument of the high-energy cosmic ray collisions was used for ANOTHER potential catastrophy: the phase-transformation of the vacuum.
According to certain theories, our vacuum is just one of many possible, and maybe not even the most stable one. Just as with supercooled water, a "seeding event" might induce a phase transformation. A high energy collision might just do that, and blow the entire universe as we know it, apart (making it go through a phase change). So switching on the LHC might just blow the universe apart... and it was against THIS argument that it was argued that many more high energy collisions occur every day in cosmic rays without the universe blowing apart.
It wasn't an argument against that other catastrophy on small scale: the black hole that eats the earth.


We seem to agree that colliding bags of potatoes might be very messy but the largest mess would occur at the center of the interaction. Are you saying this isn't right?
Indeed, this isn't right. It may sound strange, but at high energies, the potatoes in the bag have different energies and momenta (although they all move at essentially lightspeed). So individual potatoe-potatoe collisions all have entirely different centers of gravity (this is where the potatoe bag analogy breaks down in fact - so it was probably not appropriate to use it in the first place, my appologies). In the real potatoe bag, there's a relationship between the momenta of the potatoes and their energies, because they all have to go at the same "bag speed". But relativisitically, this doesn't hold anymore (the bag goes essentially at light speed, as do all the components). So it is as if there were *independent* potatoes flying around. As such, you see that the center of gravity of the potatoe potatoe collisions has nothing to do with the center of gravity of the bag-bag collisions.

That's reassurring but isn't it also speculative? We read the article about the possible nanoblackhole at the RHIC. Do you have more information on it? Was it observed to completely evaporate? Did it leave the detector?
I don't know the details. Me thinks that if they have some indication of it, that is in the data of the remnants (the Hawking explosion). Because otherwise *they wouldn't have noticed it*. It would not have left the slightest trace in the detector (at most eaten up one or 2 atoms of the detector material).

We don't know we're just college students. We think ignoring problems is stupid but we don't know enough to think about this critically. We're wondering if the scientists are similarly handicapped. Snubbabubba apparently found a weakness in their arguments. Can we safely assume they're right otherwise?

[sarcastic mode on]

Of course not. Scientists are a dangerous lot, wanting to destroy the world in their quest for fame Most of the time, they don't have kids themselves, and are blinded by their silly faith in their own ideas. We should all put them in camps !

(uh, not so irrealistic, what I write, in fact )
MelissaSweet
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Jun21-06, 10:56 PM
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Sorry guys, we tried to come up with some good questions but I guess not. Would you guys be so kind as to remove my posts? Um would you remove your responses too?
vanesch
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Jun22-06, 12:02 AM
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Quote Quote by MelissaSweet
Sorry guys, we tried to come up with some good questions but I guess not. Would you guys be so kind as to remove my posts? Um would you remove your responses too?
Eh, no, what would be the point of a forum if each time one should remove questions and responses ?
Orion1
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Jun24-06, 03:24 PM
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Quote Quote by SpaceTiger
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.
Quote Quote by vanesch
it would only eat at most a gluon or a quark, meaning that it would leave most of the mass of the nucleus behind (which would probably undergo a desintegration into another nucleus and a few pions or so).

Strong Gravitation:
(Quantum BH strong nuclear reaction with a proton)
[tex]t_p = \frac{4 E_b^2}{3} \sqrt{\frac{m_p r_p^7}{2 (\hbar c)^5}}[/tex]

[tex]t_p = 3.362 \cdot 10^{-16} \; \text{s}[/tex]
vanesch
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Jun25-06, 01:06 AM
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Quote Quote by Orion1

Strong Gravitation:
(Quantum BH strong nuclear reaction with a proton)
[tex]t_p = \frac{4 E_b^2}{3} \sqrt{\frac{m_p r_p^7}{2 (\hbar c)^5}}[/tex]

[tex]t_p = 3.362 \cdot 10^{-16} \; \text{s}[/tex]
Yes, but that is only when the BH is *gravitationally captured* by the proton (as it was gravitationally captured by the earth)...
Cane_Toad
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Jun26-06, 10:14 PM
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Sorry for the novice post, but could somebody discuss or point me at an explanation of how a mini-black hole is possible, given that

1) I thought you needed enough mass to overcome subatomic particles' resistance to compaction

2) the [cosmic ray] particle collisions I've heard about are many orders of magnitude smaller than what seems to be required

3) even if you had a particle that was energetic enough to have such a huge mass, wouldn't/couldn't it already be a mini-black hole before any collisions?

If there is a better place to post novice questions, please let me know.
vanesch
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Jun27-06, 02:12 AM
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Quote Quote by Cane_Toad
Sorry for the novice post, but could somebody discuss or point me at an explanation of how a mini-black hole is possible, given that
1) I thought you needed enough mass to overcome subatomic particles' resistance to compaction
According to "standard" physics (in casu general relativity the way we know it in 3+1 dimensions), you are right, it is not possible to have a mini-black hole with just some 14 TeV energy available at most.
However, there are several *speculative* theories out there, which say that the universe has more than 3 + 1 dimensions. The effect of this is that at small scales, gravity is a much stronger force than it is in the standard theory. In fact, the idea is that gravity in so many dimensions is as strong as, say, electromagnetism, but because at our large scale, we only see a few dimensions, it only LOOKS to us as a weak force.
Once gravity becomes much stronger, it is easier to form black holes, and 14 TeV might be sufficient.
Now, these same theories also predict (well, they don't predict much anything, but suggest :-) Hawking radiation, which is huge for a tiny black hole, so the "formation + evaporation" of a mini black hole should be something like a very spurious event, a glitch.

So in the hypothetical case that these speculative theories are right, and that mini black holes can form (in contradiction to standard theory), they also say that they'd explode almost immediately in a rain of particles (as if they didn't form in the first place). All this is thus, speculative. But the aim of these experiments is of course to explore new territory, and to verify whether some speculative ideas might be right.
Cane_Toad
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#103
Jun27-06, 05:22 PM
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Quote Quote by vanesch
....
In fact, the idea is that gravity in so many dimensions is as strong as, say, electromagnetism, but because at our large scale, we only see a few dimensions, it only LOOKS to us as a weak force.
Once gravity becomes much stronger, it is easier to form black holes, and 14 TeV might be sufficient.
....
I've heard a little about this, but I'm curious what is different about this situation that would allow that larger n-dimension gravity cross section to begin interacting with our space where it wasn't immediately before the event?
Orion1
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Jul23-06, 07:49 AM
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[tex]t_a(r) = \frac{n_e}{\lambda_b} = \frac{1}{v_e \sigma_c(r)}[/tex]

Schwarzchild radius:
[tex]t_a(r) = \frac{1}{v_e \sigma_c(r)} = \frac{1}{\pi} \sqrt{\frac{r_e}{2Gm_e}} \left( \frac{c^2}{2Gm_b} \right)^2[/tex]

[tex]t_a(m_b) = \frac{c^4}{4 \pi m_b^2} \sqrt{\frac{r_e}{2G^5m_e}}[/tex]

[tex]t_a = \frac{c^4}{4 \pi} \sqrt{\frac{r_e}{2G^5m_e}} \int_{m_p}^{m_e} \frac{1}{m_b^2} \; dm_b = \frac{c^4}{4 \pi} \sqrt{\frac{r_e}{2 G^5 m_e^3}}[/tex]

[tex]t_a = \frac{c^4}{4 \pi} \sqrt{\frac{r_e}{2 G^5 m_e^3}}[/tex]

Time required to absorb 1 m^3 of Terra:
[tex]t_a = 6.844 \cdot 10^{16} \; \text{years}[/tex]
eclipsed78
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#105
Aug11-06, 05:14 AM
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"Don't forget that the black hole we're talking about here IS MUCH MUCH SMALLER THAN A PROTON. As such, pressures on *atomic* level (such as in the center of the earth) matter little: the black hole travels most of the time in the empty space between nucleae.
A way to calculate the probability of hitting a nucleus (and somehow imagining that it would gobble up the entire nucleus, which is MUCH MUCH bigger than the black hole itself - which is a worst-case scenario) is done by calculating the "cross section" of the black hole and its probability to cross a nucleus on its voyages through the earth. We know its speed (just falling), and knowing the cross section and the density of nucleae, we can estimate how many nucleae it could eat per unit of time."

ya we are dealing with much denser material that has enormous pressure that is moving too at high speed which gives our gravity on the planet. Last time I checked, molecules are in constant movement too and the center of the planet is iron, which is much larger then one proton. Any calculations done are not taking into acount of any of these variables, and I am not impressed with caluculations that only take into account the size of a MBH and a proton. Gravity is what the cern is studing and how it works if BH are made and HR is correct. Yes the implications of knowing what the higgs partical is would allow more study on maybe making antigravity devices but, if HR is wrong, we can not know for sure how long we would have before the MBH became the size of the earth. If we know there is a possiblility (lets say 1/10^1094856306 from what we think and know about physics today) of HR being wrong, when it is wrong we go oh thats how it works and it should have been wrong all along. How could have anyone thought that in this crazy universe that entagled particals could be in exsitance? QT is weird, it makes sence only when we observe it and make note of it. These observations then become logical due to everyone being taught the observations. Come to think of it maybe a MBH not have RH should be logical too. hmmm. The point is noone has or will be able to give prove that HR is existant untill this experiment is done.

Russian rulett is what we are playing.

As for the calculations for how long a BH would devour the earth, take into acount that the core spins at a very high speed, high temperatures cause ALOT of molecular movement, and not simply calcualting one proton radius or only one type of nulcious, because there are heavier elements in the earth.

Planing how long the earth would be destroyed is one thing, and if it took alog time then why not, but if it is not possible to calculate it due to the enormous amouts of variables and Im sure I have not thought of them all, then the question goes back to should they be allowed to conduct this experiment on earth? Why not wait and do it on the moon? B/c little minded over zelous book worms want everything right now, and can not think of anything but themselves and their "life's work". There is more to life than physics, and maybe putting all of this money that is used for the cern into finding a cure for aids would be more worthwhile than pulling that trigger with at least one bullet with our planets name on it. Sorry to all you little minded book worms, i ment no affence Im sure your lifes work is very important.
ZapperZ
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#106
Aug11-06, 05:48 AM
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Quote Quote by eclipsed78
Sorry to all you little minded book worms, i ment no affence Im sure your lifes work is very important.
What in the world are you ranting about, especially for your FIRST post here on PF that is rife with over-generalizations?!

First of all, stop with the over-speculation, especially when YOU haven't done the calculations yourself. Secondly, even the SUGGESTION that such particle collisions would generate black holes is itself highly speculative in the first place! So why are you attacking the uncertainty of what would happen if a blackhole was created but totally ignoring that the creation of such blackholes is also full of uncertainty in the first place?

I've seen a lot of silly hysteria regarding this because I was at Brookhaven when Wilczek wrote the initial article about the possible creation of blackholes at RHIC. These people who can't work their way out of a simple QM text started writing petitions to stop RHIC's operation based on Wilczek's article, while totally ignoring his followup article that made a more careful calculations and predicted the extreneous circumstances for such a scenario to happen.

When you based something out of ignorance, then you will have demigods who will use scare tactics to stop something. This is the worst possible way of doing anything, not just physics. And if you think there is zero worth in the pursuit of basic knowledge, I'd like to see you live without your modern electronics when your identical clone stopped the research on quantum mechanics back in the early 1900's because he too didn't see anything worthwhile in it for mankind.

Zz.
Cane_Toad
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#107
Aug11-06, 01:05 PM
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Quote Quote by eclipsed78

Russian rulett is what we are playing.
If you think about it for a minute, we are so screwed three ways to Sunday by potential cataclysms that have real and fairly defined probabilities of wiping us all off the earth: global warming, atlantic conveyor shutdown, global ice-age, earthquakes, volcanos, super-volcanos, global magnetic field shutdown, asteroid collision, hemoragic viruses, small pox, super-tsunamis. This is not to mention small time threats like terrorists with dirty bombs, air dispersed viruses, and rampaging fembots after our mojo.

People will go after easy targets like a single institute or facility, because going after problems that have daunting political inertia like global warming, etc. has less chance of reward (i.e. getting their way). Better to spend your worry cycles on real threats, or better yet, just keep your eyes on the road, and tune in to a good tune. :-)
magnetar
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#108
Apr9-07, 04:43 AM
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I am waiting for LHC!!


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