I’m a bit confused.
A black hole, as I understand it, is an object so massive that it’s gravitational pull is so strong that not even light can escape it. Also, the rules of physics as we know it kinda get a bit wonky down there, but that’s besides the point.
If the “black holes” created by this thing are so tiny and pathetic, then how can we call them black holes? Wouldn’t they simply lack the mass to pull anything in, photons giving them the raspberry as they zip on by?
Uh oh…getting worried again…what’s the deal with this vacuum stuff? It makes even less sense to me than black holes. If there’s even a small chance of these things happening, why on earth are they doing it?
Here’s the thing.
Suppose a particle created by this experiment could destroy the earth. If so, why is the earth still here?
We regularly get bombarded by particles much more energetic than this. If particles like this could destroy the earth, we’d have been destroyed billions of years ago, long before the earth could even form. Planets would regularly implode. Stars would collapse. The universe as we observe it would be impossible.
It’s like asking, could a sneeze destroy a house? Well, I suppose a really really strong wind could destroy a house, and a sneeze is a wind. So a scientist might say that a really really strong sneeze might destroy a house. And then you read a story that scientists are going to create the largest sneeze ever, by shoving a whole cup of pepper up some guy’s nose. And you worry that this sneeze could destroy your house. Except even the largest sneeze ever created would be millions of times weaker than the winds your house withstands every day.
Well, all of these have been great responses, but I still have to wonder if it’s completely safe given that the Wikipedia article on the collider states that it has garnered concern of “people both inside and outside of the physics community.” If there’s so little risk (and your rational sounds extremely logical to me, at any rate) how could any legitimate scientist possibly get worked up over this?
The New Yorker had an article about the LHC a couple months ago. They traced the origin of the “we could destroy the universe” meme to an interview given twenty years ago by one physicist who perhaps had more scientific brilliance than common sense. CERN has now instructed every employee to tell the press that there’s no possibility of such an event.
Legitimate scientists say that there’s “a non-zero probability” of strange matter forming, or any of the other things on that list. But the great thing about quantum physics is that there’s a non-zero probability of everything. There’s a non-zero probability all the air in this room will rush to the neighboring room, or that the tree outside my window will start to dance a waltz, or that you’ll suddenly turn into a monkey. The only caveat is that all of these are extremely small probabilities. So (assuming that you’re still human) you shouldn’t worry yourself unduly about probabilities of extremely unlikely events.
'Cause it’s a lot of fun, plus it brings in the chicks.
Seriously, while I’m a little disappointed at respondants for not stretching this out and having a little fun at the o.p.'s expense (“There’s hardly any chance that the Universe will unravel…well, not much more than 1%, and besides, these’s a good chance that we can wait it out in our deepest mineshafts,”) the truth is that there’s nothing we can do in the most advanced colliders that isn’t exceeded by many orders of magnitude in Nature on a regular basis. If the laws of the Universe were so unstable that we could puncture the plenum of reality with a wee bit of superconducting conduit and a few gigawatts of energy, we wouldn’t exist today.
Just go back to your pinochle game and don’t worry about those humming generators. There’s hardly any chance at all that we’ll reverse the accelerating expansion of the Universe and cause the Local Group to collapse into a single quantum particle, or cause entropy to reverse, or some such. Heck, we kept you from even knowing about that thing with the eletrified zombies from our Omicron Project experiment…
Stranger
Isn’t everything we know about black holes basically theoretical, since we’ve never actually been able to generate one before? How are we so sure that these black holes, if they are indeed created by the collider, are going to have such a short lifespan? The wikipedia article says that Hawking radiation is theoretical and unproven.
What difference does the size of a black hole matter to its definition? A black hole can be any size, from less than a proton to the diameter of the universe. (Literally. The same calculations that lead to the mass of the earth creating a 2 cm black hole lead to the mass of the universe creating a black hole the size of the universe. That’s right, we could be inside a black hole right now! (We aren’t, but Stranger said to have fun…))
The real issue is that people have somehow gotten the idea that black holes will suck in everything around them like a vacuum cleaner. They don’t work that way. Our sun will suck in anything that gets too close to it exactly as any black hole would. But comets skim the sun on a regular basis and return to their orbits. Same with black holes. Get too close and you get pulled inside the event horizon and can’t get out. But how many things are close to a black hole? There’s one, a large one, in the center of our galaxy. So what? It took until very recently for scientists even to detect it. Hot gases may stream into it. But it doesn’t affect us at all.
The other thing to remember about black holes is that they are extremely difficult to manufacture. Getting sufficient mass into a sufficiently tiny volume requires extraordinary circumstances. There’s nothing going on in the universe today that can make a sizable black hole except a supernova. The creation of an ultra-tiny black hole in a laboratory is a parlor game, not a threat. Those can’t pull anything in, at least not in the way that a magnet pulls a piece of iron. They can perturb orbits, but that’s a very long term event and tiny black holes will evaporate so instantaneously that long-term events are not in their vocabulary.
Black holes are a fantastic example of the limits of physics manifesting themselves in an actual object. But they have been totally misrepresented in popular fiction. They’re like cooling towers, those giant curved towers that you see so often in pictures of nuclear power plants that most people think that they are the nuclear power plant. (Think Simpsons.) But they’re just cooling towers, used with any big power plant including coal-fired plants. They don’t do anything, they can’t explode, they aren’t in the least dangerous. They’ve just taken on a false identity from the way they’ve been presented.
Black holes are x amount of mass in y volume. They behave exactly like any other piece of x amount of mass in z volume. You can orbit one, you can run away from one, you can pick it up and take it home to mother if it’s small enough and you’re fast enough. You just don’t want to crash into one. The same can be said for a tree. Somehow, though, nobody gets panicky if scientists say they want to grow a tree.
On preview, my point has been pretty much covered, but I explained it in a different way, so I’ll leave it here.
First question: It’s not really a matter of how massive an object is. It’s more a question of density. As someone mentioned above, it’s possible to imagine the sun being squeezed into a tiny ball, but remaining in the same place. It would have the same mass as it does now, and we’d be the same distance away from it (well, the same distance from its center, and when you’re doing this type of calculation, it’s the center that matters) so we wouldn’t notice any change in gravitational effects.
However, if you were to fly a spacecraft toward the sun now, its surface would prevent you from getting very close to its center. And the enormous amounts of radiation coming from it, but anyway. If you flew toward crushed-sun, you could get very close to it, and at some point (the event horizon - you could calculate the value if you wanted to) it would be physically impossible for you to escape, even if you were a photon.
Still confused? Imagine two planets of the same mass, but A has a radius half as big as B’s radius. That means B is 8 times bigger than A in volume, so it’s denser. Now, you visit both planets, and take note of your weight on each one. You’ll find that you weigh four times more on the smaller planet (four, rather than two, because gravity works by an inverse-square law), even though the two planets have the same mass. This is because you’re closer to the center of the planet when you’re standing on the surface of A. Well, imagine that you keep shrinking the planet to a smaller and smaller radius, although its mass stays the same. Eventually the force of gravity will be so strong that literally nothing can overcome it. So, that’s a black hole. Hope that made sense.
Argent Towers, I don’t know much of anything about Hawking radiation, but we certainly have seen black holes. Exapno mentioned one in the middle of the galaxy, and IIRC several more have been seen. And by seen I mean not seen.
. . .just coming in to share a stupid joke:
“Is that a tau-neutrino in your pocket, or do you have a hadron?”
boo! 
There is one “unstoppable” thing about a mini black hole. Anything it touches* will become part of it, so if it was created on earth it would promptly fall straight to the center of the earth and… sit there. If it lasted that long. Which it wouldn’t.
*nothing can really “touch” a black hole… at least in a way that makes sense… remember, it’s just a bunch of matter compressed down very, very dense. The part you touch when you get caught in it isn’t a part at all, just an area. Go past this line and you’re stuck. So when people talk about the size (as opposed to the mass) they’re talking about how far out that line is drawn.
Oh, a hijack. The earth’s event horizon is something like 2 cm, right? Does anyone know if we had an earth-sized lump of neutronium (which is the densest thing I can think of other than a black hole) what its event horizon would be? Earth’s is basically 0% of its diameter. Would neutronium even make it up to like 5%?
Regarding the false vacuum: just consider it another theory on how the universe could be destroyed. The key point (which is mentioned in the “false vacuum” article and has been mentioned here thrice, I believe) – Nature is doing way more powerful stuff all the time.
Consider the following analogy which I’ve written in the form of a interview by a news guy (NG) and a particle physicist (PP) to show how these scare stories get started. Imagine that particle physicists have just recently achieved the technology needed to toss pebbles into the ocean.
NG: So, tell me about this experiment you’re doing.
PP: We want to learn what happens when you toss pebbles in the ocean. So, we’re going to toss pebbles in the ocean. We’re curious about the ripples and the noises and the effects on the pebbles themselves and …
NG: Can it be dangerous? I mean, if you don’t know what will happen, might something go wrong?
PP: Well, theoretically, if you threw the pebbles hard enough, you could start a tidal wave that could destroy all of the eastern hemisphere, or maybe an earthquake, or a fish-killing shockwave… we don’t really know how all that would work. But…
NG: Oh?! scribble scribble Okay, I’m done here, gotta go write my scare article.
PP: shrugs
Continuing the analogy: We don’t know how hard you have to throw a pebble at the ocean to make a tidal wave. We don’t know if a tidal wave is even what would happen. Maybe instead you’d first cause an earthquake when the super-fast pebble hit the ocean floor. Maybe you’d evaporate the ocean from the heat of entry, causing a greenhouse effect that cooks us all. We don’t know how any of that would work if we could throw that pebble hard enough. What we do know is that Nature has been throwing things at the ocean much harder for a long time. Rock slides, whales breaching, hail storms – they’ve all been hitting the ocean harder than our puny pebbles will be. So there’s no worry that we’re going to destroy the earth even though we admit ignorance to what is actually going to happen when our pebbles (or Nature’s pebbles) hit.
At the LHC, we also don’t know what will happen. But, we do know that what we are doing is puny stuff. Unbelievable impressive on a human scale, but puny in the grand scheme. Much higher energy collisions from cosmic rays and whatnot are well documented (like the hail storms above), and they don’t seem to destroy the earth. Maybe they will someday, maybe they’ve been realllll close to doing it – we don’t know. (Which is why the interviewed physicists will always be wishy-washy.) But we do know that we aren’t doing squat compared to the stuff that’s already going on.
At the end of the day, the LHC still just plugs into the wall socket. (Well, actually it has a dedicated substation, etc., but the point stands.)
Ook.
I’m hanging on to the discussion by my fingernails here, but given that “nothing” can escape a black hole, how do they evaporate? By quantum effects?
I dunno…everything said here makes a lot of sense to me, and I’m not quite as freaked out…but I’m still a little leery of it. I mean, “we don’t know what’s going to happen” should not ever be said by people who are messing with the capability to destroy our planet instantaneously, even if the chances are almost zero. It’s the whole “we’re not sure, we’ll see what happens, maybe we’ll be surprised” attitude that makes me raise an eyebrow. I mean…really…so much of the physics involved in this seem to be totally theoretical, like the whole thing about Hawking radiation.
About the cosmic rays that are more powerful than the collider - where are these rays coming from? How are we sure that these rays are exactly the same as the energy that would be produced by the collider?
Forgive me if I sound either like a huge wuss or anti-scientific. I mean, I support the pursuit of knowledge and everything, but scientists also gave us the atomic bombs which have now accumulated to the point of being able to destroy civilization if they were all launched. Science that is capable of mass destruction just scares the shit out of me.
As you’ve probably heard before, virtual particle/antiparticle pairs spontaneously appear (and then almost immediately disappear) all the time, pretty much everywhere. When this happens very near a black hole’s event horizon (the surface past which nothing can escape) often one member of the pair ends up crossing the horizon while the other does not. Now they can no longer collide and thereby annihilate each other, so you end up with an extra particle flying away from the black hole. This would seem to violate the law of conservation of energy–but it doesn’t, because the no-longer-virtual particle that got sucked into the event horizon had negative energy enough to exactly cancel out the positive energy of the escaped particle. (Why does it work out that way? I’m not sure. Someone should be along to tell us shortly.) So you’ve got a negative-energy particle sucked into the black hole, and a positive-energy particle flying away from it. This adds up to the following situation: The black hole itself loses energy, and a particle with just that amount of energy pops out into the world beyond. It’s just like a kind of radiation–in fact it’s called Hawking radiation.
Eventually, the hole loses all its energy this way. It evaporates.
Well, so I’ve heard.
I “don’t know” that the next slice of pizza I eat won’t cause my gut to explode through a freak chemical reaction, thereby knocking the earth just slightly off orbit in such a way as to guarantee that in fifty years it crashes into a moon-sized asteroid. But that shouldn’t stop me from eating pizza, should it?
-FrL-
Look, have you read the linked threads yet? The LHC should be capable of 14 TeV (2.2x10[sup]-6[/sup]J). Convert that to mass by E=mc[sup]2[/sup] and you get 2.4x10[sup]-23[/sup]kg. A proton has a mass of 1.67x10[sup]-27[/sup]kg for comparison sake. We’ll make a nice smudge of energetic goo and keep some PhD candidates off the streets and out of trouble.
The physics behind the experiment is not tentative or new. What the LHC is trying to do is push something called the Standard Model closer to it breaking point. If we find something, it’ll confirm that the model is still a viable description of nature. In fact a more exciting result would be if we find nothing, simply due to the model’s outstanding ability to date to theoretically predict particles energy/masses even before they’re seen experimentally.
Cosmic rays are particles (mainly protons) that arrive from interstellar space moving at speeds that make experimental physicists weep. They hit the atmosphere every day in large numbers and create showers of other particles. The normal energies range from 0.001 TeV to 100,000,000 TeV. Remember that the LHC will operate at 14TeVs. They arrive pretty much from everywhere equally and have yet to punch a hole in reality or the planet.
Yes but read on a paragraph or two and you get this:
As other people have stated, 14 TeV really ain’t that much. Google will tell you that it equals 2.2 x 10[sup]-6[/sup] joules or 5.4 x 10[sup]-7[/sup] calories. That’s about as much energy as you’d find in one tenth of a nanogram of Twinkie. 