"Hold my beer and watch this" said the CERN guy
July 16, 2013 9:04 AM Subscribe
Black holes are one of the most interesting, mysterious and cool things in the universe. So, why dont we make one in a lab?
We have already created electromagnetic black holes in lab but no gravitational ones. We have started to simulate them, though. LHC might be able to create tiny ones. But the tiny ones die very soon. Wouldn't it be cool to have something a little bigger and longer lasting?
The bigger question is, why should we create a black hole? Can a lab get enough insurance for that? After all, free energy will be awesome to have.
What if the only way to get to stars is through a black hole portal? Would we be willing to create a large black hole nearby (astronomically) then?
We have already created electromagnetic black holes in lab but no gravitational ones. We have started to simulate them, though. LHC might be able to create tiny ones. But the tiny ones die very soon. Wouldn't it be cool to have something a little bigger and longer lasting?
The bigger question is, why should we create a black hole? Can a lab get enough insurance for that? After all, free energy will be awesome to have.
What if the only way to get to stars is through a black hole portal? Would we be willing to create a large black hole nearby (astronomically) then?
Whatever anyone chooses to do, all I know is the Internet will get a little bit heavier* thanks to tin-foil-hatters and their special brand of "skepticism".
* no physics punnery intended
posted by slater at 9:10 AM on July 16, 2013
* no physics punnery intended
posted by slater at 9:10 AM on July 16, 2013
"Your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should."
(Pro-science and scientists here, but I can't help but think of Bill Joy right now.)
posted by longdaysjourney at 9:14 AM on July 16, 2013 [1 favorite]
(Pro-science and scientists here, but I can't help but think of Bill Joy right now.)
posted by longdaysjourney at 9:14 AM on July 16, 2013 [1 favorite]
TheLittlePrince: "What if the only way to get to stars is through a black hole portal?"
Doesn't matter. Once we get to black hole warheads, we'll lose all interest and funding. "Whoa, whoa, black hole space exploration is risky", our leaders will say.
posted by boo_radley at 9:22 AM on July 16, 2013 [6 favorites]
Doesn't matter. Once we get to black hole warheads, we'll lose all interest and funding. "Whoa, whoa, black hole space exploration is risky", our leaders will say.
posted by boo_radley at 9:22 AM on July 16, 2013 [6 favorites]
I am okay with you create a black hole as long as you find another gravity well to do it in.
Oh, sure, more of that NIMGW attitude! Everyone thinks black holes are great... for other people!
posted by GenjiandProust at 9:23 AM on July 16, 2013 [30 favorites]
Oh, sure, more of that NIMGW attitude! Everyone thinks black holes are great... for other people!
posted by GenjiandProust at 9:23 AM on July 16, 2013 [30 favorites]
Remember: The inverse-square law is our friend when creating black holes.
Also, try not to accelerate at near-luminal speed towards it.
posted by blue_beetle at 9:23 AM on July 16, 2013 [2 favorites]
Also, try not to accelerate at near-luminal speed towards it.
posted by blue_beetle at 9:23 AM on July 16, 2013 [2 favorites]
"Claims for perpetual-motion machines and other free-energy devices still persist, of course, even though they inevitably turn out to violate at least one law of thermodynamics."
Well, yes, perpetual motion machines violate the laws of thermodynamics by practically by definition.
posted by BungaDunga at 9:24 AM on July 16, 2013 [1 favorite]
Well, yes, perpetual motion machines violate the laws of thermodynamics by practically by definition.
posted by BungaDunga at 9:24 AM on July 16, 2013 [1 favorite]
I am okay with you create a black hole as long as you find another gravity well to do it in.
So if I somehow manage to create another gravity well, you are OK if I put a black hole in it?
posted by DU at 9:25 AM on July 16, 2013 [4 favorites]
So if I somehow manage to create another gravity well, you are OK if I put a black hole in it?
posted by DU at 9:25 AM on July 16, 2013 [4 favorites]
If a black hole as created on Earth, how long would it take for the planet to be eaten. I'm guessing microseconds?
posted by Brandon Blatcher at 9:25 AM on July 16, 2013
posted by Brandon Blatcher at 9:25 AM on July 16, 2013
Question: Can black holes violate the law of thermodynamics?
posted by TheLittlePrince at 9:25 AM on July 16, 2013
posted by TheLittlePrince at 9:25 AM on July 16, 2013
ONLY ONE WAY TO FIND OUT!
posted by slater at 9:26 AM on July 16, 2013 [4 favorites]
posted by slater at 9:26 AM on July 16, 2013 [4 favorites]
If we converted moon into a black hole and left it where it is today, it wont change things on earth even a little bit.
Except perhaps for all the Apollo missions and all those romantic novels.
Hence, brandon, the answer to your question would depend on how far that black hole is from earth and how big is its event horizon.
posted by TheLittlePrince at 9:29 AM on July 16, 2013 [1 favorite]
Except perhaps for all the Apollo missions and all those romantic novels.
Hence, brandon, the answer to your question would depend on how far that black hole is from earth and how big is its event horizon.
posted by TheLittlePrince at 9:29 AM on July 16, 2013 [1 favorite]
I am okay with you create a black hole as long as you find another gravity well to do it in.
I'm OK with it only if your lab is on a solar escape trajectory. (Because I like the sun.)
posted by The Tensor at 9:32 AM on July 16, 2013
I'm OK with it only if your lab is on a solar escape trajectory. (Because I like the sun.)
posted by The Tensor at 9:32 AM on July 16, 2013
If a black hole as created on Earth, how long would it take for the planet to be eaten. I'm guessing microseconds?
Most black holes just disappear, because they are so small. The big question is where the hell you would get all the mass to make a proper stable black hole. The removal of that mass into the black hole would likely be the bigger consequence.
posted by idiopath at 9:33 AM on July 16, 2013
If a black hole as created on Earth, how long would it take for the planet to be eaten. I'm guessing microseconds?
Size it tremendously relevant here. Black holes will dissipate if they can't absorb enough matter, that's why the microscopic ones created by the LHC are no concern. There's not enough matter nearby for them to start snowballing.
If we created a golf ball-sized black hole at the surface of the Earth, it would probably be able to sustain itself, but it would still expand slowly enough that we would get plenty of time to realize that humanity had fucked itself.
posted by 256 at 9:35 AM on July 16, 2013
Size it tremendously relevant here. Black holes will dissipate if they can't absorb enough matter, that's why the microscopic ones created by the LHC are no concern. There's not enough matter nearby for them to start snowballing.
If we created a golf ball-sized black hole at the surface of the Earth, it would probably be able to sustain itself, but it would still expand slowly enough that we would get plenty of time to realize that humanity had fucked itself.
posted by 256 at 9:35 AM on July 16, 2013
If we created a golf ball-sized black hole at the surface of the Earth, it would probably be able to sustain itself, but it would still expand slowly enough that we would get plenty of time to realize that humanity had fucked itself.
A fun sci-fi premise there. What would the survival-of-humanity Mars colony look like? You can assume almost infinite funding but absolutely no resupply and a short engineering lead time.
posted by jaduncan at 9:36 AM on July 16, 2013 [5 favorites]
A fun sci-fi premise there. What would the survival-of-humanity Mars colony look like? You can assume almost infinite funding but absolutely no resupply and a short engineering lead time.
posted by jaduncan at 9:36 AM on July 16, 2013 [5 favorites]
I'm getting an idea for a weight loss program here...
posted by goethean at 9:37 AM on July 16, 2013 [2 favorites]
posted by goethean at 9:37 AM on July 16, 2013 [2 favorites]
What would the survival-of-humanity Mars colony look like?
Pissed off.
posted by Blazecock Pileon at 9:38 AM on July 16, 2013 [4 favorites]
Pissed off.
posted by Blazecock Pileon at 9:38 AM on July 16, 2013 [4 favorites]
If we created a golf ball-sized black hole at the surface of the Earth
...and then created a space-time golf club to hit it with...
Yesssss, I am getting an idea! Science! Bwahahahahahaha!
posted by GenjiandProust at 9:38 AM on July 16, 2013
...and then created a space-time golf club to hit it with...
Yesssss, I am getting an idea! Science! Bwahahahahahaha!
posted by GenjiandProust at 9:38 AM on July 16, 2013
There's not enough matter nearby for them to start snowballing.
Forgive me, for I am ignorant in such matters, but doesn't Earth count as "enough matter"? What, we're not even a quick snack for black hole?
What would the survival-of-humanity Mars colony look like?
Probably Martian.
posted by Brandon Blatcher at 9:39 AM on July 16, 2013
Forgive me, for I am ignorant in such matters, but doesn't Earth count as "enough matter"? What, we're not even a quick snack for black hole?
What would the survival-of-humanity Mars colony look like?
Probably Martian.
posted by Brandon Blatcher at 9:39 AM on July 16, 2013
Sadly I am unable to find the short story Bobo's Star online anywhere, so it's grim warning of the dangers of home star creation will remain unheeded.
posted by Artw at 9:40 AM on July 16, 2013 [1 favorite]
posted by Artw at 9:40 AM on July 16, 2013 [1 favorite]
I don't think after Reddit and Metafilter the world needs another thing to swallow my space and time, thanks.
posted by MuffinMan at 9:40 AM on July 16, 2013 [6 favorites]
posted by MuffinMan at 9:40 AM on July 16, 2013 [6 favorites]
My favourite SF bozo James P Hogan did a "what if we create a bunch of microscopic black holes and they got loose" scenario in Thrice Upon a Time.
posted by seanmpuckett at 9:41 AM on July 16, 2013
posted by seanmpuckett at 9:41 AM on July 16, 2013
If we converted moon into a black hole and left it where it is today, it wont change things on earth even a little bit.
...except for the massive gamma ray flash as it collapses, which would pretty much sterilize the entire Solar System.
posted by localroger at 9:43 AM on July 16, 2013 [6 favorites]
...except for the massive gamma ray flash as it collapses, which would pretty much sterilize the entire Solar System.
posted by localroger at 9:43 AM on July 16, 2013 [6 favorites]
There's a fun sci-fi premise there.
It's one of the side-plots of Brin's Earth as well, IIRC.
A very small black hole (yet larger than the ones the LHC could generate) could spend quite some time orbiting inside the earth before it grew large enough to consume very much matter. I'm sure someone has calculated the critical masses and timescales.
posted by hattifattener at 9:44 AM on July 16, 2013
It's one of the side-plots of Brin's Earth as well, IIRC.
A very small black hole (yet larger than the ones the LHC could generate) could spend quite some time orbiting inside the earth before it grew large enough to consume very much matter. I'm sure someone has calculated the critical masses and timescales.
posted by hattifattener at 9:44 AM on July 16, 2013
There's not enough matter nearby for them to start snowballing.
Forgive me, for I am ignorant in such matters, but doesn't Earth count as "enough matter"? What, we're not even a quick snack for black hole?
Earth is enough matter, but it's not nearby on a microscopic scale.
posted by 256 at 9:45 AM on July 16, 2013 [1 favorite]
A black hole would be a good place to hide a body. I'm imagining something that's a mix between Looper and the end of Fargo.
posted by michaelh at 9:46 AM on July 16, 2013 [1 favorite]
posted by michaelh at 9:46 AM on July 16, 2013 [1 favorite]
If a black hole as created on Earth, how long would it take for the planet to be eaten. I'm guessing microseconds?
Someone who is better at astrophysics can correct me if I'm wrong, but I think the general conception of a black hole being a sort of cosmic vacuum cleaner that's stronger than normal gravity is off. A black hole is basically just a star that has been compressed into a single point while retaining the same mass. Gravity is based on mass and distance, so a black hole the same distance away with the same amount of mass as anything else would be basically the same in terms of gravitational pull.
So if, say, Jupiter was a black hole with the mass of Jupiter, the new black hole version of Jupiter would still circle around the Sun with us just fine and we wouldn't somehow get sucked into it any more than we are currently being affected by Jupiter's gravity. It would suck in things like asteroids and whatnot, but that's not really any different than what it does now.
Gravity is an extremely weak force compared to anything else (including, say magnets) so you would need to somehow create a really massive black hole for it to have any major effect on Earth.
posted by burnmp3s at 9:51 AM on July 16, 2013 [1 favorite]
Someone who is better at astrophysics can correct me if I'm wrong, but I think the general conception of a black hole being a sort of cosmic vacuum cleaner that's stronger than normal gravity is off. A black hole is basically just a star that has been compressed into a single point while retaining the same mass. Gravity is based on mass and distance, so a black hole the same distance away with the same amount of mass as anything else would be basically the same in terms of gravitational pull.
So if, say, Jupiter was a black hole with the mass of Jupiter, the new black hole version of Jupiter would still circle around the Sun with us just fine and we wouldn't somehow get sucked into it any more than we are currently being affected by Jupiter's gravity. It would suck in things like asteroids and whatnot, but that's not really any different than what it does now.
Gravity is an extremely weak force compared to anything else (including, say magnets) so you would need to somehow create a really massive black hole for it to have any major effect on Earth.
posted by burnmp3s at 9:51 AM on July 16, 2013 [1 favorite]
massive gamma ray flash
yeah .. well .... details, you know?
posted by TheLittlePrince at 9:51 AM on July 16, 2013 [1 favorite]
yeah .. well .... details, you know?
posted by TheLittlePrince at 9:51 AM on July 16, 2013 [1 favorite]
What would the survival-of-humanity Mars colony look like?
Probably Martian.
At least they'd be able to focus on survival, rather than on developing an Illudium Q-36 Space Modulator.
posted by Greg_Ace at 9:52 AM on July 16, 2013 [1 favorite]
Probably Martian.
At least they'd be able to focus on survival, rather than on developing an Illudium Q-36 Space Modulator.
posted by Greg_Ace at 9:52 AM on July 16, 2013 [1 favorite]
A black hole "eating" the planet is the central plot point of Earth, in fact.
Also Wil McCarthy has some interesting ideas about black hole programmable matter.
posted by bonehead at 9:52 AM on July 16, 2013
Also Wil McCarthy has some interesting ideas about black hole programmable matter.
posted by bonehead at 9:52 AM on July 16, 2013
256, just to clarify, because people get all bent out of shape and start suing and shit, the LHC did not, does not, and apparently will not create micro black holes. Even if it did, there would be no danger of it eating the Earth because it would disappear in a flash of Hawking radiation before it hit the wall of the detector.
Because of the aforementioned completely ridiculous lawsuits, some people had to spend an absurd amount of time writing up at great length why scientists are sure we were not about to destroy the planet. That document is here. And really folks, why would we want to destroy the planet? It's where we keep all our stuff.
For a hilarious take-down on the whole nonsense of physicists killing the planet by accident, watch the Daily Show clip on the subject. Apologies to people whom that link doesn't work for.
posted by physicsmatt at 9:52 AM on July 16, 2013 [11 favorites]
Because of the aforementioned completely ridiculous lawsuits, some people had to spend an absurd amount of time writing up at great length why scientists are sure we were not about to destroy the planet. That document is here. And really folks, why would we want to destroy the planet? It's where we keep all our stuff.
For a hilarious take-down on the whole nonsense of physicists killing the planet by accident, watch the Daily Show clip on the subject. Apologies to people whom that link doesn't work for.
posted by physicsmatt at 9:52 AM on July 16, 2013 [11 favorites]
So, why dont we make one in a lab?
If we're going to make black holes in a lab, then let's put the lab in Calcutta.
posted by octobersurprise at 9:57 AM on July 16, 2013 [4 favorites]
If we're going to make black holes in a lab, then let's put the lab in Calcutta.
posted by octobersurprise at 9:57 AM on July 16, 2013 [4 favorites]
A black hole would be a good place to hide a body
See. That scarabic, he didn't know it all.
Say his name three times, and he comes in the night and nobody ever finds your body.
posted by jaduncan at 9:59 AM on July 16, 2013 [2 favorites]
See. That scarabic, he didn't know it all.
Say his name three times, and he comes in the night and nobody ever finds your body.
posted by jaduncan at 9:59 AM on July 16, 2013 [2 favorites]
A fun sci-fi premise there. What would the survival-of-humanity Mars colony look like? You can assume almost infinite funding but absolutely no resupply and a short engineering lead time.
Eight Worlds universe by John Varley. Maybe start with Ophiuchi Hotline or the Persistence of Vision collection of shorts.
posted by DU at 10:08 AM on July 16, 2013 [2 favorites]
Eight Worlds universe by John Varley. Maybe start with Ophiuchi Hotline or the Persistence of Vision collection of shorts.
posted by DU at 10:08 AM on July 16, 2013 [2 favorites]
I enjoy theoretical physics, and feel like I have a reasonable grasp on the basic principles for a layman, but can someone explain to me the basis for thinking that a black hole could provide an entrance to a wormhole?
I've never really understood how we make the connection, or theoretically bridge the gap from hypercompression (singularity) to an on-ramp. It certainly sounds really cool, but I haven't heard any connection articulated.
posted by staccato signals of constant information at 10:12 AM on July 16, 2013 [1 favorite]
I've never really understood how we make the connection, or theoretically bridge the gap from hypercompression (singularity) to an on-ramp. It certainly sounds really cool, but I haven't heard any connection articulated.
posted by staccato signals of constant information at 10:12 AM on July 16, 2013 [1 favorite]
If we created a golf ball-sized black hole at the surface of the Earth, it would probably be able to sustain itself, but it would still expand slowly enough that we would get plenty of time to realize that humanity had fucked itself.
A fun sci-fi premise there.
Agreed! Instead we get shit like Sharknado and Under The Dome.
posted by Atom Eyes at 10:17 AM on July 16, 2013
A fun sci-fi premise there.
Agreed! Instead we get shit like Sharknado and Under The Dome.
posted by Atom Eyes at 10:17 AM on July 16, 2013
Consider yourself that we didn't get Sharknado vs The Black Hole, Under the Dome.
posted by Brandon Blatcher at 10:18 AM on July 16, 2013 [3 favorites]
posted by Brandon Blatcher at 10:18 AM on July 16, 2013 [3 favorites]
Question: Can black holes violate the law of thermodynamics?
Unfortunately, that's not really a question with an answer, it's an entire subfield of physics.
posted by kiltedtaco at 10:20 AM on July 16, 2013 [1 favorite]
Unfortunately, that's not really a question with an answer, it's an entire subfield of physics.
posted by kiltedtaco at 10:20 AM on July 16, 2013 [1 favorite]
Blacknado sounds vaguely racist, but Torhole sounds like NSA-themed porn.
posted by michaelh at 10:21 AM on July 16, 2013 [4 favorites]
posted by michaelh at 10:21 AM on July 16, 2013 [4 favorites]
some people had to spend an absurd amount of time writing up at great length why scientists are sure we were not about to destroy the planet.
It's called risk assessment in return for public support. There is no reason why the public shouldn't demand and scientists shouldn't provide precise answers to all risk-related questions. And if the scientists want to take a "leave it to the experts" attitude and mock the concerns of the public, then the public should refuse its support.
posted by No Robots at 10:23 AM on July 16, 2013 [3 favorites]
It's called risk assessment in return for public support. There is no reason why the public shouldn't demand and scientists shouldn't provide precise answers to all risk-related questions. And if the scientists want to take a "leave it to the experts" attitude and mock the concerns of the public, then the public should refuse its support.
posted by No Robots at 10:23 AM on July 16, 2013 [3 favorites]
michaelh: " Torhole sounds like NSA-themed porn."
This is the bean bag game physicists play.
posted by boo_radley at 10:23 AM on July 16, 2013 [2 favorites]
This is the bean bag game physicists play.
posted by boo_radley at 10:23 AM on July 16, 2013 [2 favorites]
My idea for a movie: sharknado with a black hole at the center
everyone is being dragged in ... you cant pull out of the gravity well and the sharks will keep eating you till infinity.
saying it on MeFi counts as copyrighting it, right?
posted by TheLittlePrince at 10:24 AM on July 16, 2013
everyone is being dragged in ... you cant pull out of the gravity well and the sharks will keep eating you till infinity.
saying it on MeFi counts as copyrighting it, right?
posted by TheLittlePrince at 10:24 AM on July 16, 2013
Maybe start with Ophiuchi Hotline or the Persistence of Vision collection of shorts.
No wait. Ophiuchi is very 70s and PoV is not solely Eight Worlds. Steel Beach should be the first one and you can hardly really appreciate it unless you first read The Moon is a Harsh Mistress by Heinlein (which SB is a response to).
posted by DU at 10:24 AM on July 16, 2013 [1 favorite]
No wait. Ophiuchi is very 70s and PoV is not solely Eight Worlds. Steel Beach should be the first one and you can hardly really appreciate it unless you first read The Moon is a Harsh Mistress by Heinlein (which SB is a response to).
posted by DU at 10:24 AM on July 16, 2013 [1 favorite]
Some of the analytic extensions of the original math for black holes show another region of spacetime which is in some sense reachable by going through the black hole. AIUI there's no particular reason to believe that that particular math is correct, but physics is absolutely littered with cases where some quirk or artifact of the mathematics turns out, upon doing the actual experiment, to be real.
There's also some argument that the middle of the ring singularity of a spinning hole wouldn't be connected to the other side of the ring singularity, but to some other place (where?), though I don't fully follow that one.
posted by hattifattener at 10:24 AM on July 16, 2013 [2 favorites]
There's also some argument that the middle of the ring singularity of a spinning hole wouldn't be connected to the other side of the ring singularity, but to some other place (where?), though I don't fully follow that one.
posted by hattifattener at 10:24 AM on July 16, 2013 [2 favorites]
Right, so black holes eating the Earth.
Black holes radiate energy out (making them not exactly black). This radiation is blackbody, which is to say it has the spectrum of a perfectly uniform object at some temperature. The Sun, for example, is close to a blackbody, but has spectral lines due to the presence of the elements in the Sun having excitations and de-excitations of electrons and sending out light that is non-thermal. Black holes just have the thermal bit.
The person who figured this out is Stephen Hawking. In addition to writing some excellent books and being famous for doing it all with severe physical handicaps, he's a brilliant scientist. He figured out that, in order for black holes not to violate the laws of thermodynamics, they have to have possess entropy. This means that they have a temperature; which means they have to radiate away energy. So, left on their own, a black hole will evaporate via the emission of Hawking radiation. Hawking radiation emerges from just outside the boundary of the black hole; the event horizon, and can be thought of as pairs of virtual particles appearing next to the horizon (as they do everywhere in space) but one of the pair falling into the horizon and the other escaping out. The slightly more accurate way of saying this is that empty space near a horizon does not correspond to empty space infinity far away from the horizon; someone at infinity sees particles coming from what someone near the horizon would call "the vacuum."
Now, Hawking derived the temperature of a black hole to be T = 1/8\pi M, where M is the mass of the black hole, and I've done the usual theorist trick of setting all constants of Nature equal to 1 because we theorists are all deeply lazy people. Be glad I didn't set 2\pi = 1 (aka the small circle approximation. I've done it before and I will do it again). In more reasonable units, the temperature is
(1 K) times (1.2 x 10^23 kg/ M)
The Sun's mass is 2 x 10^30 kg, so the Sun converted to a black hole would have a temperature of about 10^-7 K, which is much smaller than the temperature of the cosmic microwave background (2.7 K) and so much colder than deep space. Thus converting the Sun to a black hole would cause the resulting black hole to actually start growing (slowly) as CMB photons falling into the ex-Sun would deposit more energy per unit time than would be removed via Hawking radiation.
Notice that the Hawking temperature goes like inverse mass, so smaller black holes are hotter. The Moon converted into a black hole would have a temperature of 1.7 K. Ignoring the CMB feeding this black hole, the lifetime would be 3 x 10^52 seconds (or 10^45 years. The Universe is only 13.6 x 10^9 years old). So eventually there'd be a flash of gamma rays (as the black hole evaporates, it heats up, resulting in higher energy photons emitted), but only at the end of its lifetime. A black hole originally asteroid-sized, some 10^11 kg in mass, would be evaporating just about now if it was created in the early Universe. Smaller ones would already have poofed-away, and the lack of such gamma ray flashes is how we know dark matter is not a bunch of very small black holes. The larger black holes are ruled out for directly looking for the lensing effect they would have as the pass between us and distant stars. There is a very small window of masses that are not directly ruled out, but no one really has a mechanism for creating that many black holes in the early Universe (not that that's a deal-breaker, just a statement of our present knowledge).
So, if you managed to create a micro-black hole using a TeV of energy (the available energy at the LHC), for one thing, something's gone very wrong because there should be no way you've crammed enough energy into a small enough region for the event horizon to form. OK, we'll hand-wave that away by saying "large extra dimensions." Hawking's theory tells us that this black hole would evaporate in 10^-88 seconds. Which shorter than the shortest time we thing our theories can reasonably accommodate, the Planck time of 5 x 10^-44 s. Let's take the bigger number. In that time, the black hole could travel at most the Planck length: 1.6 x 10^-35 m (assuming it travels nearly at the speed of light). The average distance between atoms is on the order of nanometers: 10^-9 m. So the black hole couldn't get anywhere close to the nearest source of mass that would allow it to eat something and grow (not that eating even a single atom would sustain the black hole against the mass loss of Hawking radiation).
Now, if we were very wrong about how micro black holes radiate, you might be worried. And since we'd have to be very wrong about black holes to even form one, that's reasonable. However, the Universe is full of very energetic cosmic rays. Such cosmic rays occasionally have higher energies than the LHC, even in the center of mass frame of the collision (hitting two moving objects together -as the LHC does- allows more energy in the event to be used to make new objects. Hitting a stationary object with a fast moving one means most of the energy gets soaked up accelerating the fragments). So if TeV-scale black holes could be created and could live long enough to start eating atoms and growing, we'd expect massive objects out in space to have been eaten already. Objects like pulsars and neutron stars. These things exist, and are very old, which can be used to demonstrate that world-eating black holes are not realized in the physical scales that LHC can access. This is what the paper I linked to previously shows.
posted by physicsmatt at 10:27 AM on July 16, 2013 [67 favorites]
Black holes radiate energy out (making them not exactly black). This radiation is blackbody, which is to say it has the spectrum of a perfectly uniform object at some temperature. The Sun, for example, is close to a blackbody, but has spectral lines due to the presence of the elements in the Sun having excitations and de-excitations of electrons and sending out light that is non-thermal. Black holes just have the thermal bit.
The person who figured this out is Stephen Hawking. In addition to writing some excellent books and being famous for doing it all with severe physical handicaps, he's a brilliant scientist. He figured out that, in order for black holes not to violate the laws of thermodynamics, they have to have possess entropy. This means that they have a temperature; which means they have to radiate away energy. So, left on their own, a black hole will evaporate via the emission of Hawking radiation. Hawking radiation emerges from just outside the boundary of the black hole; the event horizon, and can be thought of as pairs of virtual particles appearing next to the horizon (as they do everywhere in space) but one of the pair falling into the horizon and the other escaping out. The slightly more accurate way of saying this is that empty space near a horizon does not correspond to empty space infinity far away from the horizon; someone at infinity sees particles coming from what someone near the horizon would call "the vacuum."
Now, Hawking derived the temperature of a black hole to be T = 1/8\pi M, where M is the mass of the black hole, and I've done the usual theorist trick of setting all constants of Nature equal to 1 because we theorists are all deeply lazy people. Be glad I didn't set 2\pi = 1 (aka the small circle approximation. I've done it before and I will do it again). In more reasonable units, the temperature is
(1 K) times (1.2 x 10^23 kg/ M)
The Sun's mass is 2 x 10^30 kg, so the Sun converted to a black hole would have a temperature of about 10^-7 K, which is much smaller than the temperature of the cosmic microwave background (2.7 K) and so much colder than deep space. Thus converting the Sun to a black hole would cause the resulting black hole to actually start growing (slowly) as CMB photons falling into the ex-Sun would deposit more energy per unit time than would be removed via Hawking radiation.
Notice that the Hawking temperature goes like inverse mass, so smaller black holes are hotter. The Moon converted into a black hole would have a temperature of 1.7 K. Ignoring the CMB feeding this black hole, the lifetime would be 3 x 10^52 seconds (or 10^45 years. The Universe is only 13.6 x 10^9 years old). So eventually there'd be a flash of gamma rays (as the black hole evaporates, it heats up, resulting in higher energy photons emitted), but only at the end of its lifetime. A black hole originally asteroid-sized, some 10^11 kg in mass, would be evaporating just about now if it was created in the early Universe. Smaller ones would already have poofed-away, and the lack of such gamma ray flashes is how we know dark matter is not a bunch of very small black holes. The larger black holes are ruled out for directly looking for the lensing effect they would have as the pass between us and distant stars. There is a very small window of masses that are not directly ruled out, but no one really has a mechanism for creating that many black holes in the early Universe (not that that's a deal-breaker, just a statement of our present knowledge).
So, if you managed to create a micro-black hole using a TeV of energy (the available energy at the LHC), for one thing, something's gone very wrong because there should be no way you've crammed enough energy into a small enough region for the event horizon to form. OK, we'll hand-wave that away by saying "large extra dimensions." Hawking's theory tells us that this black hole would evaporate in 10^-88 seconds. Which shorter than the shortest time we thing our theories can reasonably accommodate, the Planck time of 5 x 10^-44 s. Let's take the bigger number. In that time, the black hole could travel at most the Planck length: 1.6 x 10^-35 m (assuming it travels nearly at the speed of light). The average distance between atoms is on the order of nanometers: 10^-9 m. So the black hole couldn't get anywhere close to the nearest source of mass that would allow it to eat something and grow (not that eating even a single atom would sustain the black hole against the mass loss of Hawking radiation).
Now, if we were very wrong about how micro black holes radiate, you might be worried. And since we'd have to be very wrong about black holes to even form one, that's reasonable. However, the Universe is full of very energetic cosmic rays. Such cosmic rays occasionally have higher energies than the LHC, even in the center of mass frame of the collision (hitting two moving objects together -as the LHC does- allows more energy in the event to be used to make new objects. Hitting a stationary object with a fast moving one means most of the energy gets soaked up accelerating the fragments). So if TeV-scale black holes could be created and could live long enough to start eating atoms and growing, we'd expect massive objects out in space to have been eaten already. Objects like pulsars and neutron stars. These things exist, and are very old, which can be used to demonstrate that world-eating black holes are not realized in the physical scales that LHC can access. This is what the paper I linked to previously shows.
posted by physicsmatt at 10:27 AM on July 16, 2013 [67 favorites]
Also, the idea that the LHC would create earth-destroying black holes always reminded me of the somewhat more serious concern that the hydrogen bomb would ignite a chain reaction and destroy the atmosphere (old LANL pdf, good reading if you're a fan of radiative processes and nuclear physics a.k.a. an astronomer).
posted by kiltedtaco at 10:28 AM on July 16, 2013 [2 favorites]
posted by kiltedtaco at 10:28 AM on July 16, 2013 [2 favorites]
Joaquin Phoenix stars as the tactical genius and cult leader Arthur Dunning. Benedict Cumberbatch as the spurned physicist eager to get back into CERN's good graces who is slowly putting together the pieces. Gary Oldman as hostage and US Senator Terry Pearson.
"They fought his way in, now there's no way out"
VOID
Coming Summer 2015
A troubled mystic who models himself after General 'Stonewall' Jackson and a misanthropic physicist, Edgar Jovecheck, assume control of CERN and make hostages of her honored guests. When Dunning shows no signs of having an exit strategy, no interest in ransom, and begins powering up the machine, Edgar is left to wonder what his true intentions are. It might be up to him to save the hostages, and perhaps humanity.
posted by 221bbs at 10:29 AM on July 16, 2013 [6 favorites]
"They fought his way in, now there's no way out"
VOID
Coming Summer 2015
A troubled mystic who models himself after General 'Stonewall' Jackson and a misanthropic physicist, Edgar Jovecheck, assume control of CERN and make hostages of her honored guests. When Dunning shows no signs of having an exit strategy, no interest in ransom, and begins powering up the machine, Edgar is left to wonder what his true intentions are. It might be up to him to save the hostages, and perhaps humanity.
posted by 221bbs at 10:29 AM on July 16, 2013 [6 favorites]
Lord of the Holes : Plot Synopsis
A blackhole the size of a silver dollar is created at the Large Hadron Collider in Switzerland. It quickly migrates to South Dakota, where it is found by a mentally-challenged Farmer named Franko. Franko and his buddy same must make the difficult journey back to CERN to cast the black hole back into the super-collider from whence it came. At the end, they are rescued by unmanned USAF drones.
posted by blue_beetle at 10:32 AM on July 16, 2013 [9 favorites]
A blackhole the size of a silver dollar is created at the Large Hadron Collider in Switzerland. It quickly migrates to South Dakota, where it is found by a mentally-challenged Farmer named Franko. Franko and his buddy same must make the difficult journey back to CERN to cast the black hole back into the super-collider from whence it came. At the end, they are rescued by unmanned USAF drones.
posted by blue_beetle at 10:32 AM on July 16, 2013 [9 favorites]
And if the scientists want to take a "leave it to the experts" attitude and mock the concerns of the public, then the public should refuse its support.
But isn't that just a recipe for creating rogue mad scientists bent on world domination?
posted by Atom Eyes at 10:33 AM on July 16, 2013 [2 favorites]
But isn't that just a recipe for creating rogue mad scientists bent on world domination?
posted by Atom Eyes at 10:33 AM on July 16, 2013 [2 favorites]
Physicsmatt ..that was really interesting. Thanks for that
But this piece " He figured out that, in order for black holes not to violate the laws of thermodynamics, they have to have possess entropy."
Leads me to ask if we are making an assumption that black holes positively DO NOT violate the laws of thermodynamics...
Now I don't know much physics .. hence we might have already confirmed that its true.
Question is whether that assumption is true? Or are we waiting for experimental verification to confirm Hawking's theory?
posted by TheLittlePrince at 10:42 AM on July 16, 2013
But this piece " He figured out that, in order for black holes not to violate the laws of thermodynamics, they have to have possess entropy."
Leads me to ask if we are making an assumption that black holes positively DO NOT violate the laws of thermodynamics...
Now I don't know much physics .. hence we might have already confirmed that its true.
Question is whether that assumption is true? Or are we waiting for experimental verification to confirm Hawking's theory?
posted by TheLittlePrince at 10:42 AM on July 16, 2013
Some of the analytic extensions of the original math for black holes show another region of spacetime which is in some sense reachable by going through the black hole. AIUI there's no particular reason to believe that that particular math is correct, but physics is absolutely littered with cases where some quirk or artifact of the matheetc
Ah! *nods intelligently* In the Delta Quadrant!
posted by glasseyes at 10:43 AM on July 16, 2013
Ah! *nods intelligently* In the Delta Quadrant!
posted by glasseyes at 10:43 AM on July 16, 2013
But isn't that just a recipe for creating rogue mad scientists bent on world domination?
Yep. But the public has pitchforks and torches. And wedgies for the black hole boys.
posted by No Robots at 10:48 AM on July 16, 2013
Yep. But the public has pitchforks and torches. And wedgies for the black hole boys.
posted by No Robots at 10:48 AM on July 16, 2013
Maybe start with Ophiuchi Hotline or the Persistence of Vision collection of shorts.
No wait. Ophiuchi is very 70s and PoV is not solely Eight Worlds. Steel Beach should be the first one and you can hardly really appreciate it unless you first read The Moon is a Harsh Mistress by Heinlein (which SB is a response to).
Definitely don't read The Ophiuchi Hotline first. It's what I like to think of as a "capstone novel"—a book set in an existing fictional universe that brings together a lot of different threads and ties them up into a single story. (Ringworld is another example of this.) TOH is full of characters and locations that you won't recognize unless you've read the other Eight Worlds stories first. Which you should do—in order of publication.
posted by The Tensor at 10:53 AM on July 16, 2013 [1 favorite]
No wait. Ophiuchi is very 70s and PoV is not solely Eight Worlds. Steel Beach should be the first one and you can hardly really appreciate it unless you first read The Moon is a Harsh Mistress by Heinlein (which SB is a response to).
Definitely don't read The Ophiuchi Hotline first. It's what I like to think of as a "capstone novel"—a book set in an existing fictional universe that brings together a lot of different threads and ties them up into a single story. (Ringworld is another example of this.) TOH is full of characters and locations that you won't recognize unless you've read the other Eight Worlds stories first. Which you should do—in order of publication.
posted by The Tensor at 10:53 AM on July 16, 2013 [1 favorite]
yeah blue_beetle I don't think so. Why don't the drones just fly the black hole back to CERN to begin with?
posted by Mei's lost sandal at 11:13 AM on July 16, 2013 [2 favorites]
posted by Mei's lost sandal at 11:13 AM on July 16, 2013 [2 favorites]
Well, the only black holes we've positively identified are greater than the Sun in mass, and so we cannot directly measure the Hawking radiation.
The result has been shown to be theoretically consistent, and the set of assumptions leading up to it are very robust. Furthermore, the general argument can be used to show that any horizon in spacetime will radiate. If you accelerate, then there is some portion of the Universe you cannot see, so a horizon forms. Extending Hawking's work means this horizon radiates (Unruh radiation). This is necessary to prevent the accelerating observer from seeing entropy decrease (due to not seeing part of the Universe anymore), which is forbidden by the 2nd Law. So the horizon needs to have entropy, and entropy requires a temperature, which requires radiation. So there isn't experimental evidence, but there are multiple cross-checks we can perform in thought experiments that give us confidence that this is a reasonable theory. As always, experiment is the final arbiter, but sometimes you don't get what you want.
In addition, violating the 2nd law of thermodynamics leads to all sorts of nonsensical results, and is not recommended. I'd much prefer violating conservation of energy over allowing entropy to decrease. However, as a result of requiring the black holes to maintain the 2nd law of thermodynamics, there are many other bizarre conclusions. For example, it turns out that the maximum entropy that can be contained in any volume goes as the surface area of that volume, not the volume itself (this is because the entropy of a black hole is proportional to the surface area of the event horizon). This is massively counterintuitive: the amount of information (roughly equivalent to entropy in this context) you can cram in a room should go like the volume of the room, not the surface area, and our understanding of quantum field theory goes along with that intuition. This is saying I can figure out all the information I need about any physical system by inspecting the surface, which seems a bit odd. But we know quantum mechanics must get modified somehow to accommodate gravity, so black holes not playing well with QFT is not surprising.
Then there's the idea of the black hole firewall, which says that if an infalling observer is not to be annihilated by a wall of high-energy particles immediately inside the black hole horizon (which is fine from the point of view of an outside observer, but seems suspect from our general understanding of gravity, which admittedly is not as great as we'd like) then we're going to have to give up some long-cherished beliefs in how systems work, ideas like locality. It's not settled yet, but it just goes to show that black holes are great laboratories for figuring out how gravity and quantum mechanics must go together, even if we don't have them in our labs.
posted by physicsmatt at 12:06 PM on July 16, 2013 [14 favorites]
The result has been shown to be theoretically consistent, and the set of assumptions leading up to it are very robust. Furthermore, the general argument can be used to show that any horizon in spacetime will radiate. If you accelerate, then there is some portion of the Universe you cannot see, so a horizon forms. Extending Hawking's work means this horizon radiates (Unruh radiation). This is necessary to prevent the accelerating observer from seeing entropy decrease (due to not seeing part of the Universe anymore), which is forbidden by the 2nd Law. So the horizon needs to have entropy, and entropy requires a temperature, which requires radiation. So there isn't experimental evidence, but there are multiple cross-checks we can perform in thought experiments that give us confidence that this is a reasonable theory. As always, experiment is the final arbiter, but sometimes you don't get what you want.
In addition, violating the 2nd law of thermodynamics leads to all sorts of nonsensical results, and is not recommended. I'd much prefer violating conservation of energy over allowing entropy to decrease. However, as a result of requiring the black holes to maintain the 2nd law of thermodynamics, there are many other bizarre conclusions. For example, it turns out that the maximum entropy that can be contained in any volume goes as the surface area of that volume, not the volume itself (this is because the entropy of a black hole is proportional to the surface area of the event horizon). This is massively counterintuitive: the amount of information (roughly equivalent to entropy in this context) you can cram in a room should go like the volume of the room, not the surface area, and our understanding of quantum field theory goes along with that intuition. This is saying I can figure out all the information I need about any physical system by inspecting the surface, which seems a bit odd. But we know quantum mechanics must get modified somehow to accommodate gravity, so black holes not playing well with QFT is not surprising.
Then there's the idea of the black hole firewall, which says that if an infalling observer is not to be annihilated by a wall of high-energy particles immediately inside the black hole horizon (which is fine from the point of view of an outside observer, but seems suspect from our general understanding of gravity, which admittedly is not as great as we'd like) then we're going to have to give up some long-cherished beliefs in how systems work, ideas like locality. It's not settled yet, but it just goes to show that black holes are great laboratories for figuring out how gravity and quantum mechanics must go together, even if we don't have them in our labs.
posted by physicsmatt at 12:06 PM on July 16, 2013 [14 favorites]
The [more inside] on this one is disappointing. I was truly hoping for YouTube clips.
posted by emelenjr at 12:10 PM on July 16, 2013 [2 favorites]
posted by emelenjr at 12:10 PM on July 16, 2013 [2 favorites]
Fortunately, Trevor Eve and the British National Grid are on hand to pick up the pieces.
posted by specialbrew at 12:10 PM on July 16, 2013
posted by specialbrew at 12:10 PM on July 16, 2013
@emelenjr ... :) this was my first post to mefi .. next time I will be sure to add kittens :) .. even if the post is about monsters and why we love them.
posted by TheLittlePrince at 12:25 PM on July 16, 2013
posted by TheLittlePrince at 12:25 PM on July 16, 2013
@yoga .. I hope you don't think the little prince escaped from a black hole?
posted by TheLittlePrince at 12:26 PM on July 16, 2013
posted by TheLittlePrince at 12:26 PM on July 16, 2013
Forgive me, for I am ignorant in such matters, but doesn't Earth count as "enough matter"? What, we're not even a quick snack for black hole?
It works kind of like putting two magnets together. As you bring them closer, you feel them pulling each other with more and more strength. As some distance (analogous to the event horizon in a black hole), you won't be strong enough to keep them apart. How far this distance is depends on the strength of the magnets.
The strength of gravity depends on the mass of the object. A black hole created by the LHC wouldn't have much mass, hardly any in fact, so the distance within which an object must pass to cross the black hole's event horizon is short that nothing would be able to cross it before the black hole evaporated even if it was very close and moving towards it at the speed of light.
posted by VTX at 12:52 PM on July 16, 2013
It works kind of like putting two magnets together. As you bring them closer, you feel them pulling each other with more and more strength. As some distance (analogous to the event horizon in a black hole), you won't be strong enough to keep them apart. How far this distance is depends on the strength of the magnets.
The strength of gravity depends on the mass of the object. A black hole created by the LHC wouldn't have much mass, hardly any in fact, so the distance within which an object must pass to cross the black hole's event horizon is short that nothing would be able to cross it before the black hole evaporated even if it was very close and moving towards it at the speed of light.
posted by VTX at 12:52 PM on July 16, 2013
@TheLittlePrince: Leads me to ask if we are making an assumption that black holes positively DO NOT violate the laws of thermodynamics...
I refer you to Sir Arthur Stanley Eddington: The law that entropy always increases holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations — then so much the worse for Maxwell's equations. If it is found to be contradicted by observation — well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.
Put it another way, if you have excluded every possibility save that the laws of thermodynamics have been violated, it's time to start looking for new possibilities.
posted by It's Never Lurgi at 1:06 PM on July 16, 2013 [4 favorites]
I refer you to Sir Arthur Stanley Eddington: The law that entropy always increases holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations — then so much the worse for Maxwell's equations. If it is found to be contradicted by observation — well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.
Put it another way, if you have excluded every possibility save that the laws of thermodynamics have been violated, it's time to start looking for new possibilities.
posted by It's Never Lurgi at 1:06 PM on July 16, 2013 [4 favorites]
A fun sci-fi premise there. What would the survival-of-humanity Mars colony look like?
Add some alien interference it sounds like the plot of Greg Bear's Forge of God, if I recall correctly from decades past.
posted by aught at 1:08 PM on July 16, 2013 [1 favorite]
Add some alien interference it sounds like the plot of Greg Bear's Forge of God, if I recall correctly from decades past.
posted by aught at 1:08 PM on July 16, 2013 [1 favorite]
Franko and his buddy same must make the difficult journey back to CERN to cast the black hole back into the super-collider from whence it came.
One does not simply walk into Switzerland! Its black gates are guarded by more than just Swiss Guards. There is evil there that does not sleep. The great eye is ever watchful. It is a barren wasteland, riddled with fire, ash, and dust. The very air you breathe is a poisonous fume. Not with ten thousand men could you do this. It is folly.
posted by Naberius at 1:35 PM on July 16, 2013
One does not simply walk into Switzerland! Its black gates are guarded by more than just Swiss Guards. There is evil there that does not sleep. The great eye is ever watchful. It is a barren wasteland, riddled with fire, ash, and dust. The very air you breathe is a poisonous fume. Not with ten thousand men could you do this. It is folly.
posted by Naberius at 1:35 PM on July 16, 2013
Brandon Blatcher: If a black hole as created on Earth, how long would it take for the planet to be eaten. I'm guessing microseconds?Billions of times longer than the lifetime of the universe, for the biggest black holes we are ever going to be able to create.
posted by IAmBroom at 1:48 PM on July 16, 2013 [1 favorite]
michaelh: A black hole would be a good place to hide a body. I'm imagining something that's a mix between Looper and the end of Fargo.The "last image of the body at the event horizon lasting for an infinity of time" is a bit of a problem, though.
posted by IAmBroom at 1:59 PM on July 16, 2013 [3 favorites]
staccato signals of constant information: I enjoy theoretical physics, and feel like I have a reasonable grasp on the basic principles for a layman, but can someone explain to me the basis for thinking that a black hole could provide an entrance to a wormhole?Clearly you haven't watched the brilliant treatise on the subject, "Star Trek (The Original Series)". Additional material is provided by ST:TNG, ST:DS9, Star Wars Episodes IV-VI (I-III have been thoroughly discredited), Disney's "The Black Hole" (produced by their prestigious Quantum Dynamics and Theoretical Physics division, formerly headquartered at Space Mountain in their California institute), "Battleship Galactica" (the original series still stands as a seminal work, but the new edition raises interesting possibilities for discussion), and so on.
I've never really understood how we make the connection, or theoretically bridge the gap from hypercompression (singularity) to an on-ramp. It certainly sounds really cool, but I haven't heard any connection articulated.
Seriously, and you think you know theoretical physics? You haven't even cracked open the "Enterprise Engineering Manual" yet, bub.
Obviously, physicsmatt has studied these works.
posted by IAmBroom at 2:04 PM on July 16, 2013
There's a sense in which the 2nd Law isn't completely inviolable, but it is the very nature that makes it almost inviolate that makes it so certainly almost inviolate. It really just says in a particularly useful but not entirely intuitive way that "Probable things are more likely to happen" and with large numbers in most physical systems the improbable things are almost impossibly improbable.
By the same logic trying to claim a violation is like saying "You'll probably see something improbable" and it doesn't take a genius to spot the flaw in that. And therefore you should generally consider it a given in ways that many other physical laws aren't.
posted by edd at 2:21 PM on July 16, 2013 [3 favorites]
By the same logic trying to claim a violation is like saying "You'll probably see something improbable" and it doesn't take a genius to spot the flaw in that. And therefore you should generally consider it a given in ways that many other physical laws aren't.
posted by edd at 2:21 PM on July 16, 2013 [3 favorites]
Can we have a session where we have a proper Q+A with physicsmatt - with a time to suit him? It seems a bit unfair we keep dragging him away from important stuff at random times. Plus I'm sure I'm not the only with stupid questions ("doesn't a point mass mean infiinte density - equations don't work any more?", "as the universe expands does dark energy increase - if so, does this break the first law of thermodynamics?"). I promise to buy him hobnobs or biscuits of his choice!
posted by BigCalm at 2:51 PM on July 16, 2013 [3 favorites]
posted by BigCalm at 2:51 PM on July 16, 2013 [3 favorites]
>wants to talk about RHIC and QCD hydro duals of black holes
>is too tired
>finds oldish article that's decent instead
posted by nat at 3:33 PM on July 16, 2013
>is too tired
>finds oldish article that's decent instead
posted by nat at 3:33 PM on July 16, 2013
One does not simply walk into Switzerland!
Of course not. One books a Swissair flight into Zurich and catches a train. This is a much more pleasant mode of transportation than giant eagles, trust me.
I also find it typical that a member called "No Robots" would be prejudiced against Mad Scientists (or, to be fair, Mad Engineers). Just wait until my Dreadful Robot Army of Doom is finished....
posted by GenjiandProust at 3:51 PM on July 16, 2013
Of course not. One books a Swissair flight into Zurich and catches a train. This is a much more pleasant mode of transportation than giant eagles, trust me.
I also find it typical that a member called "No Robots" would be prejudiced against Mad Scientists (or, to be fair, Mad Engineers). Just wait until my Dreadful Robot Army of Doom is finished....
posted by GenjiandProust at 3:51 PM on July 16, 2013
BigCalm, I visit chat occasionally, so you can find me there now and then. I don't think metafilter proper is really set up to do a redditt-style AMA, and I'm also not nearly important enough to be the very first recipient of MetaAskMeAnything so I'm not sure there's an easy way to do what you have in mind. You can always send me mail or a tweet though, and if I'm not too busy I'll try to answer it. I'm moving this summer, so you all shouldn't hold your breath on timeliness. I'm not opposed to showing up to a meetup and answering physics questions over beer, but again, don't hold your breath on that being a possibility any time soon.
Also, energy is not conserved in a Universe with dark energy. It's also not conserved in general in an expanding Universe. This is because conservation of energy is a consequence of time invariance of physical laws, through Noether's Theorem. Momentum conservation is due to translation invariance - the laws of physics are the same no matter where you are - and you can think of energy as the "time" version of momentum. Angular momentum is conserved because the laws of physics are invariant under rotations. Conservation of charge and other quantum numbers are due to internal symmetries that are a bit more abstract. Anyway, the point of Noether's Theorem is that every conserved quantity has a symmetry associated with it, and vice versa. (also, like what edd said about the 2nd law, once you see the symmetry connection, Noether's Theorem becomes so awesomely obvious in retrospect, which is often a sign of a great theory in math and science. Physics is so much fun you guys.)
So, locally and over any time scale you might care about, the Universe's laws of physics are invariant under time translation, and so energy is conserved at the level that people could possibly give a damn about. However, writ large, the Universe is expanding and so is manifestly not time-invariant: the future looks different than the past. This means that a photon going through space will redshift: its energy will decrease even though it's not giving that energy too anything. And dark energy can change the "net" energy of the Universe in some accounting.
That said, if I find any of you telling people that "oh, that perpetual motion machine will totally work, physicsmatt said so" I will use my time-share in CERN's army of giant robots armed with antimatter weapons to strike down upon thee with furious vengeance. Unless your perpetual motion machine is a string between two galaxy clusters that somehow is tied to the expansion of the spacetime metric, energy is conserved to a startlingly high degree of accuracy. Don't make me dust off the giant robots.
posted by physicsmatt at 4:03 PM on July 16, 2013 [6 favorites]
Also, energy is not conserved in a Universe with dark energy. It's also not conserved in general in an expanding Universe. This is because conservation of energy is a consequence of time invariance of physical laws, through Noether's Theorem. Momentum conservation is due to translation invariance - the laws of physics are the same no matter where you are - and you can think of energy as the "time" version of momentum. Angular momentum is conserved because the laws of physics are invariant under rotations. Conservation of charge and other quantum numbers are due to internal symmetries that are a bit more abstract. Anyway, the point of Noether's Theorem is that every conserved quantity has a symmetry associated with it, and vice versa. (also, like what edd said about the 2nd law, once you see the symmetry connection, Noether's Theorem becomes so awesomely obvious in retrospect, which is often a sign of a great theory in math and science. Physics is so much fun you guys.)
So, locally and over any time scale you might care about, the Universe's laws of physics are invariant under time translation, and so energy is conserved at the level that people could possibly give a damn about. However, writ large, the Universe is expanding and so is manifestly not time-invariant: the future looks different than the past. This means that a photon going through space will redshift: its energy will decrease even though it's not giving that energy too anything. And dark energy can change the "net" energy of the Universe in some accounting.
That said, if I find any of you telling people that "oh, that perpetual motion machine will totally work, physicsmatt said so" I will use my time-share in CERN's army of giant robots armed with antimatter weapons to strike down upon thee with furious vengeance. Unless your perpetual motion machine is a string between two galaxy clusters that somehow is tied to the expansion of the spacetime metric, energy is conserved to a startlingly high degree of accuracy. Don't make me dust off the giant robots.
posted by physicsmatt at 4:03 PM on July 16, 2013 [6 favorites]
I seem to recall a short story where small contained black holes were used as an energy source. Then the company that owned them abandoned them and the locals started using a broken black hole container as a garbage disposal. Ring any bells?
posted by ymgve at 4:20 PM on July 16, 2013 [1 favorite]
posted by ymgve at 4:20 PM on July 16, 2013 [1 favorite]
Unless your perpetual motion machine is a string between two galaxy clusters that somehow is tied to the expansion of the spacetime metric, energy is conserved to a startlingly high degree of accuracy.
So what you're saying is that there's hope for my teraparsec-scale drinky-bird...
posted by ROU_Xenophobe at 4:52 PM on July 16, 2013 [1 favorite]
So what you're saying is that there's hope for my teraparsec-scale drinky-bird...
posted by ROU_Xenophobe at 4:52 PM on July 16, 2013 [1 favorite]
I seem to recall a short story where small contained black holes were used as an energy source. Then the company that owned them abandoned them and the locals started using a broken black hole container as a garbage disposal. Ring any bells?
I think that was on StarShipSofa.
posted by Artw at 4:53 PM on July 16, 2013
I think that was on StarShipSofa.
posted by Artw at 4:53 PM on July 16, 2013
I would think a Rapid Offensive Unit such as yourself would have access to the Grid, and so wouldn't need to worry about energy reserves.
posted by physicsmatt at 4:57 PM on July 16, 2013
posted by physicsmatt at 4:57 PM on July 16, 2013
It's "The Clockwork Atom Bomb" by Dominic Green.
posted by Artw at 4:58 PM on July 16, 2013 [2 favorites]
posted by Artw at 4:58 PM on July 16, 2013 [2 favorites]
It would be madness NOT to create a black hole!
posted by Mister_A at 5:36 PM on July 16, 2013 [1 favorite]
posted by Mister_A at 5:36 PM on July 16, 2013 [1 favorite]
The "last image of the body at the event horizon lasting for an infinity of time" is a bit of a problem, though.
That's why the black hole has to be in the past!
posted by michaelh at 5:39 PM on July 16, 2013
That's why the black hole has to be in the past!
posted by michaelh at 5:39 PM on July 16, 2013
This made me think of Eater by Gregory Benford which has a plot involving the possibility of earth being hit by a black hole.
posted by Gadgetenvy at 6:28 PM on July 16, 2013
posted by Gadgetenvy at 6:28 PM on July 16, 2013
A link to a previous AskMeFi about The Clockwork Atom Bomb.
posted by aeschenkarnos at 8:38 PM on July 16, 2013
posted by aeschenkarnos at 8:38 PM on July 16, 2013
physicsmatt is great! He has an amazing wisdom and power.
posted by JHarris at 12:56 AM on July 17, 2013
posted by JHarris at 12:56 AM on July 17, 2013
I seem to recall that the 'the LHC will make a non-momentary black hole that will kill us all'/'no it won't' debate consisted of a back-and-forth of 'yuh-huhs' and 'nu-uhs' that dead-ended at 'Hawking Radiation will escape the black hole causing to to disspiate' and 'Hawking Radiation has not yet been proven'. Does the fact that we're not dead prove the existence of Hawking Radiation? And if so, has Stephen won a bet?
posted by BiggerJ at 5:43 AM on July 17, 2013
posted by BiggerJ at 5:43 AM on July 17, 2013
BiggerJ, under standard assumptions, before we turned it on, we did not expect that the LHC can produce black holes. This is because a particle-sized black hole needs a mass equivalent to the Planck mass of 2 x 10^19 GeV. The LHC collides particles at 8 TeV at the moment, and will get to 14 TeV after the upgrade. That's 14000 GeV, or 10^-15th of the energy needed to produce a black hole.
There are suggestions that gravity could get strong at the TeV scale, these go by the name of large extra dimensions. If that were the case the "real" Planck scale is a TeV, and we just think gravity is weak because it "leaks" into dimensions that we cannot access easily, diluting the apparent strength. If these models were correct, we could form black holes at the LHC. You could then say "but what if Hawking were wrong and those black holes are stable?" The argument that the paper from Ellis et al that I linked to above is that this could not happen, because if it did, there would be no visible pulsars and neutron stars in the Universe. Since there are, stable black holes are not formed by TeV-scale collisions: either there are no large extra dimensions at this energy, or there are but Hawking radiation occurs and they evaporate.
So we knew the LHC was safe, and we turned it on. Hoping, among other things, to see the evidence of Hawking radiation from black holes, because that would be amazingly awesome and we'd learn a lot. We didn't see any evidence of that. Here are links to simulated versions of what such events would have looked like in the ATLAS detector at the LHC. This doesn't prove Hawking radiation right or wrong, because we didn't produce any black holes, but again, under standard assumptions, we didn't really expect to. Just that there were extensions of our knowledge that would lead to such a result, and so we considered it
posted by physicsmatt at 7:33 AM on July 17, 2013 [2 favorites]
There are suggestions that gravity could get strong at the TeV scale, these go by the name of large extra dimensions. If that were the case the "real" Planck scale is a TeV, and we just think gravity is weak because it "leaks" into dimensions that we cannot access easily, diluting the apparent strength. If these models were correct, we could form black holes at the LHC. You could then say "but what if Hawking were wrong and those black holes are stable?" The argument that the paper from Ellis et al that I linked to above is that this could not happen, because if it did, there would be no visible pulsars and neutron stars in the Universe. Since there are, stable black holes are not formed by TeV-scale collisions: either there are no large extra dimensions at this energy, or there are but Hawking radiation occurs and they evaporate.
So we knew the LHC was safe, and we turned it on. Hoping, among other things, to see the evidence of Hawking radiation from black holes, because that would be amazingly awesome and we'd learn a lot. We didn't see any evidence of that. Here are links to simulated versions of what such events would have looked like in the ATLAS detector at the LHC. This doesn't prove Hawking radiation right or wrong, because we didn't produce any black holes, but again, under standard assumptions, we didn't really expect to. Just that there were extensions of our knowledge that would lead to such a result, and so we considered it
posted by physicsmatt at 7:33 AM on July 17, 2013 [2 favorites]
Thinking about this from a layman's perspective:
There is the idea that, if it were possible to create a stable black hole in the lab, that there'd be a lot more of them in the universe, created in stars.
But on the other hand, why haven't we seen, when looking out with telescopes and such, evidence of other species in the universe? It could be we're the first (although unlikely), it could be that they're very sparse or that space travel is an extremely difficult, maybe even insurmountable, problem. Maybe they look so different from us that the signs of their culture are indistinguishable to us from randomness, or maybe we're unique among technically advanced species for wanting to explore the cosmos, or seek out other life. Maybe other intelligent cultures naturally destroy each other, which is a sad prospect to look forward to.
Or maybe it's because, as a civilization's sciences progress towards high-energy physics, that there's a land mine in the path, a kind of cultural self-destruct switch, like an atom bomb writ large, something unexpected they uncover while experimenting that wipes them out. I think it's unlikely, the the reason I gave up above, but still, the possibility is worrying.
posted by JHarris at 12:58 PM on July 17, 2013 [1 favorite]
There is the idea that, if it were possible to create a stable black hole in the lab, that there'd be a lot more of them in the universe, created in stars.
But on the other hand, why haven't we seen, when looking out with telescopes and such, evidence of other species in the universe? It could be we're the first (although unlikely), it could be that they're very sparse or that space travel is an extremely difficult, maybe even insurmountable, problem. Maybe they look so different from us that the signs of their culture are indistinguishable to us from randomness, or maybe we're unique among technically advanced species for wanting to explore the cosmos, or seek out other life. Maybe other intelligent cultures naturally destroy each other, which is a sad prospect to look forward to.
Or maybe it's because, as a civilization's sciences progress towards high-energy physics, that there's a land mine in the path, a kind of cultural self-destruct switch, like an atom bomb writ large, something unexpected they uncover while experimenting that wipes them out. I think it's unlikely, the the reason I gave up above, but still, the possibility is worrying.
posted by JHarris at 12:58 PM on July 17, 2013 [1 favorite]
JHarris, surely the fact that you can conceive of such a thing makes it very unlikely that no species would ever be able to anticipate and avoid triggering such a landmine.
posted by straight at 10:50 PM on July 17, 2013 [1 favorite]
posted by straight at 10:50 PM on July 17, 2013 [1 favorite]
straight: "JHarris, surely the fact that you can conceive of such a thing makes it very unlikely that no species would ever be able to anticipate and avoid triggering such a landmine."
But then, such a specie which was able to avoid triggering all such land mines would be very very cautious indeed and thus making it rare that they would explore or meet other civilizations without ensuring that such action wouldn't harm itself?
posted by TheLittlePrince at 11:33 AM on July 18, 2013
But then, such a specie which was able to avoid triggering all such land mines would be very very cautious indeed and thus making it rare that they would explore or meet other civilizations without ensuring that such action wouldn't harm itself?
posted by TheLittlePrince at 11:33 AM on July 18, 2013
Or maybe every alien species gets to stage of building an LHC or next-generation SuperLHC but then get cold tentacles and kills their basic physics experimental program just to be on the safe side. Then, without a fundamental physics program, the science-drones are not adequately trained, little Xzb'lly and W'nydt don't get inspired to study their thoraxes off in the learning-hive, techno-organic improvement slows, the alien space program dies an early and unlamented death, and all the alien species are confined to one planet until a local asteroid wipes them all out. That's my contribution of the solution to the Fermi Paradox.*
You can game these hypothetical all day long, but again, I do want to emphasize that physicists are not crazy people. We are not willing to take risks to an entire planet's population merely to satisfy our curiosity.
*Not that I'm suggesting that lobbying your representative for more science funding would save you from the asteroids, but please, think of baby Xzb'lly. It and it's larval mates have so much promise. With proper funding, one day both our species can reach the stars. And annihilate each other in the Great Bug/Squishy-Hairless-Ape War of 3417. And isn't that what science is all about?
posted by physicsmatt at 11:55 AM on July 18, 2013 [4 favorites]
You can game these hypothetical all day long, but again, I do want to emphasize that physicists are not crazy people. We are not willing to take risks to an entire planet's population merely to satisfy our curiosity.
*Not that I'm suggesting that lobbying your representative for more science funding would save you from the asteroids, but please, think of baby Xzb'lly. It and it's larval mates have so much promise. With proper funding, one day both our species can reach the stars. And annihilate each other in the Great Bug/Squishy-Hairless-Ape War of 3417. And isn't that what science is all about?
posted by physicsmatt at 11:55 AM on July 18, 2013 [4 favorites]
Yes physicsmatt, I am talking about gross generalities, and not that I necessarily believe them. But it is a nagging thing sometimes comes to mind with me, when spinning cycles. Thanks for the reassurances.
I don't think that physicists, or a whole culture, are crazy people. But individuals, or those with adverse motives, might be crazy people, and might also have huge resources, which could eventually lead to a supervillain kind of scenario.
posted by JHarris at 2:59 PM on July 18, 2013
I don't think that physicists, or a whole culture, are crazy people. But individuals, or those with adverse motives, might be crazy people, and might also have huge resources, which could eventually lead to a supervillain kind of scenario.
posted by JHarris at 2:59 PM on July 18, 2013
If we created a golf ball-sized black hole at the surface of the Earth, it would probably be able to sustain itself, but it would still expand slowly enough that we would get plenty of time to realize that humanity had fucked itself.
A golf-ball sized black hole would have roughly ten times the mass of the earth.
posted by empath at 8:24 PM on July 18, 2013
A golf-ball sized black hole would have roughly ten times the mass of the earth.
posted by empath at 8:24 PM on July 18, 2013
A golf-ball sized black hole would have roughly ten times the mass of the earth.
Right, so 256 was saying that if the LHC were to teleport Neptune to Geneva and collapse it into a black hole, we'd be screwed.
So don't do that, LHC physicists, okay?
posted by straight at 8:48 PM on July 18, 2013
Right, so 256 was saying that if the LHC were to teleport Neptune to Geneva and collapse it into a black hole, we'd be screwed.
So don't do that, LHC physicists, okay?
posted by straight at 8:48 PM on July 18, 2013
straight: A golf-ball sized black hole would have roughly ten times the mass of the earth.I know a guy who dates a Swiss girl, and it's not a big nation. I have him ask him to ask her to ask them.
Right, so 256 was saying that if the LHC were to teleport Neptune to Geneva and collapse it into a black hole, we'd be screwed.
So don't do that, LHC physicists, okay?
Consider it done.
posted by IAmBroom at 10:18 AM on July 19, 2013
One thing that hasn't come up yet, and I'm not exactly sure what it means except that it suggests some strange things would happen if we actually did have a black hole made in the laboratory, is that the gravity of a black hole actually warps time as well as space. I forget which it is, but I seem to remember hearing that the matter that falls into a black hole, from either its perspective or that of an observer, would never actually fall in, but just appear to be getting ever closer to the event horizon. Although, I'm unsure how this interacts with Hawkings' observation that black holes can lose mass by radiating energy; if the black hole itself is of finite age, that seems to imply the thing falling in cannot do so forever.
physicsmatt, can you shine any light on this? Am I misremembering it? Is this one of those cases where the microscopic scales of black holes and the generally macro-scale workings of gravity make it unclear what would happen?
posted by JHarris at 11:09 AM on July 19, 2013
physicsmatt, can you shine any light on this? Am I misremembering it? Is this one of those cases where the microscopic scales of black holes and the generally macro-scale workings of gravity make it unclear what would happen?
posted by JHarris at 11:09 AM on July 19, 2013
It's complicated. What happens to an infalling observer is that their future light cone (the points in space-time they can reach by traveling slower than light) starts "tipping" in the space-like direction according to someone watching from outside.
What this means in slightly-less physics-talk is that, for someone falling into a black hole, their future looks more and more like "into the black-hole." Once they pass the event horizon, their future light-cone points only towards the center of the black hole: there is no future in which they do not hit the singularity.
For an infalling observer, the time it takes for them to pass the event horizon and hit the center is finite. From a bystanders perspective, however, it is infinite: the bystander will never see the infaller pass the event horizon. Instead, what will happen is the light from the observer that radiates outwards will get more and more redshifted. If you could continue to see it, the infalling person would appear stuck like a fly in amber, frozen in the short moments of time right before they pass over the event horizon. Eventually they'd red-shift down to the Hawking radiation of the black hole, but you'd be able to watch them until then I'd imagine.
As for at what point the black hole appears to get heavier from eating this infalling matter, I'm not too sure. It's been a while since I thought hard about it. The black hole forming should take finite time from an outsider perspective.
posted by physicsmatt at 12:17 PM on July 19, 2013 [2 favorites]
What this means in slightly-less physics-talk is that, for someone falling into a black hole, their future looks more and more like "into the black-hole." Once they pass the event horizon, their future light-cone points only towards the center of the black hole: there is no future in which they do not hit the singularity.
For an infalling observer, the time it takes for them to pass the event horizon and hit the center is finite. From a bystanders perspective, however, it is infinite: the bystander will never see the infaller pass the event horizon. Instead, what will happen is the light from the observer that radiates outwards will get more and more redshifted. If you could continue to see it, the infalling person would appear stuck like a fly in amber, frozen in the short moments of time right before they pass over the event horizon. Eventually they'd red-shift down to the Hawking radiation of the black hole, but you'd be able to watch them until then I'd imagine.
As for at what point the black hole appears to get heavier from eating this infalling matter, I'm not too sure. It's been a while since I thought hard about it. The black hole forming should take finite time from an outsider perspective.
posted by physicsmatt at 12:17 PM on July 19, 2013 [2 favorites]
Thank you very much. Your responses here are greatly appreciated!
posted by JHarris at 7:51 PM on July 21, 2013
posted by JHarris at 7:51 PM on July 21, 2013
Leonard Susskind wrote a whole book about that exact question, btw -- "Black Hole War". It's worth a read.
posted by empath at 1:01 AM on July 22, 2013
posted by empath at 1:01 AM on July 22, 2013
The Tensor: "
Definitely don't read The Ophiuchi Hotline first. It's what I like to think of as a "capstone novel"—a book set in an existing fictional universe that brings together a lot of different threads and ties them up into a single story. (Ringworld is another example of this.) TOH is full of characters and locations that you won't recognize unless you've read the other Eight Worlds stories first. Which you should do—in order of publication."
Order of publication is the way to go. The thing to remember about Steel Beach/The Golden Globe is that they are not entirely consistent with the 70s Eight Worlds stories. Apparently, Varley has said he just didn't feel like going back and reading everything again. So, from a plot standpoint, they don't quite fit. Also, although I enjoyed the later novels, they don't have exactly the same feel. Start at the beginning.
posted by Chrysostom at 6:51 AM on July 24, 2013
Definitely don't read The Ophiuchi Hotline first. It's what I like to think of as a "capstone novel"—a book set in an existing fictional universe that brings together a lot of different threads and ties them up into a single story. (Ringworld is another example of this.) TOH is full of characters and locations that you won't recognize unless you've read the other Eight Worlds stories first. Which you should do—in order of publication."
Order of publication is the way to go. The thing to remember about Steel Beach/The Golden Globe is that they are not entirely consistent with the 70s Eight Worlds stories. Apparently, Varley has said he just didn't feel like going back and reading everything again. So, from a plot standpoint, they don't quite fit. Also, although I enjoyed the later novels, they don't have exactly the same feel. Start at the beginning.
posted by Chrysostom at 6:51 AM on July 24, 2013
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