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Micro-Black Holes Make Poor Planet Killers
astroengine writes "Physicists are getting excited about the possibility of micro-black holes (MBH) being produced by the LHC and an international group of researchers have done the math to see what kind of impact they could have on the Earth. Unfortunately, if you're a megalomaniac looking for your next globe-eating weapon, you can scrub MBHs off your WMD list. If a speedy MBH is produced, flying through our planet, it will only have a few seconds to accrete the mass of a few atoms. It would then be lost to space where it will evaporate. If a slow MBH is produced, dropping into the Earth where it sits for a few billion years, the results are even more boring."
I guess I know what kind of girl to look for now ;)
U+F8FF
How much red matter does the LHC use anyway?
Ah, the fear of the unknown. Yes, a classic. "I don't understand it, and I don't believe that they do either".
I've got news for you; this is as good (or should i say precise) model of these things as you are going to get right now. It's the cutting edge of our understanding of how MBHs work, and _that_ understanding in turn depends on a quite large, quite solid foundation of math and physics.
So please, this isn't speculation, it's SCIENCE.
"Total destruction the only solution" - Bob Marley
When will people see the light? MBHs don't suck so bad.
alias possession='chmod 666 satan && ls
Well, the key isn't just mass, but also radius. Gravity (I'll go newtonian, just because I'm lazy) increased linearly with mass, but decreases with the square of the radius. So for example, if you packed something the mass of Earth in just half the size of Earth, the gravity on the surface would be 4 times that of Earth. Squeeze it into a quarter of the size of Earth and get 16 times the gravity on the surface. Squeeze it small enough and you have a black hole.
If you do the proper maths, the Schwarzschild radius of a black hole with the mass of Earth is about 9mm.
Which really means, don't think something that will suck matter and bend light spectacularly all the way to Alpha Centauri. It means that if light happens to go within 9mm of that singularity, it ain't coming out. But farther away, it's still a body with the mass of Earth. The moon's orbit will still have the same radius for example.
A polar bear is a cartesian bear after a coordinate transform.
"Calculating how quickly a micro-black-hole would accumulate mass strikes me as a great undergrad tutorial question."
Which implies using existing theories to calculate it. What I think the grand parent post is saying is that we don't know for sure our current theories are all correct. After all, if we knew it all 100% correctly, there wouldn't be any need to build the LHC.
Scientific evidence accumulates over time. In science, its extremely hard to say 100% correct and be very careful of anyone who claims different.
Our current theories are our best current understanding of the universe and they do indeed work well. But we cannot be 100% sure. In the case of creating a black hole we won't know for sure until we create one under the conditions in the LHC (which due to the grouping of particle collisions in the LHC is different from a single high speed collision happening in the upper atmosphere).
Throughout the history of science we can see time and time again where theories were overturned. We therefore cannot assume all our current theories are correct under all possible conditions. There could be factors we are so far ignoring.
The problem is, the creation of a black hole in the LHC is kind of a unique experiment, as most wrong answers in science don't have such horrific results if our current theories are wrong.
There are 10 kinds of people in the world... those who understand binary and those who don't.
What people don't realize is that this study was funded by companies that produce black holes.
This is my sig.
Have you considered religion?
# cat
Damn, my RAM is full of llamas.
Mass = Energy...it evaporates by emitting other forms of energy (light, etc).
In principle, any mass, if packed densely enough, could become a black hole. For each mass - from a cluster of atoms to an entire galaxy - there is a calculable quantity called the Schwarzschild radius. If you could somehow pack the mass so that it fit inside a volume smaller than that mass's Schwarzschild radius, the force of gravity would invariably overcome all other forces and cause the mass to become a singularity. The Schwarzschild radius also defines the "edge" of the black hole - if anything, including light, gets closer than one Schwarzschild radius from the central mass, it will not be able to escape. In other words, at the Schwarzschild radius, the escape velocity is the speed of light.
It is easy to see how the core of a really big star could collapse on itself in a supernova - there's just so much mass, coupled with the force of the explosion. However, our own sun could become a black hole - if some as-yet unknown physical process could squeeze its entire mass into a 6-km diameter sphere. The Schwarzschild radius of one solar mass is about 3 km.
It is important to note that, were this to happen tomorrow, the Earth and the other planets would continue to orbit the black hole sun exactly as they have done for billions of years. The gravity of the sun hasn't changed, because its mass hasn't changed. If you were, however, unfortunate enough to come within 3 km of the center of the black hole sun, that's the last the universe would ever see of you. (As a practical matter, you'd be doomed long before then, simply because no rocket would be powerful enough to bring you away once you got closer than a few thousand kilometers. To escape the black hole sun once you were, say, 3.1 km away, you would need to somehow achieve a speed near to the speed of light, which we simply can't do.)
It is also important to note that you would not be sucked into a black hole if you came within 3 km of the center of the sun as it exists today, shining hot and bright. This is because 99.999% of the mass of the sun lies outside of that 3 km radius and so "doesn't count" in terms of the force of gravity. Aside from instantly transforming into plasma from the heat, you would actually feel far less gravity than you would on the Moon. (For reasons why, see here.) Remember: a black hole would exist only if you could compress the whole mass of the sun into that 3-km radius spherical volume. This can be applied to just about any mass. The Schwarzschild radius of the Earth is about 9 mm - smaller than a grape. This gives you a sense of how densely you'd have to pack things if you wanted to make an Earth-mass black hole. For a pair of protons smashed together at high energies - as in the LHC - I think you need to bring in other areas of physics than just general relativity. Suffice to say the Schwarzschild radius would be much, much, much smaller than the size of a proton, which in turn is much, much, much smaller than the size of an atom, which is much smaller than the distance between atoms in most solids. So in order for a micro-black-hole to accumulate mass, it would need to pass very close, on the order of its Schwarzschild radius, to the nucleus of another atom. At the length scales we are talking about, that's about as likely as me randomly shooting off a bb gun and hitting a passing bird a kilometer away.
So rest easy, the world isn't about to end.
I apologize for the long answer, but I hope it has answered your question.
"... if you're a megalomaniac looking for your next globe-eating weapon,... a speedy MBH ... flying through our planet... will only have a few seconds to accrete the mass of ... the Earth ."
WE'RE DOOMED!
Finally had enough. Come see us over at https://soylentnews.org/
Particles. A hand-waving description of what happens is as follows:
Pairs of particles (one matter, one antimatter) form randomly near the event horizon. One quantum-tunnels out of the black-hole and so appears to an observer outside the black-hole to have been emitted. Therefore, to conserve energy, the other particle must have negative energy and thus the black-hole loses a tiny parcel of energy (and thus mass).
The main point is that, because the particle was formed near the event horizon and didn't come from the black-hole itself, it carries no information out - thus, while the black-hole loses mass, no information can escape.
Photons pop out of the vacuum all the time. A photon and an anti-photon (or do they call it a virtual photon) will appear at the same time, and as long as the pair doesn't stick around longer than the mass * Plank's constant, conservation of mass is preserved.
If the photon and anti-photon appear at the edge of a black hole, sometimes the photon goes off, and the anti-photon gets sucked into the black hole where it cancels some of the mass of the black hole. Thus it looks like the BH is radiating and evaporating, but nothing actual leaves the BH.
*Note: I've left out some details, and my terminology might be off.
All ideas^H^H^H^H^Hprocesses in this post are Patent Pending. (as well as the process of patenting all postings)
The argument goes like this: There are plenty of cosmic rays which impact our atmosphere, the other planets in the solar system, the sun, other stars, everything, with energies across a huge spectrum, including LHC energies. Either the LHC will produce MBH or it will not. If it will, then cosmic rays also produce MBH, and do so without destroying any of the things we can see in the sky, so MBH from the LHC would similarly not destroy the earth. If the LHC will not produce MBH, then we have nothing to worry about in that regard anyway.
;)
This argument works for just about any Earth destroying LHC scenario, except, I suppose, the time traveling killer Higgs
SIGSEGV caught, terminating
wait... not that kind of sig.
TFA calculates the likely results based on higher dimensional brane physics. It was done earlier in more classical relativity maths and the results summarized in Alan Boyle's Cosmic Log. The max mass was greater and thus life time longer. Still, mass and accretion never crossed the limit that would allow it to reach whatever they call critical mass for these thing. The example given was that if it were charged and it were trapped within the electron cloud of an atom (both conditions lending it additional life span), it would circulate there on the order of weeks before encountering an electron which it could then consume. Even if it did so it would evaporate before it could hit the run away point, and would likely evaporate before eating even one electron. The specific results were different but the conclusion the same - too small to live long enough to do any damage.
Another point made in Cosmic Log (I don't recall if it was the same person/calculations) was that quantum black holes (a more correct descriptor than 'mini-') of the mass and life span hypothesized would be likely to occur regularly in the atmosphere due to incoming primary cosmic rays. Those have been impacting the Earth for billions of years, and we're still here. The hypothesized Hawking radiation is not obvious, thus these may not even be occurring. In any case, their creation would be a highly improbable event.
That last assertion is strictly conjecture based on calculations by my Brambleweeny 57 sub-meson brain. Now if you'll excuse me I'm for a nice hot cup of tea.
"I may be synthetic, but I'm not stupid." -- Bishop 341-B
We can't be exactly sure, no.
However, even basic physics should be enough to determine that microscopic black holes aren't going to be particularly dangerous. The kind of black holes that could be created by the LHC have a very small mass - they're created by smashing a couple of subatomic particles into each other, after all. The total mass of the black hole can not possibly be higher than the total mass of the particles that created it.
That means that the black hole will have the same gravitational force as the particles that created it. Therefore, the event horizon of the black hole will be very small. Since matter is composed mostly of empty space, the chances of it actually hitting anything are remote, to say the least. In order for it to absorb a particle, it would have to almost collide with it. This is very unlikely, although given enough time probably will happen.
Worst case scenario - Hawking radiation doesn't exist. The micro black holes will continue to exist indefinitely, and will slowly consume the planet. Before the micro black hole has absorbed even a few kilograms of matter, the Sun will expand, swallowing the planet. The black holes will continue gradually consuming the Sun, and given a few quadrillion years or so (and the entire universe will be long dead by that point) might actually start to do some damage. By this point, I doubt that any humans will still be around to care. If we've managed to survive the destruction of our own planet, the death of our own star, and the death of the universe itself, a puny little black hole shouldn't be a problem.
More likely scenario - Hawking radiation does exist, and the micro black holes will simply evaporate before they even come close to absorbing anything else. No big deal. If we detect evidence of Hawking radiation, that pretty much confirms the existence of black holes, and Steven Hawking gets a Nobel prize.
There's no such thing as an anti-photon. In the case you are describing - pair production - both of the particles are virtual particles. They can be an electron and a positron (anti-electron), a quark and its anti-quark, etc - any particle/antiparticle pair. However a photon is its own anti-particle. And your explanation of the uncertainly principle is wrong. The time-energy formulation says (uncertainty in time) * (uncertainty in energy) = hbar, so the time limit for the life of the virtual particles is Planck's constant / energy (or Planck's constant divided by mass, since mass and energy are proportional and we measure the mass of these particles in units of electron-volts anyhow). Note that if it's mass * hbar, as you have above, then the higher the mass is, the longer the particles can stick around! That's exactly backwards. It's the tiny little particles that are flickering in and out of existence, not huge massive objects! If it were mass*hbar, you'd have virtual planets, stars and galaxies - the larger the object the more likely it would be to suddenly appear out of nowhere! This is an amusing thought but doesn't accurately describe the reality that we find ourselves living in.
Which implies using existing theories to calculate it. What I think the grand parent post is saying is that we don't know for sure our current theories are all correct. After all, if we knew it all 100% correctly, there wouldn't be any need to build the LHC.
This line of logic is ridiculous. We're building the LHC to explore many things, one of which is probing a few plausible alternate theories that predict black hole production at a measurable rate. But the assumption that that means we can't come up with logically-consistent explanations of how such a black-hole would behave is ridiculous. You can put some bounds on it, right? You can say that a black hole won't make bunnies leap out of the wall. Not because it *sounds* ridiculous, but because there's no mathematically and logically internally consistent theory under which such a thing could happen. You can keep moving this line until you start finding regimes of behavior that might be consistent with new theories allowed, compatible with previous observations but allowing new ones under these new conditions. And that's what theorists are doing!
Any claim of unexpected behavior without a plausible and mathematically self-consistent theory to back it up is baseless. Which isn't to say one doesn't exist (the whole absence of evidence thing), but until one does, there's just as much sense to prepare for the coming bunny invasion.