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Phrak
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Would a miniature black hole sink through the center of the Earth, or be supsended within some sort of bubble consisting of near-vacuum and radiation?
There might be primordial black holes left over from the Big Bang that would be big enough to swallow atoms but still much less massive than the Earth--here is a paper speculating on what would happen if one fell into a star or large planet, and here is an article giving a simplified summary of the results in that paper. The same website also has this article talking about what would happen if a small primordial black hole punched through the Earth at high speed (the effects wouldn't be very noticeable).To last long enough even to begin sucking in matter rather than going off pop, a black hole would have to be many orders of magnitude bigger. According to Cliff Pickover, author of Black Holes: A Traveler's Guide, "Even a black hole with the mass of Mount Everest would have a radius of only about 10^-15 metres, roughly the size of an atomic nucleus. Current thinking is that it would be hard for such a black hole to swallow anything at all--even consuming a proton or neutron would be difficult."
A 0.25 meter diameter BH would actually be quite massive, such a black hole would be very long-lived. The Schwarzschild formula is r = 2Gm/c^2, so m = rc^2/2G, and with r = 0.125 meters, c = 299792458 m/s, and G = 6.673 * 10^-11 m^3 / (kg * s^2) that gives m = 8.42 * 10^25 kg, which is larger than the mass of the Earth (5.9742 * 10^24 kg). So, probably the main inaccuracy of the movie is that it doesn't show the huge gravitational effects such a black hole would have on the Earth as a whole, and the major tidal effects on everything near the point of impact.kev said:This film http://www.thekroneexperiment.com/videos.html has a black hole that is let loose inside the Earth and is oscillating through the core popping up in different regions of the world about every 81 minutes causing localised havoc. From the film trailer the black hole makes neat holes in the ground that appears to about 0.25 meters across. Assuming the diameter of the tunnel left by the black hole is aproximately the diameter of the black hole's event horizon (is that reasonable?) then I guess we could estimate the mass of the black hole in the Krone experiment. My guess is that the mass would be less than is required for the black hole to survive more than a few seconds.
JesseM said:An 0.25 meter diameter would actually be quite massive, such a black hole would be very long-lived. The Schwarzschild formula is r = 2Gm/c^2, so m = rc^2/2G, and with r = 0.125 meters, c = 299792458 m/s, and G = 6.673 * 10^-11 m^3 / (kg * s^2) that gives m = 8.42 * 10^25 kg, which is larger than the mass of the Earth (5.9742 * 10^24 kg). So, probably the main inaccuracy of the movie is that it doesn't show the huge gravitational effects such a black hole would have on the Earth as a whole, and the major tidal effects on everything near the point of impact.
As for evaporation, this section of the wikipedia article on Hawking radiation gives the evaporation time as 5120*pi*G^2*M^3 / (hbar*c^4). With hbar as 1.0546 * 10^-34 kg * m^2 / s, that means the evaporation time works out to M^3 * 8.4079768 * 10^-17 s/kg^3, so the black hole with a mass of 8.42 * 10^25 kg would evaporate in about 5 * 10^61 seconds, or about 1.6 * 10^54 years, much longer than the age of the universe.
Also, how would he "feed" granite bricks to it if the black hole had such a tiny diameter? Even at its maximum mass of 10^9 kg, that would make the radius around 1.5 * 10^-18 meters, about 1000 times smaller than the radius of a proton! In the quote I posted earlier, Cliff Pickover said that even for a larger black hole with the radius of an atomic nucleus, "Current thinking is that it would be hard for such a black hole to swallow anything at all--even consuming a proton or neutron would be difficult."kev said:This link http://www.moviemistakes.com/film5407 on movie mistakes suggests
"In the course of the story it's said that at the time the black hole went out of control, it had a mass of "half a mountaintop of granite." But in a flashback scene Dr. Krone is shown growing the mass of the hole by feeding it large numbers of lead bricks in the laboratory. It's a little hard to believe his lab could store, or even afford, enough lead bricks to equal that much mass."
so I guess I might have over estimated the diameter of the exit wounds
The same link suggests the krone black hole has a mass of about 10^9 Kgs (That is a lot of lead bricks)
No, that was never a danger that any non-crackpots were worrying about. See this post from the blog of two theoretical physicists for more on why this is a ridiculous idea.kev said:... "about 1000 times smaller than the radius of a proton!"
so the chances of creating an Earth threatening black hole in the LHC are pretty slim...huh.
What do you mean by "capture cross-section" here? The probability of the black hole capturing some other particle in a gravitational orbit, the probability of it actually capturing some other particle in its event horizon, or something else?Phrak said:The radius of the black hole is not important in terms of the capture cross-section.
First of all, mini black holes at the LHC are an option only if one of the theories of "large extra dimensions" was in fact true. But of course, these theories are only speculations so far. Second, should mini black holes be created in high-energy particle collisions, they would evaporate very fast, due to Hawking radiation. Though Hawking radiation has not been experimentally verified so far, its existence is expected in almost all theoretical scenarios investigated (no matter where you go, you will always find somebody who disagrees on something).
But what would happen in the (quite unrealistic) case that tiny black holes were created at the LHC, and that they did not decay by the emission of Hawking radiation?
It's important to keep in mind that black holes do not have some special "vacuum cleaner" property - they just attract other stuff by the force of gravity.
Now, the tiny black holes that could be created at the LHC if theories of large extra dimensions were indeed correct would have masses in the range of a few TeV. 1 TeV corresponds to about 1000 times the mass of a proton, which is 0.94 GeV, or 1.7×10^-27 kg. The corresponding Schwarzschild radius is about 1/1000 fm, or 10^-18 m.
Because gravity is such a weak force, it's safe to assume that nothing happens to matter that encounters the black hole at a larger radial distance than one Schwarzschild radius. Assuming for simplicity that all stuff hitting with a smaller distance gets sucked in, the black hole has a cross section of about 10^-36 m^2, or 10 nanobarn (that's more than typical neutrino cross sections).
JesseM said:What do you mean by "capture cross-section" here? The probability of the black hole capturing some other particle in a gravitational orbit, the probability of it actually capturing some other particle in its event horizon, or something else?
By the way, I also recommend reading this post by the same physicist-bloggers. According to them, the cross-section does depend on the radius:
I think you mean photon sphere rather than photosphere, and the photon sphere does not mark the boundary beyond which light can't escape (that's the event horizon), it just represents a sphere such that photons moving tangentially to the sphere will be in (unstable) circular orbits around the black hole. Its radius is only 3/2 larger than the radius of the event horizon (for a nonrotating BH anyway), so even if we were to assume things within the photon sphere would be unlikely to have the velocity needed to escape, it would make little difference in terms of an order-of-magnitude calculation.Phrak said:There is a photosphere, of a given radius, less than which light cannot escape. For ponderable matter, this radius must be greater. The radius would depend upon kinetic energy.
wheel said:In any case, I hope no one will pre-judge the film without seeing it.
A mini black hole is a theoretical object that is much smaller than a regular black hole. It is believed to have a mass equivalent to a few atoms and is thought to be created by the extreme energy of particle collisions.
It is highly unlikely that a mini black hole could be created on Earth. Even if it were, it would likely evaporate within a fraction of a second due to Hawking radiation. Therefore, the idea of a mini black hole loose on Earth is purely hypothetical and not a real possibility.
If a mini black hole were to somehow make contact with Earth, it would likely pass through without causing any significant damage. As mentioned before, it would quickly evaporate due to Hawking radiation before it could cause any harm.
No, it is not possible for a mini black hole to swallow Earth. The mass of a mini black hole is far too small to have any significant gravitational pull on Earth. Additionally, it would evaporate before it could even come close to Earth's surface.
No, there is no need to worry about a mini black hole loose on Earth. As mentioned before, it is highly unlikely that one could even be created on Earth. And even if it were, it would not pose any threat to our planet or its inhabitants.