You’re demonstrating a comprehensive lack of actual domain knowledge—you literally don’t know the thing you’re talking about—and appear to be trying to compensate for that by leveraging what you do know.
As far as I can tell, everything Yvain has said on this topic is correct. In particular, there is a further possible assumption under which it is not the case that cosmic ray collisions with Earth and the Sun prove LHC black holes would be safe, as you can find spelled out in section 2.2 of this paper by Giddings and Mangano. As Yvain pointed out in a different comment, to plug this hole in the argument requires doing some calculations on white dwarfs and/or neutron stars to find a different bound, which is what Giddings and Mangano spend much of the rest of the paper doing. These calculations, as far as I know, were not actually published until 2008 -- several months after the LHC was originally supposed to go online. It’s my impression that both before and after this analysis was done, most of those arguing the LHC is safe just repeated the simplified argument that had the hole in it; see e.g. Kingreaper in this thread. And while I’d put a very low probability on these calculations being wrong and a very low probability on the LHC destroying the world even if the calculations were wrong, it’s this sort of consideration and not 1 in 10^25 coincidences that ends up dominating the final probability estimate. Then there were all these comments about the LHC causing the end of the world being as unlikely as the LHC producing dragons etc—which if taken literally seem annoyingly wrong because of how the end of the world, unlike dragons, is a convergent result of any event sufficiently upsetting to the physical status quo. So while (just because of the multiple unlikely assumptions required) at any point and especially after the Giddings/Mangano analysis a reasonable observer would have had to put an extremely low probability on existential risk from LHC black holes, the episode still makes me update against trusting domain experts as much on questions that are only 90% about their domain and 10% about some other domain like how to interpret probabilities.
Because of conservation of both momentum and energy, particles coming out of the LHC are no slouch either. So although under extremely hypothetical conditions, stable black holes can exist without the sun being destroyed by cosmic rays, even then you need to add even more hypotheticals to make the LHC dangerous.
Note that their very hypothetical scenario is already discouraged by many orders of magnitude by Occam’s razor. I’m not sure what the simplest theory that doesn’t have black holes radiate but does have pair production near them is, but it’s probably really complicated. And then these guys push it even further by requiring that these black hole-like objects not destroy neutron stars either!
I certainly don’t disagree that there are a number of unlikely hypotheticals here that together are very improbable.
My impression from reading had been that, while the typical black hole that would be created by LHC would have too high momentum relative to Earth, there would be a distribution and with reasonably high probability at least one hole (per year, say) would accidentally have sufficiently low momentum relative to Earth. I can’t immediately find that calculation though.
If P(black holes lose charge | black holes don’t Hawking-radiate) is very low, then it becomes more reasonable to skip over the white dwarf part of the argument. Still, in that case, it seems like an honest summary of the argument would have to mention this point, given that it’s a whole lot less obvious than the point about different momenta. G & M seem to have thought it non-crazy enough to devote a few sections of paper to the possibility.
Even producing a black hole per year is doubtful under our current best guesses, but if one of a few extra-dimension TOEs are right (possible) we could produce them. So there’s sort of no “typical” black hole produced by the LHC.
But you’re right, you could make a low-momentum black hole with some probability if the numbers worked out. I don’t know how to calculate what the rate would be, though—it would probably involve gory details of the particular TOE. 1 per year doesn’t sound crazy, though, if they’re possible.
As far as I can tell, everything Yvain has said on this topic is correct. In particular, there is a further possible assumption under which it is not the case that cosmic ray collisions with Earth and the Sun prove LHC black holes would be safe, as you can find spelled out in section 2.2 of this paper by Giddings and Mangano. As Yvain pointed out in a different comment, to plug this hole in the argument requires doing some calculations on white dwarfs and/or neutron stars to find a different bound, which is what Giddings and Mangano spend much of the rest of the paper doing. These calculations, as far as I know, were not actually published until 2008 -- several months after the LHC was originally supposed to go online. It’s my impression that both before and after this analysis was done, most of those arguing the LHC is safe just repeated the simplified argument that had the hole in it; see e.g. Kingreaper in this thread. And while I’d put a very low probability on these calculations being wrong and a very low probability on the LHC destroying the world even if the calculations were wrong, it’s this sort of consideration and not 1 in 10^25 coincidences that ends up dominating the final probability estimate. Then there were all these comments about the LHC causing the end of the world being as unlikely as the LHC producing dragons etc—which if taken literally seem annoyingly wrong because of how the end of the world, unlike dragons, is a convergent result of any event sufficiently upsetting to the physical status quo. So while (just because of the multiple unlikely assumptions required) at any point and especially after the Giddings/Mangano analysis a reasonable observer would have had to put an extremely low probability on existential risk from LHC black holes, the episode still makes me update against trusting domain experts as much on questions that are only 90% about their domain and 10% about some other domain like how to interpret probabilities.
Because of conservation of both momentum and energy, particles coming out of the LHC are no slouch either. So although under extremely hypothetical conditions, stable black holes can exist without the sun being destroyed by cosmic rays, even then you need to add even more hypotheticals to make the LHC dangerous.
Note that their very hypothetical scenario is already discouraged by many orders of magnitude by Occam’s razor. I’m not sure what the simplest theory that doesn’t have black holes radiate but does have pair production near them is, but it’s probably really complicated. And then these guys push it even further by requiring that these black hole-like objects not destroy neutron stars either!
I certainly don’t disagree that there are a number of unlikely hypotheticals here that together are very improbable.
My impression from reading had been that, while the typical black hole that would be created by LHC would have too high momentum relative to Earth, there would be a distribution and with reasonably high probability at least one hole (per year, say) would accidentally have sufficiently low momentum relative to Earth. I can’t immediately find that calculation though.
If P(black holes lose charge | black holes don’t Hawking-radiate) is very low, then it becomes more reasonable to skip over the white dwarf part of the argument. Still, in that case, it seems like an honest summary of the argument would have to mention this point, given that it’s a whole lot less obvious than the point about different momenta. G & M seem to have thought it non-crazy enough to devote a few sections of paper to the possibility.
Even producing a black hole per year is doubtful under our current best guesses, but if one of a few extra-dimension TOEs are right (possible) we could produce them. So there’s sort of no “typical” black hole produced by the LHC.
But you’re right, you could make a low-momentum black hole with some probability if the numbers worked out. I don’t know how to calculate what the rate would be, though—it would probably involve gory details of the particular TOE. 1 per year doesn’t sound crazy, though, if they’re possible.