Quote:
Originally Posted by dirty_g
cool neverfly. your a good bloke. so anyway warren the MBH agrument seems sound to me. What is your specific argument to counter that?
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I have one, my friend. I think you're referring to
cjameshuff's post:
Quote:
Two possible reasons for the universe surviving to this point if Hawking radiation doesn't exist: first, it might very easily just be impossible for black holes to form from these collisions, and second, the black holes will be a tiny fraction of the size of a proton (as in, a trillionth of the radius of the proton may be overestimating it by a factor of a billion), making it extremely unlikely for them to absorb anything. Gravity is very weak...the MBH will have to absorb two electrons before it has a chance of approaching the nucleus of an atom, and it will then only interact by gravity...which is so weak it would pass through the electron shells of atoms without disturbing them at all, and is likely to pass through individual protons without absorbing them.
It would also have to avoid any interactions that give it enough velocity to escape Earth's gravity. It would not take much energy for that to happen, and considering the fact that the first time it absorbs a proton it will be a positively charged particle in the immediate vicinity of a now very unstable nucleus, it seems quite likely for it to occur.
But regardless of whether either of these is correct or whether Hawking radiation exists or any error whatsoever in our theories, the LHC is known to be safe because identical and far more energetic collisions occur constantly all throughout the universe. "We're still here" is not trite or refusing to take it seriously, it is an accurate statement. No matter how wrong our theories are, if the LHC were capable of posing a danger, we wouldn't be here.
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1. If it is very easily possible that mBH's will not form, it is also, therefore, very easily possible that mBH's
will form. In fact, the string theorists at CERN are eagerly hoping that mBH's will form, because that would be the first empirical confirmation that string theory is true. As
Steve Giddings himself put it:
"If we discover the Planck scale near the TeV scale, this will represent the most profound discovery in physics in a century, and black hole production will be the most spectacular evidence of that new discovery." (His paper
"High energy colliders as black hole factories: The end of short distance physics",
Physical Review D 6505: 6010, 2002, is one of the most cited papers ever in the physics literature.)
2. mBH's might be tiny, but they can still run into things.
3. Furthermore, if mBH's get charged, then they
strongly interact with surrounding matter. Absorbing two negatively charged electrons will cause the mBH to crash into the atom's positively charged nucleus.
4. The physicists realize that the possibility mBH's trapped within the Earth might grow exponentially is in fact poorly constrained by the laws of physics. That's because eating matter is what black holes
do.
5. So that's why the physicists reach for the astrophysical argument. They know that cosmic ray induced mBH's will pass harmlessly through the Earth (as does
cjameshuff), whereas LHC induced mBH's will be at rest with respect to the Earth. So they make a few plausible--
but non-worst case (as Mangano & Giddings themselves admit)--assumptions that white dwarfs--unlike the Earth or the Sun--are actually dense enough to stop cosmic ray induced black holes. Since white dwarfs are still here, mBH's must be harmless--or so their cherry picked theory says. Unfortunately, the theory depends on whether it is valid to extrapolate the semiclassical approximation to a realm it has never been tried before: to multi-dimensional mBH's existing deep within the quantum gravitational regime. mBH's may not decide to obey the semiclassical approximation, in which case cosmic ray induced mBH's would pass harmlessly through white dwarfs as well as Earth. In which case, astrophysics would not in fact constrain the equations of mBH growth within Earth.