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Comment by zkhalique | Hacker News Reader

First birds dropping bread, now this?

http://content.time.com/time/health/article/0,8599,1937370,0...

Perhaps the animals are trying to tell us something...

I had no idea about Nielsen and Ninomiya's theories and multiple publications on them. I love the serious way their (I assume trolling) ideas are taken. Good fun in the high energy physics communy.

Is that the one where tachyons are produced, travel back in time and ultimately interfere with their own creation? Fascinating stuff, although I struggle to believe it myself, I think that science's best ideas have historically come out of the blue - more attention to "the blue" is something that I would like to see more of from modern science.

Yes. And interestingly the GP's article spends a lot more time on that than the bird/bread. (Though that bird may have come back from the future as a saboteur[1].)

[1] Even though it doesn't have wooden shoes.

There's quite a few consequences, though - wrong as it might be. Regardless of how preposterous it is, imagine it to be true. What would that do to our concept of "science: the art of disproving falseness"? Science already struggles with the precision of components (telescopes, as an example) and, what's cognitively pleasing, is figuring out how you would devise an experiment for that. It doesn't matter if it was not true, how would you prove that? How do you say, for certain, that particles are not travelling back in time?

That's the wonder that science has seems to have lost.

Well, it can be linked to the more serious Everett's many-worlds explanation and quantum immortality ... we don't live in a world in which we successfully fired up the LHC and the black hole destroyed everyone on Earth, because in that world, there is no life on Earth. So we live in one of the other worlds in which, by whatever improbable means, the black hole never materialized.

Why is this not a serious topic?

See also the "Doomsday argument". It makes similar arguments in a different context without resorting to many worlds. Just the fact that we are alive at a certain time affects the probability that we are part of a doomsday scenario.

* https://en.wikipedia.org/wiki/Many-worlds_interpretation

* https://en.wikipedia.org/wiki/Quantum_suicide_and_immortalit...

* https://en.wikipedia.org/wiki/Doomsday_argument

These things come up and are always amusing (my favorite was the "video" of the LHC starting up). I wonder though, assuming no supernatural world-ending phenomenon, what is the worst that could happen given the energy involved? This is high-energy particle physics, using magnets to guide collisions? How high is the energy? Can we put a value on the intensity of a complete and 100% efficient conversion of the particle collider energy to kinetic energy? Would it be like a 1 megaton nuclear bomb? Not even that? 1000x that? Do all concerns involve some unknown-maybe phenomenon like a runaway black hole? If we assume conservation of energy, what is the worst? Anyone know?

> what is the worst that could happen given the energy involved?

The beam alone carries enough energy to melt a tank, that's why they need those massive, water-cooled beam dumps.

All the magnets combined store 11GJ of energy, which is 2.6 tons of TNT energy equivalent. Considering that they're distributed along the accelerator I guess it would result in a spectacular destruction of equipment, but no fireballs on the surface or anything like that.

The whole tank? Or did you mean it can make a teeny tiny hole all the way straight through it?

Now that I looked it up, the analogy used was "could melt half a ton of copper". So it's less than your average car.

Still a lot of energy to get rid off at short notice, in case of emergency shutdowns. If I recall correctly they modulate the beam with steering magnets so it sweeps through an area and water-cool the target material. And its absorption can't be too high so the energy gets deposited over some depth.

Or from wikipedia:

> Each of the two beam dumps, in case, for instance, of a dipole magnet quench, must be able to dissipate 362 MJ of beam energy in the 90 μs circulation time, which equates to a power of 4 TW.

Yes. The LHC has a beam dump off to the side, tonnes of concrete and steel buried underground, specifically for the purpose of dissipating the entire beam energy if needed. It's about the same as the kinetic energy of an aircraft carrier stopping from speed:

https://lhc-machine-outreach.web.cern.ch/lhc-machine-outreac...

http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach...

It's going to be one of those SciFi situations where:

(a) Gaia or The Planet is sending her children to stop what's about to kill the rest.

(b) The time travel implications of the black holes it might create are having the future push back on it 11/22/63 style.

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