Alan Boyle has a great interview on the upcoming research to be performed on the Large Hadron Collider.
4 thoughts on “LHC Safety And Promise”
Comments are closed.
Alan Boyle has a great interview on the upcoming research to be performed on the Large Hadron Collider.
Comments are closed.
I like the safety argument:
If the LHC was going to do anything “spectacular” to the Earth, we’d expect cosmic rays more energetic than anything the LHC will produce to have done something “spectacular” to white dwarfs and neutron stars before they got near as old as some we see.
It would be interesting to consider just how big accelerators have to get before these safety arguments become less persuasive. The fact the accelerators are colliders is important, since the available energy (in the center of mass frame) in a collision with a cosmic ray particle vs. a particle at rest is much, much less than the energy of the cosmic ray particle.
Eventually, large accelerators will also start to have problems with energetic neutrinos, since these cannot be shielded against (and become more dangerous as they become more energetic, since the total interaction cross sections increase rapidly with energy). This would be a particular problem with machines designed to produce intense neutrino beams, for example “beta beam” or “muon storage ring” machines, where unstable nuclei or particles that decay by weak interaction are accelerated and stored, and allowed to decay in-flight. Relativistic beaming would direct most of the neutrinos forward.
Paul, I think the center of mass frame would have similar energy to the energy of the cosmic ray. Some would be heavy ions, but most are probably energetic protons. And for a white dwarf or neutron star, they are likely (over time) to hit nuclei with similar masses. Meaning the max collision velocity is within a factor of 2 of the energy of the cosmic ray.
It would be interesting to consider just how big accelerators have to get before these safety arguments become less persuasive.
Supposedly the theoretic cap on energetic particles from distant sources (greater than about 160 million light years according to Wikipedia) is about 10^20 eV. That’s because at higher energies, these particles supposedly interact with the photons of the cosmic microwave background and eventually would slow down to below this upper limit. But we see some particles with higher energies. But at a guess, it looks like white dwarfs routinely experience collisions of the order of 10^19 to 10^20 eV.
In comparison, the LHC has energies of about 7*10^12 eV, that’s at least 5-6 orders of magnitude below the threshhold of uncertainty.
Paul, I think the center of mass frame would have similar energy to the energy of the cosmic ray.
No, this is not the case. It’s the case if newtonian physics applied, but when you collide a relativistic particle of (rest) mass m with a stationary particle of the same rest mass, the energy in the CoM frame is only sqrt(2 m c^2 E), where E >> m c^2 is the energy of the relativistic particle. Clearly, for ultrarelativistic cosmic rays only a small (and declining with energy) fraction of the energy is available in the CoM frame.