But there is no evidence that strangelets are real, so that might be enough to keep some people from worrying. However, it's still true that the LHC is a machine of discovery and maybe it could actually make a strangelet … well, if they really exist. After all, strangelets haven't been definitively ruled out and some theories favor them. However, an earlier particle accelerator called the Relativistic Heavy Ion Collider went looking for them and came up empty.
Those are but two ideas for how a supercollider could pose a threat, and there are more. We could list all of the possible dangers, but there remains something more unsettling to keep in mind: Since we don't know what happens to matter when we start studying it at energies only possible with the LHC that is, of course, the point of building the accelerator , maybe something will happen that was never predicted.
And, given our ignorance, maybe that unexpected phenomenon might be dangerous. And it is that last worry that could have potentially been so troubling to the LHC's creators. When you don't know what you don't know, you … well … you don't know. Such a question requires a powerful and definitive answer. And here it is…. Given the exploratory nature of the LHC research program, what is needed is an ironclad reason that demonstrates that the facility is safe even if no one knows what the LHC might encounter.
Luckily, we have the most compelling answer of all: Nature has been running the equivalent of countless LHC experiments since the universe began — and still does, every day, on Earth. Space is a violent place, with stars throwing off literally tons of material every second — and that's the tamest of phenomena. Supernovas occur, blasting star stuff across the cosmos. Neutron stars can use intense magnetic fields to accelerate particles from one side of the universe to another.
Pairs of orbiting black holes can merge, shaking the very fabric of space itself. All of those phenomena, as well as many others, cause subatomic particles to be flung across space.
Mostly consisting of protons, those particles travel the lengths of the universe, stopping only when an inconvenient bit of matter gets in their way. And, occasionally, that inconvenient bit of matter is the Earth. We call these intergalactic bullets — mostly high-energy protons — "cosmic rays. To give a sense of scale, the LHC collides particles together with a total energy of 13 trillion or tera electron volts of energy TeV. The highest-energy cosmic ray ever recorded was an unfathomable ,, TeV of energy.
Now, cosmic rays of that prodigious energy are very rare. The energy of more common cosmic rays is much lower. But here's the point: Cosmic rays of the energy of a single LHC beam hit the Earth about half a quadrillion times per second. No collider necessary. Remember that cosmic rays are mostly protons. That's because almost all of the matter in the universe is hydrogen, which consists of a single proton and a single electron.
When they hit the Earth's atmosphere, they collide with nitrogen or oxygen or other atoms, which are composed of protons and neutrons. Accordingly, cosmic rays hitting the Earth are just two protons slamming together — this is exactly what is happening inside the LHC.
Two protons slamming together. A study by Fairbairn and McElrath has clearly shown there is no possibility of the LHC beam triggering a fusion reaction in helium. We recall that 'Bose-Novae' are known to be related to chemical reactions that release an infinitesimal amount of energy by nuclear standards. We also recall that helium is one of the most stable elements known, and that liquid helium has been used in many previous particle accelerators without mishap.
The facts that helium is chemically inert and has no nuclear spin imply that no 'Bose-Nova' can be triggered in the superfluid helium used in the LHC. They all agree that the LHC is safe. The paper by Giddings and Mangano has been peer-reviewed by anonymous experts in astrophysics and particle physics and published in the professional scientific journal Physical Review D.
The American Physical Society chose to highlight this as one of the most significant papers it has published recently, commissioning a commentary by Prof. Peskin from the Stanford Linear Accelerator Laboratory in which he endorses its conclusions. The conclusions of the LSAG report were endorsed in a press release that announced this publication. Thus, the conclusion that LHC collisions are completely safe has been endorsed by the three respected professional societies of physicists that have reviewed it, which rank among the most highly respected professional societies in the world.
World-renowned experts in astrophysics, cosmology, general relativity, mathematics, particle physics and risk analysis, including several Nobel Laureates in Physics, have also expressed clear individual opinions that LHC collisions are not dangerous, as you can read on the right.
The overwhelming majority of physicists agree that microscopic black holes would be unstable, as predicted by basic principles of quantum mechanics. Moreover, quantum mechanics predicts specifically that they should decay via Hawking radiation.
Nevertheless, a few papers have suggested that microscopic black holes might be stable. The paper by Giddings and Mangano and the LSAG report analyzed very conservatively the hypothetical case of stable microscopic black holes and concluded that even in this case there would be no conceivable danger. Another analysis with similar conclusions has been documented by Dr. Koch, Prof. Bleicher and Prof. Then we discussed every single outcome of those paths and showed that none of the physically sensible paths can lead to a black hole disaster at the LHC.
Professor Roessler who has a medical degree and was formerly a chaos theorist in Tuebingen also raised doubts on the existence of Hawking radiation. His ideas have been refuted by Profs. Nicolai Director at the Max Planck Institute for Gravitational Physics - Albert-Einstein-Institut - in Potsdam and Giulini, whose report see here for the English translation, and here for further statements point to his failure to understand general relativity and the Schwarzschild metric, and his reliance on an alternative theory of gravity that was disproven in Their verdict:.
The paper of Prof. Roessler has also been criticised by Prof. Bruhn of the Darmstadt University of Technology, who concludes that:. The possibility of any dangerous consequences contradicts what astronomers see - stars and galaxies still exist.
Nature forms black holes when certain stars, much larger than our Sun, collapse on themselves at the end of their lives. They concentrate a very large amount of matter in a very small space.
Speculations about microscopic black holes at the LHC refer to particles produced in the collisions of pairs of protons, each of which has an energy comparable to that of a mosquito in flight. Astronomical black holes are much heavier than anything that could be produced at the LHC. There are, however, some speculative theories that predict the production of such particles at the LHC.
All these theories predict that these particles would disintegrate immediately. Black holes, therefore, would have no time to start accreting matter and to cause macroscopic effects. Many stable black holes would be expected to be electrically charged, since they are created by charged particles. The fact that the Earth and Sun are still here rules out the possibility that cosmic rays or the LHC could produce dangerous charged microscopic black holes.
If stable microscopic black holes had no electric charge, their interactions with the Earth would be very weak. Those produced by cosmic rays would pass harmlessly through the Earth into space, whereas those produced by the LHC could remain on Earth.
However, there are much larger and denser astronomical bodies than the Earth in the Universe. Black holes produced in cosmic-ray collisions with bodies such as neutron stars and white dwarf stars would be brought to rest. The continued existence of such dense bodies, as well as the Earth, rules out the possibility of the LHC producing any dangerous black holes. According to most theoretical work, strangelets should change to ordinary matter within a thousand-millionth of a second. But could strangelets coalesce with ordinary matter and change it to strange matter?
A study at the time showed that there was no cause for concern, and RHIC has now run for eight years, searching for strangelets without detecting any.
It is difficult for strange matter to stick together in the high temperatures produced by such colliders, rather as ice does not form in hot water. Strangelet production at the LHC is therefore less likely than at RHIC, and experience there has already validated the arguments that strangelets cannot be produced. The analysis of the first LHC data from heavy ion collisions has now confirmed the key ingredients used in the LSAG report to evaluate the upper limit on the production of hypothetical strangelets.
There have been speculations that the Universe is not in its most stable configuration, and that perturbations caused by the LHC could tip it into a more stable state, called a vacuum bubble, in which we could not exist. If the LHC could do this, then so could cosmic-ray collisions. Since such vacuum bubbles have not been produced anywhere in the visible Universe, they will not be made by the LHC.
Magnetic monopoles are hypothetical particles with a single magnetic charge, either a north pole or a south pole. In this article. The upcoming launch of the James Webb Space Telescope is the event of a lifetime. Starts With A Bang. Mathematically, it is a monster, but we can understand it in plain English. Hard Science.
0コメント