Monday, August 10, 2009

Large Hadron Collider Hopefully Starting at Christmas, Physicists preparing for Hardons

As many people have heard, at least in passing, the Large Hadron Collider was supposed to come online last September. Numerous technical problems have caused delays which I will go into shortly but first I thought I would address the actual purpose of this utterly huge machine and some of its popular misconceptions.

Particle accelerators are the microscopes of particle physics. Using something extremely big they can peer into the very small. We have been building larger and larger accelerators for decades each with higher energies, meaning they smash stuff together faster, than the previous ones. The simplified idea of particle accelerators relies on Einstein's very famous equation E=mc^2. It basically states that energy and mass are equivalent with a constant, c^2. What these accelerators do is increase the kinetic energy via magnetic fields and smash them together inside of a detector. These particles are going only tiny fractions of a percent slower than the speed of light and this translates into tremendous energy. This energy can then "freeze out" into new particles when it collides and the speed reaches zero. The energy has to go somewhere and nature converts it into mass in the form of exotic particles. A rough analogy (it doesn't really happen in the macroscopic world) would be two cars speeding towards each other on the highway. When they collide new "particles" are created in the form of tangled metal and other pieces of debris.

Scientists then look at these particles and their decay products in the detectors. They are able to measure their charge, mass and other properties. With this information they retrace the steps of these particles and hopefully discover new ones. This is how quarks and hundreds of other particles were discovered. Going back to our analogy it is like a mechanic trying to discover how to construct a Bentley by smashing them into walls at 200km/hr and looking at the debris.

We need to build more powerful, and therefore bigger machines because the particles we are looking for have successively greater masses. The holy grail of the LHC is to find a particle called the Higgs Boson. The math of particle physicists predict that this will be the particle that gives every other particle mass. It is a rather alien concept like most of quantum physics but here is another rough analogy. The Higgs Bosons are theorized to form something called a Higgs Field. When all the particles that have mass; electrons, protons, neutrons etc. pass through this field they are affected by it. The field permeates all of space-time, ie. everywhere you can dream of. The Higgs Field is similar to molasses, when you put a spoon into it and try to stir it you encounter resistance. This resistance can be roughly thought of as mass. Scientists' theories predict that the Higgs will be found at energy levels achievable by the LHC. If we look hard enough at the data they believe we should be able to see evidence of this elusive particle.

It is extremely important to note that this is just a hypothesis based on a sound and robust theory. There is zero physical evidence that it actually exists as of yet. All the other particles that the same theory (The Standard Model) predicted have turned out to be real and observable so it has some rather strong proponents but until evidence is delivered it will remain up in the air. Some of the most awesome discoveries could come if the Higgs was shown to be non-existant, opening the possibility of a myriad of other exotic theories such as String Theory or multi-dimensional space.

It is beyond the scope of this post to go into depth of other possibilities but if your curious I recommend checking out wikipedia and other resources.

This massive machine located on the border of France and Switzerland starting test firing particles in September, but not colliding them. The experiment is absolutely massive, located 100m underground with a circumference of 27km. A truly international project that had former and current enemies such as Iran and Israel cooperating on the project. It is an engineering marvel that is a testament to what our civilization can do if we decide to stop blowing the shit out of each other for a few years.






1. LHC superimposed onto the Switzerland/France Border


With any major newsworthy event the crackpots start filtering out of the woodwork. Individuals such as Walter Wagner seem to have a propensity for making end of the world claims whenever a particle accelerator is about to come online. The main ideas they put forth include microscopic black holes consuming the earth as well as more exotic theories such as a strange matter cascade in which the earth gets consumed into a tiny ball of strange matter. All of these claims are baseless on both theory as well as experiment. High energy cosmic rays with energies orders of magnitude higher from supernovae and other stellar events have been bombarding the earth for billions of years with no ill effects. It is also ludicrous from a theoretical point of view. Microscopic black holes may be created however the exact same theory that predicts then also says that they will evaporate in a tiny fraction of a second. Existing for times many orders of magnitude too short to cause any harm. Instead of standing on the shoulders of giants people are leapfrogging, getting scientific sounding theories when they are in fact based on nothing but misunderstanding and scaremongering.

If anyone out there actually has new data or a new theory these physicists would love to hear from you. They don't want to destroy the world either. They have families, loved ones and a passion for finding things out. But if you keep making nonsensible claims to some of the smartest people on earth they will continue to ignore you and proceed with real, worthwhile experiments and worthwhile concerns about safety.

Now on to the problem and the hopeful solution. Particle accelerators use magnetic fields to control the path of the particles which they eventually smash together. In order to cause a magnetic field a current must be passed through a conductor. Conductors have this annoying property caused resistance which generates heat as a current flows through the wire. They only allow a certain amount of current to pass before they start to heat up and eventually melt. This is what causes electrical fires in homes and cars. This left physicists with a problem, the magnetic field strength they needed could not be achieved with ordinary materials, they would instantly melt. In order to build these extremely large machines they needed to use something without the constraints of resistance, which led us to superconductors. A superconducting material's resistance drops to zero when it is cooled below a critical temperature allowing massive currents and generating large magnetic fields. Liquid helium is only four degrees above absolute zero, cold enough for metal to become superconducting, making the LHC possible.

Unfortunately the sharp drop in resistance also occurs in the other direction, causing the material to no longer be superconducting when it is heated. An electrical fault caused the helium to leak, the metal heated up, the coil "quenched", losing its superconductivity and generated large amounts of heat damaging the equipment. CERN then had to warm up the surrounding sections very slowly to save the expensive helium and reduce damage due to thermal stresses. Magnets were replaced and additional testing equipment has been installed to better monitor and prevent such an event from happening again. Slowly but surely the engineers and scientists are working out the problems. They are dealing with the most complicated machine ever constructed by humanity some setbacks are bound to happen. The latest press release from CERN hopes to have the experiment operating by Christmas of this year. More delays may be incoming but I for one am excited to see what this feat of human ingenuity can do and where it will lead us.

Scott

3 comments:

  1. i follow your post overall but can you explain the basis for why the expected black holes which are microscopic in size and which last for only fractions of a second, brings conclusion to discredit the ill effects people are concered about? i don't see how the scale matters when you consider high rates of chemical reactions as well the catastrophic effects which can result with only small quantities of enriched uranium used in nuclear bombs

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  2. The times we are talking about are so small that even if the microscopic black hole was to travel at the speed of light it wouldn't come close to the walls of the machine. I don't know the exact decay time but the math done by the physicists at CERN as well as numerous third parties say that it would travel a tiny fraction of a meter before decaying. Not nearly long enough by many orders of magnitude to begin sucking up nearby matter.

    Black Holes aren't quite like you see in some science fiction. If the sun was to be magically condensed into a ball small enough that it became a black hole, that is light could not escape, we would not notice a thing gravitationally. We would happily orbit the new black hole at the same radius even though all life on Earth would quickly perish. The only danger we could face would be if a black hole was shot through the earth slowly enough to begin growing (the charge of the black hole matters as well but that is a new post). The math simply shows this can't happen.

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  3. I'm preparing for a hardon as well!

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