The problem with particle physics is the difficulty of acquiring new data. The major way particle physicists get data is to accelerate individual particles to tremendous energies and smash them into each other. If you have enough E, the universe will obligingly generate some mc2 in the form of new particles flying out from the collision point. The more energy, the more kinds of particles and interactions you’ll be able to observe, and the more hard facts you’ll have to test old theories and generate new ones.
So these physicists build particle accelerators to generate these high-energy particles in order to learn more about the fundamentals of the universe. The current most powerful particle accelerator is the Tevatron at Fermilab outside of Chicago, which can accelerate protons up to about 1 TeV. It’s really hard to describe these energies on a human scale. Though the collision is not really at anything approaching statistical equilibrium enough to have a well-defined thermodynamic temperature, 1 TeV per particle is roughly equivalent to a temperature of twenty million trillion degrees Fahrenheit (around half that in Celsius).
But after a years of running and tweaking an individual accelerator, eventually you’ve squeezed most of the fundamental physics you’re going to get from it. You simply can’t get much more at that energy and you need something bigger to push our knowledge forward. In order to do this and move beyond the aging Fermilab, the Large Hadron Collider is being brought online near Geneva. Each accelerated proton will have around 7 TeV of energy, or in the thermodynamic analogy about 140 million trillion degrees F.
Not only will this give particle physicists a whole world of new data to explore, the discoveries made will almost certainly have dramatic effects in other areas of physics as well, particularly cosmology. Cosmology has always been notoriously data starved - if astronomy is like studying a forest while tied to a tree, then cosmology is like studying plate tectonics while tied to a tree. But since cosmology is intrinsically involved with the high-energy origin of the universe it will likely improve its own models with the LHC data.
That is, if the LHC doesn’t get shut down by the people who are suing because they’re convinced it will destroy the world. I’ve never really understood this line of argument. The physicists building the LHC would understand the potential risks better than anyone. Both them and their families live on earth. Therefore it’s unlikely that every single one of them would be perfectly willing to gamble their existence on an experiment. Now I suppose the report of the CERN scientists finding no risk won’t convince any of the alarmists. I suppose the expert outside review of the report coming to the same conclusions won’t convince them either. Simply put, there’s nothing fundamentally different about the LHC that the universe doesn’t already do on a much larger and more powerful scale millions of times per second.
It’s not the first time physicists have put some thought into avoiding the end of the world. Decades ago, there was some concern that nuclear weapons might be able to ignite the entire atmosphere in a fusion chain reaction. It was analyzed and found to be impossible insofar as their understanding of the processes allowed them to judge. Here’s LA-602, the original Manhattan Project report. And compared to the supposed danger from the LHC, at least that had a vague aura of plausibility about it.
However, I understand the point of the lawsuit-wielding crowd even if I think it’s mistaken. In the midst of all the “science verses the luddites” type argumentation going on here, the blog Overcoming Bias makes a good point.
It is not obvious to my inexpert eyes that the assumptions in the RHIC Review are any more firm than those in LA-602 - they both seem very firm - but the two papers arise from rather different causes.
To put it bluntly, LA-602 was written by people curiously investigating whether a hydrogen bomb could ignite the atmosphere, and the RHIC Review is a work of public relations.
You should read the whole thing. Good PR is not worth slouching into the trap of letting the conclusions write the report even if the conclusion is absolutely correct. It can breed a culture of a lack of self-examination in science and engineering, which has had fatal results more than once. While the earth is not going to be a casualty of the LHC by any stretch, let’s not let it lead us into overconfidence elsewhere.