We can’t let the official “switch-on” of the Large Hadron Collider (LHC) pass without comment. The goal of the LHC is to find the Higgs Boson, the last particle of the standard model of particle physics (“the standard model”) that has yet to appear in the debris of a collision in a particle accelerator. The standard model is a phenomenally successful theory – the existence and properties of the menagerie of particles that emerge from particle accelerators can be predicted with astonishing accuracy, using mathematical equations.
If the Higgs Boson is found, it will join the other successful predictions of modern physics. The fact that successful predictions are commonplace makes it easy to overlook the astonishing fact that mathematical equations and physical reality are somehow intertwined. Paul Davies, in his book “The Goldilocks Enigma” remembers sitting in his school library, using Newton’s laws to predict how far away a ball thrown on sloping ground will land. A girl he had taken a fancy to asked what he was doing. He explained. She was skeptical: “how can you possibly know what a ball will do by writing things on a sheet of paper?”
That’s a very good question, but not one that physicists ask themselves very often (and for good reason – we know it works so just get on with it!). I guess that the two most common answers would be: “because we can watch lots of balls being thrown and look for a pattern”, or “I don’t know, but it works!”. The problem with the first answer is that is naturally prompts the question: “then how can we predict what will happen in cases that no one has ever seen before?”. Remember: no one has ever seen a Higgs Boson, or even created a particle that heavy. And yet we’re confident that it’s there. I know it’s a metaphysical question, but I can’t help it: why does theoretical physics work? Why do we keep getting things right?
And yet, the real hope for the LHC is that it will produce something new, something we haven’t predicted. A list of possibilities and tentative odds can be found in this post over at Cosmic Variance. The reason for this hope is nicely captured in this quote, pilfered from Antony Lewis:
“Those of us engaged in scientific research generally do it because we can’t help it – because Nature is the biggest and most complicated jumbo holiday crossword puzzle you have ever seen” – Ed Hinds, New Scientist Sept. 1997
If the results of the LHC were all predictable by the standard model, then it would be like picking up a book of crosswords and discovering that they had all been solved already. On one hand, you have all the answers. On the other hand, there’s nothing left to solve, nothing to stretch your brain cells. The standard model is fantastic, but we want to know what lies beyond it.
And finally, to all those who expected the world to end today, I’m afraid you’re going to have to wait. The LHC doesn’t actually start smashing protons together until after October 21st. Today was just sending protons one-way around the ring. To say it once again: nothing will happen in the LHC that hasn’t already happened approximately
times to planet Earth naturally, thanks to cosmic rays. And you can add many more zeros to count how many times high energy particles have been created around stars, neutron stars and the like.
There seems to be a lot of confusion generated by the connection between the LHC and the Big Bang. The idea that “the LHC will recreate the conditions moments after the big bang” seems to morph into the idea that “the LHC will create a new big bang”. Let me put it this way. As we go back in time, the average cosmic temperature goes up. So, for every temperature above 2.7K (the cosmic temperature today) you can say that “we are recreating the conditions of the universe at some time t”. For example, if you light a match, you are recreating the conditions of the universe when it was over 300 times smaller than it is today. You are certainly not recreating the big bang. Saying that “the LHC will recreate the conditions moments after the big bang” is simply to say that the LHC will create some very hot (i.e. energetic) particles.
The whole thing does raise an interesting question, though. The day will come when particle accelerators will be able to create phenomena that have no astrophysical precedent (i.e. not even cosmic rays are energetic enough). Scientists will calculate the probability that the experiment will endanger the human race. But where do you draw the “too dangerous” line? ? ? ? How do you do a risk analysis when the entire universe is at stake?