By Marcelo Gleiser
While Democrats and Republicans tore each other to shreds over a much-needed health reform bill a couple of weeks back, physicists at the European Center for Nuclear Research were making a different kind of headline.
After 16 years and $10 billion, the Large Hadron Collider (LHC) managed to shatter the current energy record for particle accelerators, reaching a staggering 7 trillion electron volts. That's about 3.5 times more energy than the Tevatron, the American machine at Fermilab, near Chicago.
Over the next few years, physicists will have a new tool to probe deep into the heart of matter. The hype is well-deserved: The LHC is the largest machine ever built in the history of civilization, the collective effort of thousands of scientists from across the world. But what will it do, really? Will it be able to solve all the questions that it's meant to? Or is the PR surrounding it masking the reality that, if it fails, it may well represent the end of high-energy physics as we know it?
The list for hoped-for discoveries at the LHC is exceedingly long, representing decades of data-starved theoretical modeling. Here are the top three, ordered from least to most speculative: first, finding the elusive Higgs boson, a mass-giving particle predicted to exist more than 40 years ago. The Higgs is supposed to explain why particles like electrons and quarks have the masses they have. Of course, we will still have to figure out how the Higgs got its mass, which makes one wonder how many layers there are to this onion.
A second hoped-for discovery is the hypothetical supersymmetry, a symmetry that effectively doubles the number of particles that make up matter. Supersymmetry is also the foundation of the famed superstring theory (that's where the "super" in "superstring" comes from). So, it can provide indirect evidence for superstrings.
A third expectation is the discovery of extra dimensions in space, which would be necessary to unify Nature into a single scheme, the so-called theory of everything. Superstrings, the leading candidate for this scheme, are supposed to inhabit no less than nine spatial dimensions.
For most theorists, finding the Higgs is minor compared to discovering supersymmetry or extra dimensions. That is because proving the existence of a unified field theory would satisfy a need deeper than scientific curiosity. Such a discovery would go right to the heart of our age-old longing for the "final answer," what physicist Stephen Hawking and others call "knowing the mind of God."
Einstein spent the last two decades of his life trying to find this answer. He, and everyone else so far, have failed. The notion that Nature hides some kind of code -- an overarching mathematical structure -- is a scientific version of monotheism, a theme that has dominated philosophy for millennia. Now that the LHC has been turned on, we must ask ourselves if we're pursuing the right questions.
The experimental evidence of the past five decades sets the record straight: asymmetries -- not symmetries -- play the key role in determining the complex material structures we see in the universe. The existence of matter and of life depends on the violation of symmetries. Indeed, expectations of perfect symmetry have been methodically demolished by experiments in particle physics, especially those involving the weak nuclear interactions. We really have no evidence whatsoever that Nature is unified at its core -- even the unifications that we have achieved to date, such as the famous electromagnetic theory of electricity and magnetism, only work under certain assumptions. If Nature is telling us that it likes imperfections, that our expectations of all-encompassing symmetries are the result of centuries of monotheistic baggage, we should listen. Beauty, it turns out, is not truth.
There is no question that the LHC is an important tool of discovery and that it will open new windows into a realm presently unknown. Hopefully, the results will be relevant enough to keep this fascinating field alive. If, however, great results are not forthcoming, physicists will be hard-pressed to accept that the era of smashing bits of matter into each other with giant machines has reached an end. Nature, of course, will still have countless surprises up its sleeve. After all, the energies reached at the LHC are thousands of trillions of times smaller than those after the Big Bang. To test physics at these conditions we will need much ingenuity. We will also need the humility to accept that Nature is not what we want it to be, but what it is.