Friday, July 13, 2012

The Last One

The Universe is a very weird place. But one of the weirdest things is also one of the most subtle.

Mathematics is a thing of pure logic, something that people built up over the centuries by deducing its principles starting from a handful of axioms. It is pure abstraction. Ostensibly, it has no actual connection to the real world. Teachers of geometry in ancient Greece were actively offended if their students suggested that their studies might have practical benefit.

How very odd, then, that mathematics should be so very useful for describing the world we live in.

Isomorphism is the word for it: if two systems are sufficiently similar to one another, then insights gained in one can be applied to the other. Gradually, natural philosophers came to understand that for reasons that no one adequately understood, mathematics and physics were isomorphic. The first fruit of this insight was Isaac Newton's masterwork, Philosophiae Naturalis Prinicipia Mathematica, which laid the groundwork for both differential calculus and the science of physics as we know it today. Ever since then, advances in physics have always been preceded by advances in mathematics. Before physicists could find the words to describe new phenomena, they had to learn nature's syntax in its own native tongue.

No one knows why the Universe works this way. It just does, and we go along for the ride.

The latest stop on this road began with Einstein's discovery of Special Relativity in 1905 and his discovery of General Relativity in 1916. It continued with the development of Quantum Mechanics by Max Planck and others, in parallel with Einstein's work on Relativity. The mathematics got more and more complex, but the predictions kept bearing fruit. Scientists began to plumb the secrets first of the atoms, then of their nuclei, and at last of the protons and neutrons themselves. They began to see clues that these weren't fundamental particles after all, but were themselves made up of smaller parts.

Then, in the 1960s, Sheldon Glashow discovered an internally-consistent way to describe a unification between the electromagnetic force and the weak nuclear force. The only problem was that this method predicted that all of the particles would have zero mass. This was obviously not true, so the problem was then to figure out how to get around that issue. Later on in the decade, Steven Weinberg and Abdus Salam found a way to apply the Higgs mechanism to Glashow's theory, which then allowed the particles to gain mass. This paved the way for what we now call the Standard Model: a list of all of the Universe's fundamental parts. The Standard Model, as of 1967, was able to describe all of the sub-atomic particles then known. But it predicted a whole bunch of particles that hadn't been seen yet. Theoretical physicists then settled in for a long wait, while experimental physicists worked feverishly at ever-larger atom smashers to discover them.

Most of the quarks were found fairly early. The heavier ones took longer. The bottom quark was discovered in 1977, but the top quark wasn't discovered until 1995. By then, only a handful of holdouts remained. In 2000, the tau neutrino was discovered at Fermilab. That left one last piece to find.

Leon Lederman wrote a book about it in 1993, with the famous title The God Particle. His original manuscript had another four letters in the title, but of course they'd never publish it that way. He never meant to imply that the search for the Higgs boson was akin to finding God. He meant that it would be excruciatingly hard to find. And he was right. It would take an absurdly powerful scientific machine, straddling several national borders, to reach the staggering energies required to summon it out of its hiding place. A machine so mind-meltingly powerful that some people were afraid that if it ever ran at full power, it would mean the end of the world.

Nonsense on stilts, of course. The Large Hadron Collider is an incredibly powerful instrument, but it won't bring about the end of everything. Except, that is, for the end of the hiding place of that most elusive of particles. On July 4th, the announcement confirmed the rumors that had been flying around for a while. Not quite four years after it had been first turned on, instruments in the LHC had detected the prey for which it had been built.

Mind you, they're not quite calling it a capital-D discovery just yet. They need to do some confirmation tests, and comb over the results to be absolutely, totally sure. But they did call it a five-sigma result. To me, that says that unless someone on their team has discovered a brand-new way to screw up experiments, they've got the sucker dead to rights.

So, does this mean the end of physics? Not hardly. There's still a rather impressive list of unsolved problems in physics. They've found the Higgs boson, they still don't necessarily know why it works. And there's also dark matter and dark energy, about which we know next to nothing. What this probably does mean, though, is an end to new particle discoveries for a while. Quite probably a very long while. Unless the Standard Model is incomplete, and quarks themselves have constituent parts, that was the last one.

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