Why do we need the large Hadron Collider?

HSBC Private Bank (UK) Limited - June 2010

Probing the deepest secrets of the natural world is not a humble undertaking. The late Austrian-American physicist Victor Weisskopf described the grand particle accelerators that began to take shape around the world in the 1950’s and 60’s as the "Gothic cathedrals of the 20th century." The comparison was, and is, apt. The medieval cathedrals pushed the limits of available technology, involved the craftsmanship of literally thousands of skilled workers, and took generations (and sometimes centuries) to complete. Modern particle accelerators require decades from conception to completion and involve thousands of scientists from scores of countries, speaking dozens of languages, whose separate handiwork must mesh together perfectly on the scale of thousandths of millimetres.
 
The Large Hadron Collider (LHC), built at the CERN laboratory on the outskirts of Geneva, at 26 kilometres in circumference, is not just the most powerful particle accelerator ever constructed. It is the largest and most technologically sophisticated machine ever built. The underground hall housing just one of the LHC’s four particle detectors is probably large enough to house the entire Notre Dame Cathedral.

Cathedrals were designed to celebrate the glory of God as manifested through the human spirit in words, music and art. The LHC, on the other hand, has been engineered to celebrate and proclaim both the glory of the natural world and of our remarkable ability to comprehend it through experimental science.

More specifically, though, what will we get for all of this effort? The LHC will probe the structure of matter on scales 10 billion times smaller than anything we conventionally associate with the word "nano". In so doing it may create fleeting elementary particles that, since the Big Bang, have thus far existed almost exclusively in the imagination of theoretical physicists.

Discovery of such particles is not an end unto itself. Their existence could portend a revolution in our understanding of the fundamental structure of space and time, or, at the very least, could resolve an outstanding puzzle associated with the fundamental nature of matter. At the scale of energy at which the LHC was designed to operate (within a factor of two or so of where it is currently operating), our current theories suggest that a remarkable mechanism occurs which is responsible for giving all elementary particles different masses, a clear prerequisite for our own existence (since after all, we are made up of these very particles).

This is not all, however. We have very good reasons to believe that the LHC may reveal a whole new facet of reality currently hidden from our view. The elementary particles that make up the world of our experience - protons, neutrons and the like - may be simply the tip of a cosmic iceberg. Whole new families of elementary particles are currently expected to exist that not only serve to allow more beautiful mathematical descriptions of nature than would be possible without them, but one or several of these new particles, if stable, could turn out to comprise the ‘dark matter’ that is currently known to dominate the mass of our galaxy, and all known galaxies, and which in turn is probably responsible for the formation of the galaxy, and thus our own existence.

And if this isn’t exotic enough, there is a possibility, albeit very slight, that the LHC could reveal an even more exotic hidden reality: whole new hidden dimensions of space that might exist literally under our noses. These extra dimensions could either be curled up on sizes so small that our current detectors could not probe them, or they could be large, and only gravity, the weakest force in nature, might sense them.

Of course, nothing is guaranteed when one is pushing the forefront, so it is also entirely possible that the LHC will reveal none of the above, maybe nothing new at all! For physicists, discovering nothing might be almost more interesting than discovering something, because not seeing what we expect would mean that all of our current theoretical ideas are wrong, and we have to go back to the drawing board.

In this regard, Weisskopf’s comparison is also worth reflecting upon as we recall that Gothic Cathedrals, like their modern counterparts, strained the purse strings of the communities where they were built. The LHC’s cost has been in the neighbourhood of $8 billion. In a practical world, particularly one in which government deficits and basic human needs abound, one may reasonably ask whether such public largesse can be afforded to such a minority of special interest, particle physicists, especially when new discoveries are not guaranteed.

One argument is that the cost of the LHC, built as part of an international collaboration over a decade, pales in comparison to the cost of other government outlays, including, for example the costs that were associated with maintaining the war in Iraq for a few months. But it is disingenuous to compare apples and oranges. The real question is whether we as a culture can afford not to pursue the questions about the universe that have baffled us for millennia, especially now that we may have the capability to discern the answers.

Science is often celebrated as the source of technology, and the technological side-benefits associated with building large accelerators have been pervasive, including development of the large-scale parallel computing technology, and the development of the World Wide Web, which occurred at CERN, where the LHC now sits. But the greatest value of such scientific research may not be technological, but cultural.

Science, like great art, music or literature compels us to reassess our place in the universe - to question where we come from, and where we are going. To turn our back on these questions is to dismiss our cultural inheritance. We should thus consider continuing our explorations of the universe as a cultural imperative.

When Robert Wilson, the first director of the Fermi National Accelerator Laboratory near Chicago was summoned before a US House of Representatives committee to justify the exorbitant cost of his accelerator, he was asked whether it would aid in the defence of the nation. He answered, "It has nothing to do directly with defending our country, except to make it worth defending."

High school students today do not study the plumbing of the ancient Greeks, but we hope they still marvel at the elegance of Plato and Socrates. When we think of the great civilizations that have come before us, we associate their greatness with the ideas that drove their culture forward. The Large Hadron Collider, and the discoveries it may make, will be a part of our legacy for future generations.

Will the LHC live up to our hopes for grand discoveries? No one knows. But even the worst case scenario will tell us that many of the remarkable ideas developed in physics over the past three decades - ideas that have inspired many among the best and brightest young minds - may have to be supplanted by even more exciting ideas yet to be born.

The LHC has the possibility of providing otherwise unimaginable insights that illuminate our brief existence here on this lonely planet. It is therefore the next immodest step in the noble tradition of unlocking the mysteries of the heavens. That is its ultimate justification.