Fourteen years, thousands of physicists and $8 billion in the making, the Large Hadron Collider (LHC), the world’s most powerful particle accelerator built at the European Centre for Nuclear Research in Geneva, crossed a major milestone on Wednesday. The first proton beam was successfully switched on and steered around the full 27-kilometre circumference of the underground ringed machine, marking the beginning of a new era of discovery in physics. The world particle physics community today is perhaps in the midst of a revolution in its understanding of what the universe is made of and how it works. Even as physicists have successfully described the fundamental constituents of matter that make up the universe with increasing detail based on what is called the Standard Model, over the last 15 years they have realised that they know much less than they thought they did. For instance, the Model cannot describe the universe in the first moments after the Big Bang. Today physicists believe that visible matter — the stars and the galaxies — makes up only 5 per cent of the energy density of the universe. The rest is believed to be some mysterious dark matter and dark energy. A crucial missing link in the Standard Model is the Higgs boson, the elusive particle that is believed to endow mass to all the particles. Tevatron, the most powerful accelerator of today at Fermilab in the United States, fell short of the energy required to produce Higgs.
The LHC is designed to bring together counter-rotating beams of protons to collide head-on with seven times Tevatron’s energy and create temperatures and energy densities prevalent at a trillionth of a second after the Big Bang. This will produce a host of particles — known, expected, and totally unexpected. These may answer some outstanding questions. Is Higgs for real? What is dark matter made of? What is driving the accelerated expansion of the universe? What lies beyond the Standard Model? Is it supersymmetry? Are there higher dimensions that string theories require? Is there new physics lurking at these energies and beyond? They may also raise new ones. All these will slowly unravel as results begin to emerge from the LHC a year from now. About 600 million collisions per second will spew out 15 million gigabytes of data annually that physicists around the world will analyse. In this exciting development, there is some creditable contribution from Indian physicists, who are participating in two of the six experiments to be performed using the LHC. It is, however, unfortunate that at this time of great scientific excitement over the prospect of new discoveries, there should be irrational voices predicting an apocalypse.