The stage is set for arguably the grandest scientific experiments ever performed

It is an experiment that is not easily described, seen or understood. Yet it does not fail to inspire awe even among those casually acquainted with modern physics. Over 2,000 scientists from 34 countries will watch fundamental particles of nature go on a merry go round in a tunnel. This tunnel — straddling France and Switzerland on the outskirts of Geneva — is 27 kilometres long, 50 to 175 metres below the ground and kept at a temperature of 270 degrees below freezing point. It took several years to build this machine, although parts of it were part of another existing tunnel. The final bill can run up to $11 billion.

In two months, the Large Hadron Collider (LHC), as this equipment is known, will provide the stage for arguably the grandest — if not the greatest — set of scientific experiments ever performed. The primary aim is to test one of the basic theories of contemporary physics: the Standard Model, a theory that describes and unifies three of the four fundamental forces of nature. It is also to test the existence of one particle, the Higgs Boson, which will again confirm and substantiate the Standard Model theory.

But scientists will test many other theories too. “The experiment is most exciting,” says Rajiv Gavai, professor at the Tata Institute of Fundamental Research (TIFR) in Mumbai. “It is likely to throw up many interesting questions.”

The stakes in this project are very high. Experiments there are likely to find new particles and new laws, apart from confirming or rejecting parts of existing theories. It could provide a hint of the veracity of String Theory, which has been thought to be unverifiable for a long time. Also called the Theory of Everything, String Theory, scientists hope, can one day explain all physical phenomena in the world, from the movement of electrons in an atom to that of a faraway galaxy. The LHC could also provide some explanation for the existence of dark matter and dark energy, which together make up 96 per cent of the universe, and about which we know nothing.

Yet physicists think what the LHC could find would be only the tip of the iceberg, just like the situation at the end of the 19th century. Scientists then probed a few small chinks in existing theories which led to a big revolution — including quantum mechanics and relativity — that lasted well into the 20th century.

The Standard Model is considered one of the great achievements of modern physics. Three of the four fundamental forces of nature it deals with are the strong and weak nuclear forces and the electromagnetic force. The strong nuclear force holds the atomic nucleus together. The weak force produces phenomena like nuclear decay. The electromagnetic force is responsible for all the phenomena that we see around us — chemistry, biology, the weather and so on. The fourth, gravity, still stands apart and defies complete description.

The Standard Model has evidence from many experiments, but would have far greater credibility if a few more facts were proven. One of them is the existence of the Higgs Boson. In fact, this is the only particle predicted by the Standard Model which is yet to be observed. In fact, Higgs Boson is vital to the success of the Standard Model. “If the Higgs particle is not discovered, physics will be shaken up,” says Sunanda Banerjee, scientist at the Fermilab near Chicago, US.

It is not merely the existence of the particle that is at stake. The Higgs particle has to have a certain mass to agree with the theory. So the LHC experiments — on the Higgs particle — can lead to three results. One, the Higgs particle is discovered at the right mass, two, it is discovered at higher mass, and three, it’s not discovered at all. In all the cases, the results would lead to some new physics. If it is not discovered at all, there could be a true revolution. “All this is making us very nervous,” says Rohini Godbole, professor at the Indian Institute of Science (IISc), Bangalore. “So much theory is at stake.”

Seldom has one experiment excited physicists all over the world. In fact, Indian physicists have contributed a lot to the design and development of the LHC and later to the design of the experiments as well. Teams at the Raja Ramanna Centre for Advanced Technology in Indore, Bhabha Atomic Research Centre (BARC) in Mumbai, Variable Energy Cyclotron Centre in Calcutta and a few other institutes designed the magnets for the Precision Magnetic Positioning System at the LHC, which were later fabricated in Bangalore. These magnets accelerate and whirl around the particles, and have to be positioned correctly to one-billionth of a metre. Some of the magnets were tested at BARC.

Scientists and engineers at TIFR and BARC also built parts of a type of particle detector called Compact Muon Solenoid (CMS), which is supposed to detect proton collisions. Scientists at IISc and the Harish-Chandra Research Institute in Allahabad have contributed to the predictions for detecting the Higgs Boson. Events that produce this particle would be a billion times rarer than other events after collisions, and thus the predictions for detecting them are critical.

In the end, scientists will be looking at well beyond the discovery of the Higgs particle. One of the phenomena that physicists hope the experiments would help illuminate is the concept of dark matter and energy. All that we know of in the universe constitutes only 4 per cent of its mass and energy. The unknown is more critical for its evolution and ultimate destiny. Even a hint of these phenomena would delight physicists.