And there is an Indian connection to it.

The prestigious science journal Nature in its latest issue yesterday reported that Lene Vestergaard Hau working concurrently at the Rowland Institute for Science in Cambridge, Massachusetts, and the Harvard University, used Bose-Einstein condensate to stall the light in its path, reducing its speed to as low as approximately 71 km an hour (17 meters per second). The condensate is named after Indian scientist Satyendra Nath Bose (1894-1974) and Albert Einstein who theorised its existence.

Light tears through vacuum at a speed of about 300,000 km a second. Nothing that is known to humankind at present travels faster than light.

Dr Hau's electromagnetically induced transparency experiment has potential fundamental and technological interest in quantum optics, thejournal writes. It has potential uses in optical computers, high-speed switches, communications systems and night-vision devices as well.

The Bose-Einstein condensate is a `macroscopic' cluster of atoms cooled to temperatures approaching absolute zero. Absolute zero or zero degrees kelvin is the limit beyond which nothing can be colder. The ultra-cold temperatures were achieved by `lasers and evaporative cooling'.

In the condensate, the atoms are virtually immobilised because of the nano kelvin (low) temperatures and barely move. As a result these atoms merge into superatoms sharing the same functions.

This condensate follows the rules of quantum mechanics like the Heisenberg's Uncertainty Principle which states that matter can occur both as a wave and as a particle. If one were more likely to pinpoint the particle's position, the less likely one will be able to determine its exact momentum and vice versa.

In other words, the scientists by chilling the sodium atoms, were able to bring the momentum ofthe particles to almost absolute zero at which state they coalesce into superatoms.

After a series of a complex steps which included directing a beam of laser light into the condensate, the scientists observed that only 25 per cent of the light passed through because of the increased atomic density and steep refractive index. What was more interesting is the astoundingly low speed of the light, reduced by a factor or 20 million times compared to its speed in vacuum.