Scientists aim to slow down speed of light

Staff at the University of Sussex will make lasers travel 30 million times slower to test the theory of relativity.

Light, which zips along at 300,000km (186,000 miles) per second in a vacuum, would be slowed down to travel 100m in ten seconds. Tim Montgomery's 100m world record is 9.78 seconds.

The results could help produce the elusive "theory of everything", a unifying concept modern scientists hope will explain the universe.

They could also lead to discoveries that prove revolutionary.

Dr Ben Varcoe said: "The dream of modern physics is to discover a theory of everything, which explains all of science.

"The implications of such a theory run quite deep, in the same way that quantum theory changed our lives."

He said quantum physics, the study of sub-atomic particles, had helped create the semi-conductor industry, which had led to inventions such as the DVD.

In 1905, Einstein produced his famous equation is E=mc2 (energy equals mass times the speed of light squared).

It was hailed as the greatest discovery of the 20th Century and, by expressing the relationship between time, space and energy, helped Man grasp the mystery of the cosmos.

But because light travels so quickly, putting it to the test has been difficult.

Previously, experts have had to measure it using spacecraft or by accelerating particles as quickly as possible - both at great expense.

However, Dr Varcoe, 33, hopes useful results can be found in a small test tube in his Falmer laboratory.

He said: "Light travels at 300 million metres a second and we slow it down to ten metres a second.

"If an athlete runs 100 metres in ten seconds, that's the same speed.

"We put a laser light through a gas cell, in this case rubidium, and it interacts with the gas, making it very optically thick.

"If we make it very dense, the light travels very, very slowly."

By slowing the light, it should be possible to examine the associated light waves and test Einstein's theory more precisely.