The speed of light is a universal physical constant that is vital in several aspects of physics. Light travels at a constant and finite speed of 186,000 miles per second. But did you know that the speed of light can be manipulated?
In 1999, Lene Hau, a physicist from Denmark, was the first to slow light down to 38 mph. Later, she could completely stop, control, and move it.
Who is Lene Hau?
Lene Vestergaard Hau, a physicist born in Vejle, Denmark, on November 13, 1959, is most known for her work slowing and stopping light. She graduated from Aarhus University in Denmark with a bachelor’s degree in mathematics, a master’s degree in physics, and a PhD. (Source: Physics Today)
Lene Hau’s Research on the Speed of Light
After years of effort, Hau mastered the art of riding a bicycle at the speed of light in 1999.
Instead of cycling faster, she slowed light down to an astonishing 60 kilometers per hour, accomplishing this impressive feat. She accomplished something even more extraordinary, stopping light in its tracks.
Light travels at 186,000 miles per second. Hau has known this but never anticipated breaking the light-speed slow-speed record. She started a new research endeavor shortly after she got there: looking for the Bose-Einstein Condensate, a brand-new state of matter.
Atoms are extremely sensitive to temperature; at a few millionths of a degree above absolute zero, they lose their individuality and merge.
This collection can behave like a single superatom at low enough temperatures; it is referred to as the Bose-Einstein Condensate after the two physicists whose research predicted its existence in 1924.
I was so curious to see what this new state of matter was like. We were incredibly happy. We had succeeded.Lene Vestergaard Hau, Physicist
The Bose-Einstein Condensate was ultimately formed in June 1997 after Hau and her colleagues successfully cooled the atoms.
After creating it, Hau and her coworkers started looking for uses for the condensate. They discovered they could make light pass through the previously opaque condensate by precisely manipulating it with laser beams. And they realized that no material had ever been identified that could delay light as efficiently as the massaged condensate.
Using an electromagnet, a 0.2 millimeter-long cigar-shaped condensate was suspended inside a vacuum chamber. They used a precisely calibrated laser beam to illuminate the cigar from the side before firing a pulse of laser light along its long axis.
As soon as the pulse touched the modified condensate, it slowed and compressed. For a year, Hau labored through the night in the lab to refine her test technique for slowing light. She started to notice the light slowing in March 1998, at last.
I thought, ‘gee, you are the first person to see light go this slowly.Lene Vestergaard Hau, Physicist
She discovered she was moving quicker than her light beams when she took a flight to Copenhagen that summer. She published her findings that autumn when she successfully got light to move at a bicycle’s pace.
Her team advanced their research this year by successfully stopping all light inside a Bose-Einstein Condensate. The scientists immediately shut off the coupling laser once the light pulse had been fully compressed and trapped within the condensate. The light became trapped inside after this change. The initial light pulse emerged from the other end when they turned the coupling laser back on. (Source: Physics Central)