The speed of light is a fundamental scientific constant that governs many
aspects of physics. The constant and finite speed of light is 186,000 miles
per second. But did you know that you could change the speed of light?
In 1999, Danish physicist Lene Hau accomplished the first slowing of light
to 38 mph. Later on, she was able to fully stop, control, and move it.
Lene Hau, who is she?
On November 13, 1959, physicist Lene Vestergaard Hau was born in Vejle,
Denmark. She is most known for her work slowing and halting light. She
earned a PhD, a master's degree in physics, and a bachelor's degree in
mathematics from Aarhus University in Denmark.
Research on the Speed of Light by Lene Hau
In 1999, Hau achieved cycling at the speed of light after years of
practice.
She achieved this amazing achievement by pedaling at a modest 60 kilometers
per hour as opposed to going faster. She did something much more amazing:
she stopped the light in its tracks.
The speed of light is 186,000 miles per second. Hau was aware of this but
never intended to beat the record for light-speed slow-speed travel. Shortly
after arriving, she began a new research project: searching for the
Bose-Einstein Condensate, a brand-new state of matter.
A few millionths of a degree above absolute zero causes atoms to lose their
identity and fuse because they are so sensitive to temperature.
The Bose-Einstein Condensate is named after the two physicists whose
research first predicted its existence in 1924 and can behave like a single
superatom at low enough temperatures.
"I was really interested to learn more about this novel state of matter. We
were quite joyful. We were successful." Scientist Lene Vestergaard Hau
In June 1997, when the atoms had been effectively cooled by Hau and her
colleagues, the Bose-Einstein Condensate finally formed.
Hau and her team began exploring for applications for the condensate after
producing it. They found that by carefully controlling the condensate with
laser beams, they could make light flow through the previously impenetrable
condensate. They came to the conclusion that the manipulated condensate was
the only substance known could delay light as well as it could.
A 0.2 millimeter-long, cigar-shaped condensate was suspended within a
vacuum chamber using an electromagnet. They fired a pulse of laser light
along the cigar's long axis after illuminating it from the side with a
properly regulated laser beam.
The pulse slowed and compressed as soon as it came into contact with the
changed condensate. Hau worked all night in the lab for a year perfecting
her test method for slowing light. In March 1998, she finally noticed that
the light was becoming less intense.
I remarked, "Wow, you must be the first person to notice light moving this
slowly. Scientist Lene Vestergaard Hau
When she boarded a trip to Copenhagen that summer, she realized she was
travelling faster than her light beams. That fall, once she had succeeded in
getting light to move at a bicycle's speed, she reported her results.
This year, her team made strides in their study by completely obliterating
all light inside a Bose-Einstein Condensate. The light pulse was entirely
compressed and confined in the condensate, and the coupling laser was turned
off instantly. After this alteration, the light became imprisoned inside.
They turned the coupling laser back on and the first light pulse came out
the other end.
Reference(s):
Physics Today
and
Physics Central
