Transcription
Light moved at the speed of city traffic in a lab, not a metaphor, not a refraction trick, actually moved that slow. Light is supposed to be the rule the universe doesn't break. Nothing with mass catches it. [music] Nothing outruns it.
Then in 1999 in Cambridge, Massachusetts, Lene Hau cooled a cloud of sodium atoms to a billionth of a degree above absolute zero, colder than the depths of space. She locked them into a single quantum state, a Bose-Einstein condensate. Then she fired a pulse of [music] light into it. The pulse came out the other end 20 million times slower than it should have.
She used a technique called electromagnetically induced transparency. A second laser aimed sideways at the cloud, forcing the atoms to let light through, but only at one exact wavelength [music] and only at a crawl.
Then something stranger started happening inside [music] the cloud. The pulse stopped behaving like free light. It merged with the atoms, [music] became a hybrid, part light, part matter.
Two years later, she [music] went further. While a pulse was still inside the cloud, she switched off the sideways laser. The light didn't come out the other end. >> [music] >> It wasn't absorbed. It wasn't scattered. It just waited inside the atoms for a thousandth of a second. Then she turned the laser back on and the pulse walked out the far side.
We treat light like a constant, like the universe refuses to negotiate with it. But this looked less like a constant and more like something we could bend if we pushed hard enough. If light can hesitate, what else [music] already does? And the thing you watched move across that cloud, was it ever really light?