Monday, April 12, 2010

Slow Light - is it possible? What are the uses?

I remember reading Bob Shaw's 1968 short story "Light of Other Days many years ago about Slow Light. In this story all the windows in the house were made of slow glass. This glass was made of a material that slowed light to a crawl. The light that entered it on one side took years to pass through. The thought being that you would set out a sheet of slow glass in a picturesque local for a number of years and then install them in frames that would act as windows. The idea just blew me away.

Is it possible? Very likely... Lets look at light. the posted speed limit for light is 300,000km a second. But that is only in a complete vacuum. In real life light travels MUCH slower. What slows light down? Well any ole atom will do the trick. An atom will absorb a photon and re-emit it, imparting a delay. This is called the absorption/re-emission cycle. Now I hear the screams "photon HAVE to travel at C!" and in truth the "slowing" is just an illusion because once emitted, the photon travels again at C until it hits another atom. But the delay...that is not an illusion.

What really gets weird is when the "stop" light. Check out this mind bending statement from the IO9 article
  • When scientists stop light, they aren't actually halting a photon – they're embedding its quantum state into the nearby atoms. Later, they use another laser pulse to activate those atoms and make them emit an identical photon.
Other than Slow Glass what could be a use for "stopped light"? Well the ability to slow, stop and generate photons is a major step towards developing quantum computers. Of course as with any tech a criminal will find a way to co-opt it say by replacing windows with slow glass so that surveillance would be none the wiser or surveillance itself...You could be watching someone that would see nothing but a seascape say...for years....

For the complete article and reference links, check out the IO9 article HERE
Slow Light in Wikipedia HERE


Anonymous said...

Not to be a 'nitpicker', but there's a big mistake in this article, someone apparently forgot a few zeroes.
Light does not travel at a measly 300km a second in a vacuum, it travels at nearly 300,000km a second in a vacuum, providing I converted 186,282 miles per second to kilometers per second correctly.
At a mere 300km per second it would take light from the sun over five days to reach Earth instead of the roughly seven and a half minutes that it actually does.

Beam Me Up said...

Hey thanks for the update, I was cutting and paste and being half asleep I missed three whole zeros! duh! thanks for the heads up.