Friday, June 02, 2006

Beyond the speed of light -- light so fast it goes backwards (dude!)


In the past few years, scientists have found ways to make light go both faster and slower than its usual speed limit, but now researchers at the University of Rochester have published a paper today in Science on how they've gone one step further: pushing light into reverse. As if to defy common sense, the backward-moving pulse of light travels faster than light. Confused? You're not alone.

"I've had some of the world's experts scratching their heads over this one," says Robert Boyd, the M. Parker Givens Professor of Optics at the University of Rochester. "Theory predicted that we could send light backwards, but nobody knew if the theory would hold up or even if it could be observed in laboratory conditions."

Boyd recently showed how he can slow down a pulse of light to slower than an airplane, or speed it up faster than its breakneck pace, using exotic techniques and materials. But he's now taken what was once just a mathematical oddity—negative speed—and shown it working in the real world.

"It's weird stuff," says Boyd. "We sent a pulse through an optical fiber, and before its peak even entered the fiber, it was exiting the other end. Through experiments we were able to see that the pulse inside the fiber was actually moving backward, linking the input and output pulses."

So, wouldn't Einstein shake a finger at all these strange goings-on? After all, this seems to violate Einstein's sacred tenet that nothing can travel faster than the speed of light.

"Einstein said information can't travel faster than light, and in this case, as with all fast-light experiments, no information is truly moving faster than light," says Boyd. "The pulse of light is shaped like a hump with a peak and long leading and trailing edges. The leading edge carries with it all the information about the pulse and enters the fiber first. By the time the peak enters the fiber, the leading edge is already well ahead, exiting. From the information in that leading edge, the fiber essentially 'reconstructs' the pulse at the far end, sending one version out the fiber, and another backward toward the beginning of the fiber."

Boyd is already working on ways to see what will happen if he can design a pulse without a leading edge. Einstein says the entire faster-than-light and reverse-light phenomena will disappear. Boyd is eager to put Einstein to the test.

So How Does Light Go Backwards?
Boyd, along with Rochester graduate students George M. Gehring and Aaron Schweinsberg, and undergraduates Christopher Barsi of Manhattan College and Natalie Kostinski of the University of Michigan, sent a burst of laser light through an optical fiber that had been laced with the element erbium. As the pulse exited the laser, it was split into two. One pulse went into the erbium fiber and the second traveled along undisturbed as a reference. The peak of the pulse emerged from the other end of the fiber before the peak entered the front of the fiber, and well ahead of the peak of the reference pulse.

But to find out if the pulse was truly traveling backward within the fiber, Boyd and his students had to cut back the fiber every few inches and re-measure the pulse peaks when they exited each pared-back section of the fiber. By arranging that data and playing it back in a time sequence, Boyd was able to depict, for the first time, that the pulse of light was moving backward within the fiber.

To understand how light's speed can be manipulated, think of a funhouse mirror that makes you look fatter. As you first walk by the mirror, you look normal, but as you pass the curved portion in the center, your reflection stretches, with the far edge seeming to leap ahead of you (the reference walker) for a moment. In the same way, a pulse of light fired through special materials moves at normal speed until it hits the substance, where it is stretched out to reach and exit the material's other side [See "fast light" animation].

Conversely, if the funhouse mirror were the kind that made you look skinny, your reflection would appear to suddenly squish together, with the leading edge of your reflection slowing as you passed the curved section. Similarly, a light pulse can be made to contract and slow inside a material, exiting the other side much later than it naturally would [See "slow light" animation].

To visualize Boyd's reverse-traveling light pulse, replace the mirror with a big-screen TV and video camera. As you may have noticed when passing such a display in an electronics store window, as you walk past the camera, your on-screen image appears on the far side of the TV. It walks toward you, passes you in the middle, and continues moving in the opposite direction until it exits the other side of the screen.

A negative-speed pulse of light acts much the same way. As the pulse enters the material, a second pulse appears on the far end of the fiber and flows backward. The reversed pulse not only propagates backward, but it releases a forward pulse out the far end of the fiber. In this way, the pulse that enters the front of the fiber appears out the end almost instantly, apparently traveling faster than the regular speed of light. To use the TV analogy again—it's as if you walked by the shop window, saw your image stepping toward you from the opposite edge of the TV screen, and that TV image of you created a clone at that far edge, walking in the same direction as you, several paces ahead [See "backward light" animation].

"I know this all sounds weird, but this is the way the world works," says Boyd.

17 Comments:

Blogger monkeyfist777 said...

Don't you love the way scientists explain stuff to journalists, for us dummies. Granted the guy has some pretty sophisticated equipment to clock light speed but... Time traveling light! How is this going to affect the world of telecommunications?

I better polish up my resume.

Fiber optic is a fickle thing and some are faster than others. I won't bore anyone with details...
Surely, his students cutting and re-terminating the f/o would affect the wavelength if the cut ends weren't polished correctly. There are just too many variables.

But, MY GOD! If he's not making it up, then somebody stop him before he opens up a wormhole and kills us all!

I can predict almost word for word how Bill will reply, just because I posted. but, I will let him do that for me.

Now my weekend is totally fucked. I'm going back to bed. Thanks Brook.

Saturday, June 03, 2006 9:53:00 AM  
Blogger bill said...

But if this guy is right, and this technology grows, then you are already back in bed.

Did you really expect me to say that???

Saturday, June 03, 2006 2:21:00 PM  
Blogger monkeyfist777 said...

I thought you told me that yesterday. But I just woke up... Damn!

Sunday, June 04, 2006 2:15:00 AM  
Blogger bill said...

Hush up, you shouldn't talk in your sleep.

Sunday, June 04, 2006 8:00:00 AM  
Blogger bill said...

As Douglas Adams pointed out, the trouble with time travel isn't fucking up the past and changing the future as all of that irons itself out as more people fuck up the past. The trouble with time travel is all of the tense changes.

Sunday, June 04, 2006 5:19:00 PM  
Blogger spookygrrrl said...

I predicted that's how you would answer Bill...always quoting Douglas Adams...soooooo predictable.

Sunday, June 04, 2006 6:43:00 PM  
Blogger bill said...

Just as I knew you would say that as I already read it tommorrow....

Monday, June 05, 2006 6:45:00 AM  
Blogger tony not Tony said...

i for one, would really be excited to have some one who says they won't bore me with details, actually provide me with the alledged details and see if it puts me in a coma or actually makes sense...

otherwise, if this doesnt explain roland's drumming, it doesnt matter anyway....

fraqbkte

Tuesday, June 06, 2006 9:33:00 PM  
Blogger bill said...

I guess that makes sense, since Roland is himself a light source, and the luster of his patina is probably encrusted with erdium, he is ahead of his time, while conversly, right on beat.


fjord

Tuesday, June 06, 2006 9:46:00 PM  
Blogger monkeyfist777 said...

Well Tony, the light transfer speed through a section of fiber-optic(f/o) is based on it's width. meaning that the narrower a strand of f/o the fewer "bounces" it has to make to get from point A to B. Fewer bounces mean less distance traveled overall.
For example. A single mode strand of f/o is generally .55 microns in diameter. It's a newer standard for 1000 base or gig-speed networks

The old stuff which is still suitable for most networks (10/100 base) is the milti-mode f/o which has a standard of 6.25 microns. It's a much wider silicate thread meaning more bounces from point A to B and more distance travelled overall for the same length. (slower)

My issue is that it seems like a smoke and mirrors deal because the guy and his team could be just developing a super-fast f/o and/or tweaking the hardware controls. Which is cool... but, doesn't necessarily mean that light is beating the clock.

Terra-speed networks COOL.

Ultra responsive hardware controls COOL.

What I get geeked about is all that stuff seems so... Star Trek considering, that with all the fantasy technology we are making baby steps to techno reality.

Where are the guys working on the matter replicators and transporters?

I would love to transport car parts from JC Whiney or new clothes from Nordstroms or go to subway.com and download a sandwich.

Screw going back to the moon we need companies getting R/D grants for the replicators and transporters.

Global economy for real.

Wednesday, June 07, 2006 7:44:00 PM  
Blogger Shameless Dave said...

Can't say that I didn't see that one coming from a mile away - and I didn't even need time travel to know it was out there, lurking, waiting just to bore the hell out of us.




Zappa

Wednesday, June 07, 2006 8:05:00 PM  
Blogger bill said...

Replicators and transporters are all well and good, but when I was a child I was promised by society that I would live on the moon in a moon coloney and have a robotic talking dog to drive around with in my flying car.

I want my robotic talking dog and my flying car! (The moon base would be nice too)

fjord

Thursday, June 08, 2006 6:44:00 AM  
Blogger Shameless Dave said...

What a world, eh? Bigass robotic dogs, houses under big glass domes, and a truly sweet bitchin' flyin' Camero! Now that's some George Jetson fun, right there. I can just imagine the technical leaps in Pocket Pussy, Broadband connections EVERYWHERE - even this little 1 by 2 mile area I live in. We could eliminate drums machines and replace them with tiny little holographic Rolands with tartan covered drums to do the job. Go back in time to the mid seventies and keep George W coked up and in rehab forever.At the very least, get the money that bastard still owes me from them rebate checks I was suppose to get back in 2000. And as a special ode to you, Corso, screw Subway sandwichs, get something you can really use - Angelina Jolies for everyone!

eLIzabETh

Thursday, June 08, 2006 1:03:00 PM  
Blogger spookygrrrl said...

I'll take a couple of Jolie's to go then!



Fuck Subway

Friday, June 09, 2006 6:25:00 PM  
Blogger bill said...

Hell Dave, I forgot all about the great strides in pocket pussy. Back in the 80's, when the future was still cool, we were promised holigraphic rooms where we could all screw Heidi Klum's brains out all day. I want my robotic talking dog, my flying car and my holographic Heidi.

DDBAD

fjord

Friday, June 09, 2006 7:13:00 PM  
Blogger Shameless Dave said...

Yeah Bill, it's a brave new world, alright. And I contend that any of us could have had Heidi Klum at any time. Only thing now is she's covered in Seal funk....I mean, have you taken a good close look at him? The man's a fuckin' goblin! Therefore, if HE can do it, anybody could've climbed Mt Heidi. Anyway, where's my sweet, sweet bitchin' and flyin' Camero?

Friday, June 09, 2006 8:47:00 PM  
Blogger Shameless Dave said...

And don't forget the sweet, sweet Official RC and Moon Pie Festival here in Bell Buckle on Saturday, the 17th.
And the cool part is you can do the Moon Pie thing, and still make it to the little band dealio in JC. Sweeeeet.
Is this a cool world or what?

Butterfield 8

Friday, June 09, 2006 8:54:00 PM  

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