Breaking the Speed Limit

August 23, 2005 4:29 PM

Scientists speed up light, causing it to travel faster than "c," the long recognized speed of light in a vacuum. This, like the experiments conducted several years ago to briefly stop light, are hard for the average person to comprehend, but have important applications in fiberoptic communications.
posted by awesomebrad (38 comments total)

They did not speed up light. They speeded up some ensemble behavior - like how you can have a "wave" of motion in a traffic jam that moves faster than any individual car, or a "wave" in a stadium. This is an important distinction, because it means that everything we thought about physics is not suddenly invalidated.

The scienceblog article does a terrible job, IMHO. In some places they are clear that the "light signal" has been sped up, but they actually say "making light go faster than the speed of light", which is just stupid. Then they say some stuff about how relativity isn't invalidated, because "only part of the signal is sped up". Dood, WTF?
posted by freebird at 4:44 PM on August 23, 2005

Agreed. While this is an awesome development on the road to optical computing, it's way too gee-whiz. Articles written this poorly tend to leave the reader with less accurate knowledge of science than they had before reading it!

Thanks to the OP, but anyone got links to something heavier on details?
posted by plexiwatt at 4:58 PM on August 23, 2005

Any thoughts on how that would affect the laws of causality implied by relativity? My understanding was that ftl communication was basically impossible for the same reasons that travel was.
posted by lumpenprole at 5:04 PM on August 23, 2005

There's an overview here, alongwith comments by the lead researcher.
posted by Gyan at 5:10 PM on August 23, 2005

lumpenprole, from my link,

"I just want to mention that what we have just reported experimentally was already predicted theoretically and fully explained during the 1910s by Leon Brillouin and Arnold Sommerfeld. Nothing new and no paradox, there is nothing magic behind and no theory needs to be revisited."
posted by Gyan at 5:11 PM on August 23, 2005

Well, if you had read the article, lumpenprole...

relativity isn't called into question, because only a portion of the signal is affected.

...you'd know as little as you do know, because they don't explain a damn thing.
posted by ook at 5:14 PM on August 23, 2005

The line to drop at parties when this comes up: the phase velocity of a wave can be much larger than the group velocity of a wave. Information is transmitted only at the group velocity; thus relativity is saved.
posted by fatllama at 5:24 PM on August 23, 2005

Mine goes to 11.
posted by uncanny hengeman at 5:53 PM on August 23, 2005

> opening up the possibility of processing information at the speed of light.

I vaguely recall being promised through some advertising chanel of something going at the speed of light, and scientists are telling that it is now a possibility? These scientists better double check their stuff, marketting was advertising about things going at the speed of light way before this came out.
posted by NewBornHippy at 5:54 PM on August 23, 2005

The Science Blog story is just a verbatim copy of the press release. After reading the actual paper, it's interesting to see what science is like filtered through a PR person's eyes.
posted by betaray at 6:33 PM on August 23, 2005

Farnsworth: These are the dark matter engine I invented. They allow my starship to travel between galaxies in mere hours.
Cubert: That's impossible. You can't go faster than the speed of light.
Farnsworth: Of course not. That's why scientists increased the speed of light in 2208.

So, we've still got a while.

See also: A Futurama Math Conversation with David X. Cohen.
posted by unsupervised at 6:53 PM on August 23, 2005

I thought that demonstrating a speed of light faster than C was synonymous with proving the observer had gone back in time relative to the light.
posted by scarabic at 7:28 PM on August 23, 2005

Drat. I was hoping that with the increase of value in C we could greatly increase the amount of energy released from a unit of matter. And that would be cool because of, well, you know, bigger bombs!
posted by sourwookie at 7:36 PM on August 23, 2005

I agree with fatllama and I say lets wait for the APL article to get a description of the experiment.

I am surprised with what betaray said: the reporter did not obviously try to contact any of the scientists involved to get a better story.
posted by carmina at 7:45 PM on August 23, 2005

The telecommunications industry transmits vast quantities of data via fiber optics. Light signals race down the information superhighway at about 186,000 miles per second.

Feh. Another inaccuracy. Light signals traverse ordinary fiber optics at about 2/3rds the speed of light due to the "velocity factor" of the cable.
posted by ZenMasterThis at 7:57 PM on August 23, 2005

It's an illusion. Specifically they're looking at the group velocity as opposed to the phase velocity.

Here's an animation by Greg Egan that may help to explain what's going on: subluminal.
posted by snarfodox at 8:27 PM on August 23, 2005

If the speed of light can change, so can the 'age of the universe'
posted by bevets at 8:45 PM on August 23, 2005

Bevets: no.
posted by fatllama at 9:05 PM on August 23, 2005

Actually, if I had to guess, I'd go with Bevets! It's kind of like: if inches were shorter, I'd have a bigger john thomas.
posted by freebird at 9:36 PM on August 23, 2005

If dollars were worth less, I'd be richer. No, wait...
posted by weapons-grade pandemonium at 9:47 PM on August 23, 2005

If a gallon of gas costs me twice as much, I have to work twice as hard to go half the distance?
posted by Balisong at 10:11 PM on August 23, 2005

Well I was a bit startled for a second by that article, but then I realized it was crap. Information cannot be transmitted faster than c.
posted by Citizen Premier at 10:48 PM on August 23, 2005

Actually, I heard that the "speed of light" or c is actually slowing down as a whole.
Not a lot, but enough to screw with measurements since the time that the speed of light has been calculated.
The scientists just, you know, fudge the numbers a bit, and everything works out on paper within a degree or two of uncertianty.

I thought that this was a big revelation last year, sometime...
posted by Balisong at 10:52 PM on August 23, 2005

carmina : "I agree with fatllama and I say lets wait for the APL article to get a description of the experiment."

Does no one read the links? The page I link to, in an earlier post, has a PDF of the APL paper.
posted by Gyan at 1:46 AM on August 24, 2005

fatllama : "The line to drop at parties when this comes up: the phase velocity of a wave can be much larger than the group velocity of a wave. Information is transmitted only at the group velocity; thus relativity is saved."

I've got to start going to more parties with fatllama.

bevets : "If the speed of light can change, so can the 'age of the universe'"

If someone on the Earth is a reincarnation of Jesus, it could be me.
posted by Bugbread at 2:13 AM on August 24, 2005

Anyone can successfully prove, given that the erroneous assumption that the universe is infinite, prove that 2=3. And that there is not a single inhabited planet in the entire universe. I'll expound, with much aplomb and pretention, if asked to.
posted by malusmoriendumest at 3:42 AM on August 24, 2005

Gyan writes "Does no one read the links?"

There seems to be a mefi trend for not reading links, as well as not reading the links in the FPP before commenting. Not sure why, but I am sure Berners-Lee wouldn't approve!
posted by asok at 3:46 AM on August 24, 2005

Isn't Greg Egan great!
posted by asok at 3:48 AM on August 24, 2005

Interestingly, the speed of light might very well change every instant. It might have been different every single moment since the beginning of the universe. We'd just never know it, since it's the measure of everything, scientifically speaking at least.
posted by koeselitz at 4:07 AM on August 24, 2005

malusmoriendumest: I read that book too. It's a good one, no?
posted by koeselitz at 4:08 AM on August 24, 2005

When do we get interstellar travel, and does this put us any closer to that cherished goal?
posted by OmieWise at 5:47 AM on August 24, 2005

Wow, who knew this would be a Summon Bevets post? But wait, if the speed of light can change, Bevets can post without including out of context quotations that take up half the page.
posted by OmieWise at 5:48 AM on August 24, 2005

Everybody knows the only thing that can ever go faster than light is bad news.
posted by uncle harold at 6:04 AM on August 24, 2005

... and no, the fine structure constant isn't changing.

The Webb, Flambaum, Churchill, Drinkwater and Barrow research that so many people were jumping up an down about looks like it was wrong.

Several more recent studies using different data sets and simpler, clearer analyses can't find any change in alpha within the last seven billion years.

Variations in the fine structure constant were where certain physicists were getting the idea that c had changed. It was attractive because it could potentially do away with inflation and make for a big, bouncy universe without having to ask the topologists for help: hence the enthusiasm from certain physicists.

It wasn't likely to be right because it would have screwed up the standard model pretty badly and you'd still have to account for the fact that the standard model yields an exceptionally good description of how stuff actually works.
posted by snarfodox at 6:24 AM on August 24, 2005

The definitive explanation of group velocity vs. phase velocity (or why they didn't speed up light):

You're sitting in traffic -- there was an accident a mile up, and things are backed up as far as the eye can see. They finally clear the road. The lead car goes ahead. After a short delay, the second car goes ahead. Then the third, then the fourth...with a delay, as each driver takes a moment to realize he can accelerate.

You sit there, fuming. It's going to take forever before the guy in front of you is able to move; if only everyone would realize that if they just all hit their gas pedals simultaneously, they wouldn't hit the guy in front of them, and everyone could go from zero to at least thirty immediately. But that's just not how freeways work.

Now, it could take an hour for the car in front of you to finally start moving, or in the perfect world, every car backed up along the freeway could almost simultaneously accelerate. For a ten mile backup, that'd be ten miles almost instantaneously! Obviously no ground based vehicle can move that fast.

But the state of the system -- the speed at which the freeway goes from bumper to bumper into moving traffic -- has nothing to do with how fast any individual vehicle can travel. The guy at the front of the line may do zero to sixty in five seconds -- but it can take an hour for you to get the opportunity to hit the gas pedal.

And thus, phase velocity, the speed of systemic change, is almost totally unrelated to group velocity, the speed of individual members of the group.
posted by effugas at 6:35 AM on August 24, 2005

nformation cannot be transmitted faster than c.
posted by Citizen Premier at 1:48 AM EST

I'm certainly no expert on the matter but it is my understanding that some properties of quantum entanglement may do exactly that Citizen.
posted by nofundy at 10:33 AM on August 24, 2005

So no warpspeed travel anytime soon?
posted by MrMulan at 10:43 AM on August 24, 2005

MrMulan: "So no warpspeed travel anytime soon?"

Cap'n, I'm tryin' as hard as ah can, but she's had about all she can take!
posted by koeselitz at 11:55 AM on August 24, 2005