Scientists Speed up Light

An anonymous reader writes "With off-the-shelf components, scientists have managed to speed up light beyond the 'universal' constant of c, or roughly 300 million meters/sec. This, and the previous ability to slow light down could shake up the telecom world, according to the story at Science Blog." Also, all those posters with 186,000 miles per second as a speed limit need to be amended. At least entropy is still around!

Comments

here's an example...

[jxyama]

Not sure if it's 100% relevant, the example I remember from school is: Take a powerful spotlight and place an object in front of it. Now go, really, really far away and watch the shadow cast by the object on the wall. Further you go, more "magnified" its movement will be, i.e., since the spotlight will be bigger further away, waving an object across the face of the spotlight will move the shadow on the wall across greater distance. If the spotlight is powerful enough, you can extend the wall as far as you want and the shadow will move as fast as you want, even faster than the speed of light.

Note that no information is being transmitted faster than the speed of light in such a case. Shadow may traverse across the spotlight faster than the speed of light, but the actual information that creates the shadow is still transmitted at the epeed of light from the spotlight to the wall.

Re:Something's amiss here...

[PDAllen]

Suppose you had a chain of people 3,000,000km long, and you had them do a Mexican wave. It'd take (a lot) more than 10 seconds to go from one end of the chain to the other because people don't react that fast.

Now suppose you gave each person a Bleepy Thing (tm) which you have sychronised beforehand so they go off at staggered intervals, the last one at the far end of the line 2 seconds after the first. You have the chain of people do its Mexican wave by standing as soon as their Bleepy Thing goes off. Wave velocity will be approximately 5c. There's no problem synchronising the bleepy things, just set them to go off at the right time intervals when they're all together in one place and then move them fairly slowly (like 100km/s is fine) to the right places in the chain.

So why doesn't that break relativity? Answer: the wave does not carry information that fast. In fact the only information you get from the far end of the wave is the time the bleepy things were set to go off at - which reached you much slower than light speed when the bleepy things were sent down the chain beforehand.

This is much the same trick just done with a light wave not a Mexican wave.

Re: Information transfer *is* what's limited by c

[DavidTC]

There is no such thing as faster than the speed of light, in relativity, despite people talking about it. Reality itself propogates at the speed of light.

Which is why if you go faster than light, your reality is backwards and cause follows effect. You aren't even really going faster than light, you're going slower than light and backwards in time. If you were to approach 2x the speed of the light, you'd appear to slow down to everyone else, and end up casually strolling facing the wrong way. (And this would be trival to do, as going 2x the speed of light would be a simple matter of going 1.00001x and then trying to stop.)

So it's not a premise about the speed of light. The speed of light defines time. It is absolute. While you can't accelerate faster than the speed of light, that's not the point. The point is that light always travels at exactly the same speed, and light carries reality along with it.

By 'reality, I mean exactly that. I can see you do something while I did something else, and those events happened at the same time to me. You, being a light year away, saw them two years apart, and we're both right, from our frame of reference. That's relativity. Events happen when the light reaches you. (And by light, I mean hypothetical vacuum light, not artifically slowed light.)

People hear 'nothing can travel faster than light', and 'everything is relative' and don't quite grasp is. According to relativity, time doesn't exist independent of the speed of light, just like gravity doesn't exist independent of the distortion in space caused by mass. In fact, energy:time::matter:gravity is a pretty good analogy of what's going on.

And everything I just wrote, according to quantum mechanics, is a complete and utter lie.

Quantum mechanics has been proven to be non-local (operating faster than light) with Bell's Theorem. It's not even a theory, we have actual physical proof that events at one place can effect the outcome at another faster than light. We don't even need quantum tunnelling, good ole quantum interference does it for us.

Now, Bell's Theorem doesn't let us get information faster than light. However, it clearly knows what's going on faster than light, so at least bookkeeping information can go faster than light.

And, incidentally, you don't need quantum tunneling or any sort of equipment to get light going faster than light. Light, until you measure it, is smeared into a probability wave. Sometimes, by sheer chance, you can measure one and it will end up collapsing at the front of the wave. Thus having moved a tiny fraction faster than light.

And some will collapse at the end of the wave, moving a tiny fraction slower than light, which is just as much a crime for light to do in relativity.

I'm fairly certain we've actually measured what we think is this happening, from pulsars. Probablity waves from photons from stars can spread across meters until they hit something, where they instantly collapse into one point. (At which point relativity runs screaming from the room, because points a meter away from each other should not be able to communicate instantly.) A meter isn't a long time, lightwise, but I seem to recall something about measuring 'fast' photons.

This is why physicists have so many drunken fistfights.