Light travelling backwards is faster than light.

FrostyBoy · May 15, 2006, 21:37

http://www.rochester.edu/news/show.php?id=2544

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.

So there.

Zkribbler · May 15, 2006, 21:56

Sorry, but this doesn't make any sense.

Speed (including light speed) is non-directional. If it had direction, then it would be velocity, not speed.

For example, a train going 50 m.p.h. north is going the opposing velocity of a train going 50 m.p.h. south, but both trains are travelling at the same speed.

Speed goes from zero to "C" (according to Einstein) ...but there is no negative speed. Light cannot travel backwards... If it tried, it would just be light going in the opposite direction.

Q.E.D.

Vince278 · May 15, 2006, 22:28

Doesn't make sense. A photon traveling at the speed of light is not traveling in time by its own frame of reference. Therefore, it can be anywhere in the universe. Its vector becomes irrelevent. Things get even weirder at speeds above light (theoretically speaking, of course). The would photon then appear to travel backwards in time.

Seeker · May 15, 2006, 22:37

How can you go slower than slow?

KrazyHorse · May 15, 2006, 22:38

Originally posted by Sn00py
http://www.rochester.edu/news/show.php?id=2544

So there.

Yet another example of people not understanding the difference between phase velocity and group velocity.

Kuciwalker · May 15, 2006, 22:40

KH beat me to it

This same stupid story, along with a number of variants on it, gets reported every month or two. I suppose it's a great way to get grant money or something.

KrazyHorse · May 15, 2006, 22:42

I suppose there's probably some useful work to be done in optics using these types of experiments. But there's no fundamentally new physics here.

KrazyHorse · May 15, 2006, 22:43

Originally posted by Kuciwalker
KH beat me to it

That's why they pay me the big bucks.

Kuciwalker · May 15, 2006, 22:44

Ted Striker · May 15, 2006, 22:46

Yeah it still can't beat my time in the 40 though

KrazyHorse · May 15, 2006, 22:46

Originally posted by Kuciwalker

Seeker · May 15, 2006, 22:52

"But he's now taken what was once just a mathematical oddity—negative speed—and shown it working in the real world."

What is this pre-existing 'mathematical oddity' called negative speed?

I've never heard of it. Is this a reporter created term?

Vince278 · May 15, 2006, 22:54

Originally posted by Seeker
I've never heard of it. Is this a reporter created term?

That happens alot.

KrazyHorse · May 15, 2006, 23:02

Originally posted by Seeker
"But he's now taken what was once just a mathematical oddity—negative speed—and shown it working in the real world."

What is this pre-existing 'mathematical oddity' called negative speed?

I've never heard of it. Is this a reporter created term?

Probably not. I've never heard it used either (in this context), but then again I've never worked on modern optics. Getting a phase velocity moving in the opposite direction of the group velocity is an interesting trick, and people who specialise in the field might well have developed a term for the previously-unobserved (but solidly theoretically-based) phenomenon.

Agathon · May 15, 2006, 23:32

Who cares?

SlowwHand · May 15, 2006, 23:35

No lie. Geeks.

KrazyHorse · May 15, 2006, 23:47

Originally posted by Agathon
Who cares?

Apparently more people than care about Aristotle.

Odin · May 15, 2006, 23:52

Originally posted by Agathon
Who cares?

Bill3000 · May 16, 2006, 02:11

It would be cooler to stop a photon, IMO.

Urban Ranger · May 16, 2006, 04:44

I read somewhere that a group of researchers got purty close to doing that.

Spiffor · May 16, 2006, 08:10

This is the scientist who did the experiment

Last Conformist · May 16, 2006, 08:24

Science journalism is a conspiracy to drive all scientists insane.

Ecthy · May 16, 2006, 11:16

Einstein wasn't nearly the most intelligent man of the 20th century. Neumann!

Agathon · May 16, 2006, 11:32

Originally posted by KrazyHorse

Apparently more people than care about Aristotle.

Aristotle has staying power. Physicists cannot control their physical functions when copulating with women.

Elok · May 16, 2006, 12:03

Originally posted by Ted Striker
Yeah it still can't beat my time in the 40 though

When you say "the 40," are you talking yards, meters, or ounces?

WRT the original post, if this doesn't even claim to get us closer to ray-guns, EMP weapons, gauss rifles, teleporters, or something else cool, it's just not news by my book. Whether it's true or false.

Last Conformist · May 16, 2006, 12:06

Originally posted by Agathon
Who cares?

Feeling bitter, are we?

Urban Ranger · May 16, 2006, 22:10

Originally posted by Last Conformist
Science journalism is a conspiracy to drive all scientists insane.

Aren't they all?

MRT144 · May 16, 2006, 22:14

Originally posted by Spiffor
This is the scientist who did the experiment

steve forbes?

Vince278 · May 17, 2006, 01:02

Originally posted by Ecthy
Einstein wasn't nearly the most intelligent man of the 20th century. Neumann!

Why not Hawking or Feynman?

Vince278 · May 17, 2006, 01:04

Originally posted by Elok
WRT the original post, if this doesn't even claim to get us closer to ray-guns, EMP weapons, gauss rifles, teleporters, or something else cool, it's just not news by my book. Whether it's true or false.

Already there.