Light completely stopped for a record-breaking minute

[n2doc]

25 July 2013 by Jacob Aron

The fastest thing in the universe has come to a complete stop for a record-breaking minute. At full pelt, light would travel about 18 million kilometres in that time – that's more than 20 round trips to the moon.

"One minute is extremely, extremely long," says Thomas Krauss at the University of St Andrews, UK. "This is indeed a major milestone."

The feat could allow secure quantum communications to work over long distances.

While light normally travels at just under 300 million metres per second in a vacuum, physicists managed to slow it down to just 17 metres per second in 1999 and then halt it completely two years later, though only for a fraction of a second. Earlier this year, researchers kept it still for 16 seconds using cold atoms.

more

http://www.newscientist.com/article/dn23925-light-completely-stopped-for-a-recordbreaking-minute#.UfGFA2RASLs

[rrneck]

1. Cool. But we'restill overdue for time travel. nt

[tclambert]

8. You can't be overdue for time travel!

If you can travel in time, everything must happen exactly when you want it to, or you didn't want it to happen then. You could simply travel back and give yourself the technology on whatever schedule you want.

I also get like this whenever the Doctor calls himself the last of the Timelords. "Last" has no meaning if your people can travel in time.

[tofuandbeer]

15. +1

[ElboRuum]

17. This thread has gone precisely how I will intend it. n/t

[cvoogt]

18. we all time travel

but sadly in only one direction

[leveymg]

2. Does this mean that with 2 lasers and a crystal you have an effective cloaking device?

Or am I taking this "stopped light" phenomenon too literally? Anyone understand this well enough to be able to explain what's really going on?

[TalkingDog]

3. Not so much a cloaking device as a storage device. .... More like

storing digital information on a Compact Disk. The disk would be the crystal and the light is trapped/stored inside it for a limited amount of time. In this case they stored a crude image consisting of 3 stripes.

The applications have more to do with stuff like this: http://www.technologyreview.com/view/515871/china-reveals-first-space-based-quantum-communications-experiment/

The ability to send perfectly secure messages from one location on the planet to another has obvious and immediate appeal to governments, the military and various commercial organisations such as banks. This capability is already possible over short distances thanks to the magic of quantum cryptography, which guarantees the security of messages, at least in theory.

[bananas]

6. Slow Glass

Adapted from a classic 1960s science fiction story, Slow Glass is a project of the Movie Division of the Stereo Club of Southern California (SCSC) and was written and directed by Ray Zone.

[TalkingDog]

7. Ah... exactly. And I read that story as a teen.

Thanks!

[tclambert]

9. Slow glass, bah! I can see the past with Netflix streaming on this magic window right here.

My 3D glasses didn't quite match the colors on the video, either. The 3D effect went in and out for me.

Anyway, what I want is Fast Glass so's I can see the future. Preferably something stock market or lottery related.

[Lenomsky]

14. Laymans terms ..

So they fire a laser (photons) at a chunk of rock (crystal) and the interaction (<insert weird science stuff&gt means it's now transparent so another laser is fired at the (now transparent) rock and first laser is switched off so rock is now opaque again and the photons trapped bounce around inside the rock until it's state changes and the delayed photon's are released .. is that about right basically in simple terms?

The quantum communications part I'd need to read more - so can we assume the photons lose energy while trapped? So would need to be regenerated in a similar-ish fashion to modern day Optical Amplifiers thus that's why quantum communications is only at the 143km limit so far. I know in Optical Communications Systems you can only use Optical Amplifiers over a defined distance before it must be regenerated electrically with error correction before retransmission.

Above my pay grade but interests me nonetheless.

[xocet]

4. Here is the paper to which is being referred in the OP...

http://physics.aps.org/featured-article-pdf/10.1103/PhysRevLett.111.033601

[bananas]

5. Slow glass is a fictional material in Bob Shaw's short story "Light of other days" (Analog, 1966)

http://en.wikipedia.org/wiki/Slow_light#Slow_light_in_fiction

Slow light in fiction[edit]

Slow glass is a fictional material in Bob Shaw's short story "Light of other days" (Analog, 1966), and several subsequent stories. The glass, which delays the passage of light by years or decades, is used to construct windows, called scenedows, that enable city dwellers, submariners and prisoners to watch "live" countryside scenes. "Slow glass" is a material where the delay light takes in passing through the glass is attributed to photons passing "...through a spiral tunnel coiled outside the radius of capture of each atom in the glass."

Shaw later reworked the stories into the novel Other Days, Other Eyes (1972).

The slow light experiments are mentioned in Dave Eggers' novel You Shall Know Our Velocity. In the novel, the speed of light is described as a "Sunday crawl".

On Discworld, where Terry Pratchett's novel series takes place, light travels only a few hundred miles per hour due to Discworld's "embarrassingly strong" magic field.

In Maurice Renard's novel Le maître de la lumière (The Master of Light, 1933), the description of “luminite” might be one of the earliest mentions of slow glass.

These window panes are of a composition through which light is slowed down in the same way as when it passes through water. You know well, Péronne, how one can hear more quickly a sound through, for example, a metal conduit or some other solid than through simple space. Well, Péronne, all this is of the same family of phenomena!

Here is the solution. These panes of glass slow down the light at an incredible rate since there need be only a relatively thin sheet to slow it down a hundred years. It takes one hundred years for a ray of light to pass through this slice of matter! It would take one year for it to pass through one hundredth of this depth.[10]

[tclambert]

10. I'm gonna guess "light stopped" is more a figure of speech than a real physical event.

Like maybe they got it to bounce around in a storage medium for a minute before letting it bounce out. The photons still moved as fast as ever, but confined inside a small trap. Or the light was absorbed and the energy later re-emitted, looking like the original beam, but not the original beam.

Every time they talk about making something travel faster than light, the narrative seems to follow this arc. Some experiment gets a little press and stirs a little excitement, and gets my hopes up that maybe the speed of light doesn't impose a barrier we cannot break. Then the experimenters or their peers issue a clarification and admit that it just "seemed" like they broke the speed of light, but didn't really. Goddamn Einstein wins again.

[Posteritatis]

11. Slowing light and accellerating it beyond c are entirely different things

The former is, to a point, trivial - light travels slower than c in anything that isn't a vacuum. The challenge is how much slower a given material can make it, which is what the article's talking about.

I'm not sure how you're getting FTL anything out of that.

[tclambert]

12. Because if a photon actually moved slower than c in any case, it would imply variability of c.

Like say, if a photon actually moved 33% slower in a pane of glass, moving through the vacuum between glass molecules, it would mean you could vary the speed of light depending on circumstances. But once again, that's not the way it really works. It seems so from outside the pane of glass. Inside, though, an absorption and re-radiation delay between atoms occurs. The photons still move at c. Saying light travels slower in a non-vacuum isn't exactly correct. It propagates more slowly. That's because it isn't always traveling. For part of that time, it gets absorbed, and after a short delay it is re-transmitted and begins traveling at c again.

So I expect they will subsequently say this experiment didn't bring the speed of light to zero, but simply stored the energy of the light in this substance in such a clever way that they could later release that energy in a duplicate of the original pulse, thus communicating the original information content. Which doesn't sound nearly as exciting. No time travel. No defeating the tyranny of c.

[Peace Patriot]

13. Thank you for that lucid explanation! nt

[Saviolo]

16. I dunno...

... it still sounds pretty exciting to me! To actually store information (they said in the article that they had stored a pattern of stripes that were recreated when the light was released) in that form sounds pretty amazing. I didn't understand most (by a wide margin) of what the article was talking about, but to have light enter in a pattern, be held in a crystal for 1 minute (even bouncing around and still moving within), and then released while maintaining the information... it sounds pretty exciting to me!

But then, I'm easily impressed