Scientists slow the speed of light

[Surya Gayatri]

http://www.bbc.com/news/uk-scotland-glasgow-west-30944584

A team of Scottish scientists has made light travel slower than the speed of light.

They sent photons - individual particles of light - through a special mask. It changed the photons' shape - and slowed them to less than light speed.


Photons were shown to reach the "finishing line" at different times


The photons remained travelling at the lower speed even when they returned to free space.

The experiment is likely to alter how science looks at light.
...
The speed of light is regarded as an absolute. It is 186,282 miles per second in free space.

Light propagates more slowly when passing through materials like water or glass but goes back to its higher velocity as soon as it returns to free space again.

Or at least it did until now.

...

It's because photons exist in the exotic and rather wonderful quantum realm, where the rules of the reassuringly solid world in which we live tend to lose their grip.

They exhibit what physicists call "wave-particle duality": they behave like both a wave and a particle. So you can send them round a racetrack two by two like particles, yet change the shape of one of them as if it was a wave.
________________________

What a weird and wonderful upside-down universe, the quantum sphere.

[Archae]

1. Pffft. That's nothing, the creationists have declared light used to be faster!

That way objects billions of light-years away are really only a couple thousand light-years away. (sarcasm off)

[Surya Gayatri]

11. And, 13.7 billion years were telescoped down to a mere 6,000!

Who knew?

[rock]

2. They didn't say, so I'm guessing

they got it down to around 10 mph. Finally a manageable speed.

[F4lconF16]

47. ...

Startled my coworker a bit when I laughed at this

[Orsino]

3. Nice job, Einstein.

What we need is faster-than-light travel.

[randome]

7. Who knows what new possibilities this might unleash?

Maybe something exotic like interstellar travel will be possible by slowing light to a certain wavelength around an object? Physics is stranger than science fiction can emulate.
[hr][font color="blue"][center]No squirrels were harmed in the making of this post. Yet.[/center][/font][hr]

[Orsino]

13. Wouldn't be the first time Scotty saved us by reversing the polarity. n/t

[randome]

17. Or The Doctor!

Reversing the polarity cures many ills!
[hr][font color="blue"][center]No squirrels were harmed in the making of this post. Yet.[/center][/font][hr]

[stevenleser]

25. I'm a doctor not a pole dancer! nt

[randome]

29. OTOH, it's long past time for a female Doctor.

We need a woman's perspective on things like Silurians and Daleks. Stat!
[hr][font color="blue"][center]No squirrels were harmed in the making of this post. Yet.[/center][/font][hr]

[Paulie]

59. We had Romana

And she was smarter, both in thought and dress...

[packman]

39. Yes, but was in in phase with the tachyons?

That's what I loved about Star Trek- it sounded reasonable. You kinda knew what "phase" meant, kinda understood "polarity" and it sounded right when they said things like "inter-locking sub-atomic particles" So when they said things like "Reverse the polarity on the phase couplings to disrupt the inter-locking sub-atomic particles," You said, - Yah, shit- that'll work.
l

[randome]

50. True. At some point we tired of 'real' science fiction and opted for more of a fantasy blend.

Hard to say if that was the right way to go but it was probably inevitable.
[hr][font color="blue"][center]If you don't give yourself the same benefit of a doubt you'd give anyone else, you're cheating someone.[/center][/font][hr]

[tabasco]

71. Zackly what I was thinkin'

Them quantums sure is funny little critters!

[KingCharlemagne]

9. I blame Scottish parsimony, myself. (I'm Scotch-Irish, so hope I've earned

a pass on the prohibition on ethnic jokes

[closeupready]

10. That's a good point - if humans can alter the speed to make it slower, we can speed it up

it would seem, logically.

[KingCharlemagne]

15. If light is energy, how can we go faster than energy itself? - nt

[closeupready]

35. If we can alter the speed of energy in one direction, one would think

we can alter it in the opposite direction, no? It just seems logical - whatever you did to slow it, do the opposite to speed it.

I'm not a scientist, just thinking out loud here.

[KingCharlemagne]

48. Problem is that increasing the velocity requires additional energy. If light is the

purest form of energy, how can energy be applied to make mass travel faster than the purest form of energy? I don't want to be a Puritan and say nothing can ever travel faster than the speed of light but, based on what I know of science and physics, right now nothing can travel faster than the speed of light.

[Fantastic Anarchist]

52. The universe, itself, is expanding faster than the speed of light. n/t

[KingCharlemagne]

53. I'm not a physicist, so I can't say 'yea' or 'nay' to that

assertion. But do you have a link that supports it?

[Fantastic Anarchist]

61. It's due to inflation occurring a trillionths of second after the Big Bang:

I found one article, but there are many more. The fact that the Universe, or rather, space-time, is expanding faster than the speed of light has been accepted science for quite a while. Also, Einstein never placed a speed limit on time explicitly outside of space-time. He actually said:

"The principle of the constancy of the velocity of light is of course contained in
Maxwell’s equations."

"For velocities greater than that of light our deliberations become meaningless; we shall, however, find in what follows, that the velocity of light in our theory plays the part, physically, of an infinitely great velocity."

He's talking about light between two bodies within their relative framework. Nothing is mentioned about what's above the speed of light, if one can assume that the speed of light barrier (the precise measurement) could be bypassed or overcome. Sort of like if nothing can travel at 100 mph, then you assume nothing could travel at 101 mph. This is faulty logic when dealing with quantum mechanics. It seems intuitive, but if the 100 mph could be bypassed, or overcome without ever reaching that speed, it could still be possible to travel at 101 mph or above.


Excerpt from ScienceLine:

Now that we have a taste for Einstein’s theory, we know that baseballs don’t go faster than the speed of light. But is there anything that can? It turns out that the speed of light is only a limit on objects – like baseballs – as they move through space. The movement of space itself, however, can make the speed of light seem slow.

Right after the Big Bang, the universe had a monstrous growth-spurt called inflation. The whole thing was over in less than a trillionth of a trillionth of a second, but the universe grew exponentially in that brief blip, repeatedly doubling in size. At the end of inflation, although the universe was still smaller than a car, the outer edge had traveled many times faster than the speed of light. Since then, the universe has continued its expansion, but at a more reasonable, steady pace.

This ultra-fast growth seems to contradict what we’ve just discussed, but it makes sense if you understand the distinction between expansion and motion. When astronomers say that the universe is expanding, they’re talking about the rather abstract concept of space-time. Basically, space-time is the three physical dimensions of our existence-length, breadth and depth-combined with the additional dimension of time; think of it as a wire grid that connects every part of the universe to every other part. When we say an object has motion, we’re referring to its change in position relative to the space-time grid. The speed of light is only a constraint for objects that exist within space-time, not for space-time itself.

[KingCharlemagne]

63. Mind-blowing stuff, this is. Appreciate your digging out the extract - looks like

I need to free my mind from the petty constraints of the space-time continuum

[Fantastic Anarchist]

66. LOL ...

It blows my mind every time I think of it. I don't claim to understand it. It just is. But pains me to figure out why????



Love this stuff, but I'm basically, as we all are, an infant trying to learn about things as incomprehensible as quantum mechanics, and just think about the stuff we haven't observed directly or indirectly!

[closeupready]

57. Do you know much about quantum mechanics? Or, like me, did you read Timeline,

the Michael Crichton thriller? He did a terrific job several years ago of explaining some of the basic implications of quantum theory and how it explains reality and what might be possible.

I mean, a school of thought which implies that there are many universes is a school of thought that could explain how humans could possibly make the impossible ... possible.

Cheers.

[KingCharlemagne]

60. I take the Socratic line, i.e., the only thing I know is that I know nothing. I have not

read the Crichton book b/c, as I recall, Crichton is a RW asshole and life's too short. I have read Richard Rhodes' The Making of the Atomic Bomb which has an excellent discussion of the development of quantum physics embedded within it. As a kid, one of my all-time favorite books was Madeleine L'Engle's A Wrinkle in Time (which should appeal to every non-authoritarian Democrat

[Fantastic Anarchist]

69. I love that quote, too.

And it's so true.

Kind of along the same lines (not dealing with quantum physics per se). You may want to read about Demon Core "Tickling the Dragon's Tail" (No, it's not a move or book; it's a real-life event) about the research that went into building the atomic bomb. One scientist got careless, and the core went super-critical. Actually, it went super-critical twice within the span of a year and killed two scientists.

We gained some knowledge about radiation sickness from these events.

Demon Core at Los Alamos (Wiki)

[closeupready]

79. Oh, Wrinkle in Time, yes! Another fan here -

didn't like the film too much, though.

[Fantastic Anarchist]

68. I want to see Interstellar ....

Kip Thorn was an adviser to the director/producer.

[Rex]

82. In theory some things might move faster than light.

Tachyons, also the observance of quantum entanglement. The quantum world is strange and doesn't follow the same laws as Newtonian physics.

Quantum entanglement has implications way beyond speed or distance. It seems to defy all understanding.

http://en.wikipedia.org/wiki/Quantum_entanglement

[Surya Gayatri]

14. But, just being able to play with and manipulate this "constant"--

who knows what this may mean in future?

[Avalux]

28. If one is possible, so is the other.

Actually, ANYTHING is possible, we just have to believe it is, and step outside our self-limiting brains.

[F4lconF16]

46. That's exactly what they're doing!

If we get light to go slow enough, then we can go at our normal speeds and be going "faster than light"

[FiveGoodMen]

83. If you slow the light down ENOUGH...

...you might be able to travel faster than it.

(Shoot! F4lconF16 beat me to it )

[Marr]

4. Wow-- this will be very interesting to follow.

As I understand it, it would have big implications for the nature of light. Thanks for posting.

[Surya Gayatri]

5. De rien...! (you're welcome.)

[Avalux]

6. Quantum physics gives me goosebumps!

So....if we now know light can be slowed below 186, 282 mps - it opens the door of possibility for light to travel FASTER than 186,282 mps. This, and things like the double slit test, prove that our reality isn't all that it appears to be. The laws of physics, as we know them, may not be as absolute as we are so sure they are.

I just want to live long enough for us to figure out how to 'appear' in another time and space altogether, without the need to travel by conventional means.

[Surya Gayatri]

20. Well, philosophers and mystics have been telling us this since time immemorial...

"...our reality isn't all that it appears to be. The laws of physics, as we know them, may not be as absolute as we are so sure they are."

[KingCharlemagne]

23. See also Shakespeare: "There are more things in heaven and hell, than are dreamt

of in thy philosophy, Horatio."

~Hamlet

[Surya Gayatri]

27. Ah, a Shakespearean, after my own heart...

[Bluenorthwest]

38. The actual quote is as follows:

There are more things in heaven and earth, Horatio,
Than are dreamt of in your philosophy.
- Hamlet (1.5.167-8), Hamlet to Horatio

[KingCharlemagne]

42. Ah, geez, my sloth will get me every time. I neglected to look up

the actual quote, relying instead on a rather hazy memory. (In my defense, I think I got the gist of the quote right.)

Thanks for the annotation and I'll try to cite the actual quote from now on.

[Surya Gayatri]

45. Thanks, Blue, I knew that, as a former teacher of English Lit., but didn't want to shoot down KC...

[Avalux]

30. And because what they say cannot be proven physically....often discounted.

I am a scientist, so I live scientific theory and experimentation every day. But I also know that there is so much we cannot explain through science, at least not yet.

Take dark matter - it is thought to make up about 85% of the universe and scientists believe it exists, it's there, but it's not visible.

So what is it? We may be close to finding out.

http://physicsworld.com/cws/article/news/2015/jan/12/new-calculations-support-dark-matter-discovery-by-dama-say-physicists

[Surya Gayatri]

32. Hats off to you--so important for the scientific community to avow:

"...there is so much we cannot explain through science, at least not yet."

[Avalux]

37. It's necessary to admit it and keep an open mind.

Let's look at evolution and creationism.

The theory of evolution has remained the best possible explanation for our origins for over 150 years. There are holes for sure, and someone may come along with a completely different explanation that fits the evidence better than Darwin's theory. If that happens it will be accepted by science and we will move on. It would be so exciting!

Creationism, as is described in the christian bible, doesn't have any supporting evidence. If 'god' suddenly appeared and announced to creationists that they're wrong, they would lose their minds and might become very angry and suicidal that what they've believed isn't true.

Absolute belief in anything keeps us from expanding and progressing.

[Jackpine Radical]

67. The distinction between science and scientism is valid.

I also find certain forms of evidence (i.e. certain personal experiences) to be quite compelling in shaping my view of the universe, regardless of the fact that I cannot replicate or verify these experiences on demand.

And yeah, I'm a scientist.

[Jackpine Radical]

33. I very much believe you're right.

Bell's Theorem has stood up to more than one empirical test, and it implies instantaneous connections between particles separated by great distances.

[Avalux]

41. Loopholes!

And...everything is connected.

[pinboy3niner]

51. Wormholes! :) nt

[msanthrope]

78. Time tracks in space. nt

[underpants]

8. Gee, thanks Obama!

[hunter]

12. The immediate implication to me is that the photons are somehow forced to express

some of their energy as mass.

This one is certainly going into my mental cabinet of curiosities, of things to daydream about.

[randome]

16. Hm. Would solid light be possible, then?

Interesting.
[hr][font color="blue"][center]No squirrels were harmed in the making of this post. Yet.[/center][/font][hr]

[KingCharlemagne]

31. Sssh, don't give the capitalists any ideas! - nt

[Surya Gayatri]

49. Yeah, they'll privatize it, package it and float it on the NASDAQ...

[christx30]

76. That's an interesting idea.

Solid light. Force fields. Being able to protect something with light. Sci-fi ideas made reality.

[kentauros]

84. However, if light goes through water or glass

it speeds up again. I didn't know that, and am now wondering how it regains its momentum. Where is that energy push coming from? The idea that the mask slows the photons down is easier to contemplate than original momentum coming out of nothing/nowhere.

As an example, a car rolling in neutral will slow down if it hits a bump. The perplexing thing would be if it regained its original speed from before the bump while still in neutral

[KansDem]

18. Now, perhaps, Republicans will be able to understand it...(nt)

[Surya Gayatri]

22. Yes,......must.....slow.....it.....down.....so....they......can......catch.....on.....

[pinboy3niner]

19. Now even photons get to complain about the photon going too slow in the fast lane

[randome]

21. Oh, pinboy3niner, you light up our lives.

[hr][font color="blue"][center]No squirrels were harmed in the making of this post. Yet.[/center][/font][hr]

[KingCharlemagne]

24. Now those photons get to know what it's like on the 405 during rush hour! :) - nt

[Surya Gayatri]

26. Beep, Beep!

[DetlefK]

34. What a bunch of unphysical malarkey hiding behind a sensationalist headline.

1. Were they using single photons or a bunch of photons? They switch back and forth.

2. How do they know whether the beam stays slow on the other side? Might as well be that the mask slows the photon down, then it goes back to original speed. It still would have arrived later. Have they measured this with "racetracks" of different lengths? They don't mention so.

3. How do they think they can imprint a permanent "pattern" on a single photon? The attributes of an electromagnetic field are defined by Maxwell's equations. If you switch the environment, the equations and the structure of the field change because number and position of static and moving electric charges change. The electromagnetic field that is the photon has no incentive to keep that pattern once the influence of the mask is gone.

[Surya Gayatri]

36. Perhaps you'd like to post another OP to dissect this 'sensationalist' BBC science article?

[Maedhros]

54. Popular science writing for non-scientists is difficult.

The actual theory and experimentation details require a Ph.D in physics to understand properly. The author is translating, as best he can, incredibly complex and difficult concepts into a narrative that a reader with an 8th-grade reading level can understand. Some loss of clarity is to be expected.

You're complaining that a popular science article isn't a professional journal article.

[caraher]

55. I agree - very badly written

I've got an interlibrary loan request in for the original article, but I was able to download the supplementary materials. The answers seem to be

1. Single photons. They used spontaneous parametric downconversion to create photon pairs and manipulated them one photon at a time.

2. I'm fuzzier on this part, but they use a Hong-Ou-Mandel (HOM) interferometer. I think the pathlengths will be pretty consistent across all their measurements since they're not going to build multiple HOMs. They do address several sources of systematic error, such as variations in the refractive index of air, so I trust they've been very careful (and Miles Padgett is a very bright guy, in my experience he is both creative and careful).

3. Maxwell's Equations are being satisfied here. What the mask does is put the light into a particular transverse spatial mode, that propagates in full accord with Maxwell. One mode has a Gaussian intensity profile, another is a "Bessel beam" whose mode is a Bessel function (many of these look like "doughnuts" when you take a slice transverse to propagation).

Nevertheless, all the wild "this revolutionizes how we think of light" stuff is overblown. From what I read, they've basically observed a small correction to group velocity that should happen for any photon outside the plane wave limit. My cartoon physics notion of this is that if you think of the intensity of the instantaneous EM field as giving the probability of finding a photon within its enveloped, there's a bit of "zig-zagging" in the possible trajectories of the photon that makes its effectively average travel distance a bit longer than it would have been had it gone straight down the middle.

This isn't going to yield FTL photons, or 10 MPH photons (though there's another way to do "slow" and "stopped" light in the right kind or medium. I'm interested enough to get the full article but I don't expect it to shake physics to its core, either!

[Avalux]

58. Can you explain the other way to to slow or stop light in the right kind of medium?

Thanks!

[caraher]

81. They use something called electromagnetically-induced transparency (EIT)

This was first done in atomic vapors by Lene Hau at Harvard. Here's a general article about the technique and more recent experiments.

Back in 1999, scientists slowed light down to just 17 meters per second, and then two years later the same research group stopped light entirely — but only for a few fractions of a second. Earlier this year, the Georgia Institute of Technology stopped light for 16 seconds — and now, the University of Darmstadt has stopped light for a whole minute.

To stop light, the German researchers use a technique called electromagnetically induced transparency (EIT). They start with a cryogenically cooled opaque crystal of yttrium silicate doped with praseodymium.... A control laser is fired at the crystal, triggering a complex quantum-level reaction that turns it transparent. A second light source (the data/image source) is then beamed into the now-transparent crystal. The control laser is then turned off, turning the crystal opaque. Not only does this leave the light trapped inside, but the opacity means that the light inside can no longer bounce around — the light, in a word, has been stopped.

A more rigorous, less accessible account accompanies their Physical Review Letters article.

To stop and retrieve light pulses without destroying their quantum coherence, light coherence needs to be converted into atomic coherences. This can be achieved with electromagnetically induced transparency (EIT), a quantum interference effect that makes an opaque medium transparent over a narrow spectral range. In EIT, a control laser beam excites atomic systems with two ground spin states connected to an excited state by optically allowed transitions [see Fig. 1(a)]. Through destructive interference, the transition probability between one of the ground states and the excited state (hence the absorption at the corresponding frequency) vanishes. The change of absorption results in a very steep change of refractive index that reduces the group velocity of an incoming light pulse. Light can be slowed down to the point that it comes to a halt: by switching off the control beam when the light is within the sample, the photons can be converted into collective atomic spin excitations (so called spin waves) [2]. The spin waves can be stored in the atoms for as long as the coherence between the two spin levels survives, before being converted back into light by turning on the control pulse again. The scheme thus allows the coherent storage and retrieval of light.

[packman]

40. I suspect deflated photons

[Surya Gayatri]

43. But, how did they get inflated in the first place?

[KingCharlemagne]

44. DUzy! - nt

[bluedigger]

64. I hate it when someone goes there before me.

[tridim]

56. What happens when one photon in an entangled pair is slowed?

Hmmmmm

[MrScorpio]

62. Lazy photons

Now to get them slightly greasy in order to speed them up

[Spitfire of ATJ]

65. Wait until they learn to speed em up again....

FTL anyone?

[TexasTowelie]

70. This might be appropriate in this thread.

[Surya Gayatri]

72. Oh, no he/she didn't...Oh, yes he/she did! LOL!

[GummyBearz]

73. Somewhat misleading headline...

The speed limit of light remains at 186,282 miles/s (in this known universe). However, in the name of sensationalism, I will now attempt to move slower than the speed of light while eating a cracker I have in front of me. If I do not reply back in 5 nanoseconds, just wait longer... I'm trying to go SLOWER than the speed of light in this experiment.

[Surya Gayatri]

74. You might want to peruse this sub-thread...

http://www.democraticunderground.com/10026126912#post34

[polynomial]

75. Very curious question arises...

It’s been a journey for me these past weeks reading the book by Dan Brown “The Da Vinci Code”, all the while in studies for image processing particularly down loading a new image processing book by Richard Szeliski, fifty bucks at amazon.

Both skirt the physics in light and dark and color in particular Dan Brown describing using modern technology to validate paintings by Leonardo Da Vinci who by some critics was the Master of a secret society of the Priori Sion the keeper of the secrets of the Holy Grail. What really floored me is Da Vinci was a flamboyant gay, non of my humanities courses had that background in the sixties.

My passion is to figure out the mechanics of the Kalman Filter. Filters are also called Masks, perhaps that is what these scientists used.

Da Vinci besides being one of the first experimenters to study diffraction that is the fundamental property of light put me into a wild trip in philosophies by Penrose, LaRouche, and Feynman, and Einstein, with a new look at Maxwell and his famous four equation that explain the electromagnetic spectrum humans view as the rainbow.

Richard Feynman saying they really don’t know what these things called photons really look like yet somebody saying the shape was changed, yikes that is something. Consider that the photon has no mass how in heavens name could they possibly know the shape of the photon was changed.

[KamaAina]

77. What might one do with slow light?

Create visual effects, like black light?

New types of lasers? LEDs?

[Surya Gayatri]

80. Well, just don't let R/W capitalists get their hands on it...or

'they'll privatize it, package it and float it on the NASDAQ...'