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Science & Technology

Scientists slow down the speed of light

By T.K. Randall
January 25, 2015 · Comment icon 56 comments

The speed of light was slowed down over a range of one meter. Image Credit: CC 2.0 Andrew Adams
Physicists in Scotland have slowed down the speed at which light travels through air for the first time.
The speed of light is one of the fundamental constants of physics, yet scientists at the University of Glasgow this week announced that they had successfully discovered a way to slow light down in free space, something that has never been achieved before.

Conventionally light travels at approximately 300 million meters per second and only slows down on a temporary basis when passing through mediums such as water or glass.
Now however physicists have been able to slow light down while it's traveling through the air.

To accomplish this the team sent photons, which are individual particles of light, through a special mask that changes their shape and causes them to slow down.

"That mask looks a little bit like a bull's-eye target," said Prof Miles Padgett. "And that mask patterns the light beam, and we show that it's the patterning of the light beam that slows it down."

Source: BBC News | Comments (56)




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Recent comments on this story
Comment icon #47 Posted by Harte 10 years ago
So changing the form of the photon it can be slowed down, but regardless of the form of the photon c is still the maximum limit? Have all possibilities been scientifically demonstrated to max out at c? Here we have a experiment that demonstrated that a photon can travel at less then c in a vacuum, which till now was judged to be impossible. How can we be so quick to say that the maximum limit is also impossible to surpass? New techniques can stretch nature beyond what it would normally do. We create phases of matter that do not occur naturally. We create elements that do not occur naturally. W... [More]
Comment icon #48 Posted by DieChecker 10 years ago
There are theoretical particles - tachyons - that would always travel faster than light. If one of them slowed down to light speed, it would cease to exist. The idea of light speed as a constant is merely that light can be relied on to always travel at that speed naturally. Any massless particle would. Why it's called a "limit" is because particles with mass can't reach it. I suppose it might be possible to have a massless particle temporarily exceed c, but while it was, it would be undetectable. Harte You wouldn't have to detect it. Just know when it started and when it reached the sensor. If... [More]
Comment icon #49 Posted by Harte 10 years ago
Being more energetic wouldn't make them travel any faster anyway. No mass, remember? More energy to a photon just means a higher frequency/shorter wavelength. Harte
Comment icon #50 Posted by Noteverythingisaconspiracy 10 years ago
I think it is safe to say, that until somebody comes up with a way to increase the speed of light, it will remain constant. Like Harte says, there is a theoretical possibility that particles exist that allways travel fater than c, but so far we haven't been able to detect any. Neither directly, nor indirectly. The thing about the neutrinoes apparently travelling fater than light, turned out to be because of faulty equipment. I guess we can't say for certain that we will never be able to change the speed of light, but at the moment it isn't possible. I could imagine that we could one day be abl... [More]
Comment icon #51 Posted by sepulchrave 10 years ago
Of course this is all theory. It could be wrong. But the theory (quantum electrodynamics, QED) is the union of classical electricity and magnetism, special relativity, and quantum mechanics, and has an almost overwhelming amount of experimental evidence in favour of it. The experiment conducted by scientists in this thread is in complete agreement with the predictions of QED. So changing the form of the photon it can be slowed down, but regardless of the form of the photon c is still the maximum limit? That depends on how liberal you want to be with your definition of ``a photon''. Some phase ... [More]
Comment icon #52 Posted by DieChecker 10 years ago
Thanks for the reply Sepulchrave. I didn't understand all of that, but I know I could with a little reading. So, a way to increase the maximum speed of light, would basically be to change the parameters of the vacuum it is traveling through? Which, I'm assuming,we have no way to do at present? On a human scale anyway. And QED theory doesn't predict photons/waves being able to exceed the current max c? A quick Google search shows a couple possibilities, which QED seemed to show could have situations faster then c. http://www.newscientist.com/article/mg12617112.900-science-can-photons-travel-fas... [More]
Comment icon #53 Posted by regeneratia 10 years ago
Does anyone else think of the SF short story "Light of Other Days", Bob Shaw, on slow-glass? I always look for things that will fit into the slow-glass theory. Several recent research releases, and some within the last year, seem to be able to fit into this story. I think the speed of light can indeed be altered and/or that it is not a constant speed at the most basic level. I heard mentioned the other day that a good portion of physics will have to be rewritten and changed. Are you ready for this change?
Comment icon #54 Posted by sepulchrave 10 years ago
So, a way to increase the maximum speed of light, would basically be to change the parameters of the vacuum it is traveling through? Which, I'm assuming,we have no way to do at present? On a human scale anyway. According to theory, yes. Actually, changing the parameters of the vacuum is sort of the argument behind the Scharnhorst effect that you linked to. You can think of the Scharnhorst effect as being a consequence of a ``confined vacuum'' (the empty space between two very close metallic plates) as compared to a ``free vacuum'' (a large empty space). Although honestly I do not think the Sch... [More]
Comment icon #55 Posted by solvingthemysteries 10 years ago
Sir, the speed of Light was determined by measuring the speed of a Laser beam. Laser beam gets off from a two-dimensional flat surface of a narrow cylindrical tube, but Sunlight emanates from all around the three-dimensional spherical surface of the Sun. Moreover, Laser light travels in the form of a beam – retaining the same intensity; whereas, light emanated from the spherical Sun expands – concurrently decreasing the intensity. There are much more dissimilarity between a Laser light and the Sunlight. Therefore, the speed of light cannot be decided by measuring the speed of a laser beam.... [More]
Comment icon #56 Posted by bmk1245 10 years ago
Sir, the speed of Light was determined by measuring the speed of a Laser beam. Laser beam gets off from a two-dimensional flat surface of a narrow cylindrical tube, but Sunlight emanates from all around the three-dimensional spherical surface of the Sun. Moreover, Laser light travels in the form of a beam – retaining the same intensity; whereas, light emanated from the spherical Sun expands – concurrently decreasing the intensity. There are much more dissimilarity between a Laser light and the Sunlight. Therefore, the speed of light cannot be decided by measuring the speed of a laser beam.... [More]


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