Slashdot Mirror
Light so Fast it Travels Backward
An anonymous reader writes "Slowing down light used to be considered a neat trick for physics wonks. But researchers in New York now say they've pushed light into reverse. And as if to defy common sense, the backward-moving light travels faster than light." While there's not much use to come of it yet, it will be interesting if Einstein himself is proved wrong.
Stupid Science Stories ==> Lucy & the football
We don't see the world as it is, we see it as we are.
-- Anais Nin
Quantum Mechanics proves Einstein's theory is not one the correctly explains the entire universe just like Newton's physics did not. Why do you think Einstein was searching for a unified theory of physics?
.gnola evoM .ereh ees ot uoy rof gnihtoN
"Einstein said information can't travel faster than light, and in this case, as with all fast-light experiments, no information is truly moving faster than light," says Boyd.
Way to read the article, CowboyNeal.
A slashdotter who didn't build his own computer is like a Jedi who didn't build his own lightsaber.
I've done this too, it's called 'a mirror'.
TK
...just shift the ship's gear into R...
So, basically, what scientists have shown is that reverse light (darkness) is faster than light!
My patience is infinite, my time is not.
I hate it when headlines use the semantics of "the speed of light" to sound sensational. "The speed of light" is just used to refer to the maximum speed of information propagation because light in a vacuum travels as that speed. I can change the speed of light by wearing glasses; while experiments similar to the one in TFA are much more complex and interesting, the point is that neither one is affecting the speed of information at all.
English is easier said than done.
From a 1985 paper http://www.npl.washington.edu/av/altvw08.html/ :
When advanced-wave light travels from point A to point B it arrives at point B earlier than the time it left point A. Shortly after World War II, when radar was still new, a pulsed radar beam was first bounced off the Moon and reflected back to Earth. Measuring the round trip time of the radar pulse (about 2.5 seconds) became a very precise way of determining the Earth-Moon distance. If the same measurement were done with advanced radar waves the reflection from the Moon's surface would arrive back at the Earth 2.5 seconds before the pulse was transmitted.
From there, it isn't much of a trick to lengthen the interval with automatic repeaters which bounce the advanced waves many times, lengthening the look-ahead time from seconds to minutes or hours or even days. A computer could be hooked up to broadcast ASCII-coded advance-wave messages to the past and to receive and decode them when received. Such messages could be used in any number of schemes for fun, profit, or military preparedness. The reader who is interested in possible applications is referred to Isaac Asimov's pseudo-science-fact articles in the Astounding SF's of the 1950's concerning "thiothimoline", a kind of soluble organic crystal with the unique property that it dissolved slightly before water was added.
Guess we are almost there now.
Just think of the applications:
Knowing any stock price swing several minutes (OK, just give me one minute!) in advance.
Ah, the possibilities...
Dedicated Linux servers (root access) $45 p.M.
Last Post
...stop taking drugs.
No sig for now.
This finding will turn out to be a very arcane and unusual phenomenon, but one entirely consistent with everything we already know about physics; and every single word in this article summary will turn out to be over-simplified, over-excited vagueries with nothing to do with the actual research, created by taking the dumbed-down metaphors the scientists used to describe their findings in a press release, and then dumbed down even further by the media that read the press release
Let's see if I'm right.
Perhaps this interesting effect could be used somehow to cause light-speed spam to reverse upon itself, causing spammer inboxes to convert to pure energy, which in turn annihilates the spammers.
Hey, a fellow can dream, can't he now?
A truly excellent pizza parlor is a delight unto the heavens. Treasure the sauce and the toppings!
Well, the article says the light comes out the other end before the putting-in end has light going in, so that it goes backwards through the fiber (from the end it came out of, towards the end it came into).
What if you are about to put the photon in, and it comes out of the fiber at the other end, but you change your mind and don't put it into the going in end?
I can't wait to harness this technology. I'll be able to make First Posts without actually having to be the first poster. I will rule Slashdot!!!
Modern copyright is theft of culture from everyone and it retards the progress of the useful arts and sciences.
Doesn't anyone know the difference between group and phase velocity?
The first story was rushed out so fast it hasn't gotten here yet.
It has to explained out all over again every time an article of that type gets posted: phase velocity can exceed the speed of light in a vacuum, group velocity cannot.
Also, some of us don't know the meaning of "Two Words."
I have freaks! I did something right...
Group velocity is what carries information, faster than light phase velocity is perfectly ok with Einstein's theory.
\u262D = \u5350
They got Chuck Norris to roundhouse kick the regular light until it started moving backward!
light traveling backwards, wtf
Heat is atoms vibrating, and so we think absolute motionlessness - absolute zero - is the lowest possible temperature. But taking the concepts from this slashdot story, it's obvious we can make it even colder - by having them vibrate in the opposite direction!!! OK, can I have my Nobel price now?
Trust the Computer. The Computer is your friend.
If you add too much to a long or short or char variable, you get a negative number if the variable is signed. It seems we are programmed in C.
If they can accelerate late by making it go backwards..
I guess we can expect less lag in the future. But as a side effect you find yourself getting fragged in quake than reciving the data of the rocket that hit you moments later.
...when you look around the other way, things move in the opposite direction.
Freedom is strength, Ignorance is peace, War is slavery.
This is nothing new. Materials with negative indexes of refraction have been used in experiments before. Here is the abstract of their article in Science:
"Simultaneous Negative Phase and Group Velocity of Light in a Metamaterial"
"We investigated the propagation of femtosecond laser pulses through a metamaterial that has a negative index of refraction for wavelengths around 1.5 micrometers. From the interference fringes of a Michelson interferometer with and without the sample, we directly inferred the phase time delay. From the pulse-envelope shift, we determined the group time delay. In a spectral region, phase and group velocity are negative simultaneously. This means that both the carrier wave and the pulse envelope peak of the output pulse appear at the rear side of the sample before their input pulse counterparts have entered the front side of the sample."
The Matrix must be using two's complement arithmetic and the overflow must not've been caught.
"No one likes working in a hamster wheel, and your shop smells of cedar shavings from here." - TaleSpinner
Light's Most Exotic Trick Yet: So Fast it Goes ... Backwards?
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.
Confused? You're not alone.
"I've had some of the world's experts scratching their heads over this one," says Robert Boyd, the M. Parker Givens Professor of Optics at the University of Rochester. "Theory predicted that we could send light backwards, but nobody knew if the theory would hold up or even if it could be observed in laboratory conditions."
Boyd recently showed how he can slow down a pulse of light to slower than an airplane, or speed it up faster than its breakneck pace, using exotic techniques and materials. But he's now taken what was once just a mathematical oddity--negative speed--and shown it working in the real world.
"It's weird stuff," says Boyd. "We sent a pulse through an optical fiber, and before its peak even entered the fiber, it was exiting the other end. Through experiments we were able to see that the pulse inside the fiber was actually moving backward, linking the input and output pulses."
So, wouldn't Einstein shake a finger at all these strange goings-on? After all, this seems to violate Einstein's sacred tenet that nothing can travel faster than the speed of light.
"Einstein said information can't travel faster than light, and in this case, as with all fast-light experiments, no information is truly moving faster than light," says Boyd. "The pulse of light is shaped like a hump with a peak and long leading and trailing edges. The leading edge carries with it all the information about the pulse and enters the fiber first. By the time the peak enters the fiber, the leading edge is already well ahead, exiting. From the information in that leading edge, the fiber essentially 'reconstructs' the pulse at the far end, sending one version out the fiber, and another backward toward the beginning of the fiber."
Boyd is already working on ways to see what will happen if he can design a pulse without a leading edge. Einstein says the entire faster-than-light and reverse-light phenomena will disappear. Boyd is eager to put Einstein to the test.
So How Does Light Go Backwards?
Boyd, along with Rochester graduate students George M. Gehring and Aaron Schweinsberg, and undergraduates Christopher Barsi of Manhattan College and Natalie Kostinski of the University of Michigan, sent a burst of laser light through an optical fiber that had been laced with the element erbium. As the pulse exited the laser, it was split into two. One pulse went into the erbium fiber and the second traveled along undisturbed as a reference. The peak of the pulse emerged from the other end of the fiber before the peak entered the front of the fiber, and well ahead of the peak of the reference pulse.
But to find out if the pulse was truly traveling backward within the fiber, Boyd and his students had to cut back the fiber every few inches and re-measure the pulse peaks when they exited each pared-back section of the fiber. By arranging that data and playing it back in a time sequence, Boyd was able to depict, for the first time, that the pulse of light was moving backward within the fiber.
To understand how light's speed can be manipulated, think of a funhouse mirror that makes you look fatter. As you first walk by the mirror, you look normal, but as you pass the curved portion in the center, your reflection stretches, with the far edge seeming to leap ahead of you (the reference walker) for a moment. In the same way, a pulse of light fired through special materials moves at normal speed until it hits the substance, where it is stretched out to reach and exit the material's other side [See "fast light" anima
The main problem is that physics research is being more and more geared towards being appealing to people who don't know physics, hence all the BS taking advantage of phase/group velocity confusion, wanking about various string theories, etc. Sure, it's nice to let people know what's going on in physics, but in the end if they get the impression that most physicists are excited or even remotely interested by simple tricks like this, I don't think it bodes well.
I've been curious about this for a while... so someone please explain where I am missing the obvious.
;-)
Would not two photons/beams of light travelling in opposite directions be moving faster than the speed of light *relative* to one another?
I'm sure I'm missing something... so please, rip apart the above over-simplified statement. I hope to learn something by observing the process.
Akarsz Magyar Gentoo fórumot? Akkor
See original press release with animations.
This was posted next week.
The Kruger Dunning explains most post on
Here's a better analogy to use when visualizing this phenomenon. Let's think for a second of meridional rays on a subatomic level, wherein light will function as a wave. When the meridional rays bounce off of subatomic particles and speed up in a different direction, the process in a closed thermodynamic system would theoretically continue onto infinite. This would be sufficient evidence of perpetual and exponentially increasing inelastic motion, but not of heat being created in a closed system, therein violating the laws of thermodynamics.
Because we have in this optic fiber an open thermodynamic system, heat is able to seep into the outer system. This is just one of the many pieces of evidence I am gathering against the Green Socialist Party to prove that global warming due to industrialization is an absurd liberal myth. We can all agree that global warming can be factually supported, but not for the same reasons that the Green Reich offers. The article offers proof that global warming exists as a slow-moving process at a sub-atomic level, and has been a threat widely blown out of proportion.
Wasn't it called the Ferris Bueller Ferrari Effect?
Hope the Eschaton doesn't find out...
See also Primer.
...the reflection from the Moon's surface would arrive back at the Earth 2.5 seconds before the pulse was transmitted.
So what if we got the signal, then turned OFF the transmitter? Where does that extra energy come from? I was never one for quantum physics.
"Beware of he who would deny you access to information, for in his heart he dreams himself your master."
This does not disprove Einstein's theory, it only exposes a flaw in the implementation. For some reason the idiot who implemented it didn't use a large enough data-type to store c, causing it to overflow in certain situations.
- These characters were randomly selected.
There's an experiment we give the students to see if they are applying Cook's constant. We have them send energy down a slotted waveguide and get them to measure the wavelength. Given the frequency and the wavelength, they can calculate the velocity of propagation. What they calculate exceeds the speed of light. Those who are inclined then apply Cook's constant so that the velocity does not exceed the speed of light. Gotcha!
/.ed but strongly suspect that something similar may be happening here.
The trick is that at a high enough frequency, the wavefront is no longer orthogonal to the waveguide. Therefore the distance between the measured peaks is longer than the wavelength. Therefore the honest students calculate a velocity of propagation that exceeds c.
I can't read tfa because it is
http://gregegan.customer.netspace.net.au/APPLETS/2 0/20.html
No information ever acutally travels faster than the speed of light.
Nice visual explanation anywho.
How will this help in the developement of the lightsaber?
Must be a hell of a show watching it on LSD
Is that kinda like "(unsigned long)-1"?
The article was pretty confusingly written so I can't be totally sure what is going on but i think this only sounds cool because we confuse the speed the actual photons travel and the speed the wave appears to travel.
It is perfectly possible to get *effects* from light that appear to travel at faster than the speed of light. Just take a flashlight in a super huge room and whip it around really fast. The spot of light on the wall may very well 'travel' faster than light but no actual photons traveled faster than light so this isn't a problem.
While this experiment is somewhat different I believe a similar confusion makes it sound way more interesting than it really is. In particular there are two different speeds one needs to talk about when you are talking about how fast light goes. There is the speed at which a crest of the wave advances and then there is the speed that a photon travels (probably some other ones too than I'm forgetting). I believe all this experiment is doing is making it so the crest of the wave appears to travel faster (or with negative speed?) than light even though all the photons in the light are not moving faster than light.
Thus it is a big analagous to the flashlight case where you have some effect (in this case the crest of the light wave) which appears to move faster than light even though no actual photons or information is really doing so.
To give an idea of how this could happen (though not the mechanism here) imagine a bunch of rods in a row like this:
_____ (time 0)
Now suppose we put activators under these rods to raise them at prearranged times. If we did this right we could get a 'wave' moving like this:
-______ (time 1)
--_____ (time 2)
_--____ (time 3)
__--___ (time 4)
Now if we timed the activators right we could make this 'wave' travel down the line arbitrarily fast (in principle even faster than the speed of light) even though no information or particle is actually being moved that fast.
While clearly the mechanism is different in this case I believe this is all that is happening. Namely the peak of electric field moves faster than light (or negative?) even though no real thing is doing so.
If you liked this thought maybe you would find my blog nice too:
You see I can picture a car going forward and back. It has a front and a back. This plus the convention of designation means that one is forwared and one is Reverse. However with light this seems a bit odd. I mean if you had a perfect mirror and held it at exactly 90 degrees to the beam of light would it be going backwards or forwards to where it came from. I suppose if I think of it as obsorbtion, in that the origination source takes back the energy it pushed out it could be considered backwards. But then wouldn't this make a black hole a reverse Sun? In short. This is most likely why I'm in applied Physics (EE) not Theoretical Physics.
I'm sorry, I'm to tired to be witty at the moment so this message will have to do.
Once, I saw Chuck Norris across the street, I ran away from sheer terror and wound up 5 minutes in the past.
To understand how light's speed can be manipulated, think of a funhouse mirror that makes you look fatter. As you first walk by the mirror, you look normal, but as you pass the curved portion in the center, your reflection stretches, with the far edge seeming to leap ahead of you (the reference walker) for a moment. In the same way, a pulse of light fired through special materials moves at normal speed until it hits the substance, where it is stretched out to reach and exit the material's other side [See "fast light" animation].
Conversely, if the funhouse mirror were the kind that made you look skinny, your reflection would appear to suddenly squish together, with the leading edge of your reflection slowing as you passed the curved section. Similarly, a light pulse can be made to contract and slow inside a material, exiting the other side much later than it naturally would [See "slow light" animation]. - way to describe convex and concave mirrors/lenses.
You can't handle the truth.
This looks a lot like exploitation of transmission line effects, rather than anything particularly special to do with the properties of light
If you put a laser on an rotating mount on an artifical satillite halfway between the earth and the moon, and pointed it such that the dot it generates appears on the earthward side of the moon at one point of it's cycle, and on the surface of the earth at the opposing point of the cycle, and the cycle took less than 2.5 seconds, the dot would be 'moving' faster than the speed of light.
That's why you can play with a cat and a hand-held laser pointer and the dot can move faster then the cat, but smack a cat on the head, and your hand can't escape fast enough to avoid injury.
A paradox occurs and the earth explodes.
Sorry my bullshit sensor overloaded.
We know that we exist in multi-dimensional universe. Not like monster from a parallel dimension, but rather dimensions such as width, length, height, and time. Is it possible that they accidentally skewed the photon of light slightly off the four dimensions we can perceive and went back on the time axis?
You say things that offend me and I can deal with it. Can you?
Folks, let's PLEASE keep in mind that you don't actually change the speed of light. What you're changing is the _apparent_ speed of light. Light appears to slow in a medium because stuff is absorbing and re-radiating it, holding it for a short while and changing its apparent speed. You never actually make photons move any slower.
Course, as it's been said - this was fiction, so it had to make sense. :)
Have you been touched by his noodly appendage?
Maybe it's just going so slowly it appears to be? Make the cheque payable to BoxSocial please.
Give me good ratings or I will close down the internet.
"I know this all sounds weird, but this is the way the world works,"
says Boyd.
Warning:: Reading the article may cause brain cells to ignite!
(Brain... Burning...Please... Stop!)
who the *** is chuck norris
every day http://en.wikipedia.org/wiki/Special:Random
"it will be interesting if Einstein himself is proved wrong"
He won't be, that guy was a being from another universe.
I honestly don't know if the receiving prior to sending thing is bunk or what, I am not a physicist.
However, I believe it would be safe to assume that the prior to sending beam could only appear if you were in fact going to send the beam, as in whatever dimension that allows this to happen, the beam is a single thing moving all at once through space and time, and not travelling unusually at all. It still has to be sent from the one time point to appear at the next. Or previous in this case. I think what I'm saying is the information would have velocity through time only if granted its equivilent of force.
If we were able to receive and then not send, it would be an odd inconsistancy in things.
They're there affecting their effect.
Finally! An explanation of how spinner rims can appear to be moving backwards while the wheels are turning the other direction!
Now I can see the light at the front of the tunnel!
Read it if you are somewhat familliar with maths - its rather interesting
I think either the erbium is causing the photons to resonate at a higher frequency, or the erbium itself is transmitting the pulse data before the actual pulse can make it through.
(btw, nice human-verification word for this submittal:
"please type the word in this image: b o n e r s " )
lol...
It takes just a moment and an action to destroy. It takes some time and thought to create.
But I have to confess that I don't get it.
I'm confused about the information transportation.
I get the same confusion with entanglement experiments.
From the article: "We sent a pulse through an optical fiber, and before its peak even entered the fiber, it was exiting the other end..."
If the pulse (or its "leading edge" or whatever other phenomena created by the input) can be detected at the other end wouldn't just its mere presence there be already an information ?
For example I want to tell Lucy (that is in the other end of the fiber) that Charlie Brown just arrived.
I press a button and there goes the pulse of light through this weird aparatus.
Then Lucy detects the whatever phenomena is generated aparently instantaneously on her end of the fiber and this is the notification that Charlie Brown has entered the room.
Wouldn't I have transmitted information (Charlie Brown arrived) faster than light ?
I've read the post about phase propagation but the same thing:
Is the phase change detectable ?
If it is not how do we know it was propagated faster than light ?
If it is detectable then isn't that phase change per se a piece of information travelling faster than light ?
What am I missing here ? :)
Knowledgeable Slashdotters, please illuminate my thoughts and rescue me from the darkness of the ignorance.
Thank you for your attention.
"Think globally, act locally".
Aaah... see now instead of the people displaying how big their brains are, someone actually thinks to post to a link with a picture of why something can "appear" to travel faster than light. WITHOUT the need for stupidly complex formulae! Thanks!
I refuse to have a sig... dammit!
" But researchers in New York now say they've pushed light into reverse. "
Ah, when I were a lad, back in the days before this backwards superluminal light was deeply researched it was known more commonly as reflection.
That's very funny, but we heard you the first time.
There's a Starman, waiting in the sky / He'd like to come and meet us, but he hasn't got the time.
Speed isn't velocity. Speed isn't direction...
Where you can send an electron faster then the speed of light. Now let me explain. Speed of light in that medium is about 0.6c, where c is the speed of light in a vaccum. Electrons go about 0.8c. Relativity says nothing about whether you can break the speed of light, what it says it that you can't exceed the speed of light in a vaccum.
Whatever happened to just going 88mph?
There is such thing as time symmetry in physics. It is nonsense to say the light travelled back in time. The distinction of the "direction" of time is an observed one; it is not inherent. So I may as well say that I am living backwards, the world is spinning backwards, etc.
If I understand Dirac correctly, his meaning is this: there is no God, and Dirac is his Prophet. -Pauli
Faster than light, yes. Transferring information, no.
And as space has no negative coordinates, the light must be travelling through some sort of E-space. http://en.wikipedia.org/wiki/Warriors'_Gate
Positive speed causes the expansion of space, negative speed causes the contraction of space.
Whoa. This is heavy.
I smell time travel. Where do I sign up?
You are welcome on my lawn.
The giant spider Ungoliant had that unlight going thing some four Ages ago!
I'm pretty sure hers wasn't electric though, and the whole chance of having her devour you sort of made it impractical. Not to mention the whole giant spider thing.
On second thought I like your idea a lot more.
I read TFA. I didn't get it. I read the /. comments. I got some laughs but that's about it.
Can someone break this down into 3 year old talk and explain to me what this all means, or, better yet, send me some other FAs that are closer to my level of physics knowledge (about zero)?
Love sees no species.
(lim m->infinity)/(lim m-> infinity) = 1... because any number divided by any number is 1 (infinity is not a number) (we'll ignore zero for the moment)... If you have rather (lim A->infinity)/(lim B-> infinity) then the answer all depends on what A and B are... the answer could be zero, 1, any real number, or infinity... It all depends on which infinities you are dealing with. If the larger infinity is on the bottom then it all equals one, if the larger infinity is on the top then it all equals infinity, and if the infinities are the same then it will equal some real number... But what you have set up is a number divided by itself (assuming the infinities are the same)...
as far as I can remember
So the outcome of this experiment came from the past, just like the light it measured.
I vaguely remember reading in a text book that the math for light works both forwards in time and reversed, but I guess no one ever looked for the time reversed light before.
Does anyone remember if Fynman talked about this?
Except for the collapse of a quantum wave function upon a measurement... there's not actually time symmetry there, nor in the (related) measure of entropy; in one direction it always increases, in the other it decreases, and it's not symmetrical in the least.
I agree, those are my questions exactly, and no one has properly addressed them... Though as I have been reading I was thinking of the possibility that it's a simple phase shift... they measure the white light as it travels, but the multiple light forms move at different rates, so there is a delay between when this phase shift starts and whent the light enters the medium, so the over all time it takes for this to travel is the speed of light (or slower) because of the delay, but when the delay is over it appears to move faster than the speed of light... so something does indeed happen faster than the speed of light, but it was all set up to happen in the first place, and the over all exchange only happened at the speed of light?
I'm really just shooting in the dark here, trying to put things together... And all that group velocity vs phase velocity vs. (I think it was called) source velocity (that's not right, but there were three types)does not help. In fact, it just sounds like a bunch of college students with some fancy terms attempting to sound intelligent. If you can't reduce it to common-man terms then I doubt you properly understand it.
This site has a java applet that shows how light artifacts can move faster then c or go backwards.
2 0/20.html
http://gregegan.customer.netspace.net.au/APPLETS/
The collapse of the wave function is a cute exception, but really isn't well understood enough (there are many who think "collapse" is not the best way of describing what happens) to shed light on the time problem. Entropy is an emergent phenomenon. It is not the cause of the direction of time, it is a handy way of checking time against our notion of its direction.
I will make this easy for you. The fundamental laws of physics all obey CPT symmetry.
If I understand Dirac correctly, his meaning is this: there is no God, and Dirac is his Prophet. -Pauli
I don't understand how you could measure it through the fiber optic cable. All instruments that you use operate at the speed of light, therefore if it ran faster then the spead of light couldn't it be missed in the middle anyway? I'm sure these geniuses are smarter than I, just trying to understand how they could measure it.
I'm a Physics grad student who just happens to be doing my Master's project on negative index materials (or commonly known as NIM). I'm not an expert in this subject but our reseach group actually discussed this same subject last week. The point here is that the individual photons are not moving faster than light. In fact (what I was told by my professors and others) is that the pulse going in is NOT the same pulse going out. It's the front end 'tail' of the pulse which 'piles up' to become a new pulse which is seen coming out the other end in the shape of the original pulse. The incoming 'peak' of the pulse collapses (actually a portion of it gets reflected which for some reason doesn't ever show up in these simulations of the phenomenon) so only a portion of it exists after going in (I see this in my 1D FDTD simulation all the time). There is actually alot of distortion of the pulse at the interfaces (and inbetween) to the point that it's hard to say what is the original pulse and what isn't. In fact, if you just send light in with no 'peak' you will still detect a 'peak' coming out.
if they are saying that the light gets to the end before the middle of the light gets out, or whatever, then what abouot using this in networking computers, if its faster than the speed of light, which is supposed to be what fiber optics is right? with copper and regular cable, the electricity is , i think, supposed to move pretty fast, if you have two wires make a jump across eachother, it is light that we see, but given everything like resistance of the cable of copper, and its not the same speed of light, plus with routers and latency, and length of cable attenuation. fiber optic is better because its supposed to go at the speed of light, which is carrying information down this thin glass tube, but if information is what this light is, pulses of light acting as binary code, then the light that went faster. even if its backwards, will it produce light at the end faster than normal light creating information for a fiber optic cable? and also, wouldnt this mean carrying information faster than the speed of light? if i am being ignorant on this, say something more correct. peace
I read about this over a year ago when someone else accelerated light to 300x it's normal speed and it came out a very tiny fraction of a second sooner than it started. This just means someone has managed to duplicate it since that particular experiment was in doubt.
It's so dark in here, I think I'll turn on my flashlight.... Ack! My eyes!!! Too bright!!!!
Wait a second - if we make light go faster than the "speed of light", then doesn't that just mean we miscalculated something!? If I can run faster than I can run, its because I thought I was slower than I actually am.
Seems to me that inside of a speed for light, its just variable speed and we have calculated its speed in a normal situation and labeled it the speed of light.
"Boyd is already working on ways to see what will happen if he can design a pulse without a leading edge. Einstein says the entire faster-than-light and reverse-light phenomena will disappear. Boyd is eager to put Einstein to the test."
Way to read the article, Lord Ender
Jumping to the last paragraph of the article explains the physics very well. Observe that this is occurring in an erbium doped fiber, an amplifier. Hence, the pulse at the output is the amplified leading edge of the pulse and the physics is related to gain saturation. Now, imagine a full tube of toothpaste. Moreover, let's say you gently squeeze from the bottom of the tube to the top. Clearly, you get a lot of toothpaste and if you then do the same thing again, squeezing a tiny bit harder, you get even more toothpaste. However, as you do this you're using up the toothpaste and eventually it will run out. Obviously, at this point, even though you're squeezing harder, you're not getting more toothpaste. In the very end, there's no toothpaste left, and nothing comes out no matter what.
Analogously, the same thing is happening here. The toothpaste tube is the fiber, the toothpaste represents the amount of gain, and how hard you squeeze is the amplitude of the light.
Going back to the experiment, the "leading edge" of the pulse has a VERY SMALL amplitude, but it's amplified a whole lot; that's the start of the exit pulse. Minimally larger is the amplitude of the next part of the pulse, but since there's a lot of gain left, we get an even bigger amplitude at the output than before. After a while, it balances out, giving us a peak in the output and since most of the gain is used up, even though the input amplitude can be bigger than the start of the pulse, it doesn't see as much gain. In fact, it might see absorption (someone confirm this). Lastly, by the time the peak of the input reaches the input end, there's no gain left, and nothing comes out the other end.
Deconstructing the wavepacket into it's components, resetting the amplitude and phase, and reconstructing a new wavepacket is a more general way to explain this. Obviously, the tricky part is how to physically realize an arbitrary amplitude and phase readjustment; not an easy task by any means. Though you might be able to come up with a scheme, often the consequence is that there's no signal left at the end to measure!! (old days of trapped light/working at an aborbtion edge)
Can someone else explain the backward moving pulse inside? Ouch, my brain hurts now. Most of *my* gain has been used up. =)
The problem is that it's about Chuck Norris, instead of Jack Bauer.
Once, someone tried to tell Jack Bauer a knock knock joke. Jack Bauer found out who was there, who they worked for, and where the goddamned bomb was.
TFA Mentioned some animations, if anyone was looking for them, they are here.
Farnsworth: These are the dark matter engines I invented. They allow my starship to travel between galaxies in mere hours.
....
Cubert: That's impossible. You can't go faster than the speed of light.
Farnsworth: Of course not. That's why scientists increased the speed of light in 2208.
Cubert: Also impossible.
Farnsworth: And what makes my engines truly remarkable is the afterburner which delivers 200% fuel efficiency.
Cubert: That's especially impossible.
Farnsworth: Not at all. It's very simple.
Cubert: Then explain it.
Farnsworth: Now that's impossible. It came to me in a dream and I forgot it in another dream.
Cubert: Your explanations are pure weapons-grade bolog-nium. It's all impossible.
Farnsworth: Nothing is impossible. Not if you can imagine it. That's what being is a scientist is all about.
Cubert: No, that's what being a magical elf is all about.
Non sequitur: Your facts are uncoordinated.
Sory but light breaking lightspeed, is not breaking news. CERENKOV RADIATION has been observed for some time now. As have the negative refractive indexes of super lenses.
Because you can - or because you should?
There was a young lady called Bright,
Who travelled much faster than light.
She set off one day,
In a relative way,
And returned on the previous night.
Actually, with the aid of this new tech., i read the story yesterday.
If life is merely a joke, the question still remains: for whose amusement?
This statement, and your criticism of the experiment, is based on out of date (or simply ill-researched) information, and it worries me that it got modded up to 5.
In this case, the group velocity is indeed faster than the speed of light - the form of the wavepacket peak (the speed of which is the definition of the group velocity [1]) travels through the fibre almost instantaneously, much faster than c. This is one of the two things about this experiment is interesting, as by the old-fashioned definition you are championing, information has just been transmitted faster than the speed of light (as has been done before [2], although I believe it was generally in quantum-tunneling type situations, rather than something as normal-seeming as a optical fibre.)
The significant point to take home from that part is that the "It's the group velocity that carries information" mantra is not strictly true. In this case, the leading edge of the pulse is all that is needed to reconstruct the whole thing, and then suddenly we're faced with a battle between our definition of information transportation at the group velocity (with the wave peak) and causality. Causality obviously wins, and information transportation needs a more complex definition than is covered in introductory optics courses.
References, cos I like that sort of thing:
[1] http://www.rp-photonics.com/group_velocity.html - definition of group velocity
[2] http://www.rp-photonics.com/superluminal_transmiss ion.html - article on superluminal transmission, including a reference to situations where the group velocity is greater than c.
But Einstein should be allowed the opportunity to be mistaken. After all, he was only human. Maybe the most intelligent one in the world during his time, but alas, still only human. susceptible to mistakes and mis-perceptions. There have been others during their day, some claimed the world was flat, others claimed the earth was the center of all that rotated in the heavens. Many people died for refuting these widely held beliefs. Da Vinci nearly lost his head over some of his vocalizations. Einstein's knowledge was vast, but still limited by his own perceptions, understandings, and convictions. It is silly to believe Einstein has already exactly figured out everything that needs figuring out - and correctly.
Join the Slashcott! Feb 10 thru Feb 17!
... 'bet they didn't see that coming' gag?! :)
-- "Can't sleep, clowns will eat me!"
For years it has been believed that electric bulbs emitted light. However, recent information from Bell Labs has proven otherwise. Electric bulbs don't emit light, they suck dark. Thus they now call these bulbs dark suckers. The dark sucker theory, according to a Bell Labs spokesperson, proves the existence of dark, that dark has mass heavier than that of light, and that dark is faster than light.
The basis of the dark sucker theory is that electric bulbs suck dark. Take for example, the dark suckers in the room where you are. There is less dark right next to them than there is elsewhere. The larger the dark sucker, the greater its capacity to suck dark. Dark suckers in a parking lot have a much greater capacity than the ones in this room. As with all things, dark suckers don't last forever. Once they are full of dark, they can no longer suck. This is proven by the black spot on a full dark sucker. A candle is a primitive dark sucker. A new candle has a white wick. You will notice that after the first use, the wick turns black, representing all the dark which has been sucked into it. If you hold a pencil next to the wick of an operating candle, the tip will turn black because it got in the path of the dark flowing into the candle.
Unfortunately, these primitive dark suckers have a very limited range. There are also portable dark suckers. The bulbs in these can't handle all of the dark by themselves, and must be aided by a dark storage unit. When the dark storage unit is full, it must be either emptied or replaced before the portable dark sucker can operate again.
Dark has mass. When dark goes into a dark sucker, friction from this mass generates heat. Thus it is not wise to touch an operating dark sucker. Candles present a special problem, as the dark must travel in the solid wick instead of through glass. This generates a great amount of heat. Thus it can be very dangerous to touch an operating candle. Dark is also heavier than light. If you swim deeper and deeper, you notice it gets slowly darker and darker. When you reach a depth of approximately fifty feet, you are in total darkness. This is because the heavier dark sinks to the bottom of the lake and the lighter light floats to the top. The immense power of dark can be utilized to mans advantage. We can collect the dark that has settled to the bottom of lakes and push it through turbines, which generate electricity and help push it to the ocean where it may be safely stored. Prior to turbines, it was much more difficult to get dark from the rivers and lakes to the ocean. The Indians recognized this problem, and tried to solve it. When on a river in a canoe travelling in the same direction as the flow of the dark, they paddled slowly, so as not to stop the flow of dark, but when they traveled against the flow of dark, they paddled quickly so as to help push the dark along its way.
Finally, we must prove that dark is faster than light. If you were to stand in an illuminated room in front of a closed, dark closet, then slowly open the closet door, you would see the light slowly enter the closet, but since the dark is so fast, you would not be able to see the dark leave the closet.
In conclusion, Bell Labs stated that dark suckers make all our lives much easier. So the next time you look at an electric bulb remember that it is indeed a dark sucker.
http://www.siliconhell.com/humour/darksucker.htm
OMG! They've gone to plaid!
UofR files patent for Ideal Low Pass Filter.
UofR Researchers Split Largest PowerBall Pot.
I believe that it is a false asumption to say that the speed of light can move backwards.
Optics (light science) can prove that using a mirror through reflection.
The Rapture is NOT an exit strategy.
...unobserved things, too.
Listen, there's nothing to explain here. As far as anyone knows, backwards time travel is impossible. You don't need to invoke multiple universes or some such crap to explain something that does not even exist.
Should time travel be possible indeed, there's likely some mechanism at work that prevents inconsistencies, i.e. the student would not have been able to take the brass cube away. Imagining such a mechanism is futile speculation, though.
Why was the parent was modded funny? It's probably the most thoughtful post in the topic.
My script don't crash! She crashes, you crashed her!
Quite simple, if you get a reverse-time signal then decide not to send it, someone else will spoof the signal that you got. Indeed, it's entirely possible that someone else was spoofing all the signals you got from an even later time, by referring to your notes......
Just because I hear something while you're talking doesn't mean I heard what you said.
I think part of the problem with comprehension of what is happening here is that most people, including most scientists, talk as if time were somehow real, as if it were a "dimension" all its own. It is often depicted as a line stretching from point A (the beginning) to point Z (the end). The common conceit is that because we can measure it, it must be "real."
Time is, I believe, a side effect of our limited perception. It's a handy mathematical construct, but not real in the sense of it having a concrete existence.
What I think we're seeing in this experiment and others where things appear at a destination before leaving the origin, or where particles are made to move to arbitrary locations without passing through the intervening space is simple evidence that time does not really exist and is a human construction.
Aristotle said that time exists only in the psyche, and on this one point, at least, I think he may have been correct.
The universe is weirder than we think, and probably weirder than we can think.
Just be sure to wear the gold uniform when you beam down -- you know what happens when you wear the red one.
If the pulse exists at both ends in opposite directions, you get null time trasmission. The error checking happens at the speed of the signal coming from the opposite direction.
Fascinating. \\//=
I only look human.
My mother is a halfling and my dad is an ogre, so that makes me an Ogreling
As the pulse enters the material, a second pulse appears on the far end of the fiber and flows backward.
Would it be possible to detect the pulse that appears at the other end of a long fiber for instant communication purposes ?
There is a controversial theory that you can only exist in the universe that allows you to not die.
http://en.wikipedia.org/wiki/Quantum_immortality
As in if the universe that has a higher percentage of your survival (ie: going to the university and not being a bum who gets hit by a train after a night of drinking) you will experience that.
Of course anyone else experiencing the universe will see it as the one they are most likley to survive. So if you went to the university and createed a superweapon that blew up a nation, those people in that nation would most likley experience a universe where you were just a bum.
Of course, I'm not sure how it works when you consider old age... Perhaps there were no true observers in our time frame that were before the possiblity of a technological singularity (or those people in the past spontaneously became immortal or something but we don't see that because those universes are more improbable but that isn't really a good explanation).
"I am the king of the Romans, and am superior to rules of grammar!"
-Sigismund, Holy Roman Emperor (1368-1437)
I know this may seem weird, but it's the real world......I see a serious issue with Malware when Big Brother figures out how to use this stuff to their advantage.
Spending Resources on Defense leaves Less to defend.
I can make my daughter walk backwards if I tell her to hurry up enough times.
Cubert: That's impossible. You can't go faster than the speed of light. Prof Farnsworth: Of course not. That's why scientists increased the speed of light in 2208. Cubert: Also impossible.
It will be even more interesting if Einstein proves himself wrong.
"You know, when you take your clothes out of the dryer, they've just been washed, and dried, yet you have lint in the pockets. Ever thought about how it gets there ? Its THAT FAST!!!" Must. Defy. Laws. Of physics!
The technology to travel back in time is just getting started. The slower light travels the more forward in time it goes. The faster light travels the more backward in time it goes. Now they figured out how to make light travel inside out, which let's you turn on a light which will appear 5 minutes ago. The trick is, we are always in the current time. So we'll never see it's affect.
1. Rumors. /.
2. STD's
3. the "reply" button on
ardustry
Which bloody raises the question, please!
:)
And don't go work for Microsoft.
This is likely a very silly question, but if you have a light pulse whose peak is emerging from a fiber before it enters, what happens if you bend the fiber in a circle and feed that pulse back into the start? The backward pulse from that first loop will emerge even sooner, and so on... or no?
I believe in the 1970s that Steven Hawking showed that at the event horizon of a black hole that certain particles had to travel faster than the speed of light. I don't have the details but it also doesn't violate Einstein's theory either. That's the funny thing about all this quantum crap; you can find out that something really does exist and not violate something that says it doesn't. :)
Cheers
The ENTIRE article was ripped from the university site. Not a single added value--in fact, it was negative value as I had to go to the original for the animations. In these cases, can we please bypass to blogospammers and just get the real deal? Pretty please?
http://www.rochester.edu/news/show.php?id=2544
That's what I'd like to know as well.
Or more precisely, if you absorbed the backwards going pulse on its way back, would that cause the pulse that emerged to disappear ?
Bad news, however, is still much faster. Somebody should design a ship powered on it, or something.
You better watch out, there may be dogs about . .
From the article:
"Einstein said information can't travel faster than light, and in this case, as with all fast-light experiments, no information is truly moving faster than light," says Boyd.
I am the JUGGERNAUT bitch!! My outfit is so tight. I hit you with your own pimp.
You all are qualified to debunk these reports? I think not. If they are proven wrong then they'll done so by others in the field or related fields. That's what theory, hypothesis, and research are all about. Stop putting yourselves ahead of those other qualified people.
Of course Slashdot is about sensationalism. It wouldn't exist due to a lack of popularity if only the mundane were reported.
You can lead a man with reason but you can't make him think.
Who travelled much faster than light
She left home one day
In an Einstienian way
And returned on the previous night!
Actually Einstein was wrong about being wrong about the cosmological constant. But the fact that it got added and removed and added somewhat arbitrarily to fit the facts in evidence is a good example of a practice in modern physics that is almost commonplace these days. http://super.colorado.edu/~michaele/Lambda/blund.h tml
Disclaimer: I'm not a physicist, not even close actually ;-)
Probably this reversal has something to do with erbium. It gives a characteristic sharp absorption spectra in visible light, ultraviolet, and near infrared [Wikipedia].
When a photon is released due to de-excitation, it may go any way (including right back into the fibre and outside). Could that explain the reverse light?
Also, could it be that erbium is actually slowing down the incident beam and thus what Prof Boyd saw at the other end wasn't exactly the incident pulse coming out at all?
Probably some physics experts could help out here.
Einstein ain't law. To explain all the relativistic goings-on in this universe, the Theory of Relativity requires that nothing can go faster than light in the respective medium (it's fastest in vacuum, and space is a near-perfect vacuum).
Now if someone could reproducibly demonstrate something that does go faster than light in the same medium, we'd be forced to conclude that we need a better theory than the Theory of Relativity. Of course, since many experiments have been performed that always agreed with Relativity's predictions, any such demonstration of FTL will be met with considerable skepticism.
To repeat, there is no proof that nothing can go faster than light. It's just that no FTL has ever been observed, and that the predictions of Relativity do not include FTL.
Physics isn't maths. In maths you start with axioms, and if logical deduction from those axioms results in the Existence of Whatever, then you have proof that Whatever exists. Physics first works backwards from observation to theory, then forward from theory to predictions that are performed as experiments (whose results support or contradict the predictions and thus the theory but never the observations).
I've seen all that (my undergraduate degree is in Physics), however the value he chose was still completely incorrect and in no way supported by evidence - he should have left it as an unknown value that would have to be empirically determined!
What's incredibly ironic about people who try to explain complex and confusing physics stories is that they end up being no less complex and confusing; just annoyed at the original source and more patronizing than it. But not a lick more explanatory.
Terrorists can attack freedom, but only Congress can destroy it.
The reason I'm questioning what you wrote is precisely because I know that all movement is relative. Saying that "the relative speed of either photon from the other was 2c" is quite misleading. That certainly isn't true from the reference frame of either of the photons (see e.g. this comment). What you're saying is that in your example, from your or my reference frame, we can calculate (but not actually observe) that the distance between the two photons is increasing at a rate of 2c. However, "technically", that is not what is meant by relative velocity in special relativity, so it's not technically correct to say that "the relative speed of either photon from the other was 2c".
A poetic effort, but that doesn't have anything to do with the issue at hand, and besides, doesn't correspond to any physical theory I'm aware of (special or general relativity, quantum mechanics, or even string/brane theory).
Check it, or any of Hogan's novels, out if you like a good Sci-Fi read.
"There once was a lady named Bright,
who could travel faster than the speed of light,
she left one day,
in her perculiar way,
and came back the previous night"
I heard it many years ago. Can't remember where.
Greg Egan writes about excactly that in one of the short stories in this book... US hardback version
Quite decent book by the way, my last three weeks of New Scientist are still in the shrink-wrap/lying on the doormat because of it :)