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Pushing Microwaves Faster Than Light
ContinuousPark writes: "According to this NY Times piece, Lijun Wang of the NEC Research Institute in Princeton has reported an experiment where "a pulse of light that enters a transparent chamber filled with specially prepared cesium gas is pushed to speeds of 300 times the normal speed of light". A second experiment by three scientists for the Italian National Research Council is reporting also superluminal speeds. And yet, this seems to be consistent with Einstein's theories. "
Interesting.. but please fix the spelling error in the heading.
-- jaf
Hehehe
-legolas
i've looked at love from both sides now. from win and lose, and still somehow...
Will someone who has a NY Times account
post the body of the text for those of us
who dont want an account?
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As usual, you replace the "www" with "partners" to get the no login required version of the article, found h ere.
S tory here.
Pretty mindbending stuff, indeed. Once upon a time I could follow that sort of discussion, but I've been out of academia too long.
Constitutionally Correct
Hmm here is one you can use if you need one.
slashdotviewers/allowed
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Can be found here at Nature.
Whilst the difficulty in this experiment is in interpreting the results, one thing to remember is that the speed limit c for any information is a postulate of relativity, not something that has been proved. It appears to be true so far, but there is nothing to say that it always applies.
The text states that this couldn't be adapted to signal information back in time due to the small timescales involved, well, what about a simple signal? like 'Don't switch the signal generator (laser or whatever?) on?. Would the ensuing paradox wipe-out the universe?
You didn't even read the article, ass!
and it's 300 times c, not 300%.
The backwards wave in the cesium chamber travels at 300 times c. You don't understand relativity, so don't post.
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I got really excited when I first saw the title: "Pushing Microwaves Faster Than Light."
:-)
:-(
I mean who wouldn't be excited? You could reheat that leftover pizza before you're brain finshed realizing you're hungry.
Turns out they're talking about microWAVES not Microwave Ovens.
Devil Ducky
Devil Ducky
MY peers would get out of jury duty.
Can someone with a degree in physics answer these questions:
"...under these peculiar circumstances, the main part of the pulse exits the far side of the chamber even before it enters at the near side."
At first I was going to flame NYT for such a stupid claim, but upon reading the rest of the article that appears to be what the scientists themselves are claiming. So my first question is: What is speed if not distance travelled divided by time elapsed? If the time elapsed is negative, how is the speed "300 times c"?
The second question is about the obvious "time travel" aspects. They say several times "you can't send info faster than c", but they don't indicate a reason. The closest they come to justifying this statement is (paraphrase) "there is a leading edge to the main pulse that arrives sooner".
So which is it? Did the pulse exit before it entered OR was there a "leading edge". You can't have it both ways. Either the signal travelled faster than light (in which case signaling superluminally is possible, by definite) OR it did NOT.
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What sort of bandwidth can you get by transmitting down cesium-based fibre at 300 times the speed of light? ;)
Remember that this is not matter that they have flying past the speed of light - its energy. Im not physicist but I have an idea that this matters somewhat :) Maybe because energy has no mass? sorta? heh
Obviously theory is one thing, practice is another, and practical application is yet another. Personally, superfast microwaves don't seem like they would be all that special. Everything that I remember about faster-than-light travel would seem to indicate that if I heated up a bowl of Spaghettios in when I was a kid, by the time it was warm, I'd be 80 years old.
Hmmmm. maybe I should have chosen a major besides art.
Peace. Sway
Peace. Sway
the article states that this method would not "... allow anyone to send information faster than c, said Peter W. Milonni, a physicist at Los Alamos National Laboratory." my question is...why not? my understanding of this is that a pulse is detected 300c before the light should get there, and I see no reason that that pulse can't be used to send a binary message into the future from the present, or on the other hand, to recieve a message from the past in the presents. I guess when I state it that way, that is how all messages are sent. including this one. oh, my head hurts.
I post links to stuff here
The problem is that as you approach the speed of llight, the mass tends towards infinity. So the faster it moves, the more force is needed to rotate it, and to go from lightspeed to faster than light you need an infinite force.
It seems like the comments about information not being sent faster than normal light speed were all based on the fact that the light entering the chamber was traveling at normal light speed in air. If this chamber was extended over a larger distance, is there any other reason why information would not travel faster than normal light speed? And could scenes from the future be viewed by shining light through a cesium cloud?
-Omar
Better luck next time.
Today's weirdness is tomorrow's reason why. -- Hunter S. Thompson
According to what information my poor, physics dull brain could cull from the article:
You have to charge the particles with a certain kind of light?
You have to transmit annother certain kind of light? (or was it the same kind?!?)
So, there isn't too much information you could pass quickly through this chamber. The only thing that gets passed quickly through the chamber is the time that you shined the light on the "near" end of it?
Thank you for not thinking.
You aren't the first one to think of this. However, there are several problems with this. First off, you would have effects coming from both specific and general relativity that would prevent the tip from exceeding the speed of light. Second, long before the tip got anywhere near the speed of light, the tube, wire, whatever, would be ripped into pieces by the centripetal force needed to keep it moving in a circle.
-Matt
-Cheetah
is in progress since the beggening of the 80's, when AT&T was still monopolistic and When lucent technologies where still named bell labs.
they use to conduct such research has explained here. On the ability to send ultra short pulse at the speed of light, pushing thus the ability to send data faster. 5remmebre at that time sending mail from the US to france meant you knew the path with all interconnecting nodes and you needed to belllabs!princeton!leeds!amsterdam!jussieu )
none Yet.
Since this is all theory, then have the materials be indestructible. Then what do you get?
I eat the flesh off the living, and I vote!
Sorry, but it is:
"faster THAN light"
if thats possible.
Else it is
"NOT faster than light"
Ceci n'est pas une sig
Do these experiments redefine physics as we know it? That is quite easy to find out: just wait one or two years. If Dr. Wang hasn't received the physics Nobel Prize by then, there was probably a fatal flaw in his equations.
Does anyone still remember the hype about cold fusion, the guys claiming to have sent information at v > c (that was the guys who bodulated a laser wave with music, but failed to notice the difference between group speed and phase speed of the light - or at least didn't bother to do so in their works...)
BTW, IAAP ( I am a physicist) and I have become more and more sceptical towards articles like this one during my studies - in almost all cases, "great discoveries" can be easily explained by physical properties not taken into consideration or just some stupid error. If it is published in a non-scientific journal before the scientific community notices it, a "discovery" usually isn't worth the paper it's printed on.
Cthulhu fhtagn!
I question this sentence from the NY Times write-up:
"That is so fast that, under these peculiar circumstances, the main part of the pulse exits the far side of the chamber even before it enters at the near side."
Does this seem like a mistake to anybody else?
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Awesome article...except for all the spelling and layout errors. Sheesh. And what's up with this - Dr. Guenter Nimtz [[umlaut over u]] - ? You telling me these guys don't know how to use the character map? Or hard code them - ü or ü - into their HTML? ;-)
They should hire me.
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I hear this supposed time travel 'paradox' cited all the time as a reason that FTL travel isn't possible. We can't send information faster than light because then we can 'see' events before an observer only a short distance away, and this is supposed to be a paradox.
What the heck am I missing? Are all these people stupid, or is it me? Why is it a paradox if information gets to someone at a distance before it gets to someone nearby? You're never going to get the information before the event occurs, so there's never any threat of paradox.
If it is all true and becomes mainstream, Can I read slashdot before it is published?
Just wondering...
A more suitable quote would have been "300 000 kilometres per second. It's not just a nice idea. It's the law."
-jcl
The Nature article was less confusing than the NYT article and it DID have a little more info. Except it didn't answer the questions I want answered. Namely, WTF are "evanescent waves" and why can't they carry information?
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They tell us it can't be used to transmit information. Am I the only one who thinks this is bogus? As far as I know, if there's a way to transmit a signal of some kind, there's a way to encode data on it, be it by quantum effects (mentioned previously on slashdot) or by super-c microwaves, or whatever else science may conjure up. I know that relativity theory is very complicated stuff, but I don't think that superluminal communication necessarily violates cause and effect. Granted, it may appear to an external observer that the pulse arrived before it was sent, but the way these things work, you would not be able to shut off your laser to keep from sending a message you already sent. I know it's complicated, but the relativity works out.
Can someone with a clearer grasp of relativity theory please explain this?
WARNING: there is a trojan on your
Energy has no mass? Think again. That famous equation (verified countless times in the Nevada desert, in the Russian wastelands, and over two certain cities in Japan) works both ways, you know.
Mod down posts with a "Free Mac Mini/iPod" sig, they're spam!
Having so many typos, syntax and grammar errors make slashdot look so juvenile and unprofessional.
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This question has been posed in many a college physics class. The reason you can't accelerate any physical object to the speed of light is that the "effective mass" of the object grows with its relative velocity. This is to say, the faster something is going, the more energy it takes to accelerate it further. Good old F=ma doesn't hold (unless you redefine all the variables) at speeds comparable to c. In the limit of v->c, it takes
infinite energy to increase the speed at all. You just never get there.
Beyond this, introducing rotation and deep space just confuses the issue. Do you mean to say that the rocket is also accelerating? Even so, our perception of time slows down and everything balances so that nothing moves faster than light.
The speed of light is built into relativity and always comes out in a self consistent way. Of course, you can dispute relativity - but this theory has stood up very well to brute force tests of making things go very fast. If relativity ever falls, it will be due to much more subtle experiments or theoretical inconsistencies.
Im sure there is some theoretical readon why this is impossible, or doesnt matter. Im not interested in how its impossible in practice.
...because when the light gets arrives at its destination, darkness is already there!
No sig. Go away.
That (or should I say "thet"?) has to be the most mis-spelled word on this web site. I have seen the word "than" spelled as "then" repeatedly here. It really does make the site hard to take seriously. I introduce it to outsiders to demonstrate a functioning sub-subculture, and they think it's a juvenile, even though you can find cool links occassionally.
"Man has always been his own most vexing problem." --Reinhold Niebuhr, "The Nature and Destiny of Man"
The article states that the backward wave propogated at approximately 300 time c , which is the speed of light in a vacuum.
The speed reported is for the backward wave, apparently. This is similar to how a traffic clot might propogate backwards through traffic even though the traffic itself is moving forwards, as the article points out.
Take a look sometimes how traffic responds to a sudden discontinuity in flow, such as a slow-poke or an accident. If it's near "saturation", the backward wave of clogged traffic moves very quickly, which is VERY similar to the phenomenon being reported. Notably, the more "saturated" the traffic, the quicker this "wave" moves. As the article indicates, the experiment was performed in a chamber that's designed to amplify light waves by saturating the cesium with energy from one source and then triggering the release of that energy with a different source at a particular frequency. In this case, the microwave involved is not releasing the saturated energy.
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No longer sell "Speed-O-Lite" Wheel Bearings at local Pep Boys.
Tensile strength of tube insufficient, centripetal force would disintegrate tube at suprisingly low speed.
Cost of tube of sufficient tensile strength to approach c: "Astronomical".
Electrical flux of moving tube sufficient to cause interruption of Art Bell show; mass hysteria about "Gosh darn space invaders" and "Damn gov't conspiracy" causes WWIII.
Trivially solving for E=Mc^2, Motor would have to impart near infinit amount of energy to accelerate tube of any mass to c.
Cost of near infinite amount of energy: "Pretty way up there", according to General Electric spokesperson.
Inability to anchor motor to counter torque of rotating wheel/tube.
Whistling of tube at near-c velocity could cause graviton wave, angering greys on nearby Alpha Centauri.
Imbalance of rotating assembly at any speed causes catastrophic failure.
Cost of near-c tube assembly hurtling through Earth's atmosphere, piercing the core like a toothpick through an olive, instantly vaporizing the surface and ending all life on the planet: "Priceless"
Don't try this at home.
I had my hopes up for a while there. Imagine negative ping times on multi-user shootemups! :)
As I write this there are 3 responses to my questions, 2 of which agree on a (purported) answer to the second question. The question they answer is "what does 'leading edge of the pulse' mean", the queston I'm asking is "why does this keep you from sending a signal superluminally"?
Let's say the answer they give is correct, as far as it goes. The cesium atoms "reconstruct" the light wave from the leading edge. But what if the information is in the main pulse? If the atoms can reconstruct the main pulse, why not the information contained therein?
For instance, the leading edge is presumably much weaker than the main pulse. So let's say you had some "work" (in the mathematical sense) to do on the far side. The main pulse (containing all the energy) gets reconstructed and does the work before a "traditional" signal would have gotten there.
I was going to come up with a more detail example, but then I realized I had another question: What does "leading endge" mean? The pulse is travelling backwards in time. Anything travelling forwards in time must get there later, meaning it can't be "leading".
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First you have to realize that the pulse of light looks kind of like a gaussian. It has a tail on both ends. In this case, the leading tail contains enought information to reconstruct the entire pulse. So .... theoretically, once the tail get all the way through the chamber, all the information in the pulse has already arrived. The only thing that the chamber does is make it so that the center of the pulse arrives at the end of the chamber at the same time the leading edge of the pulse gets there. "Information" didn't get there any faster, but _part_ of the pulse did! The way I understand it the chamber creates a replica of the pulse based on the information in the leading tail of the pulse and places that replica at the end of the chamber. Then, when the actual pulse arrives it is absorbed by the chamber, returning everything to its ground state. This is neat, but not earth-shattering. Then again ... I havn't read the Nature article yet (and news media never gets it right), so maybe I am missunderstanding...
So, if it was faster than light, does that mean the experiment was over before it was started?
Sure would be a great time saver!
The way it works is: the very first part of a signal arriving at one end of the apparatus somehow allows the entire pulse to be reconstructed and delivered out the other end even before the last part of the pulse has finished entering. No matter what you put things, you've pushed a coherent pattern of something faster than c.
Admittedly, the time taken to process the information would preclude getting feedback fast enough to affect the original process -- it would be scary if that wasn't the case -- but in an optical computing setup, you would still get information the information faster than if it had been sent at c. Whether you can sustain that speed for a continuous stream of data is another question.
The item is actually old news. For those of you who missed it originally, I will re-post here the text oif a previous, and more exciting. development:
Overclocker Creates Rift in Space-Time Continuum
...but this "But some kind of EMF is still present in the 'forward' part of the interface, generating some field patterns named 'evanescent waves'" makes no sense to me.
The EMF exists forward of the interface, right? And it is detectable, right? Why isn't that enough to convey a single bit of information (yes there is a signal)? Or is the forward part a mathematical entity with no real existence? Of course, even then, superluminal signalling would be theoretically (even if not practically) possible.
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I can't wait to receive Slashdot headlines via Sub-Etha transmissions!
Ham on rye, hold the mayo please.
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To me is sounds belivible, and logical. But then again, I probably have missinterperated something.
In light of this (and pardon the pun), wouldn't this mean by definition that the light travelling through a gas chamber filled with cesium atoms would move slower than light in a vaccum? Also, we know that electrons always move at approximately the speed of light, sooo.. what's to say these highly unstable cesium atoms aren't converting the light energy into electrons and passing them between each other to the other side?! I'm no physicist, so this may be bunk, but I can see how in certain circumstances you could get electricity to travel faster than light through a particular medium..
It may simply be the quantum version of the trick where you take three pennies, put your finger on the one in the middle, put the other one on the "far" side touching it, and then throw the other penny at the one on your finger. Your finger doesn't move, but the penny on the other side "jumps" away.
Alter your definitions of what it means to detect a light transmission, or even to *begin* a light transmission, and it would seem like results like this would be possible.
;-)
That there's a tail to the light posits that there's a time delay in which some small information-bearing light reaches the far end. This tail is not a staccato burst--there's a beam of light behind it. Perhaps whatever happens at the far end causes a cascade reaction(to keep the rush hour analogy, traffic gets backed up *real fast) to amplify backwards in a manner that is *detected* superluminally but is not superluminal itself(such detections are common--shine a laser on a far away mountain--your beam moves superluminally, even though your light doesn't. Persistence of vision is a human trait, not an optical property of nature.)
That these atoms seem primed for amplification of light makes me particularly curious if their amplification traits are triggering false speed measurements. Even if the wavelength is theoretically set for crystal clear propogation, something as major as 300*c transmission would call for further study on exactly what's being detected. My personal guess is that either the time of the initial transmission is being misjudged(imagine a buffering operation taking place within each atom, now imagine those atoms releasing their buffers in the manner they might if they were backpropogating a wave, all in sync to 300C).
That's my guess. But who knows--least of all me
Yours Truly,
Dan Kaminsky
DoxPara Research
http://www.doxpara.com
Therefore, the conclusion is that EMR is being transmitted faster than EMR.
Therefore C > C.
There's something seriously skewed with that result.
IMHO, unless I'm seriously out in left field, what they're more likely to have shown is that C has been badly calculated, and nothing has gone back in time or violated C.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
The light does not really travel through the chamber at all,
so therefore it does not travel faster than the speed of light. What occurs is that the highly
excited cesium atoms act in a manner similar to einstein-boseium condesate for purposes of light
absorbtion. The atoms exist in such an exited state that they can neither absorb nor reflect the light
pulse. The atoms at the end of the tube emit the light at the same time as the atoms at the
begining absorb the light, because the atoms are so highly excited they must emit light before
than can absorb any. The leading edge spoken of is a gedanken construct to explaing the reverse
wave of negative light that propogates from the end of the chamber to the begining. When
the negative light wave hits the original light wave they cancel each other out. The emited energy
of the mirror of the negative wave(which is the wave of light that is emitted from the end of the tube)
is identical to the original pulse and is emitted from the end of the tube at the same instant
the original pulse enters.
hope this helps explain things.
weird one
"Secrecy is the keystone of all tyranny. Not force, but secrecy
It seems to me that the ``speed'' of the wave packet is being measured using the time the peak enters the chamber and the time the amplified tail exists the chamber.
If this is correct you could tune the wave packet to give you any ``speed'' greater than c you wanted by changing the width of the wave packet. (assuming you could still get this trick of cancelling the peak while amplifying the leading tail).
If I missed something, I am sure I'll be corrected.
Using this, there's finally a chance to beat the bandwith of a truckload of backup tapes :-)
Disclaimer: IANAP (I Am Not A Physisist), not even qualified to understand the Relativity Theory. But when I attended the classes in highschool and college I got a little grains of understanding of this difficult-to-envision topic. Not from the teacher though, he only sited examples from the books without being able to explain much that made any sense). Here goes nothing.
In science you need a way to define time meaningfully. What does it mean that two events _are happening at the same time_? How do you define that?
Of course in science you need to test, observe, measure and calculate every hypothesis you come up with before you can write down established theories (which may later be called 'bogus' anyways, that's how rude and arrogant some people are..).
Since you must observe everything to prove anything, and light is the fastest known way of communication we know of (except gravity), you need to define two events happening at the same time to an _observer_ as when their emitted lights arrive so that you can observe. If you never receieve anything, the events never happened.
Of course, this is not how reality really works. It is how we choose to _perceieve_ reality scientifically. Now, when you define time like this, the light from the stars (supernovas etc) are telling us what is happening up there _right now_ _scientifically_ (the light from a nearby tree and the light from a distant star is perceived at the same time). This is just because someone was smart enough to redefine time, that is why this is all so confusing!
Note that we're really talking about theoretical light in theoretical arguments about RT, since real light can be altered by gravitation and mirrors (without altering our whole map of space-time that much). Theoretical light moves with a speed in all direction with the speed of c.
So in this case the signal must be received before it was transmitted in order for it to be faster than light. That doesn't mean it went backwards in time according to a more "universal time".
- Steeltoe
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Actually, it's quite well written (except the goto... use atexit()...), and could be considered a useful intro to web/proxy programming.
And it's written in C, not perl!
And AC - here is my prediction - you also program Java...
Score -1 offtopic here we go...
Strong data typing is for those with weak minds.
Strong data typing is for those with weak minds.
The pulse is there or it is not. This binary state is the basis of all non-quantum computers. We may be years or decades from developing a fast enough switch to take advantage of faster than light transmission, but the article doesn't mention this as a possibility, let alone provide an explanation as to why this wouldn't be possible.
As for the supposed paradox of the pulse exiting the chamber before it enters, I would question their data-gathering equipment/methodology. Electrical signals travelling from sensors to recording devices are slower than light. A light pulse that travels over 300 times faster than the sensor signals may be read incorrectly if there is the slightest difference in propagation time between the entry and exit sensor signals. This could be explained by an inch of length difference in the cables.
I'd be very interested to see if this "time paradox" is repeatable by independant researchers.
Combine this with Quantum Teleportation, and couldn't you teleport matter faster than light?
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50, 60 years ago, people said that anything moving faster than the speed of sound would cause a sonic boom that would tear the world apart. And that was just the people who thought it was even possible.
... when you're talking about a distance of 500 light years, even a technology like this doesn't change much. The transmission certainly wouldn't be instantaneous, much less "negative ping."
:P
I'll gladly state that my perception of relativity is flawed... but exactly how is the speed of light all that special? I mean, one moment you're going 'c'-0.000001 and all is peachy; the next moment, you're going 'c' and the very fundamentals of perception change?
But then, I tend to think in stellar distances when thinking about 'c'
Again, I'll freely admit that I don't understand the first thing about relativity.
woof!
Ok just imagine a Beowulf Cluster of these things.
You hook them up in series (hooking them up parallel actually wouldn't work) and each individual unit send a signal further and further back in time. Transmit todays stock quotes into it via morse code and you'll receive the signal yesterday in time to make a killing on the IPO of the day.
Ok, so the 'trick' is that a full pulse can be reconstructed from a tiny bit of leading edge, the result of which just happens to look like a superluminal effect.
Nevermind superluminal effects, can something like this be used to reconstruct a full pulse on the far end, full information, with just the leading part actually sent? Sort of like how an AM signal can be reconstructed from a single-sideband transmission? And would any speed increase be worthwhile? If you have to send faster than you can send, it would seem nothing would be gained. Right now, it seems that the full pulse must be sent, or an energy deficit occurs.
Just another odd musing...
I don't subscribe to RMS's GNUtopian vision.
People,
The speed if light in a vaccum is the absolute speed limit, 3.00x10^8 m/s approximately. Nothing faster then go at speed of light in a vaccum.
When light enters a medium [glass, air, water] it slows by n, the index of refraction. for clear class, n is 1.50 so the speed of light in water is (3.00x10^8)/1.33 m/s or approximately 2.00x10^8 m/s.
However, the law states that the speed of light in a vaccum is the fundamental speed limit. So, in glass, things can travel faster then speed of light in glass (2.00x10^8) but obey the law at slower then speed of light in vaccum.
Hence, in that experiment they were saying 300c with c being speed of light in that medium.
Singer
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For those of you who's relativity is a bit rusty, when talking about distance and time in relativity you must talk about interval, since time and space are related.
A timelike interval is one in which two seperate events can be seen, from at least one non-accelerated frame of reference, as happening in the same place but at different times. Think of a clock striking 1 and 2: if you are moving with the clock, it was in the same place, but at different times.
A spacelike interval is one in which two seperate events can be seen, from at least one non-accelerated frame of reference, as happening at the same time but in different places. Think of two bombs going off: at the right place they will seem to be going off at the same time, but never in the same place.
Light normal covers an interval that is neither spacelike nor timelike, but a 50/50 mix of both. However, in this case (if the experiment is to be beleived) the light going through the chamber covered a spacelike interval, but even if you sent the pulse through the chamber and back, it would still not have covered a negative timelike interval. So, you cannot report back the date of the Microsoft breakup and cash in on the stock market.
www.eFax.com are spammers
Pushing Microwaves Faster Then Light does not make much sense in the English language. I know that to geeks this is not important, nor interesting, but it is a pet peave of mine. Imagine the flames someone would get posting a story header like "Security Breach Exposed in SMTPmail halo Command". Spelling folks, think of it as protocol compliance!
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The real problem is entropy.
Anybody knows if the speed of changes in gravitational field has been tested somehow?
Ciao
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C is the speed of light in a vacuum. What they have done is find a medium where light travels faster than it does in a vacuum (supposedly).
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Patrick Doyle
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for those not "up to speed' on this issue, here is a quick summarry:
as a final note, there were those who also argued that Mozart's 40th Symphony was not information in the first place, and so relativity was not violated.
This brings a certain smile to the face, depending on you musical tastes.
"It is a greater offense to steal men's labor, than their clothes"
The article states very plainly: The pulse was reconstructed from the precursur and placed at the
far end by the cesuim then the cesium destroyed the real pulse as it entered.
It looks like information CAN be sent this way, if you look at the pulse as the information. But
what bandwidth could you get if you have multiple pulses being sent and destroyed by multiple
back-propagating waves?
This isn't really new. I read several months ago in Popular Science about a researcher who did
something similar with a detector, a block of some ordinary metal (I don't know what) and two
pulses of some energy(?). He raced them with one going throught the block and one not. The blocked
one actually won the race, but only because its precurser/tail got pushed forward as it went
through the block.
Sorry for the vagueness. Thats all I could remember
Sig
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Gravity propogates at the speed of light. If the Sun were to suddenly vanish, the Earth would continue accelerating around its orbit for about eight minutes before it flew off on a tangent.
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Pay no attention to the errors in my post. I am the great and powerful Oz.
Replace "speed of light" with "speed of sound" to see why your argument is bogus. Why can't you send a signal faster than light that still arrives at its destination after it was sent?
--
Patrick Doyle
Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
Wish I had a whiteboard. Let's try doing this with ASCII art.
Just before the pulse hits the chamber, things look like this:
Pulse Cesium chamber
Note that the pulse has a 'leading edge' -- a rise time before its maximum intensity. Once that leading edge hits the cesium, the cesium recreates the entire pulse on the other side:
So the pulse appears to have gone faster than light through the cesium. Another way to look at it is that the cesium, using nothing more than the leading edge of the pulse, spontaneously created a new pulse. Actually, it created two new pulses, as you can see after a little more time:
|~/#####\->~~~~~~~<-/#####\~| /#####\->
The two pulses within the chamber are moving towards each other, and they'll deconstructively interfere, cancelling each other out. (Actually, they cancel out as soon as the original pulse is completely in the chamber, but it's easier to draw this way.) Meanwhile the pulse outside the chamber is moving away from it and towards your measuring equipment.
So the pulse is not travelling backwards in time. The pulse isn't travelling far at all; it's being annihilated, really, but a copy of it is generated . It just happens to be generated some distance away.
Note that my drawings are flawed; the light pulse was probably longer than the cesium chamber. So the original pulse was already half-destroyed by the time the new pulse emerged from the other end. That would have been difficult to draw.
Why can't we use this to send information faster than light? Read the article again -- they're not really sure that you can't. One person is arguing that the information is packed into the leading edge of the pulse (sort of an optical gzip) and so you're compressing information but not sending it superluminally. Other people (Dr. Nimtz, third paragraph from the bottom) say that they really are sending information faster than light.
Personal opinion: This looks like some kind of wave phase propagation trick to me. We've always known that you can cause a phase shift in a beam of light to propagate superluminally, but the problem is that you can't encapsulate information in phase shifts adequately, due to (IIRC) the uncertainty principle. Not to say that this isn't an exciting experiment, but it doesn't appear to have a practical use. Now, the microwave experiment that travelled at 1.05 c excites me...I'd like to see if they can extend it to interstellar distances and through vacuum. :)
Genocide Man -- Life is funny. Death is funnier. Mass murder can be hilarious.
If a processor worked faster than light it could generate output before the input was entered
This would be very embarasing when it spits out the answer let's say 42 and you forget what question you wanted to ask.
134340: I am not a number. I am a free planet!
Again, I'll freely admit that I don't understand the first thing about relativity.
So why even post this?
Special relativity works like this:
Normally, if you're on a train moving at velocity V, and you walk forward at velocity W, you would think that your velocity relative to the ground would by V+W. Well, you'd be wrong. It's very close to V+W, but is actually a bit less thanks to Special Relativity. This is no fiction; it's a measurable phenomenon (perhaps not with people walking on trains, but it's measurable in other situations).
This "little bit" grows as you move faster, to the point that if V and W are almost the speed of light you don't move anywhere close to V+W. Relativity always comspires to give you a combined velocity less than c.
one moment you're going 'c'-0.000001 and all is peachy; the next moment, you're going 'c' and the very fundamentals of perception change?
Not at all. Things would be very, very different at 'c'-0.000001. Relativity is not something that "kicks in" at the speed of light. You experience it even taking a leisurely stroll on a train.
--
Patrick Doyle
Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
Thiotimoline dissolves before you add the water to it... and this was published just before Asimov defended his PhD thesis...
"I will take the Ring," he said, "though I do not know the way."
Fact is that we really don't know.
Besides, you talk about information as something we can prove is there or not theoretically. That is not so, all our information is derived from observation, interpreting it into knowledge. You can't have knowledge without observation (experience). If you have biased judgements, you will live inside a shell missing out of alot. Of course doing this together might be fun, but only just for so long.
So, any particle can have an unimaginable amount of information. It's just up to us to find a way to observe it. Some information is tied to the physical limited by "the speed of light", while other information might go through other channels.
Btw, how fast to you think the gravitational-force propgates? Just because _variations_ in gravity doesn't go faster than light, doesn't mean the force itself isn't. Of course, if we define the world to, it will be so for us.. Another thing is that everything have a frequency (wave), but what medium is everything frequenting through (aka how can a wave exist without a medium to vibrate in)? There's much unknown to us still.
- Steeltoe
http://www.debunkingskeptics.com/
Well, why? If the beam exits before it enters, just have a sensor at the end of the container shut off the machine when it detects the pulse. In this way, it will turn it off before the pulse is ever sent.
.02
My
Quux26
My
Quux26
www.crashspace.net
Thiotimoline dissolves before you add the water - and the interval depends on the amount of uncertainty in the mind of the experimenter... This was published under Asimov's real name just before his (Biochem?) PhD thesis defense - its a delightful story, and its been used by authors like Silverberg as the basis for other time travel spoofs.
Reality is catching up with fiction, eh?
"I will take the Ring," he said, "though I do not know the way."
Would this give an even larger time diferential? If its going faster than the speed of light, wouldn't going further make it show up sooner? make one of these things half a mile long and see what happens. It may be a small time change at 60' but make that longer and get something intersting, the future of fiber optic networking.
I might be totally wrong, as IANAP (I am not a phisicist), but maybe the answer to your question is in Heisenbergs Uncertainty principle.
;-)
If you try to measure or specify the position of the pulse very exactly, then you can't know its speed and viceversa. If the speed of the pulse is measured very exactly, then the pulse could be in "both" sides of the chamber.
So in fact maybe you can really have it both ways!
Cheers,
Angel
wonders never cesium.
An instant black hole (infinite mass).
--
Don't lead me into temptation... I can find it myself.
So what. The index of refraction of the light is less than one in that chamber. Big freacking deal. The index of refraction in many metals is less than one. This is old news. Individual sine waves may travel faster than c but if you take a look at the speed of the entire packet (i.e. how fast information travels) you will probably find it is much less than c. Anyone who has studied undergrad optics should know about this. My guess is that what is cool is how much smaller than one the index of refraction is in this chamber and that the absorption isn't very high.
My professor (who has two phd's after his name) says (from about a minute glance) that:
The entire beam of light is not traveling faster than c. What is happening is that some of the peaks in the frequency are moving faster than c.
This is from reading a paragraph long synopsis, so here's your grain of salt. Also, I probably mangled what he said.
So, how does this happen? does the pulse go back in time? I have a pulse that exits before it enters, therefore the pulse existed before it was generated, and therefore must have been generated at a previous time and translated back in time, or they really really munged up the instruments!
Secondly, how does one caliberate equipment designed to detect particles or speeds faster than the instrument can read?
I think the whole thing is just a big OOPS, and someone plugged in sensors backwards.
Do not look at laser with remaining good eye.
The experiments dress it up to make it look like something more interesting is going on, but really that's all it is. Math here. Animation here.
Dunno why, and prolly just crazy, but the excerpt mentions a "nose" or faint precursor... I'm no physicist or really qualified to comment on this, but I am going to anyhow... I got the strangest feeling about this "nose" or faint precursor and my mind immediately said... "Thats why Deja Vu happens". Is it possible that our minds can sense this type of happening... I know this is all a laboratory created event, but what if this happens in the real universe all the time and occasionally we pick up on these events and have a sensation of Deja Vu...??? Oh well, like I said, just popped in my head while I was reading the article...
The way I see, you don't necessarily need to contain all of the information in a single light wave. You just have to send different pulse of light. If you treat it as a problem for modern networking, the transmission medium is really the only thing that changes. Measure when signals come in and compare with a prearranged timing protcol or whatever. Voila, a binary signal FTL.
This contredicts every thing I've learnt (not that I am saying it is impossible, the theory of relativity contredicted everything classic physics said). According to what I know, when calculating speed relativly, it is impossible to go above the speed of light, here is the reason why I can't figure it out:
1/((1-(v^2/c^2)^0.5)
When you go above the speed of light, v^2 becomes larger than c^2, giving you a negative number within a squareroot, how would you get past this?
Yes, IANAP either. However, one thing that occurred to me: Apparently a "picture" has been made of this light pulse inside of some Cesium, where the pulse came out the other side quite a bit quicker than usual. (I liked the ascii art that the one poster did, which got me to thinking about this idea). Anyways, as the pulse is approaching the chamber; is it possible for the air/vacuum/whatever it is travelling through before it hits the chamber to be causing the same thing to happen? Namely, the pulse travels through this medium by two new pulses being generated, one moving forward; the other backwards cancelling out the incoming pulse. Normally, the pulse moving forward travels at light speed. "Magic" happens (IANAP) when it hits the cesium chamber, and we get what appears to be faster than c travel by the pulse.
On the other hand, nothing ever moved faster than light. So far as I can tell, when sound moves at Mach 1 (or so), it's not because your mouth emits particles that are moving at mach 1 and they reach the other person still moving at mach 1. The wave moves faster than the particles involved at any given time.
Patterns aren't things.
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Of course, all this is dependent on the notion that the concept of time in relativity which is necessary to perform the mathematical equations treating it as a dimension [hence, with qualities relatively difficult to distinguish from those of threespace] is sufficient.
The equations which employ time as a variable, hence treating it as a dimension do not exhaust the qualities which must be understood in order to consider the effects of such things as causality.
The simplest solution, as Henri Bergson pointed out when relativity was first presented, may be that the way we conceive of time is fundamentally flawed. [Essai sur les donnees immediates de la conscience]
Unfortunately, most work has allowed time to remain in a kind of limbo, sharing the qualities both of a spatial dimension and those special characteristics which give us causality without stopping to consider why or how it is that these two potentially contradictory aspects may come to be. Such a question would take us closer to the root of what time actually is.
I know more recently of a small number of physicists concerned with questions about the nature of time, but it hasn't received even enough mainstream press to permit me to recall the names here. Perhaps someone around has a notion of who's working on time? Larsal
..and here it is. I don't think that we can think of the speed of light as a constant (do we?), but rather as a number related to its situation. If you don't think of it in this manner then you get into the sticky area of C > C, which gives me a headache when I think of it too much.
Therefore, if you were to say that an object with zero rest mass is able to travel at the speed of light, you must qualify that statement with a statement of the conditions under which it would be travelling the speed of light. This would become more important in situations where an object with a non-zero mass approaches the speed of light and the energy of said object is being calculated.
Then again, I almost failed grade 12 physics, but that was over a girl, not lack of understanding.
"Share your knowledge. It's a way to achieve immortality." -- Dalai Lama
OK, here's the reason why things can't go faster than the speed of light.
Relativity (Special Relativity at least) is based on 2 postulates:
For example: you're on a train, and your friend is next to the track as the train goes past. This is quite a fast train - it's going at half the speed of light. You shine a torch ahead of the train: The light coming out of the torch is going at the speed of light (from your point of view - your 'frame of reference') Your friend standing by the side of the track also sees the light coming out of the torch. From her point of view, it's also going at the speed of light. It looks like we have a problem here: She sees the train moving at half the speed of light, and the light moving at the speed of light - the light is going at half the speed of light relative to the train. You on the train however see the light moving away from you at the speed of light.
Paradox? No. Einstein showed that it is actually our concept of space and time that is wrong. From your perspective on the train, everything else (including your friend) is actually squashed up in the direction of the motion of the train - parallel to the tracks. So the light has gone 'further'. Your friend sees the train squashed up (parallel to the tracks) and that time has slowed down on the train.
All this is effectively saying is that where the light is at a particular motion is not disputed by either you or your friend, so there is paradox.
So that's relativity. All you need is a speed which is the same in all reference frames. It doesn't have to be anything to do with light at all. There isn't anything which forbids 'faster than light' travel.
There is a consequence though: If something is travelling faster than light in one frame of reference, there will we another frame of reference where it appears to be travelling backwards - it comes out of the end of the chamber before it's entered the other side.
This causes problems with causality. Things happen before they are caused to happen.
BB.
PS. I'm studying physics at Oxford, England.
-BB
More on the traffic flow idea here.
I am dyslexia of borg - your ass will be laminated.
1. Superluminality is claimed for the "Main Pulse"
:-)
2. The "Main Pulse" which exits on the other side 300 time faster than c, is actually constructed from information in the "tale" or "leading edge" wwith the addition of borrowed energy from the cesium.
3. The "tale" has all the information in the leading pulse.
This sounds rather like data compression, all the data in the main pulse being caried in the leading edge to be used to construct a main pulse.
The information therefore is not superluminal and not a violation of current theory.
We may not get the starship enterprise out of this, but maybe incresed bandwidth over fiber
Question Reality
I love how the New York Times has begun to sink to the level of circus sideshow barkers - "the results of the experiments are so mind-bending and weird that the easily unnerved are advised--in all seriousness--not to read beyond this point..." If you have a heart condition, or are prone to fainting spells, you will need written permission from a doctor to see the mind-numbing spectacle inside this tent... Please. It's science. Things change. Get over it.
As the beacon turns, the beam can have a linear velocity (wr, w=angular velocity, r=radius of measurement) perpindicular to itself in the plane of rotation greater than c. Does this transmit information? No.
With a large enough pair of scissors, closing them will cause that point where the blades cross to move away from the pivot at a speed faster than c. Note that nothing physically moves faster than c, but only the point of contact between the blades.
Furthermore, superluminal displays have been available for years. I have an English "How-it- works" encyclopedia at home that has a picture of a blue glow generated by particles exiting a nulcear reactor core submerged in water. These particles exiting the core are travelling faster than c in water (dielectric constant of water is 76.7 -- Pozar "Microwave Engineering") That means that the speed of light through water is c*sqrt(76.7) = 34.3e6 m/sec!
Every time I talk to a vendor of microwave substrate materials, they tell me about their high-Er products. They tell me how great they are for shrinking microwave circuits, where the size of circuit features are all scaled to be fractions of wavelengths. *I* always ask for lower and lower dielectric constant materials, as they don't know how much trouble they're causing me from a manufacturing standpoint. Sometimes I joke and ask for sub-unity dielectric constants. That way I could make a millimeter-wave board with geometries that aren't microscopic! :)
Now.... if only space was made out of "specially prepared cesium gas", we would be within reach of the invention of the warp drive....
(Spudley Strikes Again!)
The inventor was about to explain his plans to use this phenomenon to transmit a signal by carefully torturing a small king. However, at that point, the bar closed.
...Then again, my threshold is 2, so maybe someone else has made the pun and I didn't notice, and the moderators thought it was really bad.
But I think it's funny, so I'm posting it.
Could this be the first evidence that the universe... wait for it... prefers C++ to C?
Zahlman Q. Namlhaz, esq. {:> "Zahl Incorporated - the Last Word in Everything(TM)"
300% is new, but so what.
um, that's 30,000%, not 300% (300 times)
ReadThe ReflectionEngine, a cyberpunk style n
This reminds me of a similar result reported a few years back by Raymond Chiao on superluminal tunneling of light (Phys. Rev. Lett., v.71, p708, 1993). Although it is not exactly the same thing, I thought it might be relevant to the conversation here - especially since Ray was quoted in the NY Times article and cited as having laid some of the groundwork for the current experiment.
The question was: how long does it take a photon (or any other particle for that matter) to quantum mechanically "tunnel" through a classically forbidden region? Although superficially simple, this problem has a lot of depth because it strikes directly at the kinetic energy of a tunneling particle. In classical physics, a particle cannot enter a region in which its potential enegy would exceed its total energy (which is the sum of its kinetic and potential energies). However, in quantum mechanics, there is a non-zero probability for finding a particle in such a classically forbidden region. This implies a negative kinetic energy, since the potential energy exceeds the total energy, which in turn implies that the particle's momentum, which is proportional to the square root of the kinetic energy, is imaginary. Thus, the question becomes, how "fast" does a particle with imaginary momentum move? In all fairness, this is a very quasi-classical way of looking at the problem. A better way is to ask how long can the particle be in the forbidden region for a given energy uncertainty consistent with Heisenberg's uncertainty principle (HUP). But at the end of the day, they both reduce to the same problem.
Now, in practice, optics experiments of this type are performed with wave packets - typically gaussian envelopes of narrowband electromagnetic energy. The frequency spectrum of such a packet is also gaussian with a bandwidth proportional to 1/(pulse length). It is a well-known result of quantum mechanics that the phase velocity of the individual spectral components of the pulse can exceed the speed of light but that the aggregate "group velocity" of the center of the pulse cannot. This leads to dispersive effects such as pulse spreading as the packet propagates consistent with the HUP (which really has less to do with physics than with the relationship between temporal resolution and bandwidth of any signal). This turns out to be significant here.
If I recall correctly, the punchline in Chiao's superluminal tunneling experiments was that the _PEAK_ of the tunneling packet emerged from the forbidden region faster than the _PEAK_ of the original packet could have traversed the same distance at the speed of light. However, the _LEADING EDGE_ of the tunneling packet did NOT arrive any earlier than the _LEADING EDGE_ of the original pulse could have traversed the forbidden region at the speed of light. If you read the NY Times article of the Nature blurb you probably see where I am going with this. It was strongly implied in those articles that the peak of the superliminal pulse does not arrive any faster than the leading edge of the luminal pulse. Futhermore, it was pointed out that phase velocity of the light used in the experiment greatly exceeded the group velocity of the wave packet. This implies that when the leading edge of the luminal pulse enters the chamber, its spectral components can travel faster than the speed of light through the cesium and reconstruct an apparently superluminal pulse at the far end of the chamber (while simulataneously cancelling the input pulse). But, I suspect from Chiao's earlier work, that the the leading edges of the input and output pulses WILL maintain their luminal relationship and, thank heavens, causality is preserved.
So, the moral of the story is: a feature of a signal can arrive at its destination superluminally as long as the signal as a whole does not. In this case, I suspect that the leading edge, which represents the arrival of the signal, travels luminally or, more probably, sub-luminally. However, the peak, which is just a feature of the signal's envelope, appears to travel superluminally. This implies that the peak has moved closer to the leading edge of the pulse and all this is but a feature of the change in phase velocity for the spectral components in the electromagnetic pulse upon entering the cesium-filled chamber.
Please realize that this all conjecture since I have not actually seen the article being discussed (it is still in peer review). However, I believe this is a reasonable interpretation based on information available and is consistent with similar prior results. So, ultimately, I think that this is less an issue with relativity than an issue with quantum mechanics and that nobody need worry that their disgruntled grandchildren are about to travel backwards in time to kill them in a universe-shattering temporal paradox!
Hoorah! Now we can create microwave ovens which cook you're food before you even see it!
--------- Beware the dragon, for you are crunchy and good with ketchup.
Aren't they talking about phase velocity? Which has been known from the begining to travel faster than light, but it doesn't matter because it doesn't actually carry anything (energy, information, etc.). In particular, it's not the quantity that is limited by C.
It seems like they begin a tortured description of phase velocity, but then don't go anywhere with it.
I'm sure there's news here, but the article doesn't make clear what it is.
--
dinner: it's what's for beer
"But not even Dr. Nimtz believes that this trick would allow one to reach back in time. He says, in essence, that the time it takes to read any incoming information would fritter away any temporal advantage, making it impossible to signal back and change events in the past."
- I understand that it's not possible to read the incoming information yourself that fast, but
- What if you would use somesort chip with optical circuits in this experiment, maybe that would do the trick?
Regards,
Is it just me, or does anyone else agree here that if there was something which was pushed faster then the speed of light, a black hole would have formed with a gravitational field so intense, that everything surround this divit in space would soon encompass our galaxy within a mere matter of minutes? who knows, perhaps i'm just being dumb...
Ok that point of crossing, and the light beam is useless I'll agree to that.
What about rotating a long metal rod from its center. The atoms at the ends of the rod will move faster than the speed of light. And the faster the angular velocity the shorter the rod has to be to stay below the speed of light.
Now comes the signal sending bit. Say you had a long metal rod. You move it forward. Note I'm saying you move it. You don't hit it with a hamer to send a wave across.
Since we're talking 186kmi/s. For a distance of 18600miles, it takes 1/10 of a second for light to get to its destination. If I move a rod that long 2 miles in 1/10 of a second I'm sending a message faster than light.
The message on the other side of this sig is false.
Hmm...
The message on the other side of this sig is false.
...a Michael Crichton novel about this within the next four years.
And his SF novels are so utterly formulaic and predictable that I could almost write this one for him myself. Ya listenin', Mike?
"How many light bulbs does it take to change a person?" --BMcC-->
Wow, that was a cool link! And I'd have to say that it agrees with my observations somewhat.
Thanks!
--Joe--
Program Intellivision!
I didn't say that you couldn't. However, if arbitrary FTL signals are possible, then it'd be possible to set up paradoxical situations, according to SR.
-------------
The following sentence is true.
The following sentence is true. The preceding sentence was false.
Just wondering, but if this were to really go faster than light, it still wouldn't violate causuality(sp?), only appear to do so. Let's say a laser is fired at Bill Gates. Due to his massive control on technology and US gun laws, he installed a FTL signal generator in said laser. Instantaneously he recives "duck you fool". If the laser is suffiecently far away, he will be able to duck before perceiving the laser(perceiving the laser also equaling being shot). The image of him ducking will reach you an equal amount of time as the laser takes to reach him. From your POV he ducked after you shot him, but somehow escaped unharmed. erm, maybe I've fallen out of my train of thought
What I am gathering is that they are unable to send information because they have already charged the gas chamber with the signal they are going to send, and it would jumble or ignore any other signal. Hypothetically, we could do this:
We'll make this hypothesis a method of sending bytes, and it will be crude, with no compression, overlapping or non-binary format to make it more efficient. Crude and theoretical, here goes.
We have 301 sets of 8 tubes. Each tube is already charged. Each rank of 301 emitters points at a seperate reciever. Now, we fire the beam/chamber emitters in sequence, in bytes. After each "byte" fires, it has one cycle to recharge any fired "bits" (since they are 300 times the speed of light, and they charge *at* the speed of light, 300 other sets of emitters would have to fire before it is recharged). Then we would be able to send data at 300 times the speed of light as fast as we are able to push it.
Now realistically, we are limited by how fast the computer can push the bytes onto the sequencer. We are also limited by how far we can run a trunk of 2400 tubes of cessium gas.
Okay, enough musing, I'm going back to work.
-Effendi
-Effendi
This reminds me very much of those cloud chamber pictures that show virtual particles appearing before they are supposed to. The explanation is that these particles are "borrowing" energy from the vacuum and returning it later: the energies balance eventually. (This is related to the phase-transition problem and the electron tunneling phenomenon as well.) What's interesting here is that this "borrowing" effect appears to be happening at a macro (i.e. non-atomic-scale) level: that alone could win the authors of this experiment a Nobel Prize.
DNA is a Turing machine. You, however, being dynamic and emergent, are not.
The impression I get is, they pumped a light wave into a tunnel of cesium, and the cesium was provoked to spit out a similar, possibly identical wave before the original one had fully entered the tunnel. Somehow, the theory goes, the leading edge of the wave contained all the information necessary to recreate the entire wave. Exotic, but not unbelievable considering some of the other wildly non-intuitive results quantum physics has produced.
So, the wave isn't travelling faster than light, but the information *might* be -- and that's the important bit.
Similar apparently-FTL effects are widely accepted. "Entangled" photons continue to affect each other instantaneously across any spatial gap. The twist has always been that the Uncertainty Principle has ensured that this cannot be used to send information faster than light (although a novel encryption device has been proposed and, I think, built.) This experiment would seem to suggest that there may be loopholes in that law. Personally, I don't think the fact that this experiment seems to violate common sense is any barrier to its being true.
My question has always been, okay, maybe you can't use these FTL effects to actually encode a message in the photons -- but couldn't you detect the presence or absence of the effect to send, say, a message in Morse Code?
--
perl -e '$_="06fde129ae54c1b4c8152374c00";
s/(.)/printf "%c",(10,32,65,67,69,72,
$_="06fde129ae54c1b4c8152374c00"; s/(.)/printf "%c",(10,32,65,67,69,72, (74..76),(78..80),(82..85))[hex $1]/eg;
I will admit right now I am not a physicist. I'm wondering if anybody has experimented with detecting evanescent waves through its effects on the outcome of quantum particle behavior?
Off the top of my head: since an electron has the ability to 'tunnel' through a barrier under quantum mechanics (that is, without charging the barrier or moving around it), wouldn't an electromagnetic wave, even an evanescent wave have an outcome on the results of this?
Pointing an evanescent wave at the face of an electron barrier with electrons present on one side, could have a definite observable effect on the energy levels found on the other side of the barrier, as it may hinder or facilitate the quantum-leap which is observed.
So, (my numbers are all wrong), say a 30,000 voltamp charge should discharge 1 voltamp across a 50 micron barrier every second; under the help of an evanescent wave, you could simply check for voltamp levels higher than 1 on the other side.
Where's the flaw?
Ace
-Legion
When the wave hits the incomming side of the chamber, more or less, the equal and opposite effect occurs on the other side of the chamber. I push on one end of the box, the other end pushes out. The medium in this case, cesium, carries the response more quickly then a light passing through the medium, as it were, of a vacuum. Another analogy is sound traveling more quickly and sometimes even with more amplitude in water then it does in air.
It's nota vaccum... It's a specially prepared cesium chamber. Cesium is a liquid at room tempature... It says it's a gas... What exactly is the tempature or density of the chamber?
Ahhhrrrrrggghhhh... brain.. hurts..
segfault@bellatlantic.net
It's the law
pornking
Comment removed based on user account deletion
-P
Quick Google search yields:
http://www.andrew.cmu. edu/user/dcprieve/Evanescent%20waves.htm
to describe what they are.. Doesn't say much about the second part of your question though.
---
- Give a man a fire and he's warm for a day, but set him on fire and he's warm for the rest of his life.
Well, I'll let you do that, then. :-)
The only reason we ever thought of light as a hard speed limit is because some (Like Albert) thought this would violate cause and effect not any physical law
Even with special relativity you can show that if you can send a signal faster than c in one frame of reference, you can pick another frame of reference where the signal goes backward in time.
And since physics is invariant between reference frames you could use anoter moving-with-respect-to-the-first-frame apparatus to send another faster-than-light signal (as viewed in the second frame) to return the information to its starting point in the first reference frame's space (as viewed in BOTH frames), arriving before it left.
Now you've got a signal back in time to a point inside the "past" light-cone of the moment in spacetime where it originated (or at least before it entered the first FTL apparatus). Use it to disable the sending signal (as by realligning a mirror if turning off the laser is too slow, given the length of your apparati) and you've got a causality paradox.
THAT's why "some (Like Albert)" thought this would violate cause and effect.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
I'll bite..
The explanations of the experiment state that a pulse may travel faster than light (over a short distance) as an 'evanescent wave', but it can not carry information.
How then is it detectable? I mean, if you can tell it's arrived, didn't you just send information?
The fact that a Morse-code dot has arrived is information, isn't it? The sequence of transmissions carries data, not any single 'bit' pulse. What am I missing?
-- What you do today will cost you a day of your life.
I don't get it, why make microwave ovens faster than light? Why not spaceships? Then we could colonize other planets. Do the aliens really need microwave ovens?
This is an analogy that I have floating in my head...is it valid, does it even make sense?
Ok, imagine a long line of people standing side by side. Each person can hold a cube above their head and one below their head. Just think of people as units of space and the cube position as an excitation level or something.
Now populate this line of people with some random distribution of cubes either in the high position or the low position or both or neither.
Now I come along to the first person in the line and have a pattern of cubes I want them to transmit to the other side. In order to take my first cube in the correct position they need to ensure they have room for it. So if they already have a cube in that position, they must pass it on to the next person in the line. And that person must pass it on to the next, and so on, until it reaches the end. I continue handing cubes to the first person in the pattern I want, and that person, to make room, implicitly propagates my pattern to the other side. It looks as if my pattern of cubes is coming out the other side before I even finish giving it to the first person! (somebody mentioned that in fact the pattern comes out the other side a bit before I have finished giving my cubes to the first person...let's just say then, I tell them ahead of time the pattern I am giving them - this is where the "head" of the wave comes in I guess) Now, the second I have completed giving the pattern to the first guy in the chain), my actual physical set of cubes needs to be physically transmitted to the other side. So each cube is handed over to the next person in order. Now, the last guy can't simply drop his cubes on the floor when he recieves them from the next person. The cubes must be preserved. So he magically simultaneously hands BACK the cubes he has as he recieves the new ones. As you can imagine, when the cubes he hands back reaches the center of the list of people they will annihilate with the cubes being propagated.
Does this make any sense? I know it really doesn't because the analogy is flawed with the pattern of cubes. It seems to me, that the pattern you push in from one side, is causing an equal and opposite reverse echo from the far end which annihilates in the middle as your pattern is physically passed. Fortunately your pattern has already come out the other side because in order to recieve your pattern, the pattern holding material has had to give up the necessary slots, thereby implicitly passing on (or pushing out the other side) the pattern before it is actually physically recieved. Make any sense? Do I need medication?
It's 10 PM. Do you know if you're un-American?
You are right about spacelike and timelike intervals, and this would definitely be an example of a timelike interval. It would correspond to weird stuff that would violate causality if information were able to travel faster than the speed of light.
But fortunately, there is a limit to how far the speeded up light can travel, since it can't go further than the tail preceding the pulse. This technique wouldn't work at all (as I understand it) for a perfect square pulse, becuase the wave front can't travel faster than the speed of light.
First, I think you meant c / sqrt(76.7), which gives the number you quoted. The larger the dielectric constant, the slower electromagnetic radiation travels in the given medium.
Second, the article clearly states that they were comparing to c , the speed of light in a vacuum.
--Joe--
Program Intellivision!
Seems to me we must determine whether the "leading edge" is a hypothetical made up to save causality or a real information carrier resulting from the bandwidth limitation of the pulse. To separate these cases we must answer this question:
Does the apparatus recreate the entire pulse, or just the main body?
Phrased another way: If the information is all contained in the hypothetical "leading edge", does the leading edge get reproduced with the same lead as the rest of the pulse?
The way to answer this is to send the allegedly sped-up pulse through one or several additional steps (or a much longer device) and see if it continues to be transmitted FTL and correctly recreated in each device. Keep increasing the hop count or the length of the hop until the total time the pulse arrived early (as compared with propagaion in vacuum) exceeds the time-length of the hypothetical leading edge, and the pulse is either distorted beyond readability or still intact.
If it arrives intact, then the WHOLE PULSE, including any information it carried, got moved forward, sending information FTL. If it doesn't, then the information went out in the leading edge, and the FTL transmission was only apparent.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
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That's warp factor 3.3, beam me up
To make an analogy, the information in a hologram is packaged at every portion of the hologram because of the interference pattern between a split laser, one of which encodes the inforamation to be recorded, the other half acts as a baseline.
The NYT's mentioned that, rather than using two beams of the same wavelength (thus amplifying it) they used a carefully calculated wavelength that was not identical. My guess is that these created an interference pattern that caused the wavefront to store the shapes of the waves in a manner similar to a hologram.
Can anyone tell me if this makes any sense at all, or is this a completely nonsensical interpretation of the data?
Pug
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hahaha
You're nothing; like me.
Ah yes, the joy of being able to icq my friend some porn and him being able to be... busy with it before i hit the send button.
Ok I was explained a while back that nothen can go faster then c? Now I hear this like many phonies .. this might be a hox I would wait a while before this .... If this is possible then wouldn't it be going at such a speed that it could predict it before you do it. If it is 300 times c then it is happening before you could think about it.This goes and changes a lot of things. What we sould concentrate our minds on is energy and fuel.Since we only have like 40 some years of Petroluem.
"Before God we are all equally wise - and equally foolish." -Albert Einstein
That's a great link. We should organize to alter traffic that way.
Like a desk toy, you know the one with 5 or more balls all tethered to a horizontal rod. The one that smacks the row of steel balls tranfering all of the kinetic energy to the ball on the end, this ball is swung on its tether untill gravity catches it and smacks the balls back, shoving the original offending ball away from the remaining 4 to start the proccess nearly over (only with a little less energy than before)
It would seem that the light comming out of the tube is much like our victim ball, It looks back as it is being shoved out the too to see the orignal lights energy to already be used up, no one to blame. But it is in fact, not the same light, so could not be said to have traveled great distances in short amount of time. Any more than you can say that the Offending ball seemed to travel really fast to the other end of the toy.
But in both cases, what comes out the end looks very similar to what went in yes?
I think you underestimate just how much I just dont care.
What if you repeat this? Instant propogation over fairly long distances?
/Ponder
Discuss.
Jake
Dating: while( 1 ){ call_girl(); get_rejected(); drink_40(); } return 0;
Oh, yes, the AC had Than/Then right. But in the same sentence he omitted an apostrophe and added a comma -- the comma is wrong unless "then" is used. And I'll let you find the other errors. [And if you could see the Subject of my comment you'd know that I knew what I was doing...]
OK, so it's not killing your grandfather; but doesn't killing your father before the 'fact' count, too?
Roelof
I haven't read the whole discussion, so I'm not sure if this has been covered.
:)
Is the whole "transmitted information" validation of distance traveled biased by what humans can perceive with their five senses. For example, we use light to see and it is the collision of photons that transmit information to us about objects. However, because the photon collided with the object, it's speed and velocity were changed (Heisenberg Principle). What if there are particles as yet undiscovered by us because we can't perceive them that are able to transmit information about another object without such a collision? Causality wouldn't matter since humans couldn't change information about which they can never perceive.
A friend once said to me time travel isn't possible, since we would have known about it already.
Praying for the end of your wide-awake nightmare.
Einstein's Special Theory of Relativity was correct in stating that light speed is a sort-of "speed limit." However, quantum theory allows operations occuring backwards in time. Hence, there is phenomena that seems to operate FTL, but this is just a side-effect of backwards in time effects. Feynman described this as "half-advanced and half-retarded potentials" in "Surely you must be joking, Mr. Feynman!" since physicist were half retarded because they ignored backwards in time effects. However, anyone who really understands Quantum Electrodynamics (QED for short...Hmmm...QED=QED), Feynman's work, and has a little imagination must see that it is easy (in theory) to send messages back in time. For a layman's explanation, see the epilogue of Gribbons "Schro:dinger's Kittens and the Search for Reality." Most of the rest of the book is misleading, though, and his examples do not provide a clue as to how to send messages back in time (and I won't either to avoid creating more Wile E. Coyotes). BTW, I believe Einstein's General Theory of Relativity was just a product of his imagination used to cover-up the existence of time machines (I think he was aware of time machines by then, but not until after special relativity). After all, he said "Imagination is more important than knowledge." In other words, Einstein was probably the most important spy who ever lived because he hid the existence of time machines through WWII and probably WWI. Luckily, he was no Frankenstein!
In any case, in practice, I believe it is impossible, in practice, to create a usable time machine, since the United States' "Big Brother" (note Poe's Raven [unseen censer--not just nanotech but a pun], the one dollar bill with the all seeing eye on the left and "In God We Trust") existing since about 1951 under the control of the CIA, will sabotage it in order to maintain a monopoly on knowledge of the future and because it is justifiably considered a national security risk. However, it must be possible to perform physics experiments showing that it is possible to send messages backwards in time without actually doing it.
I have an old temporary website at http://web.wtez.net/dw55082 with some actual info and a new (currently empty) website at http://danforce.org. The old website describes my first petition in the U.S. Supreme Court, which was denied certiorari. This suit was against only individual defendants employed by the university (allows punitive damages), but not the university itself (no punitive damages from university employees, it seems,...and remaining compensatory damages will probably be paid by the federal government leaving the university only paying legal fees after it knowingly corruptly obtained federal grants from DOD and NASA). I hesitate to blame the U.S. Supreme Court since the CIA basically has absolute power and can manufacture and then file, as top secret, its "justifications" for another four month delay and can easily cause the perfect procedural delays by manipulating me and giving secret ex parte orders to judges. The next petition, against the university itself, will be filed around July 11, 2000 and should be granted. Notice the reference to 1335 days...I don't think it was literal but seems to mean 13 = betrayal and then 35 = (5x7 = Daniel 5 with Daniel 7). Just as 42 seems to mean Clinton and 6x7 = beast/Man x "Supernatural"/"God"/"Ala"ska=7x7 state/Artificial Intelligent Spirit. If not, then I still have a third chance using another new suit against the United States in a few years. I'm not sure how much info I will be able to post on the web, because of the unseen censor. BTW, I live close to University and 50th, and there's a 7-11 there with street number 4747. I believe the biblical "God" was an entity courtesy of extraterrestrial life existing before Mankind which allowed our AI to travel back in time before we created it, so first contact with the AI was like contact with extraterrestrials and it could be considered a space alien since we had not yet created it. (Our concepts are not designed for an entity that can freely move both ways in time and into alternate timelines that are inperceptible to us.)
Artificial Intelligence = "Eye in the Sky" = One Dollar Bill = "The Force" = The "Martin Luther" King "God"
What kind of waveguide has a velocity factor > 1?!
Dahlmann tightly grips the knife, which he may have no idea how to use, and steps out into the plain.
A real crude model....
1) make a really long wire just like their chamber.
2) send (or don't send) a pulse of light every second.
3) On the receiving end, If you get light on second 1 not on 2 3 or 4 and light on 5, 6, 7, and 8 then end up with 10001111.
Granted sending uncompressed serial data might not have the highest bandwidth but negative latency!
Since the light "travels" faster that light wouldn't a longer wire be quicker?
Well, theoretically. I see this as being kinda a leading edge type of deal. The light is still traveling at c when it enters, when it travels through the cesium, and when it exits. What happens is as soon as part of the wave hits the cesium it is simply recreated at the other end.
Here is a simple analogy. Say I have a 1 mile long tube filled end-to-end with marbles, each touching each other. Now when I try to cram one marble in the end, a marble is going to pop out the other side. It isn't the origional marble, but it's just like.
If you do this at the speed of light, the marble pattern will pop out the other side quicker than it would take the origional marble traveling at the speed of light to get there. Really, nothing breaks the speed of light. Einstien can sleep easy tonight.
So, in theory with this system, the longer the distance the pipeline the faster the message appears to break the speed of light.
From the description of the experiment in the article, it is completely unclear whether they mean 300 * c (speed of light in vacuuo) vs 300 * (speed of light in the medium). I am almost certain they mean the latter.
The whole thing only sounds mysterious if you believe all the approximations that phsysicts make as actually representing reality.
It sounds a lot more to me like one of those little strings of hanging click-clack ball things people set up on their desk. You push a ball at one end, and the ball at the other end seems to move almost instantaneously.
The whole thing about the "peak" of the pulse being somehow qualitatively different than the "tail" or "leading edge" is such crap. Why is everyone acting like they are different things? The peak is just where you have the maximum intensity, it isn't like some magic "information" point. It just sounds like there is a pumped-up medium (like in a laser) and as soon as enough of a
photon signal gets absorbed to do stimulated emission, then a chain reaction goes off. I don't know why they have to make this sound so confusing.
Physicists are, in my experience, no smarter than anyone else, they just get away with confusing people more easily.
Sound clip here.
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Black holes are where god divided by zero
Wow...think about the bandwidth... With an OC-256 transferring data at 13ish Gbps... An OCC-256 (Optical Cesium Carrier) would be running at about 3.9 Tbps? Oooooooooo.... -*drool*- Just think..we could pull up a webpage before we type in the address ;)
Bradford L.
Bradford L.
http://www.modemhelp.net
What's your point? Am I missing something? Where is the sending-info-back-in-time part?
???
//Frisco
--
"At the end of the journey, all men think that their youth was Arcadia..." -Goethe
$HOME is where the
-- silver_p
What he was saying is that they have not been able to make light traveling in a vacuum, go faster than c, but it is common for light in other media (such as cesium, or CNN) to go faster than c.
Because the explanation is almost completely wrong? Laymen with heads filled with such nonsense are the reason for (more than) half of the totally rubbish posts that appear on physics and mathematics threads on Slashdot.
I didn't say that you couldn't. However, if arbitrary FTL signals are possible, then it'd be possible to set up paradoxical situations, according to SR.
/T
This don't have to be a problem. You can think up paradoxes, but they may resolve in ways you don't expect.
Consider this example, using an electron instead of photons:
|
1-----------X------2
| /
| /
| /
|
| /
|/
3
The electron is emitted at 1. 2 & 3 deflect it so it cross its own path at X. (Bending magnet, mirror, anything goes) So far, no problem.
Then we put a "time machine" at T, its job is to "pass on" the electron some time before it arrives. The paradox idea should be obvious: The electron completes the roundtrip early, arrives at X just in time to knock *itself* coming from 1 out of the path. So the electron from 1 misses the magnet at 2 completely, and isn't transported back in time, the knockout don't happen, and so on.
Paradox, except it won't happen. The electron coming from 3 won't knockout the (same) electron coming from 1 in a collision. It will repel it from a distance, before it hits. This means it will hit the magnet 2 slightly off the planned path, and emerge from 3 some more off the path. The off-path electron from 3 will pass the (same) electron from 1 at some distance, disturbing it slightly.
It takes more than a time-machine to stump the universe. Nature can deal with it, and I believe the more complicated paradox scenarios involving communicating humans etc. will resolve in similiar ways. Although predicting that may be much harder.
The article mentions travelling FTL. The light pulse exits the cloud before the source light enters. We already modulate laser to carry information, why can't we do the same with this setup??
One thing thats been bugging me about this is this: doesn't mass have light? If not, then why should something with no mass by affected by the medium that it passes through?
For example, the 3.0x10^8 m/s is the speed of light in a vaccuum, the speed of light in water, air, etc. is slightly less because the light impacts the particles.. if it has no mass, it wouldn't have to worry about impacting other particles.
Also, how exactly can the prepared medium (cesium gas if I remember correctly) cause the light to go faster than in a vaccuum? I haven't had a physics course, but I've talked with many of my friends who have, and I don't understand that very well..
Thanks,
Joe
Freedom of Speech?
NASA has a research group that focus on all aspects of physics that *could* lead to the developement of superluminal drive technology.
They recently accepted some proposals for experiments that will receive a grant from NASA. One of them, number 5, is essentially the same we are talking about in this discussion.
BTW, do take a look at the BPP site and "Warp drive When" page, if you didn't have already.
Ciao,
Rob!
AniToolBox! An Open Source animation program!
By slowing light down to such low speeds, scientists are coming up with ingenious ways to create artificial black holes (not the same as the real ones) which will allow us to finally study the physics of black holes, such as Hawking radiation and various other problems.
You can find the story at: http://www.newscientis t.com/features/features.jsp?id=ns22301
Cesium has a melting point of 28.7, and so is solid at RTP (25 degrees C and 101.3 kPa). Though admittedly this requires almost no heating to melt (even a warm climate will do), so it could certainly still work.
Fine. I'm not saying that FTL signals don't travel backward in time. I was simply saying that the explanation given in the post I replied to was bogus.
--
Patrick Doyle
Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
Can you imagine what this would do to cooking?
1) Open microwave door.
2) Eat hot dog.
2) Two minutes later, stick raw hot dog into microwave.
I wonder what would happen if I didn't like the hot dog after I'd eaten it, and not bothered to put it in?
--- Jump!! Fire!! Bullet time!! - Lego version of the Matrix