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Science

Speed Of Light Broken With Off Shelf Components 527

Posted by Hemos from the breaking-the-limits dept.
jukal writes "An interesting article at NewScientist.com: " Now physicists at Middle Tennessee State University have broken that speed limit over distances of nearly 120 metres, using off-the-shelf equipment costing just $500.", " it may be possible to use this reflection technique to boost electrical signal speeds in computers and telecommunications grids by more than 50 per cent. Electrons usually travel at about two-thirds of light speed in wires, slowed down as they bump into atoms. Hache says it may be possible to send usable electrical signals to near light speed. ""
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Speed Of Light Broken With Off Shelf Components More

Speed Of Light Broken With Off Shelf Components

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  • i wholehearteddly believe this (Score:4, Funny)

    by krog ( 25663 ) on Monday September 16, 2002 @03:10PM (#4268236) Homepage
    anyone selling a bridge?

  • 186,000 miles per second (Score:5, Funny)

    by sulli ( 195030 ) on Monday September 16, 2002 @03:11PM (#4268244) Journal
    it's not just a good idea, it's the law!

  • First Post at Light Speed! (Score:5, Funny)

    by Anonymous Coward on Monday September 16, 2002 @03:11PM (#4268247)
    Ack! I bet by the time I hit submit, some other guy using electrons travelling faster than light will have beaten me to first post!

    Damn you technology!

  • I did this years ago (Score:4, Funny)

    by briglass ( 608949 ) on Monday September 16, 2002 @03:11PM (#4268248)
    Using onion skins, sixty-four removed coke labels and an ampersand.
  • That explains why I've been getting sunburned lately.

  • Finally! (Score:5, Funny)

    by SkOink ( 212592 ) on Monday September 16, 2002 @03:12PM (#4268258) Homepage
    Now I can view my pr0n before I go through all the trouble of looking it up!

    I bet I get modded: -1, Temporal Paradox.

  • Namely: a hammer and a mighty fine pick.
  • Someone verify these results so they don't have to be retracted 2 years from now *grin*

  • A few points: (Score:3, Insightful)

    by Xerithane ( 13482 ) <xerithane AT nerdfarm DOT org> on Monday September 16, 2002 @03:16PM (#4268290) Homepage Journal
    This is a perfectly acceptable technique. The purpose of this (known) technique is to show students how to verify the results of previous scientists and work with "faster than light" physics.

    The thing is, how is this practical in a real environment? They mention at the end that this can improve the speeds inside electronics, however this requires two signal generators so I don't see the benefit. It seems the latency involved in synchronizing the two signal generators and all the overhead associated with that would counter-act the speed benefits. Of course, I may just be stupid. This isn't my area of expertise, I just don't see how it would actually work in practical use.

    As for all the people boasting their superior knowledge of physics in regards to faster-than-light-particle travel, go read the article.

  • This is a message from the future (Score:5, Funny)

    by Pratip ( 14939 ) on Monday September 16, 2002 @03:16PM (#4268294)
    Using this technology 5 years from now, I was able to send this message to the past, and to this news release on Slashdot...or as we call it now "SlashNation".

    The message?

    They will never cancel Friends! They are still going at it! Help us, please!

  • Confusing headline (Score:4, Insightful)

    by Bonker ( 243350 ) on Monday September 16, 2002 @03:17PM (#4268301)
    Speed Of Light Broken With Off Shelf Components

    Careful here, guys. Breaking the speed of light would be a truly wondrous, nobel-prize winning acheivment. Building transmission eqipment which boosts signal speed is really good and worthwhile, but nowhere near as important an advanced as superluminal transmission.

    Please check your headlines!

  • Links & a question (Score:5, Informative)

    by alienmole ( 15522 ) on Monday September 16, 2002 @03:18PM (#4268306)
    Of course, we're going to have the usual back and forth about how this isn't really breaking the speed of light, it's just the group velocity, etc. For those unfamiliar with the issue, the following links might help:

    http://scienceworld.wolfram.com/physics/Superlumin al.html [wolfram.com]
    http://www.weburbia.com/physics/FTL.html [weburbia.com]
    http://physicsweb.org/article/world/13/9/3 [physicsweb.org]

    The thing that really seems interesting about this is that they're doing this with cheap equipment, which will make experimenting with this a lot easier.

    Can anyone explain how this would be used to increase subluminal transmission of electrical signals, as mentioned in the article? This whole group velocity thing has always seemed like a bit of an illusion to me, and none of the explanations I've seen has really clarified how it's anything more than that.

  • From the article: Signals also get weaker and more distorted the faster they go, so in theory no useful information can get transmitted at faster-than-light speeds, though Robertson hopes his students and others can now rigorously and cheaply test those ideas.

    Obviously FM transmission would not be useful by this method. After the speed of light you would loose frequency integrity. But it maybe useful as an Amplitude Modulation(AM) medium where the frequency only has to be approximated.
    • no, you still get into problems with the frequencies traveling at different speeds (dispersion). think of an AM wave, you have a set carrier frequency and then you modulate it's amplitude to convey the information. you can take a fourier transform of the wave to see the component frequencies. if you do this, you'll see a large peak at the carrier frequency, but there will be other smaller side peaks (side bands) in there too. if you only had one frequency present, all you'd get would be a sine wave which carries no information. you need to constructivley and destructively add waves of different frequency to carry information. once you have more than one frequency, you get into problems with phase velocity and group velocity, and no matter how hard you try, the information will not travel faster than the speed of light.

  • Isn't this like the moving beam of light? (Score:4, Insightful)

    by ocie ( 6659 ) on Monday September 16, 2002 @03:19PM (#4268329) Homepage
    Imagine a rotating laser light source. If you had a laser beam that was rotating at only 2rpm, the beam would move across the surface of the moon at approx 1.7 times the speed of light, but you are not really moving anything (not even light) at more than c. You can't use this to transmit any information or power.

    • Re:Isn't this like the moving beam of light? (Score:2, Insightful)

      by Anonymous Coward
      The analogy does not hold.

      Think of the laser more like a machine gun to see what I mean. (Particle part of light's wave-particle nature)

      When you sweep the moon, you do not leave a solid contiguous marker trail. Instead, you leave bullet holes with gaps between them. The gaps are proportional in length to the differential of speed between the sweep and the speed of the bullets.

      In other words, the laser is landing photons on the moon in such a way that they get there when they get there. Of course, they get there at the speed of light. And the "sweep" as an entity that moves is a fiction.

    • Now if you were standing at the end where the laser (or bullet, in another poster's machine gun analogy) impacts are coming to, what would it look like to you (assuming it stops just short of hitting you)? The answer is, you'd see the closer impacts first, and the more distant impacts later. It would appear that they are going away from you. So from this perspective, time would appear to be going backwards.

      The thing is, we might actually see such things happen out in space. Stars that are emitting energy in a specific direction, other than their poles, and are rotating, can illuminate dust clouds at some distance off to the side. On the side where the rotation is coming towards us, and at a distance sufficient to make the effect traverse faster than light, we'll actually see (if we can see that level of resolution) the effect go backwards. Combining the effect with an accurate rotation rate measurement, a very accurate distance from the star to the dust cloud can be measured. Then from there you can work back to an accurate mesure of the distance. In reality the distances will be rather small for quickly rotating stars, so it can't be observed directly. But surely it's effects can be predicted from other determinations of that distance and rotation rate, and then used to confirm those measurements.

  • GAH (Score:4, Interesting)

    by gclef ( 96311 ) on Monday September 16, 2002 @03:19PM (#4268330)
    Ye gods, I hate these types of stories. The real physics is always more subtle and interesting than the press makes them out to be.

    The vast majority of the experiments I've seen like this (I've really only looked at photon tunneling, but this sounds *very* similar from the write-up) are explained by wave-shaping, and the side-effects of that, and are not actually FTL at all. But of course, that's hard to explain to people, so the New Scientist, et al, just go for the "Speed of light broken!" headline, which mis-leads everyone.

    Grrr.

  • This article is so bad it's not funny. (Score:5, Insightful)

    by rsidd ( 6328 ) on Monday September 16, 2002 @03:21PM (#4268342)
    The "peak of the signal" (ie, the phase velocity) can travel faster than light -- big deal. It's been known for a long time. The "group velocity", as the article points out, is not faster than light, so no energy is being transferred faster than light, so relativity isn't being violated.

    If you want to see a "thing" travelling faster than light, sweep a searchlight across a cloudy sky. That lit-up patch can, in principle, travel faster than light -- but it's not matter or energy, only an appearance.

    And the last paragraph: "electrons usually travel at two thirds the speed of light". Wow, who needs particle accelerators?

    What is a writer who can't distinguish the speed of electrons from the speed of the electrical signal doing writing for New Scientist? What is New Scientist doing publishing such crap?

    • In my admittedly limited experience with New Scientist, I have found that the only thing they publish is this crap. All of their articles are some combination of poorly informed, poorly written, inaccurate and over-hyped. Frankly, if I were filtering through article submissions, I would ignore anything coming from New Scientist. If it's actually important, someone else will write it up, and their article will be better written.
    • If you want to see a "thing" travelling faster than light, sweep a searchlight across a cloudy sky. That lit-up patch can, in principle, travel faster than light -- but it's not matter or energy, only an appearance.

      You're using an assumption that always bugs me.

      Let's say, for example, that I've got a 1 AU (about 8 light-minitue) long indistructable rod and I'm out in space. I push the rod. Common sense says that the far tip of the rod moves at the same time I move the near tip. But that'd break the speed of light; forgetting about inertia for a moment, it'd take at least 8 minutes for the rod to move after I push the near end.

      If I have a powerful laser out in space that points out to 1 AU, and a spin it 180 degress, the "spot" of light doesn't move; light just starts moving out at c in the opposite direction.

      Yeah, and that's probably not what you meant... but it's bugged me ever since High School.

      • Let's say, for example, that I've got a 1 AU (about 8 light-minitue) long indistructable rod and I'm out in space. I push the rod. Common sense says that the far tip of the rod moves at the same time I move the near tip. But that'd break the speed of light; forgetting about inertia for a moment, it'd take at least 8 minutes for the rod to move after I push the near end.

        If I have a powerful laser out in space that points out to 1 AU, and a spin it 180 degress, the "spot" of light doesn't move; light just starts moving out at c in the opposite direction.

        If you define the "spot of light" as "the area illuminated by the laser," and "to move" as "to change location," the spot of light most certainly does move. 8 minutes after you turn the laser, it will move across whatever you're illuminating at a speed exceeding that of light. I don't know what else you could possibly mean by "spot of light" or "move." Of course, this does not violate relativity at all.

      • Re:Nitpick (Score:3, Insightful)

        by alienmole ( 15522 )
        I'm not clear on what exactly bugs you about this. In your laser example, when you spin the laser 180 degrees, light travels out from the laser as it's being spun, and as a result, the appearance can occur of a moving spot which travels faster than c. The spot is not a single "thing" - it's the result of a succession of related events, as the emission source describes an arc. From the point of view of physics and special relativity, the fact that the resulting "spot" moves faster than c is unimportant, and doesn't break any rules. A projected spot or shadow is not a "thing" from the physical perspective, even though people tend to think of it as such.

    • group velocities can exceed c (Score:5, Informative)

      by alienmole ( 15522 ) on Monday September 16, 2002 @03:51PM (#4268590)
      Can't argue about New Scientist - it seems to have lost all credibility, perhaps since it began publishing on the web, I'm not sure. Luckily, we have Slashdot to correct it! ;o))

      Regarding phase velocity vs. group velocity, both phase velocity and group velocity can exceed c - see Superluminal [wolfram.com], second paragraph. Group velocities exceeding c have been done for decades - for a bit of a history, see No thing goes faster than light [physicsweb.org].

      The innovation in this case seems to be that it's doable with cheap equipment, and over fairly long distances.

    • The article is interesting, but really only to physcis students with a no budget for interesting experiments.

      As for that "electrons usually travel at two thirds the speed of light" nonsense, who is the editor?

      I have calculated the drift speed of electrons myself (you could too, it isn't hard). It depends on a couple factors, but the normal US 120V circuit humming along at maximum capacity (15 A) has an electron drift speed along the wire *orders of magnitude* lower that 2/3*c. I don't remember the exact number, but it was something likt 6 CM per hour! Eg, a snail moves faster.

      The e/m field propation is at the speed of light, not the electron motion. Perhaps he didn't meant drift speed. Individual electrons can and do move much faster, but their paths are quite random, in all directions. The aggregate speed comes out very low.

      Tim
    • "electrons usually travel at two thirds the speed of light"

      Unless its an AC circuit of course, where they normally travel at an average of 0mph. These electricity companies are ripping us off.

    • >What is a writer who can't distinguish the speed >of electrons from the speed of the electrical >signal doing writing for New Scientist? What is >New Scientist doing publishing such crap? In terms of journalistic calibre, New Scientist falls somewhere between the National Enquirer and Popular Science.

  • Phase vs. Group velocity (Score:5, Informative)

    by Mendenhall ( 32321 ) on Monday September 16, 2002 @03:22PM (#4268353)
    Here comes this problem again. The article explains it, but buries it at the bottom.

    What the group has attained is a transmission line with a phase velocity greater than the speed of light. This is actually not too hard to do with a resonant line (which they have), but they have constructed a cute, cheap way to demonstrate it. The group velocity, which is the speed at which information moves, is still less than c, and they explicitly say so.

    The best use for a setup like this is to bring a good demonstration of the difference between the two to an undergraduate laboratory setting, to hammer into students forever the importance of the difference.

    • Right, but it's slightly more complicated then that. What is really going on is that the nearly resonent wave is interfering with the signal wave, canceling out the stretching effect you get. That is, different frequency components of any EM wave will travel at different velocities with the fastest component going near the speed of light. So the information packet stretches as it goes down the wire. Conventional electronics cannot predict the entire wave from just the fastest component but the universe can as a quantum mechanical effect. You can't pass information without multiple frequency components (even just changing the phase will temporarily create additional frequency components, which stretch). In anycase, since conservation of energy is required by the universe (at least so far), the canceling out of the slower components of the wave causes the energy associated with those components to accumulate in the faster components of the wave. These faster components happen to be moving at near the speed of light so, overall, you wind up with a non-attenuated (or less attenuated) signal at the far end whos entire contents reaches the far end at near the speed of light.


      Now the complication: you cannot simply create a resonent wave to cancel out the slower components at point X because you do not know what those slower components are at point X (they haven't arrived yet). But since the signal itself knows (quantum mechanically speaking), you can use reflections of the signal itself, at near resonence, to cancel out portions of itself which have not yet arrived. Confused yet? The result is that the cancelation gives the whole signal 'a push'. This cancelation effect appears to move faster then the speed of light because it is canceling a wave that has not yet arrived. This is the phase velocity they are talking about I think. but it is only using information that has traveled at the speed of light (quantum mechanically speaking the universe only needs the leading edge of the attenuated signal to know the whole signal), so there is no way this technology could be used to actually achieve FTL data transfer.


      This is for real, a number of universities have been working on it for years. How useful it winds up being in the end is a matter of opinion, though.


      -Matt

  • 4x FTL? (Score:3, Funny)

    by bytesmythe ( 58644 ) <bytesmythe@@@gmail...com> on Monday September 16, 2002 @03:22PM (#4268356)
    Electric signals can be transmitted at least four times faster than the speed of light...

    This is known because researchers observed the results of the experiment a month before it was actually attempted.

    At first, they were confused by their output terminal spewing phrases like "Hello world!", "Is this thing on?", "How can we tell if it's working??", "What's WRONG with this FSCKING THING??", "FSCK IT! I'm going home!!!" late last month. Earlier this week, one researcher was sending keyed kignals into the system, and becoming frustrated at the lack of output, until he and a colleague accidentally picked up a stack of printed logs from 4 weeks ago and discovered the system had worked before it had been turned on.

    Neither researcher could be reached for comment, as they both suddenly became multi-quadrillionaires and are living on private islands in the South Pacific.

  • Information transfer is essentially energy transfer. It is possible to make something change in response to something at the other end of the coax faster than the speed of light, but at the end of the day no information can be transfered.

    So, in my opinion, this isn't going to make those electrons in your computers and comms links move any faster.... oh well.

  • Related Stories (Score:4, Funny)

    by RedWolves2 ( 84305 ) on Monday September 16, 2002 @03:25PM (#4268393) Homepage Journal
    Did you see the related stories associated with this article?

    Related Stories

    Black hole theory suggests light is slowing
    8 August 2002

    Light may have speeded up
    15 August 2001

    So which is it light is speeding up or slowing down???
  • With a headline like "Speed Of Light Broken With Off Shelf Components" I can see why.

    For shame!

  • No signal faster than light (Score:3, Insightful)

    by mocm ( 141920 ) on Monday September 16, 2002 @03:28PM (#4268414)
    Just to get some things straight:
    Although it is possible to define and even measure speeds faster than the speed of light in vacuum, you cannot transmit signals with a speed faster than light.
    You can have electrons faster than the speed of light in a certain medium, that's when you get Cherenkov radiation.
    You may think tunneling can give you speeds faster than light, but that's only possible for a part of the particles that tunnel and on average you won't be faster. Since you don't know which particle is going to be faster, no increase in signal speed.
    You may even see that the peak of a signal arrives faster, but that is only because the whole shape of your signal is changed and amplitude of your signal is reduced, so that the peak moves forward during the tunneling process. There is no way that
    the signal front is faster than light.
    The experiment is interesting in so far that it gets you closer to the speed of light which is your limit.
  • it may be possible to use this reflection technique to boost electrical signal speeds in computers and telecommunications grids by more than 50 per cent. Electrons usually travel at about two-thirds of light speed in wires, slowed down as they bump into atoms. Hache says it may be possible to send usable electrical signals to near light speed.

    Apple [apple.com] already does this stuff for their Faster Than Light(tm) G4 Processors [apple.com].

    Oh wait, take that back. They removed that line.

    -- Len

  • This one may not stand the test of peer review. If you read the article, you'll note that the apparatus used was a maglite, a mirror and a stopwatch, with all results certified by Victor Ninov.

  • use a laser (Score:3, Interesting)

    by g4dget ( 579145 ) on Monday September 16, 2002 @03:34PM (#4268461)
    Shine a laser at a mountain a hundred miles away and rotate at modest speed--the spot of light will move faster than light. From the fluffy description in the New Scientist, it sounds as if they roughly did an electrical version of that--what moves is something you construct in your mind, not anything tangible or anything you could use to "send signals faster than light". And, unlike the "complicated setups" they are referring to, their effect is purely classical.
  • Does this mean the Dolorean now only has to go 22MPH now?
  • As I vaguely understood the explanation, it seems to rely on properties of wave interference. Some components, if you will, of a combination of waves travel faster than light, but the aggregate doesn't. OK, that's not too far fetched for my basic physics knowledge to comprehend.

    But we all know that electrons have properties of particles as well as waves. So that makes me wonder if all electrons travel at the same speed, or are they traveling in a range of speeds, with the average electron going at the nominal speed for a given medium? In other words, are some going slower and some going faster? And if so, is it possible that some are actually going much closer to the speed of light than others?

    • But we all know that electrons have properties of particles as well as waves. So that makes me wonder if all electrons travel at the same speed, or are they traveling in a range of speeds, with the average electron going at the nominal speed for a given medium? In other words, are some going slower and some going faster? And if so, is it possible that some are actually going much closer to the speed of light than others?


      Don't get quantum mechanics and electrical transmission mixed up. It sure seems like electrons are spouting out of the wire at some crazy speed, but what you're seeing is the interaction of electrons on each other (to put it really simplistically). Think of it like a hose that's full of water, but with the valve shut off. When you open the valve, water rushes out, not because it traveled really quickly from one end to the other, but because the water at the valve end pushed until the water at the open end came out. It's the same thing with a wire. The electrons themselves move quite slowly, maybe a little faster than you can walk (in something like the copper wire in your house). In fact, if you equate electrical current to the flow of water in the hose and electrical voltage to the pressue of the water, you have a pretty accurate analogy!


      -h-

  • Sandurz: Prepare for light speed. Helmet: No, no, light speed is too slow. Sandurz: Light speed too slow? Helmet: Yes, we'll have to go right to...Ludicrous speed! Sandurz:Ludicrous speed! Sir, we've never gone that fast before. I don't think the ship can take it. Helmet: What's the matter, Colonel Sandurz...CHICKEN?!

  • Ludicrous speed! (Score:5, Funny)

    by McFly69 ( 603543 ) on Monday September 16, 2002 @04:07PM (#4268707) Homepage
    Sandurz: Prepare for light speed.
    Helmet: No, no, light speed is too slow.
    Sandurz: Light speed too slow?
    Helmet: Yes, we'll have to go right to...Ludicrous speed!
    Sandurz:Ludicrous speed! Sir, we've never gone that fast before. I
    don't think the ship can take it.
    Helmet: What's the matter, Colonel Sandurz...CHICKEN?!
  • Since the speed of light in copper is zero, anyone with a flashlight battery and a length of wire is able to send electrons faster than light!!!

    With such bloated cost estimates, those scientists must be working for the Pentagon, because the last time I checked, those materials were much cheaper than $500.

  • Time machine: Here I come!

    Next step: finding a deLorean on eBay...

  • This is misleading sensationalism (Score:3, Insightful)

    by Dr. Spork ( 142693 ) on Monday September 16, 2002 @04:13PM (#4268753)
    No, don't worry, nothing actually traveled faster than the speed of light, and nobody can send information faster than the speed of light. You have to read pretty far down in the story to get that... Well, either that, or you had to have gone to school.

    You know, non-physical object can travel faster than the speed of light. You can do these experiments very cheaply. Take a laser, point it at the moon, and shake it around. The image you make with it traverses the surface faster than the speed of light. That doesn't mean anything is actually moving faster than c. The experiment described is of the same sort. Interesting, but packaged in a terribly misleading way.

  • Anyone have a mirror of the NewScientist web site? Their web programmer is clueless (and has been told about this a few times) and developing stuff that is incompatible with some proxy servers.

  • phbbt, I already did this in 5 years! (Score:3, Funny)

    by gosand ( 234100 ) on Monday September 16, 2002 @04:22PM (#4268821)
    I have already proven that you can break the speed of light barrier, in 5 years. I was visited today by myself. I guess in 4 years I am going to fall while hanging a picture in the bathroom, and hit my head on the sink. I'll be knocked unconscious and have a vision of something called the flux capacitor. It will take a year to develop, and I will be able to travel faster than the speed of light. Oh wait, or was it travel in time? Crap, I can't remember what I told me.

  • Phase Velocity vs. Group Velocity (Score:5, Insightful)

    by Effugas ( 2378 ) on Monday September 16, 2002 @04:28PM (#4268865) Homepage
    I'm going to munge this pretty righteously, but it's for a good cause (explaining how the speed of light wasn't violated).

    Take a bunch of cars in traffic -- stop 'em, say there's an accident. Cops go ahead, clear the accident. Open road, right? Clear to go 65.

    Does the entire traffic jam disappear immediately? Nope. Each *car* may be able to go 65 now, but they have to wait for the car in front of them to go away. That takes time -- two to five seconds. There's a bit of a blurring, as people see cars three or four cars ahead start to speed up -- but just because the cars *could* go sixty five, doesn't mean they *are*.

    If you were sitting above the traffic in a copter, you'd look down and see a "pulse" travel slowly back through the crowd, as slowly everyone saw the car in front speed up. Eventually the entire group would speed up to some maximum speed.

    The speed of the cars forward is the group velocity (more or less).

    The speed that "all clear" pulse went backwards, that's the phase velocity.

    Imagine everyone was drunk -- that pulse would go back really, really slow. Imagine everybody's car had a computer, linking 'em together. The *moment* the guy in front of them moved, they'd speed up too. That pulse would go quite fast, and traffic would be rather more bearable.

    Same speed limit -- same group velocity -- but phase velocity ranges from near zero to past the speed of light, depending on whether drunk drivers or synchronized computers are behind the wheel.

    At no point does any care break the speed of light, though :-)

    --Dan
    • Same speed limit -- same group velocity -- but phase velocity ranges from near zero to past the speed of light, depending on whether drunk drivers or synchronized computers are behind the wheel.

      Only if all the computers had atomic clocks and were told beforehand an exact time to set off. If the computers were daisy-chained together, the signal would travel back through the jam at no more than the speed of light. I was with you right up until that point... :)

      • Pi--

        I thought about explaining that, figured I'd just throw it in the inevitable response.

        Basically, you schedule all the cars to start driving forward some time in the future. Given sufficient distance between the cars to begin with, it isn't hard to cause the discretized speed of the pulse transfer to exceed the speed of light, even with arbitrarily drifting clocks.

        --Dan
  • ...how about this:

    "MAN USES OFF-THE-SHELF COMPONENTS TO TRAVEL BACK IN TIME"

    Story: 34-year-old Miami resident tapes Thursday's Weakest Link for viewing on Saturday morning.

  • Painfully inaccurate (Score:3, Insightful)

    by fegu ( 66137 ) <FinnNO@SPAMGundersen.net> on Monday September 16, 2002 @04:36PM (#4268923) Homepage
    From the post: "Electrons usually travel at two-thirds of light speed in wires".

    Now that would be truly remarkable and fairly dangerous, what would happen if you cut the cable and pointed the end at someone?

    In reality, electrons move abysmally slow, something along 2cm/hour if I remember my high-school physics classes correctly. What moves at 2/3 the speed of light in wires is the signal.

    Think of it this way: when you turn your kitchen hotwater tap, water starts flowing from your tap immediatly and water starts flowing within the pipes very quickly as the sudden _change in water pressure_ (signal) propagates through your pipes.

    The water itself however, is not really moving this fast. It is not the same water going in that is coming out.

    Someone please sign Hemos up for physics 101? I would do it but I live in Norway and I doubt he would be able to concentrate on anything else than our fjords if he bothered coming here.
  • When the scientists talked about transmitting peaks of waveforms at four times the speed of light, it wasn't anything new. The group velocity of a set of signals can easily exceed the speed of light, but the caveat that was included in the text of the article was spot on the money. Although the interference signals were traveling very, very fast, no useful information was available from them. Thus, in and of themselves, the interference patterns have no value, and again, that's not news.


    On the other hand, increasing transmission speeds in computers, whose signals typicall travel at around .5c, by 50% would be a big gain. The time that it takes a signal to get from, say, the input of a chipset's driver to its output is on the order of 2ns. In an area where every picosecond counts, a significant reduction in propagation time is priceless!


    -h-

    • Doh!!! (Score:3, Informative)

      by HardCase ( 14757 )
      Whoops, let me correct this...where I said group velocity, insert phase velocity.


      The group velocity is the speed at which the information travels. Obviously that's the thing that we'd dearly love to increase.


      -h-

  • Obligatory Futurama Reference... (Score:3, Funny)

    by Cyno01 ( 573917 ) <Cyno01@hotmail.com> on Monday September 16, 2002 @10:32PM (#4270721) Homepage
    from ep. 2ACV10 - A Clone of My Own

    Prof. Farnsworths Clone: Thats impossible, you cant go faster than the speed of light. Prof. Farnsworth: Of course not, thats why scientists incresed the speed of light in 2208.

  • Wow. (Score:3, Funny)

    by Decimal ( 154606 ) on Tuesday September 17, 2002 @04:43PM (#4276771) Homepage Journal
    Whew! Imagine how many points that speeding ticket will add to your driver's license!

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