What is Digg?128 Comments
- pershiki, on 10/12/2007, -5/+89Uhh.. What?
I feel stupid after reading that. - wendelgee2, on 10/12/2007, -0/+39Soon, Ludicrous Speed will become a reality. Spaceballs was so prescient.
- itistoday, on 10/12/2007, -3/+37As many people have already said (not quite clearly enough), *no object here traveled faster than the speed of light*. It's just that the submitter probably felt he'd get more diggs with a sensational but inaccurate title.
http://en.wikipedia.org/wiki/Group_velocity - illectronic, on 10/12/2007, -0/+27Description is a bit misleading. The experiments had to do with group velocity.
“The key to understanding this seeming paradox is that no wave energy exceeded the speed of light,” said Robertson. - ChillHomie, on 10/12/2007, -1/+28To rephase the spectral components, the sound waves were sent through an asymmetric loop filter on a waveguide....
You lost me at anomalous dispersion. - RaistlinMajere, on 10/12/2007, -2/+26"Ludicrous Speed? Sir, we've never gone that fast before. I don't know if this ship can take it."
"What's a matter, Colonel Sandurz? CHICKEN???" - 16777216, on 10/12/2007, -0/+23Yeah, and if you count group velocity a herd of snails could exceed c.
- weizilla, on 10/12/2007, -0/+20@vudicarus
your link didn't work. I found the applet here: http://gregegan.customer.netspace.net.au/APPLETS/20/20.html - STKD, on 10/12/2007, -1/+17Next step: Transmitting people as soundwaves*.
*Note: May require person as > 320kbps mp3 to do so. - squeevey, on 10/12/2007, -0/+14Where's the flux capacitor?
- spac3m0nk3y, on 10/12/2007, -0/+14"They've gone plaid!"
- sirius889, on 10/12/2007, -1/+14Sure but do I own a DRM for my body to prevent copying?
- noseeme, on 10/12/2007, -10/+221.) I'd hit it.
2.) In Mother Russia, the speed of light travels you!
3.) ???
4.) Profit! - sirloin, on 10/12/2007, -3/+14group velocities above c can be obtained by any macro object (with enough of them)
light can even travel faster than c that way.. still kind of cool to see the waves appear to go faster than time. - 4NDr01D, on 10/12/2007, -4/+14you had me at anomalous dispersion
besides this is not news,
I totally saw this happen at a Rave once - Shizlanski, on 10/12/2007, -0/+10Dont worry I dont think many of us did. However, the title is inacurate. No sound actually travelled at or near c, they are actually describing group velocities. Title got me excited. How sad...
-Edit, beat to it... several times... =) - Qenton, on 10/12/2007, -0/+9Everyone knows that bad news travels faster than the speed of light.
- imthepresident, on 10/12/2007, -0/+8Tell me future boy, who's president of the united states in 1985?
- SEMW, on 10/12/2007, -0/+7To expand on my reply; If you want a more specific explanation; there's no such thing as uncompressable; only not very compressable. The 'signal' (the carbon rod moving) is transmitted down the carbon rod by electrostatic forces between atoms; the less compressible the carbon rod is, the faster the propogating wave will travel, up to the the theoretical limit of c.
- vudicarus, on 10/12/2007, -6/+13this page helped me out with a nice java app
http://gregegan.customer.netspace.net.au/APP
"how a wave composed of a multitude of frequencies moving at different velocities — all less than or equal to c, the speed of light in a vacuum — can appear to have features moving faster than c."
i think (i guess) the the big deal about the experiment was getting sound waves (much, much slower than light) to do this fancy schmancy group wave faster than c type thing - SEMW, on 10/12/2007, -0/+7Chairboy: Wrong. Nothing; not information, not transmitted force, not anything can travel faster than the speed of light in a vacuum (quantum entanglement nonwithstanding). The person on the other end of the carbon rod would feel it a little after a year later.
- SEMW, on 10/12/2007, -3/+8Replied to the wrong person, mod down
- SEMW, on 10/12/2007, -0/+5Nah; the article was about group velocity; which can indeed be faster than the speed of light in a vacuum -- but articles about it are highly misleading to anyone who doesn't understand exactly what group velocity is; and the speed of signal propogation still remains firmly less than c.
- Brutusfly, on 10/12/2007, -1/+6This is nothing more than how a spoked wheel sometimes APPEARS to be going backwards when it is actually rolling forward. (And I'm not talking about spinners on your Civic.)
- xBiTReaVeRx, on 10/12/2007, -1/+6Are we plaid yet?
- AlfieJ, on 10/12/2007, -0/+5Great Scott !!!
- raw10, on 10/12/2007, -0/+5It is possible for the group velocity of a wave packet to travel pretty much as fast as you like! This is not a remarkable result! Here are some "interesting" (not!) things about group velocity:
1. Energy cannot travel at the group velocity
2. Information cannot travel at the group velocity
This is simply something that falls out of having different frequencies travel at different speeds (dispersion). In other words, this happens all the time around us every day and is really a construct of the mathematics of waves. Again, not very interesting, so read the article closely and ignore the INCORRECT TITLE. Don't worry, the waves themselves are traveling at the speed of sound. - masgrada, on 10/12/2007, -15/+20I'm just surprised something like this came from Tennessee.
- banditski, on 10/12/2007, -1/+5"...the universe is not only queerer than we suppose, but queerer than we can suppose." - J.B.S. Haldane
- xyphur, on 10/12/2007, -2/+6...that would be *optic* boom, no?
- inactive, on 10/12/2007, -3/+7@sirloin
How can something move faster than time? I don't get it. - wmoonw, on 10/12/2007, -0/+4Well, it looks like the "whooshing" sounds in sci fi movies when something passes the camera at light speed finally make sense . . . thanks, physorg!
- Jugalator, on 10/12/2007, -0/+4"and i know.. nothing can travel faster than the speed of light... "
Correction: No *information* can be carried faster than the speed of light.
Oh and time was definitely not more "man made" than e.g. "mass".
It's a fundamental part of our universe, playing an important role in spacetime physics. - TheElectricMonk, on 10/12/2007, -2/+6thats a whole lotta gay
(couldnt resist) - STKD, on 10/12/2007, -1/+4Sure. Just stay away from those evil allofmp3.com people.
- SEMW, on 10/12/2007, -0/+3"Velocities faster than" implies that you take the modulus anyway, so that's not really a problem -- especially compared to how misleading and just plain wrong the *actual* *title* is...
- adolfojp, on 10/12/2007, -1/+4Can we please move this discussion to slashdot where it will not go to waste?
- mobialflow, on 10/12/2007, -0/+3@ OMGWTFROFLMAO
I believe sirloin is referring to time dilation. In special relativity, due to the Lorentz factor, as the speed of something approaches that of light, the time between ticks on an observer's clock will grow. As the speed of that something goes to the speed of light, the intervals between ticks on a clock become infinite. That is, time stops. But, as stated many times, nothing here actually moved faster than light. - ifire, on 10/12/2007, -5/+8You forgot to ask if it would blend!
- SEMW, on 10/12/2007, -0/+3> I still fail to understand how such things can't transmit information faster than light if something, anything is going faster than light..
Because nothing *is* going faster than light. Read the comments above; the title is misleading -- it refers to 'group velocity': the actual sound wave is definitely not travelling faster than the speed of light, and the implication from the title that a physical wave capable of carrying information is travelling faster than the speed of light is just wrong
Information cannot propogate faster than c because *nothing* can travel faster than c.
/(hopes he won't mention quantum entanglement) - GenerousLinus, on 10/12/2007, -1/+4This comment and all of the replies need to pack up and move to slashdot where you belong.
- echohtp, on 10/12/2007, -2/+5speed and velocity are two different things. you all forgot to mention that.
http://en.wikipedia.org/wiki/Speed
http://en.wikipedia.org/wiki/Velocity
welcome to physics 1 digg. - shredswithpiks, on 10/12/2007, -0/+2that's actually a clear analogy. good job!
- double0jimb0, on 10/12/2007, -1/+3Group velocity does not transmit any information of the propagating wave, and is a fairly trivial measure of a wave's properties. The article is misleading in that it implied that information was sent at a velocity > c. The information (a differential sound pressure in this case) is still traveling at the sonic speed of whatever medium it is traveling in.
- inactive, on 10/12/2007, -1/+3"Easy, time is man created. Why couldn't there be something that could move faster than it?"
1) The concept of time was created by man. Time itself has literally been and will continue to be around, forever.
2) How can you move faster than time when movement/action itself is dependent upon time? That's like saying you can travel farther than distance or travel undistance. It doesn't make sense. There is no such thing as a movement that can take place outside of time itself. Even imagining such a movement takes time as you cannot stop time to do so. Even if you were to teleport (which is, to my understanding, basically moving really really really fast) and it only took 0.00000000000000000000000000000000000000000000000000000000000000000000000001 of a second, that is still time.
***** my brain hurts just thinking about that. - Aesculapius, on 10/12/2007, -2/+4Things can move faster than the speed of light.....through a medium. Relativity states that nothing can move faster than the speed of light through a vacuum. Wave propagation, such as this article, move faster than light through that same medium.
An example of this phenomenon is Cherenkov radiation. This is a blue glow that comes off of nuclear reactor pools caused by large particles traveling faster than light inside of that medium. - Gryffydd, on 10/12/2007, -0/+2"Nothing travels faster than the speed of light with the possible exception of bad news, which obeys its own special laws."
Douglas Adams
He was right all along! - profOblivion, on 10/12/2007, -0/+2@jugalator: "No *information* can be carried faster than the speed of light."
Very true. In fact, EM waveguides regularly have a phase velocity greater than c, but information isn't received at the other end any faster. I'm foggy on the details, though (EM Waves class didn't treat me well :( ). - inactive, on 10/12/2007, -0/+2AGAIN, the news gets all hyped up about things that sound new but aren't (like that nullity *****).
If you are a physics student, you already know this, this is not news at all.
If you aren't a physics student, read:
http://en.wikipedia.org/wiki/Group_velocity
"...it is possible to design experiments where the group velocity of laser light pulses sent through specially prepared materials significantly exceeds the speed of light in vacuum. However, superluminal communication is not possible..." - Otto, on 10/12/2007, -0/+2When you push the rod, you're only transmitting force to one end of it. That force has to propagate through it in a wave-like action, because you're not acting on the whole of the rod at the same time.
Gravity acts on all parts of a mass, albeit with different values depending on distance.
Magnetism does the same thing as gravity, it acts on all the bits at once..
But you shoving something with your hand does not act on all parts of the mass at once. -
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