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Speed Of Light Broken With Off Shelf Components
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. ""
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!
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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.
JET Program: see Japan, meet intere
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?
Just a quick reminder that ``c'' and "the speed of light" aren't exactly the same.
``c'' is the speed of light in a vacuum at a temperature of absolute 0, and it is a constant. Guess what? Alter the temperature or remove the vacuum, and it's not ``c'' any more.
Bill Nye the Science guy is rolling in his grave over CmdrTaco's stupidity.
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.
***Quis custodiet ipsos custodes***
. . . that this is nothing new at all. As they say in the article, no energy gets sent faster than light. It's just a pattern of interfering waves. Nothing spectacular at all.
It's analogous to this:
A (strong) flashlight is pointing to a screen very far away.
When you put your hand in front of the flashlight, the shadow that your hands casts is thus hugely magnified - say 100 million times.
Thus, you can move your hand at a non-relativistic speed, like 4 meters per second, but the magnification causes the shadow to move *faster* than the speed of light - in this case, 4x10^8 meters per second.
This is OK, because the shadow doesn't carry any energy or information. Nothing here violates causality.
Admittedly, I don't know how the authors of this article expect to get taken seriously coming out quickly with claims of FASTER THAN THE SPEED OF LIGHT!
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.
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
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.
"There is no substitute for thinking" - Bjarne Stroustrup
I think the best analogy I've ever seen is the one using ping pong balls.
Imagine you have a long tube filled with pingpong balls all the way to each end. Then, when you push another ball in one end, what happens? Another ball immediately pops out the other end, at exactly the same speed that you pushed in the first one, but potentially miles away from your end of the tube. But still, none of the pingpong balls ever went faster than you pushed in the first one.
I can't read the article because the server is crying, but there is a minor fact that many people on here are missing. Nothing can travel faster than the speed of light in a vacuum. There are other mediums through which objects can travel faster than light.