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Author Topic:   Can information travel faster than the speed of light?
coffee_addict
Member (Idle past 477 days)
Posts: 3645
From: Indianapolis, IN
Joined: 03-29-2004


Message 1 of 29 (125397)
07-18-2004 3:54 AM


Imagine that you have a rod that is made of a material that is indestructable. The rod is 30,000,000,000 meters long. If I push one end of the rod, theoretically, the other end instantaneously move away from me as well.
By the way, it takes light about 10 seconds to travel 30,000,000,000 meters.
Is there something wrong with this scenario? Can information really travel faster than the speed of light?

The Laminator

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Adminnemooseus
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Joined: 09-26-2002


Message 2 of 29 (125398)
07-18-2004 3:57 AM


Thread moved here from the Proposed New Topics forum.

  
Minnemooseus
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Posts: 3941
From: Duluth, Minnesota, U.S. (West end of Lake Superior)
Joined: 11-11-2001
Member Rating: 10.0


Message 3 of 29 (125399)
07-18-2004 4:02 AM
Reply to: Message 1 by coffee_addict
07-18-2004 3:54 AM


No such rod exists - the question is moot
quote:
Imagine that you have a rod that is made of a material that is indestructable.
You are trying to describe a perfectly elastic rod. One that will tranfer energy with absolutely no internal deformation (internal friction). The is no such substance.
Moose
{Edited to change ID from admin mode}
This message has been edited by Adminnemooseus, 07-18-2004 03:05 AM

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arachnophilia
Member (Idle past 1344 days)
Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 4 of 29 (125402)
07-18-2004 4:11 AM


well, as minne said, the rod wouldn't transfer energy perfectly, and would be subject to compression and damping of course...
however, i've heard that two subatomic particles linked in counter rotation will realign themselves instantly if one changes direction, no matter distance. i have no idea if it's true or not (i doubt it) and i'm too lazy to check at the moment.
but if it is, you could send binary messages faster than the speed of light.

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NosyNed
Member
Posts: 8996
From: Canada
Joined: 04-04-2003


Message 5 of 29 (125410)
07-18-2004 5:01 AM
Reply to: Message 4 by arachnophilia
07-18-2004 4:11 AM


quantum entanglement
You are talking about entanglement. It is true and has been lab tested. (Einstein would be surprised). But you can't transmit information that way.

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arachnophilia
Member (Idle past 1344 days)
Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 6 of 29 (125415)
07-18-2004 6:03 AM
Reply to: Message 5 by NosyNed
07-18-2004 5:01 AM


Re: quantum entanglement
no? why not, exactly?
presumably if you can check the spin, and calibrate it somehow so that on a sender clockwise is 1 and counterclockwise is 0 and vice versa on the reciever, you should be able to send binary messages. right?

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 Message 7 by Percy, posted 07-18-2004 10:22 AM arachnophilia has replied

  
Percy
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Posts: 22392
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 7 of 29 (125437)
07-18-2004 10:22 AM
Reply to: Message 6 by arachnophilia
07-18-2004 6:03 AM


Re: quantum entanglement
NosyNed writes:
You are talking about entanglement. It is true and has been lab tested. (Einstein would be surprised). But you can't transmit information that way.
Arachnophilia in reply writes:
no? why not, exactly?
presumably if you can check the spin, and calibrate it somehow so that on a sender clockwise is 1 and counterclockwise is 0 and vice versa on the reciever, you should be able to send binary messages. right?
Keeping it simple, let's say that two particles are entangled, and that they must, by conservation laws, have equal and opposite spin. Before the particles are observed, each particle has a superposition of the probabilities of both spins. Once the particles are observed, the probability functions collapse with one particle taking on one spin, and the other taking on the opposite.
Even if the particles are separated by millions on miles, when one particle is observed and takes on one spin, the other immediately takes on the opposite spin.
The reason you cannot use this to communicate information is because you have no control over which spin a particle takes on when you observe it.
Say you wanted to transmit the binary sequence 101, and you've got three pairs of entangled particles, call the pairs A, B and C. You have one particle of each pair, and your partner on the opposite side of the globe has the other. You've agreed that positive spin corresponds to 1, and negative spin corresponds to 0. At the agreed upon time (your observations have to be synchronized) you try to send the first bit of the 101 sequence by observing your particle A. But you have no control over which state it collapses to, and by sheer bad luck with 50% probability it collapses to a spin of 0. So much for sending information using quantum entanglement.
But it has strong and very useful applications in coding and security. Some think faster computers will one day take advantage of quantum entanglement. While I agree this is possible, just like you'll never see nuclear reactors on your desktop, you'll never see quantum computers there either. Or, to put it more optimistically, there's a ways to go technologically before quantum computing finds its way into the home.
--Percy

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SRO2 
Inactive Member


Message 8 of 29 (125441)
07-18-2004 10:54 AM
Reply to: Message 7 by Percy
07-18-2004 10:22 AM


Re: quantum entanglement
Hey! You said you would keep it simple!. Sending messages over long distances by quantum entanglement faster thant the speed of light, would likely also have to violate the physical laws (as we know them) of the time/space continuum. The method of excitation could only approach "c" and not exceed it...if I'm understanding the application here.
Transmitting information "faster" that the speed of light, still requires physical changes in the environment of the sender and the reciever (through whatever mechanism)...so to send info faster then the speed of light still involves problems with the physics of time as we know it..time itself would need to be reversed at the receiving end for the information or Code to get there before light.

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Tony650
Member (Idle past 4033 days)
Posts: 450
From: Australia
Joined: 01-30-2004


Message 9 of 29 (125468)
07-18-2004 2:16 PM
Reply to: Message 5 by NosyNed
07-18-2004 5:01 AM


Re: quantum entanglement
NosyNed writes:
You are talking about entanglement.
I understand that this was recently used to perform the first successful teleportation of matter. Is this the same principle?

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NosyNed
Member
Posts: 8996
From: Canada
Joined: 04-04-2003


Message 10 of 29 (125474)
07-18-2004 3:37 PM
Reply to: Message 9 by Tony650
07-18-2004 2:16 PM


Re: quantum entanglement
I think so.
As I recall it depends on particle in the same quantum state being indistinguishable. The quantum states are "teleported" so the particles are. I don't have time to read over it now and don't remember clearly.

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arachnophilia
Member (Idle past 1344 days)
Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 11 of 29 (125499)
07-18-2004 6:02 PM
Reply to: Message 7 by Percy
07-18-2004 10:22 AM


Re: quantum entanglement
hm. ah well.
seemed like a good idea.

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Tony650
Member (Idle past 4033 days)
Posts: 450
From: Australia
Joined: 01-30-2004


Message 12 of 29 (125642)
07-19-2004 10:14 AM
Reply to: Message 10 by NosyNed
07-18-2004 3:37 PM


Re: quantum entanglement
NosyNed writes:
I think so.
As I recall it depends on particle in the same quantum state being indistinguishable. The quantum states are "teleported" so the particles are. I don't have time to read over it now and don't remember clearly.
Yep, that sounds right. Thanks Ned!

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Loudmouth
Inactive Member


Message 13 of 29 (125749)
07-19-2004 5:36 PM


Tachyons are perhaps another choice for FTL communication. However, as one site claims: "The truth is that most physicists consider tachyons to be a sign of pathological behaviour in field theories, and the interest in them among the wider public stems mostly from the fact that they are used so often in science fiction." A tachyon is a particle that has an imaginary mass (sqrt of -1, I am guessing) with real energy and momentum. The largest drawbacks are that tachyons (theoretically) would disrupt a vacuum and produce causality violations. At the same time, who thought the Detroit Tigers would have 40 some wins half way through this season?
As to quantum entanglement and sci-fi, the "ansible" in the "Ender's Game" universe used something similar. If Orson Scott Card can find a use for them . . . never mind.

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SRO2 
Inactive Member


Message 14 of 29 (125765)
07-19-2004 6:38 PM
Reply to: Message 13 by Loudmouth
07-19-2004 5:36 PM


Tachyons and Sci-Fi
A lot of great scientic realty was developed from Sci-Fi.01
415
The damn kitten keeps walking across my keyboard and batting at the mouse!!! He doesn't know I got connections with the admins here...he could end up on kitten suspension if he don't watch it!

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Loudmouth
Inactive Member


Message 15 of 29 (125768)
07-19-2004 6:46 PM
Reply to: Message 14 by SRO2
07-19-2004 6:38 PM


Re: Tachyons and Sci-Fi
quote:
A lot of great scientic realty was developed from Sci-Fi.
Perhaps Sci-Fi's greatest contribution is in sparking the imagination of young minds that then go into the sciences. Just to get off topic for a second, are there any sites that list Sci-Fi inspired discoveries or technologies?

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