Faster than light communication?

Question

Lets imagine you had a rope with zero stretch....meaning, as hard as you tugged at it, it simply woyld not stretch. I know this is theortial, as no rope exists like that, but for arguments sake. Anyhow, you stretched, say, a billion light years of this across the universe from earth to some planet on the other end of the universe. Now, to say hi to the martian on planet X, all you do is give the rope a tug. Since there is no stretch to the rope, it instantly pulls, and the other end, a billion lightyears away, pulls instantly, sending your hello aross an expanse that would have taken light a billion years to traverse. Why can't this system work? It doesn't technially violate special relativity, since nothing is really moving faster than light...at most the rope moves a couple of inches per second for an instant.

Answer 1

Thoeretically it could work.... but they already have a method of faster then light communication. I dont full understand this, I was just talking to my physics teacher outside class and he mentioned it and I looked it up, but they can use large amounts of energy to create mass, and when they create more then one atomic partical at once, they are like perfectly synced... its more like 1 partical in two places then 2 seperate particals. Whatever happens to one of them happens instantaniously to another. If one of them is heated up, for instance, the other one, no matter how far away it is, instantly heats up. My teacher only mentioned it as someone he had just been reading, and it got me thinking. Suppose you could create more then one partical at once, and make two lumps of stuff in tune with each other. Then, you could put on in a space ship in interplanetary travel, and keep the other on earth, and make it vibrate at different frequencies to give off different sounds, which would all have their own meanings. That would effectively give an instant communication tool through no matter how much distance. But I like your idea, I can't see anything breaking rules of physics. You could use a steel bar instead of rope... then there wouldnt be any stretch to worry about.

Answer 2

The only reason I can see why it wouldn't work is because it is impossible to get a rope with zero stretch.

You are not talking about motion (wave or particle) through a medium, you are talking about force and tension.

Answer 3

It DOES violate relativity, because to be that rigid the electrostatic force would have to exceed light speed. This is not possible.

No signal transmission faster than light has ever been acheived, nor is it thought it will ever be possible.

Answer 4

Material strength comes from the electrostatic forces.  You know, shared electron shells, and all that.  And guess what?  These forces transmit force at the speed of light.  That's why the material doesn't exist.

But, if you could break the laws of physics and have such a material, sound would travel faster than light, i guess.

Some interesting places to look a material that isn't based on electrostatics.  The early Universe was very dense, and could support sound waves.  Black holes must have something absurdly dense inside.  Don't want to venture into a black hole for this experiment?  (I wouldn't blame you.)  How about neutron stars?  But as far as i know, the speed of sound in a neutron star isn't as fast as the speed of light.  This has been measured, i think.

Answer 5

You are correct.  A string that would not stretch could be used to communicate faster than the speed of light.  You may therefore conclude, that such a string (or a perfectly stiff rod) can not exist if locality is to be maintained.

You are not correct in staying that this doesn't technically violate special relativity.  It most certainly would.

If you look at the string at the microscopic level, it is obvious why the string can't be perfectly un-stretchy.  Neighboring mollecules in the string are bound together by electromagnetic forces.  The electromagnetic force propagates at light speed.  So when one mollecule starts moving, it's neighbor does not notice right away and start moving.  And it's neighbor doesn't notice for longer than that.  So no signal can progagate down the string faster than light speed.  So when I pull one end of the string, it will be a long time before the other end on the other planet notices.  Consequently, there is no such thing as an un-stretchable string.

If you want to hurt your brain some more.  Go look up the pole-in-a-barn or ladder paradox.  Imagine what would happen if the ladder were perfectly stiff.  If you could have such a thing, then the paradox really would be a paradox.

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Kate, sorry, that doesn't work.  The particles can't communicate with each other faster than the speed of light unless you subscribe to a peculiar philosophical interpretation of quantum mechanics.  And even if you do, the information they transfer cannot be accessed in any way.  Also, you don't think a steel bar can ever stretch?  Go talk to an engineer some time.