# Information Transfer and the speed of light

1. May 27, 2010

### Bevels

Hi, I have a question about the transfer of information at speeds faster than c. I have devised a thought experiment in order to express the logical problem I am having.

Suppose you have a string of beads in a tube from here to alpha centauri where each bead in the tube touches the next sequential bead in the tube and so on. Now suppose you place a bead into the earth side of the tube forcing the bead on the end of the alpha centauri side out of the tube. Would one have effectively transfered information faster than light?

2. May 27, 2010

### mgb_phys

The push from one side of a bead to the other travels at the speed of sound through the bead.
It's the same as the old push a lightyear long rod proposal.

3. May 28, 2010

### HallsofIvy

What your thought experiment proves is that, in relativity, there cannot be "perfectly rigid" objects. As each bead presses against the other, it compresses slightly. That is the "push" mqb phys is talking about.

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