B Can Info Travel FTL? Understanding Speed of Information

[Jenga_89]

TL;DR Summary

Can the speed of information be faster than light?

Summary: Can the speed of information be faster than light?

Say you had two people in space and they were 10 light years apart. Each person has a light bulb and battery connected to an electrical switch. Pressing the switch turns the light on, once it is released it springs back to the off position and the light goes out. This means each person has a way of representing 1s and 0s with the light on and off respectively.

Now say the two switches are connected by a metal bar that is 10 light years long. Connected in a way that both switches operate in relation to each other.

If the switch at one end was pressed and the bar moved, would the switch at the other end operate at the exact same time (instant) ? Or would there be a delay in the opposite end of the bar moving ? Would the bar move equal to or slower than the speed of light ? If so what would thatspeed be ?

If the bar did move instantly, and both switches operated at the same time, wouldn’t the mean information could be transmitted faster than the speed of light?
(The person at one end would flash a binary message on his own light, and it would be replicated at the other persons light, via the bar, without the 10 light year delay)

Thus meaning information can travel faster than the speed of light ?

I’m probably way wrong lol If so could someone explain why please ?

 

[PeroK]

Summary: Can the speed of information be faster than light?

Say you had two people in space and they were 10 light years apart. Each person has a light bulb and battery connected to an electrical switch. Pressing the switch turns the light on, once it is released it springs back to the off position and the light goes out. This means each person has a way of representing 1s and 0s with the light on and off respectively.

Now say the two switches are connected by a metal bar that is 10 light years long. Connected in a way that both switches operate in relation to each other.

If the switch at one end was pressed and the bar moved, would the switch at the other end operate at the exact same time (instant) ? Or would there be a delay in the opposite end of the bar moving ? Would the bar move equal to or slower than the speed of light ? If so what would thatspeed be ?

If the bar did move instantly, and both switches operated at the same time, wouldn’t the mean information could be transmitted faster than the speed of light?
(The person at one end would flash a binary message on his own light, and it would be replicated at the other persons light, via the bar, without the 10 light year delay)

Thus meaning information can travel faster than the speed of light ?

I’m probably way wrong lol If so could someone explain why please ?

Any shock wave through a metal bar will travel at sublight speed. The bar cannot be truly rigid. On a microscopic scale the wave makes its way along the bar atom by atom.

Super slow motion cameras may reveal this lack of total rigidity for objects that are not too rigid.

 

[Nugatory]

This question has been moved to the Relativity subforum from Classical Physics because it's basically about relativistic effects.

There's an answer in our FAQ (at the top of the relativity forum page): https://www.physicsforums.com/insights/can-i-send-a-signal-faster-than-light-by-pushing-a-rigid-rod/

 

[Dale]

Summary: Can the speed of information be faster than light?

Would the bar move equal to or slower than the speed of light ? If so what would thatspeed be ?

It would move at the speed of sound in the bar which is far far slower than the speed of light.

 

[Jenga_89]

Thank you for the replies

Ahh I see, so the initial movement of the bar would travel the length of the bar like a wave, moving from atom to atom at the speed of sound in that material ?

 

[phinds]

Thank you for the replies

Ahh I see, so the initial movement of the bar would travel the length of the bar like a wave, moving from atom to atom at the speed of sound in that material ?

Exactly.

 

[Herman Trivilino]

Ahh I see, so the initial movement of the bar would travel the length of the bar like a wave, moving from atom to atom at the speed of sound in that material ?

It travels like a sound wave because it is a sound wave. The rod is an elastic medium, and when an elastic medium is disturbed the disturbance travels through the medium.