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Difficult Question

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So we know that light takes ~8 minutes to get from the sun to the earth. But what If I have a friend standing on the sun and he waves to me (Lets pretend he can in fact stand on the sun, and I can see him waving :s) it would take me 8 minutes to see him waving.


But what if we are both holding onto a rope, and I pull the rope. Would it take him 8 minutes to feel and notice that I'm pulling the rope?



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It will take longer than 8 minutes. It would take 8 minutes if the peak of each wave were travelling at the speed of light. Which it's not. It's more like 1 meter a second (tie a 1 meter long jump rope to a post and move it up and down, takes a bout a second for the crest to hit the post).


This applies for all things. Sound takes even longer, the rope is just a wave (like light and sound) except much slower.


Oh pulling the rope not waving it? Assuming the rope is 100% taught, then you'd feel it immediately. But that's impossible and there will be a delay. :P

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But nothing can travel past the speed of light, correct? So the rope therefor can't be felt instantly. So if you pull it, it would still take you a while to feel it, but If you pull a rope from 10 feet away, you'd feel it instantly, along with most other distances. So which one is it?



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It's not travelling faster than the speed of light. By pulling the rope the difference is about 1/2 a meter. The rope is only travelling 1/2 a meter total.


You feel it "instantly" because the time between the slack of the rope turning taught it less noticeable. So assuming no gravity affecting the rope, yes you'd feel it instantly. But you never feel a rope being pulled instantly.

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@Redmonke: The rope would not be travelling faster then light, but you would send information faster then light (something which is also not possible). Even a rigid body (a thick iron staff for example) would exhibit a longitudinal wave moving at less then the speed of light.

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