Lets say there is a 10-20 lightyears deep cave and someone who is heavier than the rope going down with a rope attached to him -changes in gravity probably affects on such a scale so gravity is equal-. Normally, rope should be tensioned as long as person doesn’t put his feet on the ground. But what happens if the cave is that deep? Could someone on the surface feel caveman hitting the bottom faster than light could travel that distance? If he can, how can something be faster than light which isn’t obviously subatomic scale? If he can’t, isn’t tension equal everywhere on a rope?
In: Physics
Lets assume a massless rope because any known material would break because of their own weight and the mass of the rope would be many times higher than the cavemen.
The answer is that takes many years for the tension to move in the rope because it moves at the speed of sound in the material.
If you push on one end the movement will propagate as a pressure wave. Sound is a pressure wave, compare to if you tap a hammer on the end of the rod. So you push travel in the metal rod at the speed of sound in the material.
The speed of sound in steel is around 5900m/s. Light travel at 299 792 458m/s that is 299 792 458/5900 =50812 let’s use 50 000 faster the speed of sound in steel.
So when the person reaches the bottom of 10 light-years long steel rope you have to wait 500 000 years to feel the difference in tension.
I would assume that given weight is a function of gravity and the tension is a function of the weight, the release in tension would also be a function of gravity, so the effects would travel at -9.8m/s^2 (since the acceleration is going against gravity)
Pretty much any question “is it faster than speed of light” can be answeared with “no”.
The explanation is that tension is not equal everywhere on the rope.
This is pretty much reverse of the falling slinky.
Latest Answers