Strange Question

[amidst]

Hi there i have a question a rather silly one but here goes. If i had length of solid rod like material,say the diameter of a straw and this length of material was a whopping one LIGHT year long and was in a dead straight line between its two end points, impossible i know but lets just assume thats the way it is. Now then lets also assume that this length of material is made from some exotic substance that cannot be stretched or compressed in any way and is ultra super light and only weighs say a few kilos, impossible again i know. Now then my mate paul is at the other end of this length one light away, now if i pull this length of material say one metre towards me, will my mate paul see it move away from him the same distance and at the same time? Now remember this length of material cannot stretch or compress and is in a dead straight line. ANY IDEAS.

[Jay-qu]

Ok, well lets simplify this a bit, when you pull on your end, lets assume that you pull on the first set of atoms in this (possibly lattice) material. When you do that the electrostatic force that binds that atom to the next will yank on the next atom, then the next atom after that will get yanked towards you and so on - as if each atom has a little rope tied to the next. The thing is this electrostatic force between the atoms propagates at c like the other forces and so over all your mate paul wont see the rod move till after at least one year ;)

[amidst]

hi there Jay-qu and thanks for your response. Yes i fully understand your explanation and you explained it very well, but what i was trying state is that the material used CANNOT stretch or compress in any way in other words the atoms will stay the same distance apart, impossible i know but lets just assume this material behaves like this, what would happen now if i pulled it.

[Erasmus00]

Yes i fully understand your explanation and you explained it very well, but what i was trying state is that the material used CANNOT stretch or compress in any way in other words the atoms will stay the same distance apart, impossible i know but lets just assume this material behaves like this, what would happen now if i pulled it.

 

The answer is this: either relativity is true AND your hypothetical material exists

 

OR your material can exist, AND relativity is not true.

 

Because we believe relativity is true, we believe your hypothetical straw cannot work.

-Will

[Jay-qu]

The problem is that any material that is made up of atoms will be held together by electromagnetic forces and these forces are mediated by the photon - which only travels at c. So you would have to find some other type of matter (?) that is not known to exist that behaves in a way as to contradict all we know about chemistry and physics..

[OldBill]

Amidst -

Under the circumstances that you imposed, ignoring the true physics of material behaviour, your mate still wouldn't see the rod move. This is because, traveling at the maximum rate of our current technology, he'd have died of old age long before his ship could have reached the other end of the rod.

 

And, assuming you're both the same age, you'd have died even a lot sooner than that.

 

That said, then ignoring all reality, you may have your mate seeing the rod move - or not move - according to your own new set of physics laws. Your choice.

[Jet2]

How can 'my' or 'other's' answer answer 'your' question?

 

Jet2 :eek_big: