Before I get to the description of this stupid hypothetical invention, I have to say that I know that it is a fatally flawed idea. There is absolutely no practical way to ever create a device like I’m going to describe, so I’m not too interested in a long list of what’s wrong with it practically. What I want to know is what’s wrong with it theoretically.
Okay, so imagine a tug of war game. The two sides pull against each other. When one team pulls, it exerts a force on the other team that is felt immediately. When you tug on one end of a string, the other end moves at the same time and rate as the end you’re pulling. If you had a hypothetical “string” that was a lightyear long, pulled taut, when you pulled one end of the string, wouldn’t the other end move immediately? What if the string was attached at the other end to a device that pulled it back to its original position, every time you pulled your end? You could communicate instantly with Morse code using a method like this, even though the receiver is a lightyear away, right?
So what theoretically prevents this from happening? Forget about issues like keeping the string taut, or planetary orbits disrupting the string, the string not being strong enough, or any other “practical” problem. Obviously information can’t travel faster than light, even theoretically, because of a causality paradox (right?), so something has to be flawed in the theory of this idea. What is it?