how is causality maintained for an observer across vast distances?

Question

This is a little thought experiment that has been bugging me, and I’d like to know if I’m even close:

Imagine a string tied between the Sun and Earth. You are holding this string.

You wiggle the string, generating a wave that travels from the Earth to the Sun, along the string. You watch this wave move along the string with a telescope.

When we look at the sun from Earth, we see it as it was 8 minutes ago, because it takes 8 minutes for the light to travel to Earth.

When the wave reaches the sun, you will see it 8 minutes after it has actually reached it. But you have watched it travel away from you in real time, uninterrupted. You have essentially watched the wave move backwards in time.

So my question is, how is causality and a present moment maintained in this scenario? Is it simply that, from the waves POV, time would move 8 minutes slower relative to the observer on Earth? The string isn’t actually moving backwards in time, but instead experiencing it at a slower rate, thus resolving the seeming paradox of watching the wave go back in time and preserving causality?

Let me know if this is stupid thank you <3

In: Physics

Answer 1

> When the wave reaches the sun, you will see it 8 minutes after it has actually reached it. But you have watched it travel away from you in real time, uninterrupted. You have essentially watched the wave move backwards in time.

When you first wiggle the string you look at the sun as it was 8 minutes ago. From your perspective the wave in the string is going to take at least 8 minutes to reach the sun, as it cannot travel faster than light.

However you won’t be able to see it reach the sun 8 minutes after you saw it leave. After all that would imply it traversed the distance instantly! Instead you would see it arrive 16 minutes after it left; 8 minutes to travel there and another 8 minutes for the light to reach you on the way back. As the wave moves away from you it is going to seem to slow down because your news is smoothly becoming more and more behind.

Causality is not breached by this state of affairs.