how is causality maintained for an observer across vast distances?

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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

4 Answers

Anonymous 0 Comments

>So my question is, how is causality and a present moment maintained in this scenario?

How do you think causality breaks here?

Let t be the time it takes the wave to travel to the sun. At time 0, you see the wave start next to you. At time t+8 minutes you see the wave reach the sun.

At time 0.5t+4 minutes, you saw the wave get halfway to the sun.

Nothing is happening out of the expected causal order.

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