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If you were stationary, and talking to someone moving at lightspeed, would they appear to be speaking in slow motion due to time dilation? (lemmy.ca)
submitted 2 weeks ago by a_gee_dizzle@lemmy.ca to c/askscience@lemmy.world
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I'm asking this because there is a scifi book I'm reading, and in the book there's a scene where someone is communicating with a person in a spacecraft moving at lightspeed. I know their ability to communicate would probably not be possible, but let's just put that aside for a second. Hypothetically, if you could communicate with someone moving lightspeed, would the time dilation make it so that they would appear to be moving and speaking very slowly relative to you?

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[–] givesomefucks@lemmy.world 2 points 2 weeks ago (1 children)

Huh?

What manner of communication moves faster than light?

It would have to be some sort of entanglement, And I think the entanglement would also normalize any time dilation. There's not exactly a way to test that yet, it's all hypothetical.

But it should just cancel out and be like you're talking to someone in the same room.

Like, there's no way for the communication (in any form) to go faster than light continuously. If it was two stationary points than wormholes or other stuff could work.

But moving at light speed, it has to be entanglement

[–] a_gee_dizzle@lemmy.ca 1 points 2 weeks ago (1 children)

What manner of communication moves faster than light?

It would have to be some sort of entanglement, And I think the entanglement would also normalize any time dilation. There’s not exactly a way to test that yet, it’s all hypothetical.

Yeah, in the book I'm reading this conversation is facilitated through quantum entanglement. Though I know in real life that wouldn't be possible because entanglement still can't be used to transmit information faster than light.

And I think the entanglement would also normalize any time dilation.

This is interesting. How does that work?

[–] givesomefucks@lemmy.world 2 points 2 weeks ago (1 children)

Though I know in real life that wouldn’t be possible because entanglement still can’t be used to transmit information faster than light.

The entire point of it, is that it can...

How does that work?

It's still entangled...

Everything about the two still has to be exactly the same, even adjusted for time dilation.

So if one is experiencing 10x the speed, 1 second of its "input" takes 10 seconds on the slow side to "output". The 1/10th speed replies and 1 second there is "output" as 10 seconds, just like it's relatively spinning 10x the speed as the reference particle.

Again, technically hypothetical because we can't build anything like that yet to actually see if it wouldnhappen. It's just one of those things where it just has to work out like that logically even though we can't see it.

[–] a_gee_dizzle@lemmy.ca 2 points 2 weeks ago

Though I know in real life that wouldn’t be possible because entanglement still can’t be used to transmit information faster than light.

The entire point of it, is that it can…

Intuitively it seems like it should, but apparently that doesn't work.

So if one is experiencing 10x the speed, 1 second of its “input” takes 10 seconds on the slow side to “output”. The 1/10th speed replies and 1 second there is “output” as 10 seconds, just like it’s relatively spinning 10x the speed as the reference particle.

Ah okay I see what you mean. So I guess, for one participant in the conversation would seem like they were talking very slowly, and the other would seem to be talking very fast. But they could still be in sync, they would just perceive the time differently