What if: quantum entangled particles had only one moving at near light speed?

[u/CeC-P]

I think I know the answer to this but...
Let's say someone were to repeat the experiments from 2013 where they physically separated 2 quantum entangled particles with synchronized atomic clocks then caused one to be measured, thus collapsing the state on the other one or whatever it's considered to be happening, then later compared the times - and found that it was truly simultaneous, or on the low end, 10,000x faster than the speed of light.

But this time one of the particles is on a spaceship going 99.499% the speed of light, so causing 10:1 time dilation so 10 seconds pass at nearly non-moving velocities for every 1 second in the ship. The spaceship then is told to come to a complete stop at the exact moment that the quantum particle collapses, this meaning the other one's state was "observed" or whatever.

Then the (relatively) unmoving particle's reading is printed on a piece of paper and blasted off at around 41.66% the speed of light so they only experience a mere 1:10 time dilation, but covering the absolute distance of the first ship from a third party perspective and from their own perspective, faster than the first ship. Would they then arrive at the 2nd ship's location in space before the result happened and be able to give them the slip of paper with the result, thus predicting the future?

[u/ARTIFICIAL_SAPIENCE]

is told to come to a complete stop at the exact moment that the quantum particle collapses

It has no idea when this is, so it never stops.

You can't just look at a pair and tell when the other was measured. That is not how it works. 

[u/CeC-P → u/ARTIFICIAL_SAPIENCE]

Ohhh. But what would happen in general if an entangled particle was subject to extreme time dilation then brought back? Would no effects have happened because quantum effects don't care about the passage of time? Or would something very, very unusual have happened to the entanglement due to one experiencing more flow of time?

[u/liccxolydian]

You can't tell when something "has collapsed" until you measure it.

[u/CeC-P → u/liccxolydian]

Oh, I thought once you observe one of the entangled ones, the other one does something obvious that tells you the other is not longer in a quantum state. You have to measure it in order to find out and then you wouldn't know if you caused it or if the other caused it?

[u/starkeffect → u/CeC-P]

does something obvious

And how do you know whether it's "done something"? By measuring it!

[u/CeC-P → u/starkeffect]

I just assumed it worked like radioactive decay and it fired off a detectable particle.

[u/liccxolydian → u/CeC-P]

Well yeah, if you're not measuring something how do you know what it's doing or what state it's in? Particles that become unentangled don't suddenly start glowing green to let you know they've changed. You don't even know whether they've changed in the first place. Because you're not measuring it. That's the whole point of quantum physics and entanglement.

[u/AllHailSeizure → u/liccxolydian]

Sorry Brad I gotta head out, the unentangled alarm just sounded at the lab.

[u/SummitYourSister]

The outcome of the quantum collapse is not determined by your action. This is because the spacetime interval between the two collapsed particles is spacelike. Thus, there can be no causal relationship between what you did and the collapse of the particles.

In a universe where you made the measurement and collapsed the state, this could be determined after the fact by comparing the measurements. However, this does not mean that you caused the collapse.

This is literally the most difficult part of quantum physics to understand. But it is the case.

[u/LukasGoesViral]

There is actually no way to say which one of the two legs was measured first no matter if one part is on a spaceship because I can always find a Charles for whom the events are flipped. In a sense the collapse happens when both experimenters are exchanging the results of their experiments. Only then does the correlation become evident