Runaway pulsar has astronomers scratching their heads

[FBM]

Cheezus. A perfect example of, 'If you think you understand it, you don't understand it.'

[pErvinalia]

I gave up trying to understand it years ago. Now I just glaze over when I read about it..

[FBM]

I gave up trying to understand it years ago. Now I just glaze over when I read about it..

tl;dr.

[pErvinalia]

[mistermack]

From what people have posted, it appears that if you make a change to one of an entangled pair that are a thousand light years apart, there is no detectable change to the second particle. They may be no longer entangled, but the second particle doesn't know it.

So no information has passed from one to the other. There isn't much prospect of sending information that way.
It would be nice, and fascinating, if it was possible, but it seems that it's not.

[MiM]

I'd say that's fairly well put, mm.

[Xamonas Chegwé]

But there must be, as the properties of one particle determine the properties of the other, don't they?

Your problem is that you are thinking at the particles in a classical way. Classical thinking just leads to strangeness and error in the quantum world.

The way quantum people like to "explain" this, is by thinking of the entangled particles as parts of one single wave function. This wave function is defined in all space. Once you make a measurement on one of the particles the wave function immediately collapses into two separate wave functions for the particles. This happens everywhere in space, not only at the "location" of the particles. But nothing moves anywhere. No I don't claim to understand this myself, our brains are just not warped to understand this kind of stuff.

Think of it like this. The two particles are two balls - one white, one black - in a bag. You and a friend both take a ball without looking and put it in your pocket. Now, until one of you looks at their ball, it has a 50% chance of being black (or white) but when you look at your ball, you immediately know the colour of your friend's. So, tell me how this enables instantaneous communication?

The entangled particle case is directly analogous.

[Rum]

My friend has black balls?

[cronus]

My friend has black balls?

They need to be jiggled to be sure it isn't a trick of the light.

[MiM]

But there must be, as the properties of one particle determine the properties of the other, don't they?

Your problem is that you are thinking at the particles in a classical way. Classical thinking just leads to strangeness and error in the quantum world.

The way quantum people like to "explain" this, is by thinking of the entangled particles as parts of one single wave function. This wave function is defined in all space. Once you make a measurement on one of the particles the wave function immediately collapses into two separate wave functions for the particles. This happens everywhere in space, not only at the "location" of the particles. But nothing moves anywhere. No I don't claim to understand this myself, our brains are just not warped to understand this kind of stuff.

Think of it like this. The two particles are two balls - one white, one black - in a bag. You and a friend both take a ball without looking and put it in your pocket. Now, until one of you looks at their ball, it has a 50% chance of being black (or white) but when you look at your ball, you immediately know the colour of your friend's. So, tell me how this enables instantaneous communication?

The entangled particle case is directly analogous.

Umm, yes as far as "no-communication" that analogy might be useful, but the big difference is that the balls in your pockets have their colours all the time, even before you look at them. But the entangled particles don't have a well defined spin, until we measure one of them (as shown by experimental validation of Bell's theorem, or a lot longer and more demanding Bell's).

The reason we still cannot transfer information is (asfaiu) that by looking at only our own measurement, we cannot conclude if the other measurement has taken place or not.

[mistermack]

But the entangled particles don't have a well defined spin, until we measure one of them (as shown by experimental validation of Bell's theorem, or a lot longer and more demanding Bell's).

The reason we still cannot transfer information is (asfaiu) that by looking at only our own measurement, we cannot conclude if the other measurement has taken place or not.

The thing is though, is there any evidence that the spin of the second particle is affected instantaneously, upon measurement of the other?
If they are a million light years apart, will the second particle be affected immediately, or a million years later? If it's because of a change to a field, you would expect that change to take at least a million years to show itself at a point a million light years away.

That's apart from the difficulty of detecting the change.

[Xamonas Chegwé]

But there must be, as the properties of one particle determine the properties of the other, don't they?

Your problem is that you are thinking at the particles in a classical way. Classical thinking just leads to strangeness and error in the quantum world.

The way quantum people like to "explain" this, is by thinking of the entangled particles as parts of one single wave function. This wave function is defined in all space. Once you make a measurement on one of the particles the wave function immediately collapses into two separate wave functions for the particles. This happens everywhere in space, not only at the "location" of the particles. But nothing moves anywhere. No I don't claim to understand this myself, our brains are just not warped to understand this kind of stuff.

Think of it like this. The two particles are two balls - one white, one black - in a bag. You and a friend both take a ball without looking and put it in your pocket. Now, until one of you looks at their ball, it has a 50% chance of being black (or white) but when you look at your ball, you immediately know the colour of your friend's. So, tell me how this enables instantaneous communication?

The entangled particle case is directly analogous.

Umm, yes as far as "no-communication" that analogy might be useful, but the big difference is that the balls in your pockets have their colours all the time, even before you look at them. But the entangled particles don't have a well defined spin, until we measure one of them (as shown by experimental validation of Bell's theorem, or a lot longer and more demanding Bell's).

The reason we still cannot transfer information is (asfaiu) that by looking at only our own measurement, we cannot conclude if the other measurement has taken place or not.

You are right to draw a distinction between the quantum states of two particles and the colours of two balls - I should have made it clearer that the analogue I was referring to was between the quantum state of the particle and the probability of the ball colour being black - not the actual colour of the ball. Obviously, the ball is either black or white all of the time BUT its probability of being black is 50% until observed.

[MiM]

But the entangled particles don't have a well defined spin, until we measure one of them (as shown by experimental validation of Bell's theorem, or a lot longer and more demanding Bell's).

The reason we still cannot transfer information is (asfaiu) that by looking at only our own measurement, we cannot conclude if the other measurement has taken place or not.

The thing is though, is there any evidence that the spin of the second particle is affected instantaneously, upon measurement of the other?
If they are a million light years apart, will the second particle be affected immediately, or a million years later? If it's because of a change to a field, you would expect that change to take at least a million years to show itself at a point a million light years away.

That's apart from the difficulty of detecting the change.

The effect is immediate, so you can measure the other particle immediately after the first measurement, and then compare the results later, when the information about the first measurement arrives by light signal, to conclude that the effect is there. If I remember correctly this has been done over 10 km or so, more than enough to measure the time difference.

[Xamonas Chegwé]

But the entangled particles don't have a well defined spin, until we measure one of them (as shown by experimental validation of Bell's theorem, or a lot longer and more demanding Bell's).

The reason we still cannot transfer information is (asfaiu) that by looking at only our own measurement, we cannot conclude if the other measurement has taken place or not.

The thing is though, is there any evidence that the spin of the second particle is affected instantaneously, upon measurement of the other?
If they are a million light years apart, will the second particle be affected immediately, or a million years later? If it's because of a change to a field, you would expect that change to take at least a million years to show itself at a point a million light years away.

That's apart from the difficulty of detecting the change.

The effect is immediate, so you can measure the other particle immediately after the first measurement, and then compare the results later, when the information about the first measurement arrives by light signal, to conclude that the effect is there. If I remember correctly this has been done over 10 km or so, more than enough to measure the time difference.

It's been done many times. And with many different particles - even up to small molecular size!

If simultaneous measurements are taken a distance apart, it is actually impossible to say which affects which as both appear to occur before the other from its POV!

[mistermack]

Is there a theoretical explanation for how that happens?