Is simultaneous impossible?

[fleetwoodPC]

I am a science laymen.
I just saw the Veritasium video about entanglement and Bell (https://www.youtube.com/watch?v=ZuvK-od647c) and have a few questions ... which hopefully will not also be entangled.

He says no matter how far apart the entangled electrons they flip "at the same time". How do they know? ... how does one measure both at the "same time"?

Can multiple events actually occur at the same time?...or must there be some minimum time difference between any two events (measured events? .. macro? events?)

(Is there a 'quantum time' that is different than a 'relative/macro? time'?)

Dr. Don Lincoln says (https://www.youtube.com/watch?v=JFozGfxmi8A) "we measure the second one in less time, in "quick succession", so that the 'communication time' must be less than c would need. So isn't THAT communication faster than light? ... that you can read the transfer of information faster than if it were transported over c?  (6:15sec). 

In other words, if c has a limit why isn't time (events) held to that same limit?  There's no such thing as time without distance, correct? ... such is space-time?  Isn't the nature of distance is that it's two sets of coordinate with a different time stamp?... and vise versa?

Furthermore, why is it called 'travel at a distance' ... if "travel" means 'bounded by light' then isn't it something else than 'travel' or 'transfer'?

If you had a rod that was incompressible wouldn't the far end literally move at the same time as the near end is moved? (assuming there's no relativistic compression by the observation of transferring energy, right?)

Is space-time like that? ... waves get compressed with motion, correct? What is the ƒ of the wave is infinite? ... yes, this is just a crazy thought experiment ... then is there no compression and you in-effect get faster than light communication like the thought experiment rod? (I'm trying to concoct some way for instantaneous action at a distance.)

My main questions are bolded but I included these other thoughts as I have the fantasy they help explain what I'm thinking.

Thank you, Randy

 

 

 

And if they are truly 

[Strange]

6 minutes ago, fleetwoodPC said:

He says no matter how far apart the entangled electrons they flip "at the same time". How do they know? ... how does one measure both at the "same time"?

Theory says it happens at the same time (in other words, time does not appear in the description of what happens).

People have attempted to do experiments that measure any delay (I don't know the details off the top of my head) and found that the "speed of communication" (note: there is no communication) is at least 10,000 times the speed of light (again, can't remember the exact number, will try and find it). So as close to "the same time" as we can measure.

Edit. This is the paper: https://arxiv.org/abs/1303.0614 

[fleetwoodPC]

Wow. Thank you for that.

And I also just found https://en.wikipedia.org/wiki/Relativity_of_simultaneity
"According to Einstein's special theory of relativity, it is impossible to say in an absolute sense that two distinct events occur at the same time if those events are separated in space. If one reference frame assigns precisely the same time to two events that are at different points in space, a reference frame that is moving relative to the first will generally assign different times to the two events (the only exception being when motion is exactly perpendicular to the line connecting the locations of both events)."

... which seems to verify my kinda thinking that no such thing as "simultaneous" in the absolute regard (whatever that might really mean) ... distance means time.

Edited April 22, 2020 by fleetwoodPC

[Strange]

7 minutes ago, fleetwoodPC said:

So isn't THAT communication faster than light? ... that you can read the transfer of information faster than if it were transported over c?  (6:15sec). 

Explaining why there is no communication involved is tricky. But, basically, all we can say is that the measurements made by two people, A and B, are correlated in some way. So, if Alice measures spin up (for example) then Bob will measure spin down. And vice versa. 

So let's imagine that Alice and Bob each have one of a pair of entangled particles. If Alice looks at her particle she has a 50% chance of seeing spin up or spin down. And Bob has a 50% of seeing spin up or spin down.

Imagine Bob looks at his particle. It could be spin up or spin down. Let's say he sees spin up. What does that tell him? Well, it tells him that if Alice has already looked at her particle, then she saw spin down. Or, if she hasn't yet, then it will be spin down when she does.

Now imagine Alice looks at his particle. It could be spin up or spin down. Let's say she sees spin up. What does that tell her? Well, it tells her that if Bob has already looked at his particle, then he saw spin down. Or, if he hasn't yet, then it will be spin down when he does.

So they both know what the other has seen / will see, but they can't use this to send any information. They can exchange information "classically" (at no more than the speed of light) and end out that their results were always opposite. But they can't transfer any information knowing that.

4 minutes ago, fleetwoodPC said:

Wow. Thank you for that.

And I also just found https://en.wikipedia.org/wiki/Relativity_of_simultaneity
"According to Einstein's special theory of relativity, it is impossible to say in an absolute sense that two distinct events occur at the same time if those events are separated in space. If one reference frame assigns precisely the same time to two events that are at different points in space, a reference frame that is moving relative to the first will generally assign different times to the two events (the only exception being when motion is exactly perpendicular to the line connecting the locations of both events)."

... which seems to verify my kinda thinking that no such thing as "simultaneous" in the absolute regard (whatever that might really mean) ... distance means time.

Indeed. There is no such thing as absolute simultaneity. That means that one observer might see Alice look at her particle before Bob, while another observer might see Bob look at his first. (And another might seem them look at the same time.)

But you can take that into account if you want to calculate how much time elapsed between the two events. So it isn't directly related to entanglement. (Note that Einstein never really accepted that part of quantum theory.)

[studiot]

1 hour ago, fleetwoodPC said:

I just saw the Veritasium video about entanglement

At 1minute 25 seconds in the speaker says

After measurement (ofspin) the particle maintains its spin

Then immediately says

So measurement changes the spin

 

Anyone any comments?

Edited April 22, 2020 by studiot

[Strange]

3 minutes ago, studiot said:

At 1minute 25 seconds in the speaker says

After measurement (ofspin) the particle maintains its spin

Then immediately says

So measurement changes the spin

 

Anyone any comments?

I would say that you can't say it has changed because you don't know what it was before you measured it (and it may not even have a value until you measure it).

[studiot]

At 2 minutes in the speaker says

" so long as the second measurement is taken in the same direction as the first"

Therefore you have the same difficulty identifying 'the same direction' at distance as 'the same time' at distance  -  a point raised by the OP

Edited April 22, 2020 by studiot

[swansont]

15 hours ago, studiot said:

At 2 minutes in the speaker says

" so long as the second measurement is taken in the same direction as the first"

Therefore you have the same difficulty identifying 'the same direction' at distance as 'the same time' at distance  -  a point raised by the OP

"The same direction" means relative to the quantization axis, e.g. a magnetic field you have in place. Not a difficult situation to engineer to a decent level of precision. 

In a similar fashion, "at the same time" can be done to a reasonable experimental precision, which is where the "10,000c" number Strange mentioned comes from. It's a matter of synchronizing clocks that are physically separated but in the same reference frame. 

[studiot]

16 hours ago, studiot said:

'the same direction' at distance as 'the same time' at distance 

at distance  = Earth v Alpha Centauri.

 

And why are we allowing this viewing of a youtube?

Edited April 23, 2020 by studiot

[swansont]

23 minutes ago, studiot said:

 And why are we allowing this viewing of a youtube?

From rule 2.7:

"members should be able to participate in the discussion without clicking any links or watching any videos. Videos and pictures should be accompanied by enough text to set the tone for the discussion"

Videos can be included if there is enough text so that discussion can proceed without watching, and that seems to have been fulfilled.