Explain this to me, pls

I've read an Sci-Fi story which says: "one was brought up against Einstein and relativity, which, as you know, denies the possibility of determining motion absolutely and consequently leads into the idea of the four-dimensional space-time continuum. ... although the infinite point which we may call a moment (now) must occur throughout the continuum, it exists only in relation to each observer, and appears to have similar existence in relation to certain close groups of observers. However, since no two observers can be identical -- that is, the same observer -- each must perceive a different past, present, and future from that perceived by any other; consequently, what he perceives arises only from the factors of his relationship to the continuum, and exists only for him."

Is this still thought to be correct? Was it ever thought so?

Originally posted by Scriabin
I've read an Sci-Fi story which says: "one was brought up against Einstein and relativity, which, as you know, denies the possibility of determining motion absolutely and consequently leads into the idea of the four-dimensional space-time continuum. ... although the infinite point which we may call a moment (now) must occur throughout the continuum, it exi ...[text shortened]... um, and exists only for him."

Is this still thought to be correct? Was it ever thought so?

I think the deal now is not the observer but the measurement of a phenomena that interacts with the target. Don't forget, the idea that the quantum phenomena associated with an observer effects is only true now because there is at least one planet in the universe with observers. Right when stars were first forming and before that, there was an extremely high probability of there being no observers so in that sense we do live in a special time so the rules of the universe were presumable the same back then when there were no observers and now that we have popped up, the universe didn't just snap to attention and change its ways just in response to us.

Originally posted by sonhouse
I think the deal now is not the observer but the measurement of a phenomena that interacts with the target. Don't forget, the idea that the quantum phenomena associated with an observer effects is only true now because there is at least one planet in the universe with observers. Right when stars were first forming and before that, there was an extremely hig ...[text shortened]... ped up, the universe didn't just snap to attention and change its ways just in response to us.

What is an obsever in this sense? Is it a being with concousness? Or is it something that reacts accordingly? I say the latter.

If two particles interact on eachother, then one of the particles must observe the other, and vice versa.

Originally posted by FabianFnas
What is an obsever in this sense? Is it a being with concousness? Or is it something that reacts accordingly? I say the latter.

If two particles interact on eachother, then one of the particles must observe the other, and vice versa.

When particles or photons are entangled in quantum physics, it takes a THIRD party, some measurement to un-entangle the two and reveal the state of the other particle even if it is far away, that un-entanglement, that realization of an ambiguous state is not conscience based but measurement based but not by each other, they remain entangled till the environment ruins it or till a measurment is made on one of the pair, even if someone does not observe the results of the experiment till much later, the recording of the transaction shows all the dis-entanglement and dropping into a particular state happens in the past as far as the actual observer is concerned. Record the transaction, the scientist is off on holiday, comes back a month later and the measurement itself causes the loss of entanglement, which can be read in the recording.

Originally posted by sonhouse
When particles or photons are entangled in quantum physics, it takes a THIRD party, some measurement to un-entangle the two and reveal the state of the other particle even if it is far away, that un-entanglement, that realization of an ambiguous state is not conscience based but measurement based but not by each other, they remain entangled till the environ ...[text shortened]... and the measurement itself causes the loss of entanglement, which can be read in the recording.

An instrument is also observing a phenomenon, and disrupt the outcome of it. Doesn't have to have a scientist behind.

Originally posted by FabianFnas
What is an obsever in this sense? Is it a being with concousness? Or is it something that reacts accordingly? I say the latter.

If two particles interact on eachother, then one of the particles must observe the other, and vice versa.

To "observe" in a quantum mechanical sense, no conscious being is required. However, an interaction between two or more particles does not necessarily imply an "observation". For example, a Bose Einstein condensate consist of a single state ( "wave" ) of many particles. Quantum entangled particles are another example of such a single state of many particles.

Originally posted by KazetNagorra
To "observe" in a quantum mechanical sense, no conscious being is required. However, an interaction between two or more particles does not necessarily imply an "observation". For example, a Bose Einstein condensate consist of a single state ( "wave" ) of many particles. Quantum entangled particles are another example of such a single state of many particles.

We agree that no conscious being is required to be called an observer.

But if two particles interact to eachother, then some sort of information should be brought from one to the another. Hence 'observe'.

The weak part of my knowledge and reasoning is - information cannot be brought over from one particle to another with a speed greater than light. Two entangled electrons with a separation wider apart than the time needed for any information can travel across with the speed of light 'react' fast than it should. A explanation is that no information really are sent between the two.... As I said, a weak part of my knowledge...

Originally posted by FabianFnas
We agree that no conscious being is required to be called an observer.

But if two particles interact to eachother, then some sort of information should be brought from one to the another. Hence 'observe'.

The weak part of my knowledge and reasoning is - information cannot be brought over from one particle to another with a speed greater than light. no information really are sent between the two.... As I said, a weak part of my knowledge...

You should read this, because Einstein had similar problems with entangled particles, but in retrospect he was wrong. The key idea is that the entanglement itself does not carry information to the other particle faster than light, and to do anything with the "knowledge" one has to know the outcome of the "measurement" on the other particle. (again, I mean this metaphorically, for any event in nature to happen through the measurement of the one entangled particle information will be transferred slower than light)

http://en.wikipedia.org/wiki/EPR_paradox

Originally posted by FabianFnas
An instrument is also observing a phenomenon, and disrupt the outcome of it. Doesn't have to have a scientist behind.

It sounds like the word 'observer' is too loaded with nuance, perhaps the word 'Interacter" better describes this process.

Originally posted by sonhouse
I think the deal now is not the observer but the measurement of a phenomena that interacts with the target. Don't forget, the idea that the quantum phenomena associated with an observer effects is only true now because there is at least one planet in the universe with observers. Right when stars were first forming and before that, there was an extremely hig ...[text shortened]... ped up, the universe didn't just snap to attention and change its ways just in response to us.

Yes, I get that the universe isn't that which changed -- it is we who change. The story concerned the usual physics gadget gone wrong -- it explodes and our hero is put into what appears in our continuum to be a 24-day coma. but he awakes and eventually tells us what, subjectively, occurred from his point of view. His consciousness was transported or transposed with an alternative history in which WW II never happened. So, our hero lived a different life and most things while very similar were also quite noticeably different -- friends who were wounded in the war he meets are not missing the fingers they lost, etc. And, of course, he meets the perfect woman, to whom he is married in this alternative life. When he wakes from the coma back in the main thread of his life, he is distraught and sets out to find that woman, whom he insists must exist also in his own continuum.

The story is well done, but dated -- not too many folks today would find it styled for their taste. But the SF aspect of the story prompted my question -- the author, John Wyndham, who died in 1969, posited that among all the infinite quantum universes that diverge from a single "atom of time," enough of one continuum would also exist in most if not all others, even if quite clearly altered.

So in this story, I doubt there is a "target." He wasn't suggesting Heisenberg's idea that the observer changes the universe, he was saying the universe one observes may be different depending on where you happen to be in relation to it in four-dimensional space-time. At least that's what I think he meant.

Originally posted by FabianFnas
What is an obsever in this sense? Is it a being with concousness? Or is it something that reacts accordingly? I say the latter.

If two particles interact on eachother, then one of the particles must observe the other, and vice versa.

in the context of the story, the observer is a conscious entity -- a person

Originally posted by sonhouse
It sounds like the word 'observer' is too loaded with nuance, perhaps the word 'Interacter" better describes this process.

Then we use the word 'observer' as a synonym to 'interactor'.

Are two entangled electrons eachothers 'interactors'?

Originally posted by FabianFnas
Then we use the word 'observer' as a synonym to 'interactor'.

Are two entangled electrons eachothers 'interactors'?

No, they are a single "thing".

Originally posted by Scriabin
I've read an Sci-Fi story which says: "one was brought up against Einstein and relativity, which, as you know, denies the possibility of determining motion absolutely and consequently leads into the idea of the four-dimensional space-time continuum. ... although the infinite point which we may call a moment (now) must occur throughout the continuum, it exi ...[text shortened]... um, and exists only for him."

Is this still thought to be correct? Was it ever thought so?

Sort of, but not really, science fiction writers (except in very hard SciFi) are more concerned with it sounding good than being accurate. I have to say that quantum theory has nothing to do with this I don´t see why the posters above started talking about that.

In relativity theory observers are point-like entities who come equipped with imaginary clocks and rulers, they have a natural coordinate system in which they are stationary and space-time is locally (but not globally) flat. A point in the 4 dimensional space-time is called an event. Suppose you have 2 events and two observers. The two observers will, in general, disagree about the time between the two events and the distance between the two events. What they will agree on is a quantity called the interval.

For simplicity I´ll stick to special relativity. The interval is the generalization of Pythagoras´ theorem to 4 dimensions, instead of adding on the square of the time (*) between the two events you subtract it from the squares of the space-like coordinates. All observers will agree on this quantity. Further, if the interval is time-like (negative), then all observers will agree on the order that the events happened in. The Lorentz transforms allow you to get between what two different observers see. So the statement at the end about what an observer sees existing only for them is just wrong. Although in a real (non-flat) space-time it is true that all observers must have different natural coordinate systems,

(*) - I have set the speed of light equal to 1. The formula in spectial relativity is ds² = - c²dt² + dx² + dy² + dz². Where dt is the difference in times and dx is the difference in x-coordinate. You´ll also hear people talk about proper time, this is just the interval expressed as a time-like quanitity: c²dT² = - ds².

Originally posted by FabianFnas
Then we use the word 'observer' as a synonym to 'interactor'.

Are two entangled electrons eachothers 'interactors'?

I would take the meaning of 'interacter' to be the outside force that say, dis-entangles an entangled pair for whatever reason, energy interference because of a measurement say. Basically a quantum monkey wrench thrown at an entangled pair.