The pop-sci press (New Scientist to be precise) tells me that quantum theory requires that information is never lost, and that the state of a particle at any instant precisely reveals its entire history and also its entire future. TATE says much the same.

But how can that be when its position and velocity at any instant cannot be precisely defined?

The Rev Dodgson said:

, and that the state of a particle at any instant precisely reveals its entire history and also its entire future.

You can say that about the state of an entire closed system, not a single particle

https://en.wikipedia.org/wiki/No-hiding_theorem

just read that^, damaged my neuron the effort did, being early after a late night, well I was up for a while which makes it feel early

dv said:

The Rev Dodgson said:

, and that the state of a particle at any instant precisely reveals its entire history and also its entire future.

You can say that about the state of an entire closed system, not a single particle

How can you say it about an entire closed system when the closed system is made up of particles that do not have a precisely defined position and/or velocity?

The Rev Dodgson said:

dv said:

The Rev Dodgson said:

, and that the state of a particle at any instant precisely reveals its entire history and also its entire future.

You can say that about the state of an entire closed system, not a single particle

How can you say it about an entire closed system when the closed system is made up of particles that do not have a precisely defined position and/or velocity?

Because the probability waveform can be predicted.

dv said:

The Rev Dodgson said:

dv said:

You can say that about the state of an entire closed system, not a single particle

How can you say it about an entire closed system when the closed system is made up of particles that do not have a precisely defined position and/or velocity?

Because the probability waveform can be predicted.

How does a “probability waveform” define actual behaviour, past or future (or present for that matter)?

The Rev Dodgson said:

dv said:

The Rev Dodgson said:

How can you say it about an entire closed system when the closed system is made up of particles that do not have a precisely defined position and/or velocity?

Because the probability waveform can be predicted.

How does a “probability waveform” define actual behaviour, past or future (or present for that matter)?

I don’t understand the question. The entire state of the universe, right now, can only be described in terms of a spatial probability function and it can be theoretically be predicted into the future

The Rev Dodgson said:

dv said:

The Rev Dodgson said:

How can you say it about an entire closed system when the closed system is made up of particles that do not have a precisely defined position and/or velocity?

Because the probability waveform can be predicted.

How does a “probability waveform” define actual behaviour, past or future (or present for that matter)?

Ψ(𝑥, 𝑡)

SCIENCE said:

The Rev Dodgson said:

dv said:

Because the probability waveform can be predicted.

How does a “probability waveform” define actual behaviour, past or future (or present for that matter)?

Ψ(𝑥, 𝑡)

I have no idea what that means. Could I have an English translation?

dv said:

The Rev Dodgson said:

dv said:

Because the probability waveform can be predicted.

How does a “probability waveform” define actual behaviour, past or future (or present for that matter)?

I don’t understand the question. The entire state of the universe, right now, can only be described in terms of a spatial probability function and it can be theoretically be predicted into the future

The question is, how can a future state be predicted, and how is a past state defined, when the current state can only be described with probabilities, which to me suggests there are infinite numbers of possible future states and past states?

The Rev Dodgson said:

SCIENCE said:

The Rev Dodgson said:

How does a “probability waveform” define actual behaviour, past or future (or present for that matter)?

Ψ(𝑥, 𝑡)

I have no idea what that means. Could I have an English translation?

time dependent spatial quantum wavefunction

SCIENCE said:

The Rev Dodgson said:

SCIENCE said:

Ψ(𝑥, 𝑡)

I have no idea what that means. Could I have an English translation?

time dependent spatial quantum wavefunction

OK, so what about it?

The Rev Dodgson said:

SCIENCE said:

The Rev Dodgson said:

I have no idea what that means. Could I have an English translation?

time dependent spatial quantum wavefunction

OK, so what about it?

you tell us, that’s what you were talking about

The Rev Dodgson said:

SCIENCE said:

The Rev Dodgson said:

I have no idea what that means. Could I have an English translation?

time dependent spatial quantum wavefunction

OK, so what about it?

you tell us, that’s what you were talking about

SCIENCE said:

The Rev Dodgson said:

SCIENCE said:

time dependent spatial quantum wavefunction

OK, so what about it?

you tell us, that’s what you were talking about

lol

SCIENCE said:

The Rev Dodgson said:

SCIENCE said:

time dependent spatial quantum wavefunction

OK, so what about it?

you tell us, that’s what you were talking about

What information about it would you like dear sir?

The Rev Dodgson said:

SCIENCE said:

The Rev Dodgson said:

OK, so what about it?

you tell us, that’s what you were talking about

What information about it would you like dear sir?

we think it’s not really about that, you talk about quantum theory and how that requires information to be never lost, well

we argue that to qualify for a useful theory, generally the assumption that the information you have is information you get to keep

you suggest that the state of a particle at any instant precisely reveals its entire history and also its entire future, so

we suggest that being a theory, it is a modelling exercise, and the model is of a wavefunction that describes the spatiotemporal state of a particle, id est necessarily including all time and space

you express concern that its position and velocity at any instant cannot be precisely defined, but

a possibly more workable interpretation is that (1) as dv say, the probability distribution is defined, and (2) actually it’s that certain quantities cannot be measured (rather than defined) without correspondingly altering other quantities

In the quantum world, however, the conservation of quantum information should mean that information cannot be created nor destroyed.

If true then could it be reordered, from less complex to more complex

SCIENCE said:

The Rev Dodgson said:

SCIENCE said:

you tell us, that’s what you were talking about

What information about it would you like dear sir?

we think it’s not really about that, you talk about quantum theory and how that requires information to be never lost, well

we argue that to qualify for a useful theory, generally the assumption that the information you have is information you get to keep

you suggest that the state of a particle at any instant precisely reveals its entire history and also its entire future, so

we suggest that being a theory, it is a modelling exercise, and the model is of a wavefunction that describes the spatiotemporal state of a particle, id est necessarily including all time and space

you express concern that its position and velocity at any instant cannot be precisely defined, but

a possibly more workable interpretation is that (1) as dv say, the probability distribution is defined, and (2) actually it’s that certain quantities cannot be measured (rather than defined) without correspondingly altering other quantities

Thanks, that makes your point much clearer.

So the assumption is that if you had two separate closed systems, with identical particles all in an identical state, to infinite precision, then the past history of those systems must have been identical, and the future development of both systems will be identical, for so long as they remain closed?

Is there any evidence or reasoning to support this assumption?

Cymek said:

In the quantum world, however, the conservation of quantum information should mean that information cannot be created nor destroyed.

That is the assumption (which is apparently accepted as an unquestionable truth) that I am trying to understand the reasoning behind.

Cymek said:

If true then could it be reordered, from less complex to more complex

That would still be a change in information, wouldn’t it?

The Rev Dodgson said:

SCIENCE said:

The Rev Dodgson said:

What information about it would you like dear sir?

we think it’s not really about that, you talk about quantum theory and how that requires information to be never lost, well

we argue that to qualify for a useful theory, generally the assumption that the information you have is information you get to keep

you suggest that the state of a particle at any instant precisely reveals its entire history and also its entire future, so

we suggest that being a theory, it is a modelling exercise, and the model is of a wavefunction that describes the spatiotemporal state of a particle, id est necessarily including all time and space

you express concern that its position and velocity at any instant cannot be precisely defined, but

a possibly more workable interpretation is that (1) as dv say, the probability distribution is defined, and (2) actually it’s that certain quantities cannot be measured (rather than defined) without correspondingly altering other quantities

Thanks, that makes your point much clearer.

So the assumption is that if you had two separate closed systems, with identical particles all in an identical state, to infinite precision, then the past history of those systems must have been identical, and the future development of both systems will be identical, for so long as they remain closed?

Is there any evidence or reasoning to support this assumption?

Uh the way we see it is that the wavefunction description includes the time evolution, so identical history is by definition.

If you ask whether, {if t = T sections ψ(𝑥) through arbitrary wavefunctions Ψ₁(𝑥, 𝑡) Ψ₂(𝑥, 𝑡) are identical, then Ψ₁ ≡ Ψ₂}, then we don’t see why that should be true.

You know a lot more about this than I do. But I want to play devil’s advocate here.

Isn’t information lost every time you make an observation of a quantum state?

A quantum state exists in the absence of observation as a superposition of states and where the probability of state depends on the time since the previous observation. As soon as you make an observation, you collapse that superposition into either state or state , and so lose the information of when the previous observation was.

I can accept that information in a quantum system may not be lost when it is not being observed, because of the probability functions. But as soon as you take an observation you collapse the probability function and lose the information that had been held in that probability function.

(Oops, reposting this using round brackets rather than square brackets.)

You know a lot more about this than I do. But I want to play devil’s advocate here.

Isn’t information lost every time you make an observation of a quantum state?

A quantum state exists in the absence of observation as a superposition of states (0) and (1) where the probability of state (0) depends on the time since the previous observation. As soon as you make an observation, you collapse that superposition into either state (0) or state (1), and so lose the information of when the previous observation was.

I can accept that information in a quantum system may not be lost when it is not being observed, because of the probability functions. But as soon as you take an observation you collapse the probability function and lose the information that had been held in that probability function.

What is meant by information

Does it include actual information we create and destroy all the time

The Rev Dodgson said:

dv said:

The Rev Dodgson said:

How does a “probability waveform” define actual behaviour, past or future (or present for that matter)?

I don’t understand the question. The entire state of the universe, right now, can only be described in terms of a spatial probability function and it can be theoretically be predicted into the future

The question is, how can a future state be predicted, and how is a past state defined, when the current state can only be described with probabilities, which to me suggests there are infinite numbers of possible future states and past states?

That’s kind of not how the probability function works. It’s not that the position and speed of the electron is unknown. It’s that it is solely defined by the probability function.

The Rev Dodgson said:

The pop-sci press (New Scientist to be precise) tells me that quantum theory requires that information is never lost, and that the state of a particle at any instant precisely reveals its entire history and also its entire future. TATE says much the same.

But how can that be when its position and velocity at any instant cannot be precisely defined?

The position and momentum of a particle can be precisely defined; it’s measuring the state that introduces the uncertainty.

but is it uncertainty or noncommutativity

mollwollfumble said:

(Oops, reposting this using round brackets rather than square brackets.)

You know a lot more about this than I do. But I want to play devil’s advocate here.

Isn’t information lost every time you make an observation of a quantum state?

A quantum state exists in the absence of observation as a superposition of states (0) and (1) where the probability of state (0) depends on the time since the previous observation. As soon as you make an observation, you collapse that superposition into either state (0) or state (1), and so lose the information of when the previous observation was.

I can accept that information in a quantum system may not be lost when it is not being observed, because of the probability functions. But as soon as you take an observation you collapse the probability function and lose the information that had been held in that probability function.

I’ve been pondering the incompatibility of Quantum Mechanics and General Relativity on and off for many years.
Quantum Mechanics does contain Special Relativity, so they have that in common.

The conservation of information in Quantum Mechanics provides another link between QM and GR. In the absence of observations, both QM and GR conserve information. By observation in QM, this information is lost. So when looking towards a unification of QM and GR by way of symmetry breaking we should be only looking at QM in the absence of observations. Because only in the absence of observations is information retained in QR.

Now for the maths?

mollwollfumble said:

Isn’t information lost every time you make an observation of a quantum state?

The thing to note about the conservation of quantum information is that it is about the unitarity of the universal wavefunction. Because any observer or measuring device is part of the universal wavefunction, there is no collapse of the universal wavefunction. An observation or measurement is the entanglement of one part of the universal wavefunction with another part of the universal wavefunction. This gives rise to the appearance of wavefunction collapse, but only because one is considering only a part of the universal wavefunction and not the entire universal wavefunction.

KJW said:

mollwollfumble said:

Isn’t information lost every time you make an observation of a quantum state?

The thing to note about the conservation of quantum information is that it is about the unitarity of the universal wavefunction. Because any observer or measuring device is part of the universal wavefunction, there is no collapse of the universal wavefunction. An observation or measurement is the entanglement of one part of the universal wavefunction with another part of the universal wavefunction. This gives rise to the appearance of wavefunction collapse, but only because one is considering only a part of the universal wavefunction and not the entire universal wavefunction.

Is the universal wavefunction real or a human theoretical device?

Bubblecar said:

KJW said:

mollwollfumble said:

Isn’t information lost every time you make an observation of a quantum state?

The thing to note about the conservation of quantum information is that it is about the unitarity of the universal wavefunction. Because any observer or measuring device is part of the universal wavefunction, there is no collapse of the universal wavefunction. An observation or measurement is the entanglement of one part of the universal wavefunction with another part of the universal wavefunction. This gives rise to the appearance of wavefunction collapse, but only because one is considering only a part of the universal wavefunction and not the entire universal wavefunction.

Is the universal wavefunction real or a human theoretical device?

All reality is a human theoretical device.

SCIENCE said:

Bubblecar said:

KJW said:

The thing to note about the conservation of quantum information is that it is about the unitarity of the universal wavefunction. Because any observer or measuring device is part of the universal wavefunction, there is no collapse of the universal wavefunction. An observation or measurement is the entanglement of one part of the universal wavefunction with another part of the universal wavefunction. This gives rise to the appearance of wavefunction collapse, but only because one is considering only a part of the universal wavefunction and not the entire universal wavefunction.

Is the universal wavefunction real or a human theoretical device?

All reality is a human theoretical device.

True but some of it is also real.

Bubblecar said:

SCIENCE said:

Bubblecar said:

Is the universal wavefunction real or a human theoretical device?

All reality is a human theoretical device.

True but some of it is also real.

I would say that the universal wavefunction is as real or a human theoretical device as any other wavefunction, and as real or a human theoretical device as information.

I think it’s the only thing that’s real

dv said:

I think it’s the only thing that’s real

On the face of it that’s a rather extreme position.

Bubblecar said:

SCIENCE said:

Bubblecar said:

Is the universal wavefunction real or a human theoretical device?

All reality is a human theoretical device.

True but some of it is also real.

I was just going to say that I disagreed, but maybe I could accept the bubblecar perspective.

Either way, it seems to me a question worthy of debate, rather than accepting the mathematical model as the indisputable and complete truth.

What would be the observable consequences if information was not conserved?

mollwollfumble said:

mollwollfumble said:

(Oops, reposting this using round brackets rather than square brackets.)

You know a lot more about this than I do. But I want to play devil’s advocate here.

Isn’t information lost every time you make an observation of a quantum state?

A quantum state exists in the absence of observation as a superposition of states (0) and (1) where the probability of state (0) depends on the time since the previous observation. As soon as you make an observation, you collapse that superposition into either state (0) or state (1), and so lose the information of when the previous observation was.

I can accept that information in a quantum system may not be lost when it is not being observed, because of the probability functions. But as soon as you take an observation you collapse the probability function and lose the information that had been held in that probability function.

I’ve been pondering the incompatibility of Quantum Mechanics and General Relativity on and off for many years.
Quantum Mechanics does contain Special Relativity, so they have that in common.

The conservation of information in Quantum Mechanics provides another link between QM and GR. In the absence of observations, both QM and GR conserve information. By observation in QM, this information is lost. So when looking towards a unification of QM and GR by way of symmetry breaking we should be only looking at QM in the absence of observations. Because only in the absence of observations is information retained in QR.

Now for the maths?

Why are “observations” treated as any different to any other interaction?

Corrected quote markers:

mollwollfumble said:

mollwollfumble said:

(Oops, reposting this using round brackets rather than square brackets.)

You know a lot more about this than I do. But I want to play devil’s advocate here.

Isn’t information lost every time you make an observation of a quantum state?

A quantum state exists in the absence of observation as a superposition of states (0) and (1) where the probability of state (0) depends on the time since the previous observation. As soon as you make an observation, you collapse that superposition into either state (0) or state (1), and so lose the information of when the previous observation was.

I can accept that information in a quantum system may not be lost when it is not being observed, because of the probability functions. But as soon as you take an observation you collapse the probability function and lose the information that had been held in that probability function.

I’ve been pondering the incompatibility of Quantum Mechanics and General Relativity on and off for many years.
Quantum Mechanics does contain Special Relativity, so they have that in common.

The conservation of information in Quantum Mechanics provides another link between QM and GR. In the absence of observations, both QM and GR conserve information. By observation in QM, this information is lost. So when looking towards a unification of QM and GR by way of symmetry breaking we should be only looking at QM in the absence of observations. Because only in the absence of observations is information retained in QR.

Now for the maths?

Why are “observations” treated as any different to any other interaction?

The Rev Dodgson said:

Why are “observations” treated as any different to any other interaction?

What else collapses the wave function?

mollwollfumble said:

The Rev Dodgson said:

Why are “observations” treated as any different to any other interaction?

What else collapses the wave function?

I presume that every interaction between any two particles collapses the wave function.

The Rev Dodgson said:

mollwollfumble said:

The Rev Dodgson said:

Why are “observations” treated as any different to any other interaction?

What else collapses the wave function?

I presume that every interaction between any two particles collapses the wave function.

Yes, but since every interaction is a form of measurement, the anger is no.

The Rev Dodgson said:

Corrected quote markers:

mollwollfumble said:

mollwollfumble said:

(Oops, reposting this using round brackets rather than square brackets.)

You know a lot more about this than I do. But I want to play devil’s advocate here.

Isn’t information lost every time you make an observation of a quantum state?

A quantum state exists in the absence of observation as a superposition of states (0) and (1) where the probability of state (0) depends on the time since the previous observation. As soon as you make an observation, you collapse that superposition into either state (0) or state (1), and so lose the information of when the previous observation was.

I can accept that information in a quantum system may not be lost when it is not being observed, because of the probability functions. But as soon as you take an observation you collapse the probability function and lose the information that had been held in that probability function.

I’ve been pondering the incompatibility of Quantum Mechanics and General Relativity on and off for many years.
Quantum Mechanics does contain Special Relativity, so they have that in common.

The conservation of information in Quantum Mechanics provides another link between QM and GR. In the absence of observations, both QM and GR conserve information. By observation in QM, this information is lost. So when looking towards a unification of QM and GR by way of symmetry breaking we should be only looking at QM in the absence of observations. Because only in the absence of observations is information retained in QR.

Now for the maths?

Why are “observations” treated as any different to any other interaction?

I think there’s a bit of a pop-sci misunderstanding about this concept of observation.

dv said:

The Rev Dodgson said:

Corrected quote markers:

mollwollfumble said:

Why are “observations” treated as any different to any other interaction?

I think there’s a bit of a pop-sci misunderstanding about this concept of observation.

Well of course the introduction of the observer must not be misunderstood to imply that some kind of subjective features are to be brought into the description of nature. The observer has, rather, only the function of registering decisions, i.e., processes in space and time, and it does not matter whether the observer is an apparatus or a human being; but the registration, i.e., the transition from the “possible” to the “actual,” is absolutely necessary here and cannot be omitted from the interpretation of quantum theory.

ChrispenEvan said:

dv said:

The Rev Dodgson said:

Corrected quote markers:

Why are “observations” treated as any different to any other interaction?

I think there’s a bit of a pop-sci misunderstanding about this concept of observation.

Well of course the introduction of the observer must not be misunderstood to imply that some kind of subjective features are to be brought into the description of nature. The observer has, rather, only the function of registering decisions, i.e., processes in space and time, and it does not matter whether the observer is an apparatus or a human being; but the registration, i.e., the transition from the “possible” to the “actual,” is absolutely necessary here and cannot be omitted from the interpretation of quantum theory.

wiki of course.

dv said:

The Rev Dodgson said:

Corrected quote markers:

mollwollfumble said:

Why are “observations” treated as any different to any other interaction?

I think there’s a bit of a pop-sci misunderstanding about this concept of observation.

Quite possibly.

But why is the term “observation” used rather than “interaction”?

ChrispenEvan said:

ChrispenEvan said:

dv said:

I think there’s a bit of a pop-sci misunderstanding about this concept of observation.

Well of course the introduction of the observer must not be misunderstood to imply that some kind of subjective features are to be brought into the description of nature. The observer has, rather, only the function of registering decisions, i.e., processes in space and time, and it does not matter whether the observer is an apparatus or a human being; but the registration, i.e., the transition from the “possible” to the “actual,” is absolutely necessary here and cannot be omitted from the interpretation of quantum theory.

wiki of course.

https://en.wikipedia.org/wiki/Observer_(quantum_physics)

That’s a good example of the problem I have with this stuff.

It states quite explicitly that observation has nothing to do with consciousness, then goes on to use language that suggests that an observation is different to a common or garden interaction, without stating exactly how, then quotes a respected physicist (Bell) who implies it does have something to do with consciousness at some level.

Then there’s that bloody cat. Why do people still go on about that if the definition of observation makes the whole story nonsensical?

ChrispenEvan said:

dv said:

The Rev Dodgson said:

Corrected quote markers:

Why are “observations” treated as any different to any other interaction?

I think there’s a bit of a pop-sci misunderstanding about this concept of observation.

Well of course the introduction of the observer must not be misunderstood to imply that some kind of subjective features are to be brought into the description of nature. The observer has, rather, only the function of registering decisions, i.e., processes in space and time, and it does not matter whether the observer is an apparatus or a human being; but the registration, i.e., the transition from the “possible” to the “actual,” is absolutely necessary here and cannot be omitted from the interpretation of quantum theory.

wait are you implying that WINTATE is as bad as popsci

no way

The Rev Dodgson said:

ChrispenEvan said:

ChrispenEvan said:

Well of course the introduction of the observer must not be misunderstood to imply that some kind of subjective features are to be brought into the description of nature. The observer has, rather, only the function of registering decisions, i.e., processes in space and time, and it does not matter whether the observer is an apparatus or a human being; but the registration, i.e., the transition from the “possible” to the “actual,” is absolutely necessary here and cannot be omitted from the interpretation of quantum theory.

wiki of course.

https://en.wikipedia.org/wiki/Observer_(quantum_physics)

That’s a good example of the problem I have with this stuff.

It states quite explicitly that observation has nothing to do with consciousness, then goes on to use language that suggests that an observation is different to a common or garden interaction, without stating exactly how, then quotes a respected physicist (Bell) who implies it does have something to do with consciousness at some level.

Then there’s that bloody cat. Why do people still go on about that if the definition of observation makes the whole story nonsensical?

because it sounds cool to your friends if you’re looking for seminerd friends

SCIENCE said:

The Rev Dodgson said:

ChrispenEvan said:

wiki of course.

https://en.wikipedia.org/wiki/Observer_(quantum_physics)

That’s a good example of the problem I have with this stuff.

It states quite explicitly that observation has nothing to do with consciousness, then goes on to use language that suggests that an observation is different to a common or garden interaction, without stating exactly how, then quotes a respected physicist (Bell) who implies it does have something to do with consciousness at some level.

Then there’s that bloody cat. Why do people still go on about that if the definition of observation makes the whole story nonsensical?

because it sounds cool to your friends if you’re looking for seminerd friends

That’s if you want those kind of friends.

roughbarked said:

SCIENCE said:

The Rev Dodgson said:

https://en.wikipedia.org/wiki/Observer_(quantum_physics)

That’s a good example of the problem I have with this stuff.

It states quite explicitly that observation has nothing to do with consciousness, then goes on to use language that suggests that an observation is different to a common or garden interaction, without stating exactly how, then quotes a respected physicist (Bell) who implies it does have something to do with consciousness at some level.

Then there’s that bloody cat. Why do people still go on about that if the definition of observation makes the whole story nonsensical?

because it sounds cool to your friends if you’re looking for seminerd friends

That’s if you want those kind of friends.

Maybe they look for you and you can’t control what others do ¡

When I hear talk of Schrödinger’s cat, I summon my Bayraktar TB2.

The Rev Dodgson said:

ChrispenEvan said:

ChrispenEvan said:

Well of course the introduction of the observer must not be misunderstood to imply that some kind of subjective features are to be brought into the description of nature. The observer has, rather, only the function of registering decisions, i.e., processes in space and time, and it does not matter whether the observer is an apparatus or a human being; but the registration, i.e., the transition from the “possible” to the “actual,” is absolutely necessary here and cannot be omitted from the interpretation of quantum theory.

wiki of course.

https://en.wikipedia.org/wiki/Observer_(quantum_physics)

That’s a good example of the problem I have with this stuff.

It states quite explicitly that observation has nothing to do with consciousness, then goes on to use language that suggests that an observation is different to a common or garden interaction, without stating exactly how, then quotes a respected physicist (Bell) who implies it does have something to do with consciousness at some level.

Then there’s that bloody cat. Why do people still go on about that if the definition of observation makes the whole story nonsensical?

Sometimes a man needs a few sunny hours of fraudulent hope so that when night comes, he will have a more perfect inward vision of the truth of his hopelessness.

transition said:

https://en.wikipedia.org/wiki/No-hiding_theorem

just read that^, damaged my neuron the effort did, being early after a late night, well I was up for a while which makes it feel early

Reading that now. I see that I was wrong. The act of observation does not collapse the probability function, contrary to the Copenhagen interpretation of QM.

Rather, the act of observation scatters the information from the observed entity into the entities that carry out the observation, in such a way that this information can be reconstructed externally. This is news to me.

In following up on this I’m finding heaps of false information on the web.

Fiction 1. Information is not lost in QM but is lost in GR at black hole boundaries.
Fact. To outside observers it takes an infinite amount of time for a particle to reach the black hole horizon, so in GR the information remains still available for all future time. Or to put it another way, Susskind’s solution to the so-called black hole information paradox is correct. To co-moving observers there’s no loss of information at the black hole event horizon either.

Fiction 2. General relativity has an arrow of time. QM has no arrow of time.
Fact. GR has no arrow of time either, the equations in GR are completely symmetrical with time, too.

Fiction 3. General relativity cannot be probabilistic. QM is probabilistic.
Fact. It’s just as easy to create probability density function in GR as it is in QM.

Fiction 4. In General relativity everything exists to infinite future, but not in QM.
Fact. In QM, in order to calculate even the simplest things such as the results of the double split experiment, we need to precisely integrate both back to the infinite past and into the infinite future and out to infinite space. So predetermined infinite future is a common factor of both QM and GR.

Fiction 5. There is a factor of 10^120 difference between GR predictions and QM predictions.
Fact. This was a joke, damnit. But it entered popular literature and has been re-quoted hundreds of thousands of times since. It’s not true.

So, where does that leave us in the question of QM vs GR?

Well, physicists use both QM and GR, together.
QM on the small scale gives us confidence in classical mechanics on the large scale.
Using GR classical mechanics on the large scale we get a background space-time on which QM field theory is superposed to to get microscale events.

What, then, is the fundamental difference between QM and GR?

Let’s start here.

1.
GR tells us that an oscillating electric charge always generates an electromagnetic wave, which robs energy from the oscillation.
QM tells us, and observation confirms, that this doesn’t happen for electrons (electric charge) oscillating in orbit around an atom. The Planck blackbody radiation function. This became known in 1901, I think.

2.
QM field theory tells us that there is a spin 2 subatomic particle called the graviton. But gravity acting by means of the graviton would not tell space how to curve so gives wrong results for things such as the gravitational bending of light. This became known in 1934, I think.

Wikipedia says this about gravitons:

“When describing graviton interactions, the classical theory of Feynman diagrams and semiclassical corrections such as one-loop diagrams behave normally. However, Feynman diagrams with at least two loops lead to ultraviolet divergences. These infinite results cannot be removed because quantized general relativity is not perturbatively renormalizable, unlike quantum electrodynamics and models such as the Yang–Mills theory. Therefore, incalculable answers are found from the perturbation method by which physicists calculate the probability of a particle to emit or absorb gravitons, and the theory loses predictive veracity. Those problems and the complementary approximation framework are grounds to show that a theory more unified than quantized general relativity is required to describe the behaviour near the Planck scale.”

The mention of “ultraviolet disturbances” takes us straight back grom gravitons to point 1 above, the Planck blackbody radiation curve.

But hold on.
I, personally, did a lot of work several decades ago on infinite numbers. Starting from a very simple hypothesis, I ended up with the Veronese continuum and with Robinson’s hyperreal numbers from the 1950s and 1960s.

This work on infinite numbers allowed me to numerically and analytically evaluate integrals involving the product of a smooth function and an oscillatory function that classical mathematics (ie. Cantor’s cardinality) failed to evaluate.

I turned from that work into how subatomic physics works and found that my methods got the same answers as renormalisation methods. The physicists had already incorporated my results into their own work, and if anything had gone beyond what I had been able to do.

So just perhaps General Relativity really is renormalisable in Quantum Mechanics. Using Robinson’s mathematics.
Or perhaps when GR is renormalised, the answers it gives differ from observation – that seems more reasonable.

Hmm.

This wasn’t where I was trying to get. I was trying to get to a symmetry breaking event at high energies between GR and QM.

The Rev Dodgson said:

Why are “observations” treated as any different to any other interaction?

The measurement of a quantum state is like other interactions between quantum states in that they result in quantum entanglement. But the measurement of a quantum state is special because the measuring device is a macroscopic object that changes state according to the state being measured. The macroscopic nature of the measuring device means that the dimensionality of the associated Hilbert space is extremely large, and arbitrary vectors in high-dimensional spaces are almost certainly orthogonal. I believe this leads to the Born rule of quantum mechanics. By contrast, the interaction of microscopic states leads to an entangled state that is also microscopic, and therefore pretty much as non-classical as the original quantum state, and not a classical state like the measuring device (although it’s important to note that a classical state is a limit and not a qualitatively different state… the correspondence principle). Another way that measuring devices are special is that they are specifically designed to respond to particular properties of quantum states. Measuring devices don’t just interact with quantum states, but they do so in a very specific way, allowing us to deduce the quantum state from the state of the measuring device.

KJW said:

The Rev Dodgson said:

Why are “observations” treated as any different to any other interaction?

The measurement of a quantum state is like other interactions between quantum states in that they result in quantum entanglement. But the measurement of a quantum state is special because the measuring device is a macroscopic object that changes state according to the state being measured. The macroscopic nature of the measuring device means that the dimensionality of the associated Hilbert space is extremely large, and arbitrary vectors in high-dimensional spaces are almost certainly orthogonal. I believe this leads to the Born rule of quantum mechanics. By contrast, the interaction of microscopic states leads to an entangled state that is also microscopic, and therefore pretty much as non-classical as the original quantum state, and not a classical state like the measuring device (although it’s important to note that a classical state is a limit and not a qualitatively different state… the correspondence principle). Another way that measuring devices are special is that they are specifically designed to respond to particular properties of quantum states. Measuring devices don’t just interact with quantum states, but they do so in a very specific way, allowing us to deduce the quantum state from the state of the measuring device.

OK, so why are observations different to other interactions between quantum objects and macroscopic objects?

The Rev Dodgson said:

OK, so why are observations different to other interactions between quantum objects and macroscopic objects?

Are they? Bear in mind though that measuring devices respond to the property of the quantum object being measured, and that one needs to use a particular type of measuring device to measure particular properties of the quantum object. But any macroscopic object that responds to some property of the quantum object can be used to measure that property of the quantum object.

KJW said:

The Rev Dodgson said:

OK, so why are observations different to other interactions between quantum objects and macroscopic objects?

Are they? Bear in mind though that measuring devices respond to the property of the quantum object being measured, and that one needs to use a particular type of measuring device to measure particular properties of the quantum object. But any macroscopic object that responds to some property of the quantum object can be used to measure that property of the quantum object.

Also, measuring devices amplify the interaction between the microscopic object and the macroscopic object. For example, a moving ping-pong ball will have an effect on a truck, but the effect will be so small that one would not use a truck to measure the momentum of a ping-pong ball. But if there was some way to amplify the effect of the ping-pong ball on the truck, then the truck could be used to measure the momentum of a ping-pong ball.

KJW said:

The Rev Dodgson said:

OK, so why are observations different to other interactions between quantum objects and macroscopic objects?

Are they? Bear in mind though that measuring devices respond to the property of the quantum object being measured, and that one needs to use a particular type of measuring device to measure particular properties of the quantum object. But any macroscopic object that responds to some property of the quantum object can be used to measure that property of the quantum object.

Well I don’t see how they are, but people talk as though they are. That’s the basis of my question.

The Rev Dodgson said:

KJW said:

The Rev Dodgson said:

OK, so why are observations different to other interactions between quantum objects and macroscopic objects?

Are they? Bear in mind though that measuring devices respond to the property of the quantum object being measured, and that one needs to use a particular type of measuring device to measure particular properties of the quantum object. But any macroscopic object that responds to some property of the quantum object can be used to measure that property of the quantum object.

Well I don’t see how they are, but people talk as though they are. That’s the basis of my question.

maybe an analogy might be like driving down a country road on a moonlit night without your headlights on, contrasted with the proposition of having your lights on

consider all those skippies in the trees on the roadside, further consider the native fauna an other world

the information imparted, or transfer, is different of the two propositions

perhaps further consider the quantum world an other representational dimension, even encrypted might do it

dunno