Did I miss the point of Schrodinger's Cat?

[eon_rider]

I think I'm actually asking in my question number 2 about "local realism".

 

Einstein said the the Moon is "out there" even when no one is observing it,

otherwise checking physical laws empirically would become unworkable.

 

Albert Einstein "Quantum Mechanics and Reality"

"Quanten-Mechanik und Wirklichkeit", Dialectica 2:320-324, 1948

 

"The following idea characterises the relative independence of objects far apart in space (A and B): external influence on A has no direct influence on B; this is known as the Principle of Local Action, which is used consistently only in field theory. If this axiom were to be completely abolished, the idea of the existence of quasienclosed systems, and thereby the postulation of laws which can be checked empirically in the accepted sense, would become impossible. "

 

It seems the same would apply to "matter in boxes, and an observer's affects on that matter."

 

So it would seem my question number 2 is a non-starter.

[swansont]

1 )How would one possibly get that information without opening the box?

If you poked a hole in the side of the box and extracted some DNA you'd be interfering with the state of the binary system? Wouldn't you? So how could one get that DNA with out interfering with the system? (and collapsing the alive vs dead wave function.)

 

I certainly don't know the answer.

 

 

 

It's a gedanken experiment, so you don't really need to have a working mechanism in mind, but a robotic contraption that took a blood or saliva sample, processed it and gave you the results would work. The result tells you nothing about whether the being is alive or dead.

[MetaFrizzics]

There is a philisophical trap here, involving sloppy semantics.

 

Quantum measurements measure 'states', but only at individual points in space-time. That is, 'events' according to GRT or even local SRT. But what people usually mean by 'alive' is an ongoing 'state' that is more like a whole (possibly continuous and infinite) series of 'events' or space-time locations, like a worm-line or time-line tunnel.

 

The quantum measurement can only determine the cat was 'alive' or 'dead' at some specified instant or space-time coordinate set.

[DQW]

There is no such thing as space-time in Non-Relativistic Quantum Mechanics.

[Tom Mattson]

Why come? Galilean spacetime has a well-defined metric, and you can draw Galilean spacetime diagrams.

[DQW]

Tom, I've never come across the term "space-time" in QM, but that may just be from my limited knowledge. Also, I know that QM treats time very differently than it treats spatial displacement. For instance, time is handled as a parameter in (NR)QM, not a hermitian operator (or observable, unlike displacement).

 

If you can have a hermitian time operator in (NR)QM that is one component of a (4-component) space-time operator, there must be a reason why this is not done (or is it ?). I do not know what such a reason may be (nor have I given it much thought), but to the best of my knowledge, this just doesn't exist in QM.

[Tom Mattson]

Tom' date=' I've never come across the term "space-time" in QM, but that may just be from my limited knowledge.

[/quote']

 

I don't recall ever seeing "spacetime" explicitly referred to in NRQM either, but I have heard of "Galilean spacetime" numerous times when talking about Galilean relativity. The keywords "Galilean spacetime" turn up several non-trivial Google hits (by "non-trivial" I mean "dot-edu" sites, as opposed to say, geocities).

 

Also, I know that QM treats time very differently than it treats spatial displacement. For instance, time is handled as a parameter in (NR)QM, not a hermitian operator (or observable, unlike displacement).

 

Yeah, I was just at PF and I noticed you looking up this thread when I clicked "Who's Online?" Ain't I clever?

 

If you can have a hermitian time operator in (NR)QM that is one component of a (4-component) space-time operator, there must be a reason why this is not done (or is it ?). I do not know what such a reason may be (nor have I given it much thought), but to the best of my knowledge, this just doesn't exist in QM.

 

Yes, it is true that you can't define a Hermitian operator for time in NRQM. But doesn't the notion of a "spacetime" come from coordinates, intervals, boosts, rotations, etc...? Why should Hermitian operators come into the definition of what is and is not a spacetime?

 

Galilean spacetime is the background for NRQM. All wavefunctions are defined on it. Also, the Schrodinger theory is covariant under Galilean boosts. In these respects Galileo's spacetime plays the exact same role in the Schrodinger theory that Minkowski's spacetime plays in the Dirac theory. The asymmetry of space and time with respect to operators in NRQM doesn't suggest to me NRQM isn't formulated on a spacetime. It suggests to me that NRQM is formulated on the wrong spacetime.

[eon_rider]

Just for fun. Apoligies if it's boring. It's not just about time.

 

Why come? Galilean spacetime has a well-defined metric,

well-defined by who?

by space-time?

or by us?

 

 

 

"...in mathematics you don't understand things, you just get used to them."

--John von Neumann

 

Our neurology does some serious filtering of the raw data of the universe.

Our measuring instruments are caught up in that bias, to suit our biological make up and perception. It's a bit self evident.

 

Bell, Einstein, Mermin, Feynman and many others have said some interesting things about human perception and physics.

 

"...contemporary physicists come in two varieties. Type 1 physicists are bothered by EPR and Bell's Theorem. Type 2 (the majority) are not, but one has to distinguish two subvarieties. Type 2a physicists explain why they are not bothered. Their explanations tend either to miss the point entirely (like Born's to Einstein) or to contain physical assertions that can be shown to be false. Type 2b are not bothered and refuse to explain why."

--David Mermin

 

 

"I think it is safe to say that no one understands quantum mechanics. Do not keep saying to yourself, if you can possibly avoid it, ' But how can it be like that?' because you will go 'down the drain' into a blind alley from which nobody has yet escaped. Nobody knows how it can be like that."

--Richard Feynman

 

so back to time...

 

I don't think one can't use or build an instrument to empirically gather data unless it interfaces with our human brain and body. (perceptual bais is passed onto any instrument we build be it a clock or a super collider)

 

We can't see out of the fish bowl so to speak at the current time.

But we're getting better at it, I believe.

That makes science really important and interesting.

 

"What we observe is not nature itself, but nature exposed to our method of questioning."

--Werner Heisenberg

 

TOM WROTE: and you can draw Galilean spacetime diagrams.

 

The calculus is the last word?

Singularities, and the 12, 20, 24 plus dimensions of respectable main stream science are not exactly empirically testable and do seem to have a kind of math building the multi-dimensional reality.

 

Perhaps if we build it, it will come.

Some beautiful and brilliant math, I am told.

But how can math build reality?

 

Can't a Galilean spacetime diagram also be just a diagram and

not a proof that our current notion of time is spot on?.

 

Best and apologies for lack of clarity.

I'm no expert. I'm just asking questions like my science teachers

taught me to.

 

Anyway...What's your view of time?

Any good links?

 

best,

 

eon.

 

"Physical conceptions are free creations of the human mind, and are not, however it may seem, uniquely determined by the external world."

--Albert Einstein

[DQW]

Ain't I clever?

Would I ever deny this ?!

 

(In fact, I had a sneaking suspicion, you might be keeping tabs on me.)

 

Yes, I was looking into that thread and a few others along those lines to see if someone had anything to say that was essentially contradictory to what I had just said. Also, I noticed a link you provided over there, which I can now look into - the computer I was using then did not have Acrobat Reader on it.

 

And now, I shall read the rest of your post.

[Tom Mattson]

Tom: Why come? Galilean spacetime has a well-defined metric,

 

eon rider: well-defined by who? by space-time? or by us?

 

The metric is well-defined mathematically. That means that it wouldn't be rejected out of hand by a theorist.

 

Tom: and you can draw Galilean spacetime diagrams.

 

eon_rider: The calculus is the last word?

Singularities, and the 12, 20, 24 plus dimensions of respectable main stream science are not exactly empirically testable and do seem to have a kind of math building the multi-dimensional reality.

 

I have no idea of how you got from 'A' to 'B' there, but I'll say that the point of discussion at hand here is that NRQM (a man-made mathematical construction used to describe reality) either does or does not make use of a spacetime, which is characterized by a metric (another man-made mathematical construction used to describe reality). So it only makes sense that I am talking mathematics here.

 

Perhaps if we build it, it will come.

Some beautiful and brilliant math, I am told.

But how can math build reality?

 

It can't.

 

Can't a Galilean spacetime diagram also be just a diagram

 

It is just a diagram.

 

and not a proof that our current notion of time is spot on?.

 

I said that much myself in my next post.

 

(Incidentally Galilean spacetime is not our current notion. Galileo has been supplanted by Einstein.)

 

Anyway...What's your view of time?

Any good links?

 

My view of time is that it is "that which is measured by a clock". The best link I can think of is this one:

 

http://www.fourmilab.ch/etexts/einstein/specrel/specrel.pdf

[eon_rider]

Thanks for replying so expertly and patiently.

 

I did jump from A to B. Apologies,

 

I was being chatty due to interested in the subject.

 

You are a scholar and a gentleman.

Thanks for the link.

 

I'll read it now.

 

Time is an interesting subject for me.

Always has been.

 

very best,

 

Cheers,

 

I have no idea of how you got from 'A' to 'B' there, but I'll say that the point of discussion at hand here is that NRQM (a man-made mathematical construction used to describe reality) either does or does not make use of a spacetime, which is characterized by a metric (another man-made mathematical construction used to describe reality). So it only makes sense that I am talking mathematics here.

 

Point taken. I understand what you are saying.

Non-relativistic quantum mechanics is truly the abode of a serious

mathematician. Talking mathematics with in a thousand foot radius of NRQM is completely germane. The maths is well well well beyond me.

 

Very best again sir.

 

 

Eon.

 

PS. There is no "respectful tipping of the hat" smilie...lol...so the effusive yellow smiley face above is the best I can offer.

[Zeth]

Can the cat destroy its own wave funtcion by observing if it's alive or dead?

[DQW]

1. Wavefunctions are not "destroyed" by an observation; they are altered (or rotated)

2. The wavefunction that the cat uses to describe itself is independent of the wavefunction that you use to describe it.

[Evangelante]

The cat is dead.

It could be possible that the cat tapped into the Jedi Force and saved the world five times over from space invaders that are invisible that could have run a rampage.

 

But I don't think a cat is seriously going to do that.