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Started by Ebadlun on Jun 12, 2018 12:47:40 AM
Schroedinger's Cat - what is 'the observation'?

This has been being doing my head in for years - what counts as an electron 'being observed'?

Obviously it's not thinking 'damn, those humans are looking at me, act normal!'

pranzingfrogg - 12 Jun 2018 01:07:32 (#1 of 72)

They’re tricky beggars to observe, electrons. Very small and they don’t half dart about.

virgil5 - 12 Jun 2018 01:21:51 (#2 of 72)

A Mr Heisenberg is a bit uncertain, it seems.

brooklyn - 12 Jun 2018 02:17:20 (#3 of 72)

I've always felt sorry for the cats. I wonder what the survivors of these experiments think of Schroedinger? not much, I suspect.

we should alert the animal rights groups.

virgil5 - 12 Jun 2018 02:27:38 (#4 of 72)

Sloppy experiment variables if you consider the "nine lives" thing.

YouGotTheMoney - 12 Jun 2018 03:31:03 (#5 of 72)

damnit. I'm sure I saw a pretty good video on youtube that talked about this (and if I remember correctly, the answer is maximally weird, i.e. the electron acts differently even before you observe it if you're going to observe it), but can I find that sodding video? no, no I cannot.

johnnythesailor - 12 Jun 2018 07:02:08 (#6 of 72)

I think you're thinking of the quantum eraser YGTM. There's a good PBS Spacetime video about it on YouTube.

The thing to remember about the various flavours of QM is that they are a mathematical not a physical description of reality. Thus what the maths actually means is open to interpretation.

The key component of QM is the Schrodinger equation - the wave function - which describe how a system evolves over time. The output of the equation is a not a definite prediction but a set of probabilities. These probabilities appear to exist at the same time. This is called superposition (the cat is both alive and dead).

There are various interpretations of what this means. The 2 you hear about most are Copenhagen - where the wave function "collapses" into definite reality - and Many Worlds - the universe splits into a multiverse of every possible outcome. Neither of these really explain what the "observation" actually is.

More modern interpretations are more subtle. Decoherence is very popular now. The idea is that when you "observe" something the quantum system becomes entangled with you (you being another quantum system). Entanglement is becoming increasingly seen as something really fundamental about the universe (ER=EPR).

Elsewhere there's a school of thought that the wave function describes not physical reality but the state of our knowledge. There is no observation per se. For example if the weather forecast says that there's a 50% chance of rain tomorrow then it just means that all we know is that it might rain or not. Nobody expects it to be both raining and not raining. There's a recent Perimeter Institute video about this.

It's all up for grabs. There's clearly a deeper reality that we have yet to discover and understand. When we do, it will be stunning.

TRaney - 12 Jun 2018 08:24:24 (#7 of 72)

‘Observation’ is measurement.

fenderstrat - 12 Jun 2018 08:27:12 (#8 of 72)

Is it? I thought it was something before measurement - the act of looking?

WibbleAgain - 12 Jun 2018 09:24:26 (#9 of 72)

TRaney is right. The observation is done with some instrument or other.

johnnythesailor - 12 Jun 2018 09:51:43 (#10 of 72)

Are you saying that the instrument collapses the wave function (or whatever) or is it the physicist observing the instrument i.e. the instrument is in a superposition but the physicist is not? Is one more special than the other? Why?

WibbleAgain - 12 Jun 2018 09:53:51 (#11 of 72)

WibbleAgain - 12 Jun 2018 09:56:03 (#12 of 72)

The physicist is also an instrument. It's a philosophical discussion about reality, subjective reality, multi-dimensional reality, paradoxes, etc etc etc.

WibbleAgain - 12 Jun 2018 09:57:18 (#13 of 72)

Hilary - 12 Jun 2018 10:09:52 (#14 of 72)

"In the new, post-1925 quantum theory the ‘anarchist’ position became dominant and modern quantum physics, in its ‘Copenhagen interpretation’, became one of the main standard bearers of philosophical obscurantism. In the new theory Bohr’s notorious ‘complementarity principle’ enthroned [weak] inconsistency as a basic ultimate feature of nature, and merged subjectivist positivism and antilogical dialectic and even ordinary language philosophy into one unholy alliance. After 1925 Bohr and his associates introduced a new and unprecedented lowering of critical standards for scientific theories. This led to a defeat of reason within modern physics and to an anarchist cult of incomprehensible chaos."

thisonehasalittlehat - 12 Jun 2018 10:10:06 (#15 of 72)

The observation is the point at which the state of the system matters for some definitive reason. It's needn't involve consciousness.

That would be silly.

johnnythesailor - 12 Jun 2018 10:19:32 (#16 of 72)

The physicist is also an instrument.

So why does the physicist collapse the wave function and not the detector? What if there's someone watching the physicist?

It's turtles all the way down.

Decoherence gives a much more satisfying explanation. There is no collapse, or otherwise, just entanglement.

It's a philosophical discussion

<<<<<< Issues

JohnIlly - 12 Jun 2018 10:22:30 (#17 of 72)

They’re tricky beggars to observe, electrons.

But easier to work with than cats.

TommyDGNR8 - 12 Jun 2018 10:23:22 (#18 of 72)

<In the style of The Minister's...>

Schrodinger's cat is a hypothetical cat...

virgil5 - 12 Jun 2018 10:24:38 (#19 of 72)

Look at it this way: What is "thinking"?

Some sort of metaphysical revealing process between a Word in a Void delivered by Divine Intervention?

No. It's a chemical/electrical process involving atoms, electrons and fields of frequency totally 'entangled' with itself, but obeying the laws of physics like everything else.

Mr Heisenberg and his "Uncertainty Principle" pointed out that we can know the momentum of an electron, or we can know the position of the electron, but so far we can't know both.

So that electron theoretically could be anywhere/anytime 'entangled' (if you will) with everything else.

Everything we finally perceive ourselves as "thinking" actually happened long (in a sub atomic time sense) before we actually register it as a "thought" in the pondering, slow moving unclear process we call "deliberation".

Where do our thoughts end and the experiment involving electrons begin?

Do electrons know what we're going to do before we do it?

No, but when "non observation" ends and "observation" begins may not be as obvious as we'd like to assume.

johnnythesailor - 12 Jun 2018 10:29:20 (#20 of 72)

Everything we finally perceive ourselves as "thinking" actually happened long (in a sub atomic time sense) before we actually register it as a "thought" in the pondering, slow moving unclear process we call "deliberation".

That's tautology surely? Registering a thought is thinking.

Where do our thoughts end and the experiment involving electrons begin?

That's the point of decoherence. One quantum mechanical system becomes entagnled with another, so the idea of a boundary between them is meaningless.

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