[watercooler_guy]

It was my understanding that the observer effect (the act of observing a system can affect that system) is not due to the system "knowing" that a conscious mind is observing it, but rather that the instruments used to observe the system alter the system. But then this essay says

> the wave function is collapsed simply by your human mind seeing nothing. The Universe is entirely mental.

So what is this "mental nature of the Universe"? If the things we see at the macro scale are not made of underlying particles and waves, what are they made of?

[n4r9]

The essay cites this thought experiment to back up that quote: https://en.wikipedia.org/wiki/Renninger_negative-result_expe...

The idea is that by clever positioning of detectors, it is possible to make a quantum observation before the detection physically occurs. That challenges the notion that wave-function collapse is a result of instruments interfering with the system.

This doesn't imply that the system "knows" anything about the conscious mind observing it. Very few physicists actually believe that consciousness affects physical mechanisms in this way. A more plausible interpretation may be that the wave-function collapse represents a belief-update process on the part of the observing agent.

[prox]

What is a “belief-update on the part of the observing agent” Can you clarify?

[n4r9]

There is a class of interpretations of quantum theory which take a so-called epistemic perspective of the wave-function. In the epistemic perspective, the wave function represents an agent's knowledge, belief or information regarding a system.

This has a lot of appeal partly because wave function collapse looks very similar to the way that probabilities are updated in bayesian statistics when new information comes to light. For example, if I measure the polarisation of a photon in the vertical component and get a "yes" results (V1=y), then I have complete confidence that future measurements of the vertical will again get a "yes" result (V2=y), whereas future measurements of the horizontal component will be 50-50 between a "yes" result (H2=y) and a "no" result (H2=n).

P(V2=y | V1=y) = 1

P(V2=n | V1=y) = 0

P(H2=y | V1=y) = 0.5

P(H2=n | V1=y) = 0.5

You can sum this up as "the wave function is a way for me to keep track of probabilities, rather than an objective fact about the system".

Of course this idea has its own set of challenges. For many people the question becomes "what does the wave function represent knowledge of"? Also, a few years ago there was a thought-experiment known as the PBR theorem, which rules out some epistemic interpretations: https://en.wikipedia.org/wiki/PBR_theorem

There is a good set of slides on the PBR theorem and its implications by Jon Barrett here (he was my external viva examiner): http://www.cs.ox.ac.uk/qisw2012/slides/barrett.pdf

One class of epistemic interpretations that persists are the so-called bayesian interpretations of quantum theory: https://en.wikipedia.org/wiki/Quantum_Bayesianism .

A "strong" version of quantum bayesianism is QBism, which asserts that quantum theory is no more than an effective user manual for organising subjective beliefs about the outcomes of future interactions with the world. Chris Fuchs and Ruediger Schack are two prominent theorists advocating QBism.

[prox]

Wow! Down the rabbit hole we go! Looks like I got some reading to do. I love this topic.

[EmilyHughes]

Particles and waves are mental. What was the dream you had last night made up of? Maybe you dreamt of running scientific experiments and finding atoms, would that get you any nearer to the metaphysical truth of what that particular dream is made up of?

Consider you never stopped dreaming when you woke up, the dream just shifted into a more concrete and physical state. But there is no physical you sleeping in some higher reality.

Mind is the rock bottom.

[yellowflash]

"Once, Zhuang Zhou dreamed he was a butterfly, a butterfly flitting and fluttering about, happy with himself and doing as he pleased. He didn't know that he was Zhuang Zhou. Suddenly he woke up and there he was, solid and unmistakable Zhuang Zhou. But he didn't know if he was Zhuang Zhou who had dreamt he was a butterfly, or a butterfly dreaming that he was Zhuang Zhou. Between Zhuang Zhou and the butterfly there must be some distinction! This is called the Transformation of Things"

[lioeters]

Right, this is what Buddhist philosophy and psychology have been saying for centuries, for example, the Mind-Only School.

https://en.wikipedia.org/w/index.php?title=Mind_only

Quantum mechanics and the "observer effect" seem to be coming to similar conclusions, dragging postmodern materialists to consider the "mind" as fundamental to physics.

[yellowflash]

My understanding is rudimentary, but it doesn't alter the system. But it fixes what state the system should have to produce the given observation, retroactively. Which is counterintuitive in lot of ways. It can be thought as if the observation caused the determination of past state. Do I make sense or I am just talking absolute non-sense.

[inphovore]

I find your description more appropriate.

And what are they made of? Potential! Universal potential collapses as state in the moment of now through entropic resolve.

Measurement (as part of the collective resolve of the environment) disturbs this resolve, affecting its distribution.

[tresqotheq]

> what are they made of?

The same stuff that all the stuff in your dreams are made of...