Thread: Consensus Reality

Feynman used to say that you could explain the entire field of quantum
mechanics, just by Young's double-split experiment.

Originally Posted by Xei

I don't know very much about QM, but tell me if this is right:

As I understand it, the moment you observe or measure the phenomenon,
the electron behaves like a particle, if you don't you get the interference
pattern of a wave. So you basically understand correctly. To really recall
all the details, I'd have to re-read that chapter on it in the elegant universe..

A little later de Broglie found out that this wave-particle dualism is correct
for all materia, btw. (Which was later yet proven by experimental data)

Originally Posted by Xei

Now, this is what I'm confused about:

- Is it essential that the data at the slits is observed by a conscious being?

No, I don't think so... didn't it have something to do with light?

Edit: This is a little bit vague, but I remember reading that you only got the interfernce
patterns, in a very carefully isolated experiment. As soon as you observe or try to measure
it, you'd have to "shine light at what you want to look at" (in lack of better wording), which
is when the wave-pattern brakes down and behaves as particles. I might be wrong, though.

But as far as I remember, particles only behave like waves in a completely unobserved environment,
which is impossible outside of the lab. I don't think it's limited to a conscious observer..

If you were to set up the equipment so that it measured which particle went through which slit, but then the data was stored in a cardboard box, what would you see on the screen?

But if you measure it, you'll get a different (particle-)result.
So, I might be wrong, but I would guess you'd see this: | |

I'm not sure, if I understood the questions
now I do want to reread that stuff again..

Thanks for bringing that up Xaqaria, this is the crux of the matter.

Originally Posted by Xei

- Is it essential that the data at the slits is observed by a conscious being?

Yes.

Originally Posted by Xei

If you were to set up the equipment so that it measured which particle went through which slit, but then the data was stored in a cardboard box, what would you see on the screen?

If it is dependent on a conscious person observing what is in the box, I don't see how that could play out. Because when you observe the screen, it must be an interference pattern or not. But then you still can choose to look in the box, or to burn it

First, we must understand that looking at the screen is an act of observation, it collapses the wave-function.

If you are collecting the data in the experiment, and if the information is available, one will see the two slit pattern. If the information is not available at the time of observation, an interference pattern will occur. One constrain the probable future of the probability distribution by measuring the photons at the slit. When you understand that everything is probability distributions, it won't seem that strange, when you understand that consciousness is fundamental in the equation, it will be the solution instead of a problem.

As an extension to Xaqaria's post, I can provide some modified experiments and the results.

1. The electron detectors at the slits are turned off, everything is intact but there is no detection.

The result is an interference pattern at the back wall, so we can rule out the mere passage as significant to collapse of wave-function.

2. Have the electron detectors on, but not gathering the information. The electron detectors do exactly the same as always, but in this case we do not look at the results of the detectors nor record it. In this way we cannot obtain any information of the which-path of the electrons.

The result: An interference pattern. Even though the electron detectors are fully functioning, and detect the electrons.

3. Record and gather information at the slits, but erase the information before looking at the back wall. The information is available, but it is destroyed before the collapse of the wave-function.

Results: An interference pattern. Note that it the exact same procedure as the initial experiment, but instead we removed the information before looking at the results. This is not retro-causality, but could appear so from a classical point of view. Simply, the probability distribution is changed back again since the information is not available. The result is no longer constrained by the measurement, as the measurement never really happened as there was no conscious observation. Things only happen in the present as Xaqaria wrote.

4. The experiment is arranged in such way that a choice can be made after the experiment is "complete", to whether or not use the information gathered by the electron detectors.

The information is recorded, so the results are available if we choose to look at them.

The information available will be manipulated in different ways.

4(1). The information is mixed with additional irrelevant garbage data as it is recorded. It is thus incomprehensible.

4(2). We design a program to analyse the data coming from the slits and either: A: Filter the garbage data so the information is readable again. B. Analyse the the mixed-up data so the results can't be obtained.

Get some random person to make the choice, it can be days and even years after the experiment.

Results: 4(2)A: A two slit pattern appears. 4(2)B: An interference pattern appear.

See this, the physicist Thomas Campbell explains a part of it, with excellent slides. The visual makes it easier to understand. http://vimeo.com/10778333

From 28:00 to some minutes forward. If you want to understand why it is such, see the whole thing.

Originally Posted by Xei

If you were to set up the equipment so that it measured which particle went through which slit, but then the data was stored in a cardboard box, what would you see on the screen?

If it is dependent on a conscious person observing what is in the box, I don't see how that could play out. Because when you observe the screen, it must be an interference pattern or not. But then you still can choose to look in the box, or to burn it.

This is a really interesting question, and I don't have an answer for you. let me try to find one.

And somehow this is relevant to consensus reality?
By observation...
Reality is shaped by observation....
And expectations...
So what the majority believe to be reality
manifests to confirm their expectations?

Wow. I'm really surprised to see how active this thread became. Heh. Haven't been able to read much, but I'll have to get caught up soon.

No takers on post #128?

Oh, I looked at that post this morning. Haven't watched the slides you linked to yet though, I've been busy. I have heard of this experiment before, and it's always fascinated me. I honestly don't know what to say about it. By all accounts it seems to suggest that our observations can change the past, but some part of me really can't fathom that. It's a tough one to wrap your brain around, that's for sure.

That is hard.
But our thoughts definitely change the future.
But how can anything change the past?
I've tried to change the past after I did something extremely stupid or harmful that I regret or when I lost someone that I love, but never did manage to change the past.
Has anyone? If nobody has done it then it must be impossible.

My take is that we're not "changing the past," simply choosing which of the photons' pasts to observe. The classical assumption is that the photon has a fixed path regardless of whether it is observed, and observation simply discovers a fixed value that was always present; this hypothesis does not stand up to testing. One interpretation of the experimental outcomes--the one that yields the "changing the past" confusion--is that the photon does not have a fixed path before observation, but does afterward, implying that observation somehow caused the photon's actions retroactively. There is another possibility: the photon has no single, fixed path either before or after observation. Instead, the photon is always taking all possible paths, because neither it nor anything else in the universe was ever a single, discrete object to begin with, and what changes due to observation is simply how much of the photon we can see. Before the observation is made, we can "see" a wider range of the proton, but only dimly, whereas after the observation we can see and interact with only a narrow subset of the total proton: what the classical model would take for the whole thing.

Originally Posted by Dannon Oneironaut

And somehow this is relevant to consensus reality?
By observation...
Reality is shaped by observation....
And expectations...
So what the majority believe to be reality
manifests to confirm their expectations?

The reality that is viewed is shaped by the viewing. The reality that is looked for is shaped by expectations. Expectations are created by ideas and interpretations of what has been viewed. Collectively accepted ideas and interpretations are expected to be closer to what has been viewed and what can be viewed, and so we only look for those things that we know most people collectively expect to find, and therefore that is what we see when we observe.