Freethought & Rationalism Archive

echidna · 02-13-2002, 10:57 PM

Sorry, I misunderstood.

tronvillain · 02-13-2002, 11:37 PM

I'm going to go out on a limb here and say the first experiment doesn't won't turn out to show a conscious observer is required. Anyone want in?

echidna · 02-14-2002, 01:00 PM

Apparently not.

But I still don�t see how an experiment can distinguish between a conscious observation and an objective interaction. The system just keeps growing until consciousness is included, by definition.

Disproving the CI, seems to be more about determining other verifiable predictions from one of the alternatives, and verifying them. I don�t know that the CI makes any predictions which we are able to objectively verify for this reason.

David Gould · 02-14-2002, 03:20 PM

Quote:

Originally posted by tronvillain:
<strong>I'm going to go out on a limb here and say the first experiment doesn't won't turn out to show a conscious observer is required. Anyone want in?</strong>

I think you may be correct, on thinking about it.

The reason that I thought it demonstrated that a conscious observer is required is that the decision about which set of results to look at was randomly made after they had been stored for a while.

In other words,

1.)the mechanical detections had been made.

2.)The results were not examined for a while.

3.)A random selection of which result to look at first was made.

4.) Whichever result was looked at first was the meaningful one - this never varied.

I took this to mean that the mechanical observation had no meaning - it was not until the conscious observation was made that the wave form collapsed.

However, I see that this can also be reverse causality in action. It could also be many universes, with us simply always going into the universes that have the meaningful result first.

No reply from my lecturer. I think that the ANU is open for business but maybe he does not get back until the students do in a couple of weeks.

I will try to remember to talk to him - if other people are interested, can you remind me? I do not want to leave a thread dangling because of forgetfulness.

When I leave a thread dangling and refuse to answer it will be by choice, damn it!

case · 02-15-2002, 10:31 PM

I believe the experiment you're refering to is known as the Aspect Experiment. Gribon goes into this in "Shrodinger's Kittens", though I'm not sure how much faith I would put into his writing. Also, look into Bell's papers, where he deals with the hidden variables problem. And while we're on the subject, does anyone know where I can get a copy of "The Many-Worlds Interpretation of Quantum Mechanics"?

Miles in Mi · 02-20-2002, 10:17 PM

There is nothing in Quantum Mechanics that depends on consciousness.

There's a Richard Feynman book called "Six easy pieces", which explains the the phenomena in question at a non-physicist level. There is also QED (quantum electrodynamics) by Feynman, which is good, too. Both are exerpts taken from his "Lectures On Physics", which is very good, but also costs a lot more.

Here's a link to a good description on the web of the double slit experiment:
<a href="http://www.upscale.utoronto.ca/GeneralInterest/Harrison/DoubleSlit/DoubleSlit.html" target="_blank">http://www.upscale.utoronto.ca/GeneralInterest/Harrison/DoubleSlit/DoubleSlit.html</a>

Here's a good link on the Copenhagen Interpretation:
<a href="http://www.wikipedia.com/wiki/Copenhagen_interpretation" target="_blank">http://www.wikipedia.com/wiki/Copenhagen_interpretation</a>

David Gould · 02-21-2002, 02:30 PM

That is interesting. We were never told about the fact that consciousness has been demonstrated to not be required - as I said, we were basically shown the opposite.

It is a pity there are no more details on that aspect of it.

At this stage, my lecturer is yet to get back to me. The experiements I am talking about are not the Aspect ones - we covered them separately in the course.

Oh, well. My (non-original) theory appears to have been invalidated.

echidna · 02-21-2002, 03:35 PM

Quote:

Originally posted by Miles in Mi:
<strong>There is nothing in Quantum Mechanics that depends on consciousness.</strong>

Regardless of what Schroedinger intended (which I would be curious to see evidence of), his Cat Paradox, remains a paradox, not an absurdity, counter-intuitive but not wrong per se.

Since when was saying it is absurd a valid scientific proof ?

That the CI remains an alternative today (albeit unpopular), indicates the difficulty of proving any of the predictions made by the alternatives. Is this a boundary to our knowledge ?

tronvillain · 02-21-2002, 06:40 PM

<a href="http://www.telp.com/philosophy/qw2.htm" target="_blank">Schroedinger's Cat: The Role of the Observer</a> quotes Schroedinger:

Quote:

One can even set up quite ridiculous cases. A cat is penned up in a steel chamber, along with the following diabolical device (which must be secured against direct interference by the cat): in a Geiger counter there is a tiny bit of radioactive substance, so small that perhaps in the course of one hour one of the atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges and through a relay releases a hammer which shatters a small flask of hydrochloric acid. If one has left this entire system to itself for an hour, one would say that the cat still lives if meanwhile no atom has decayed. The first atomic decay would have poisoned it. The [wave] function of the entire system would express this by having in it the living and dead cat (pardon the expression) mixed or smeared out in equal parts.

It is typical of these cases that an indeterminacy originally restricted to the atomic domain becomes transformed into macroscopic indeterminacy, which can then be resolved by direct observation. That prevents us from so naively accepting as valid a "blurred model" for representing reality. In itself it would not embody anything unclear or contradictory. There is a difference between a shaky or out-of-focus photograph and a snapshot of clouds and fog banks.

The rest of the article is quite interesting.

David Gould · 02-24-2002, 09:25 PM

It appears I was confused. My lecturer has responded thusly:

David,

It sounds like you may have confused a "thought" experiment with a real
experiment. Taken literally no experiment such as you described has been
done, and if it had been it would not produce the results you describe.
This is because the action that produces the measurement effect is the
recording of the data - not the examination of it.

However, if you replace "examined" with "recorded" in your description,
such experiments have been done, with the results you describe. They are
called "quantum eraser" experiments.

A recent reference is:

Delayed "Choice" Quantum Eraser, Yoon-Ho Kim et al., Physical Review
Letters, January 3, 2000 -- Volume 84, Issue 1, pp. 1-5.

Craig

This is my email to him:

I did the Big Questions unit a while back and am now involved in a discusion on QM. I have remembered an experiment that was mentioned but have no references for it.

It took place in Adelaide as far as i can remember and involved setting up detectors monitoring each slit and another detector checking for interference patterns.

They did the experiment a few times. The results were recorded but no-one looked at them.

They were stored for a while and then examined, with it being randomly determined which one was looked at first.

The results were that if the slit detector results were looked at first,
there was no interference pattern.

If the inerference pattern was looked at first there was no meaningful result from the slit detector.

I was wondering if you could point me at some info on this experiment or failing that tell me if it QM actually works like that or not?

Craig's answer confirms that measurement and not conscious observation is the inportant factor. It is still an interesting result, however.

Thread Tools	Search this Thread
Show Printable Version	Search this Thread: Advanced Search

02-13-2002, 10:57 PM	#41
echidna Veteran Member Join Date: May 2001 Location: Melbourne, Australia Posts: 2,832	Sorry, I misunderstood.

02-13-2002, 11:37 PM	#42
tronvillain Veteran Member Join Date: Oct 2000 Location: Alberta, Canada Posts: 5,658	I'm going to go out on a limb here and say the first experiment doesn't won't turn out to show a conscious observer is required. Anyone want in?

02-14-2002, 01:00 PM	#43
echidna Veteran Member Join Date: May 2001 Location: Melbourne, Australia Posts: 2,832	Apparently not. But I still don�t see how an experiment can distinguish between a conscious observation and an objective interaction. The system just keeps growing until consciousness is included, by definition. Disproving the CI, seems to be more about determining other verifiable predictions from one of the alternatives, and verifying them. I don�t know that the CI makes any predictions which we are able to objectively verify for this reason.

02-15-2002, 10:31 PM	#45
case Regular Member Join Date: Jan 2002 Location: Missouri Posts: 420	I believe the experiment you're refering to is known as the Aspect Experiment. Gribon goes into this in "Shrodinger's Kittens", though I'm not sure how much faith I would put into his writing. Also, look into Bell's papers, where he deals with the hidden variables problem. And while we're on the subject, does anyone know where I can get a copy of "The Many-Worlds Interpretation of Quantum Mechanics"?

02-20-2002, 10:17 PM	#46
Miles in Mi Banned Join Date: Apr 2001 Location: Grand Rapids, Michigan Posts: 10	There is nothing in Quantum Mechanics that depends on consciousness. There's a Richard Feynman book called "Six easy pieces", which explains the the phenomena in question at a non-physicist level. There is also QED (quantum electrodynamics) by Feynman, which is good, too. Both are exerpts taken from his "Lectures On Physics", which is very good, but also costs a lot more. Here's a link to a good description on the web of the double slit experiment: <a href="http://www.upscale.utoronto.ca/GeneralInterest/Harrison/DoubleSlit/DoubleSlit.html" target="_blank">http://www.upscale.utoronto.ca/GeneralInterest/Harrison/DoubleSlit/DoubleSlit.html</a> Here's a good link on the Copenhagen Interpretation: <a href="http://www.wikipedia.com/wiki/Copenhagen_interpretation" target="_blank">http://www.wikipedia.com/wiki/Copenhagen_interpretation</a>

02-21-2002, 02:30 PM	#47
David Gould Senior Member Join Date: Jun 2001 Location: Australia Posts: 759	That is interesting. We were never told about the fact that consciousness has been demonstrated to not be required - as I said, we were basically shown the opposite. It is a pity there are no more details on that aspect of it. At this stage, my lecturer is yet to get back to me. The experiements I am talking about are not the Aspect ones - we covered them separately in the course. Oh, well. My (non-original) theory appears to have been invalidated.

02-24-2002, 09:25 PM	#50
David Gould Senior Member Join Date: Jun 2001 Location: Australia Posts: 759	It appears I was confused. My lecturer has responded thusly: David, It sounds like you may have confused a "thought" experiment with a real experiment. Taken literally no experiment such as you described has been done, and if it had been it would not produce the results you describe. This is because the action that produces the measurement effect is the recording of the data - not the examination of it. However, if you replace "examined" with "recorded" in your description, such experiments have been done, with the results you describe. They are called "quantum eraser" experiments. A recent reference is: Delayed "Choice" Quantum Eraser, Yoon-Ho Kim et al., Physical Review Letters, January 3, 2000 -- Volume 84, Issue 1, pp. 1-5. Craig This is my email to him: I did the Big Questions unit a while back and am now involved in a discusion on QM. I have remembered an experiment that was mentioned but have no references for it. It took place in Adelaide as far as i can remember and involved setting up detectors monitoring each slit and another detector checking for interference patterns. They did the experiment a few times. The results were recorded but no-one looked at them. They were stored for a while and then examined, with it being randomly determined which one was looked at first. The results were that if the slit detector results were looked at first, there was no interference pattern. If the inerference pattern was looked at first there was no meaningful result from the slit detector. I was wondering if you could point me at some info on this experiment or failing that tell me if it QM actually works like that or not? Craig's answer confirms that measurement and not conscious observation is the inportant factor. It is still an interesting result, however.

Freethought & Rationalism Archive

The archives are read only.