Author Topic: Today's LessWrong moment  (Read 6016 times)

Cain

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Re: Today's LessWrong moment
« Reply #30 on: May 27, 2014, 02:28:57 pm »
Somewhat related to what Scott Alexander wrote here, btw:

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What annoys me about the people who harp on moon-hoaxing and homeopathy – without any interest in the rest of medicine or space history – is that it seems like an attempt to Other irrationality.

(yes, I did just use “other” as a verb. Maybe I’ve been hanging around Continental types too much lately.)

It’s saying “Look, over here! It’s irrational people, believing things that we can instantly dismiss as dumb. Things we feel no temptation, not one bit, to believe. It must be that they are defective and we are rational.”

LMNO

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Re: Today's LessWrong moment
« Reply #31 on: November 13, 2014, 03:50:07 pm »
Ok, in light of some stuff floating around my FB feed, here's a couple of posts that relate to the idea of quantum conciousness; or rather, relate to why quantum conciousness is not necessary for QM to function.

http://lesswrong.com/lw/pe/joint_configurations/
http://lesswrong.com/lw/pf/distinct_configurations/

If I can try to summarize without messing it up too much: This is about how when photons are shot through a sequence of half-silvered mirrors at two detectors, they arrive at each about half the time, as if the mirror "lets" the photon through half the time, and reflects it the other half.  But that's not really what's going on.

QM uses something called "configurations" which are, essentially, a "state of the system" calculation.  It is not linear, all the calculations occur simultaneously, and include all parameters.  When calculating the configuration "detector 1 gets a photon", it has the same value as "detector 2 gets a photon."  So when you run the experiment, you get results equally from 1 and 2.

If you set up a few more mirrors, you now have four configurations to calculate.  Of course, the configurations now need to take the added mirrors into account in their calculations. And as it turns out, two of these configurations effectively cancel each other out and give you an answer of zero for the photon arriving at detector 2.  Which means when you run the experiment, you only get results from detector 1.

Weird, but the math works, so it kind of makes sense.

Ok, now lets get crazy, and fire two photons into a mirrored array from two different directions.  You could end up with two photons at detector 1, two photons at detector 2, or one at each.  Your configurations now must include both photons, in addition to the mirrored array, and you once again have four calculations to make.  And again, two of the calculations cancel each other out, which means when you run the experiment, you'll have either two at 1, or two at 2, but never one at each.

This is where it really starts differentiating itself from classical mechanics. If you were in a linear framework, you would calulate a "one at each" result as a 50% probability.  But since we're doing configurations, we get a different answer.

Ok, here we go.  We want to see when a photon is going in a certain path, so we put a sensor at a certain point, which changes state when a photon zooms by.  But remember, your configuration has to take into account everything going on, and that includes the sensor.  So when you calculate your configurations, the two that canceled out before no longer do, because one of them now has the sensor.  So when you run the experiment, you're now seeing what you'd expect in classical mehanics.

And those calculations are true, even if we don't bother to look at whether the sensor changed state as when we run the experiment.

So, run the previous experiment, and you get a weird result.  Add a detector to see what's going on, the weird result goes away.

Take it away, Elizer...
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I mean, now how crazy is that?  What kind of paranoia does that inspire in some poor scientist?

Okay, so in the 21st century we realize in order to "know" a photon's history, the particles making up your brain have to be correlated with the photon's history.  If having a tiny little sensitive thingy S that correlates to the photon's history, is enough to distinguish the final configurations and prevent the amplitude flows from canceling; then an entire sensor with a digital display, never mind a human brain, will put septillions of particles in different positions and prevent the amplitude flows from canceling.

But if you hadn't worked that out yet...

Then you would ponder the sensor having banished the Mysterious Phenomenon, and think:

The photon doesn't just want to be physically free to go either way.  It's not a little wave going along an unblocked pathway, because then just having a physically unblocked pathway would be enough.

No... I'm not allowed to know which way the photon went.

The mysterious phenomenon... doesn't want me looking at it too closely... while it's doing its mysterious thing.

It's not physical possibilities that have an effect on reality... only epistemic possibilities.  If I know which way the photon went, it's no longer plausible that it went the other way... which cuts off the mysterious phenomenon as effectively as putting a block between the mirrors.

I have to not observe which way the photon went, in order for it to always end up at Detector 2.  It has to be reasonable that the photon could have gone to either mirror.  What I can know is the determining factor, regardless of which physical paths I leave open or closed.

STOP THE PRESSES!  MIND IS FUNDAMENTAL AFTER ALL!  CONSCIOUS AWARENESS DETERMINES OUR EXPERIMENTAL RESULTS!

You can still read this kind of stuff.  In physics textbooks.  Even now, when a majority of theoretical physicists know better.  Stop the presses.  Please, stop the presses.

So, hope that helps.

Reginald Ret

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Re: Today's LessWrong moment
« Reply #32 on: November 13, 2014, 08:38:07 pm »
That was very confusing.

I think I understood the essence of it though.

Is the effect of the sensor the same as the effect of the mirror when making the calculations?
Because if that is the case you could replace mirrors with sensors, keeping the calculations the same. That should reinstate the 2 photons at detector 1 XOR 2 photons at detector 2, but never 1 at each.

Is my thinking anywhere close to reality?
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Re: Today's LessWrong moment
« Reply #33 on: November 13, 2014, 10:18:01 pm »
It's not so much they're the "same", it's that the sensor needs to be taken into account. So, while before you had two identical calculations canceling out, now you have two different calculations.

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Re: Today's LessWrong moment
« Reply #34 on: November 14, 2014, 01:08:26 pm »
The LW post explains it more thoroughly, but check it:



Without the sensor, the photon can go
A -> B -> D -> Detector E
A -> B -> D -> Detector F
or
A -> C -> D -> Detector E
A -> C -> D -> Detector F

When you do the calculations and combine all results of Detector E, you get Zero.
When you do the calculations and combine all results of Detector F, you get Two.
(the math is more complicated, and involves i, but the general point is the same.  If you want confirmation, read the actual article)

So, your experimental result is that you get no photons detected at E.

Now, for the sensor:



So, taking the sensor into account:
A -> B -> D -> Detector E [sensor NO]
A -> B -> D -> Detector F [sensor NO]

A -> C -> D -> Detector E [sensor YES]
A -> C -> D -> Detector F [sensor YES]

This time, when you do the calculations, the addition of the sensor state means that when you combine the results for detector E, they don't cancel out.  Therefore, you'll see photons at both detectors equally.

Elizer again:
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Configurations are not belief states.  Their distinctness is an objective fact with experimental consequences.  The configurations are distinct even if no one knows the state of S; distinct even if no intelligent entity can ever find out.  The configurations are distinct so long as at least one particle in the universe anywhere is in a different position.  This is experimentally demonstrable.

Which is to say: your conciousness, what you believe, has absolutely no impact on configurations.  The configuration is like a barstool. It exists, regardless of what you think about it.

Reginald Ret

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Re: Today's LessWrong moment
« Reply #35 on: November 15, 2014, 12:20:44 pm »
I think I get it, thanks.

Probability and mankind's inability to make accurate estimates of probability bites us in the ass again.

I should read the LW post, but i'm not feeling up to it at the moment.
Lord Byron: "Those who will not reason, are bigots, those who cannot, are fools, and those who dare not, are slaves."

Nigel saying the wisest words ever uttered: "It's just a suffix."

"The worst forum ever" "The most mediocre forum on the internet" "The dumbest forum on the internet" "The most retarded forum on the internet" "The lamest forum on the internet" "The coolest forum on the internet"