Who or what throws the dice for atheists?
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11-11-2013, 05:41 PM
RE: Who or what throws the dice for atheists?
(11-11-2013 05:07 PM)cjlr Wrote:  
(11-11-2013 03:31 PM)Impulse Wrote:  ... And I think it logically follows that any event, given identical circumstances in every possible respect, will have the same outcome every time. Therefore, if you had complete knowledge and complete information about the event, you would be able to predict the outcome.

Fair enough, as a philosophical point of view. But that is, indeed, not what modern science indicates!

Find a particle with some two-state quantum aspect (eg spin), in more than one separable dimension (spin is 3-dimensional). Such as, say, the electron in a hydrogen atom.

Measure its spin along a spatial axis (convention says the experimenter's primary axis be designated 'z'). Spin is a form of quantized angular momentum; the half-integer spin of an electron admits of two outcomes - up or down (to be a little crude). Before measuring, you don't know what its z-spin is. After, measuring, you know exactly what its z-spin is (either up, or down). Let's say it's z-up.

But suppose you measure its z-spin and then its x-spin. What is its x-spin before the second measurement? What is its x-spin after the second measurement? What is its z-spin after the second measurement?

The answers are, respectively, a simultaneous superposition of x-up and x-down, an exact value of either x-up or x-down, and a simultaneous superposition of z-up and z-down. After we've measured z (and gotten z-up) the probability of measuring either x-up or x-down (being the square of the probability density) is one half. Fifty-fifty. One or the other, equal odds.

According to our current understanding, there is no possible way for these two exact values to coexist (the electron quite literally cannot have simultaneously well-defined spin in multiple axes). Which is to say, non-commuting operators imply an uncertainty relation. This is The Famous Uncertainty Principle (and it often gets Heisenberg's name attached to it).


tl;dr - quantum mechanics is probabilistic.

And then comes hidden variables (evidence suggests: not a thing). Mostly that's a matter of saying, "but I don't want the universe to be quantum! Maybe underneath the quantum it's classical again?"

Blink

I really didn't understand that at all, sorry. However, if you're getting 2 different outcomes, are you 100% sure that there were no differences at all in any way between the two measurements?

"Religion has caused more misery to all of mankind in every stage of human history than any other single idea." --Madalyn Murray O'Hair
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11-11-2013, 06:10 PM
RE: Who or what throws the dice for atheists?
Yes. Because that's how quantum physics works. It pisses off other physists.
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11-11-2013, 06:22 PM
RE: Who or what throws the dice for atheists?
(11-11-2013 05:07 PM)cjlr Wrote:  And then comes hidden variables (evidence suggests: not a thing). Mostly that's a matter of saying, "but I don't want the universe to be quantum! Maybe underneath the quantum it's classical again?"

Yup, at least the last I checked on you batshit insane fuckers.

Colbeck and Renner write: "In the present work, we have ... excluded the possibility that any extension of quantum theory (not necessarily in the form of local hidden variables) can help predict the outcomes of any measurement on any quantum state. In this sense, we show the following: under the assumption that measurement settings can be chosen freely, quantum theory really is complete".

But then I see this.

In January 2013, GianCarlo Ghirardi and Raffaele Romano described a model which, "under a different free choice assumption [...] violates [the statement by Colbeck and Renner] for almost all states of a bipartite two-level system, in a possibly experimentally testable way."

Different free choice assumption? You fuckers are batshit bonkers. What's that even mean?

As it was in the beginning is now and ever shall be, world without end. Amen.
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Or your shadow at evening rising to meet you;
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11-11-2013, 08:46 PM
RE: Who or what throws the dice for atheists?
(11-11-2013 05:41 PM)Impulse Wrote:  Blink

I really didn't understand that at all, sorry. However, if you're getting 2 different outcomes, are you 100% sure that there were no differences at all in any way between the two measurements?

Yes. 100%. All that is knowable in quantum mechanics is the amplitude of the probability density (and how it varies in space, time).
(and actually the number of problems which can be solved exactly and analytically is frustratingly small regardless)

But that's electron spin. I mean, I assure you, you can set up a two-axis measurement, and go 'measure z', 'measure x', 'measure z', 'measure x', and it'll be the universe's only true coin flip, but why take my word for anything? Tongue

You can see for yourself, with the ol' double slit experiment. Take a light. A laser works great. (Young's original experiment used candles so that's waaaay more high tech than you need to go!). Point it at two slits (like, literally slits in a black card - the narrower and closer the better, again, but it's possible to do this with 1810s technology). Observe the pattern (a wall works nicely for this).

Now, I doubt you can isolate single photons with the equipment lying around your house ( Wink ), but the interference pattern (which you can see!) is necessarily their sum total. Therefore the photons, which all begin on the same trajectory, finish in some statistical distribution (most land in the centre, and also in constructive and destructive bands decreasing in intensity as one moves outward).

To interpret this and think on its implications we need an outside bit of knowledge - the original experiments were explained as being indicative of a purely wave-like nature for light; quantum hadn't been invented yet - but we know that photons are discrete excitations! Which is to say, photons are quantum phenomena (and of course, it so happens that the original quantization theories - proto quantum mechanics - were precisely to explain the behaviour of light, ie photons) and thus play with themselves (as it were).

Of course, then we must move to the realm of the though experiment (so far as our immediate apparatus is concerned). What if you could send one photon at a time? What if you did? The answer is, the same interference pattern results. This experiment has been done probably millions of times in the last century plus (and incidentally it was totally Feynman's favourite experiment). Though usually if you want single particles you use electrons...

So; for each single photon, how is its path determined? We know (statistically, in aggregate) what the outcome is - that there are many possible paths for a photon to take. What happens when we send them one at a time? The same pattern. Send one identical photon from an identical source through an identical apparatus, and the result is exactly the same interference pattern. Each time it will take a different path according to probabilities which are exactly calculable. And there is no possible way to know beforehand which path an individual photon will take. Only the probabilities are knowable.

...

All kinds of people (and even very, very smart people - Einstein!) absolutely could not stand the idea that reality is fundamentally not completely knowable or deterministic. And so ever since there've been attempts at hidden variables and such to make the scary quantum go away and get back to a nice, pure, deterministic classical state of affairs.

None of them have worked.

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11-11-2013, 08:59 PM
RE: Who or what throws the dice for atheists?
There is no such thing as 'random' only the illusion of randomness. We live in a deterministic universe to large and complex to allow for the prediction of the mundane movements of us bags of flesh and water, but which determines them none the less.

Even your computer cannot create truely random numbers and instead it uses clock cycles to fake randomness.

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11-11-2013, 09:01 PM
Who or what throws the dice for atheists?
(11-11-2013 03:31 PM)Impulse Wrote:  Black_squirrel,
No it's not something I can prove, but could anyone? Trying to prove randomness doesn't exist is like trying to prove that god doesn't exist. You would have to examine every last situation. It would be easier to show any believe randomness is not random at all.
One can also be agnostic about whether the universe is deterministic.
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11-11-2013, 09:19 PM
RE: Who or what throws the dice for atheists?
(11-11-2013 08:59 PM)ridethespiral Wrote:  There is no such thing as 'random' only the illusion of randomness. We live in a deterministic universe to large and complex to allow for the prediction of the mundane movements of us bags of flesh and water, but which determines them none the less.

Even your computer cannot create truely random numbers and instead it uses clock cycles to fake randomness.

No, Spiral, no!

Did you even read all the stuff I just wrote about quantum?
Tongue

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11-11-2013, 09:25 PM
RE: Who or what throws the dice for atheists?
(11-11-2013 09:19 PM)cjlr Wrote:  
(11-11-2013 08:59 PM)ridethespiral Wrote:  There is no such thing as 'random' only the illusion of randomness. We live in a deterministic universe to large and complex to allow for the prediction of the mundane movements of us bags of flesh and water, but which determines them none the less.

Even your computer cannot create truely random numbers and instead it uses clock cycles to fake randomness.

No, Spiral, no!

Did you even read all the stuff I just wrote about quantum?
Tongue

Lol no. Not until after posting. Damn you and your cat that is neither living nor dead.

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11-11-2013, 09:36 PM (This post was last modified: 11-11-2013 09:39 PM by GirlyMan.)
RE: Who or what throws the dice for atheists?
(11-11-2013 06:22 PM)GirlyMan Wrote:  In January 2013, GianCarlo Ghirardi and Raffaele Romano described a model which, "under a different free choice assumption [...] violates [the statement by Colbeck and Renner] for almost all states of a bipartite two-level system, in a possibly experimentally testable way."

Different free choice assumption? You fuckers are batshit bonkers. What's that even mean?


Help a Girl out here physicist, 'cause I got no clue what that fucking means.

As it was in the beginning is now and ever shall be, world without end. Amen.
And I will show you something different from either
Your shadow at morning striding behind you
Or your shadow at evening rising to meet you;
I will show you fear in a handful of dust.
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11-11-2013, 10:28 PM
RE: Who or what throws the dice for atheists?
(11-11-2013 12:17 PM)Chas Wrote:  Others have already stated this. Non-determinacy may be intrinsic at some level.

That is the consensus view of quantum physicists is it not? The Laplacian idea that randomness == ignorance is not a widely supported view.
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