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Old 04-08-2005, 03:25 PM   #1
QuikSand
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Join Date: Oct 2000
Location: Annapolis, Md
Modern physics, Heisenberg, and questions of free will

On Heisenberg and the clockwork universe...


I have been trying to educate myself a bit on modern physics – a subject that I find generally interesting, despite having dropped off the real-sciences academic track many years ago. I have been listening to some lectures on relativity, and now getting into quantum mechanics. It’s a lecture series that is deliberately non-mathematical, trying to get through these topics with more description than calculation. So far, not so bad.

I’m not prepared to post a “What Do You Know” thread here, and explain relativity to everyone, but I think I understand a specific issue that has come up well enough to be troubled by it. I thought I’d share – see if some of the better minds here might be able to either straighten me out a bit, or else buck me up by saying that my skepticism is at least fair.


The issue is, essentially, getting past the notion of the “clockwork universe.” I have heard this phrase used before, to essentially describe a theory that goes something like this:

If the universe is made up of things, and the things all behave according to various physical laws relative to one another – then presumably everything that is going to happen a moment from now is simply a function of where the things are and how they are interacting. Therefore, stepping to matters of philosophy, how can there be free will? If all that is happening is a series of physical interactions of things with one another, where is there room for something like an idea in all this?

(That’s my language, not necessarily a perfect statement of the concept, but it ought to do okay)


Anyway, in the lectures, we are presented with Heisenberg’s well-known uncertainty principle, basically with a promise that this would help us out of this particular conundrum.

Simply stated (oversimplified, probably), Heisenberg says that when measuring the location and velocity of particles (things), we can never measure both with complete accuracy. And in fact, the very act of measuring things tends to disturb the things themselves, thereby contributing to the inherent error in the measurements. So, even if we had some way to warehouse all the data, we could never actually know the location and velocity of every particle in the universe, which renders the clockwork universe concept essentially impossible – we could never know that much, which would be necessary to know if we wanted to calculate everything that was going to happen.

So far, I’m on board. I get it. (And for those who understand this stuff well, I hope my simplification as been fair)


Okay – here’s where I have trouble. In my mind, I still want to say something like this:

Fine, we can’t measure everything, so we won’t be able to know where things are and how they are moving. But they still are somewhere, and they still are moving, right? So they still do, in fact, have all those various physical interactions with one another, even if we cannot measure them in any practical way.

So, if that’s the case… how do we escape from the clockwork universe concept? I buy Heisenberg’s uncertainty in measurement, but it doesn’t (intuitively, at least) translate to reality for me.



Now, I get a little shaky at this point, but I understand there is a so-called Copenhagen school of thought, which essentially suggests that anything which cannot be measured and quantified does not itself exist. (Probably a ghastly mis-summary there, I don’t really understand this leap in logic) The scientists (apparently most) subscribing to this belief argue that if something does not have effects which can themselves be measured, then it (for practical purposes) itself does not have existence. Or something like that.

And this line of thinking then leads one to conclude that Heisenberg not only determines that there is inherent imprecision in the measurement of position and velocity of particles, but indeed there is such imprecision in those things themselves. The connection between measurability and reality being the underlying link (which I don’t claim to understand).


As I understand it, this was a point of some great debate among great physicists of the 20th century. Neil Bohr, representing the emerging group of quantum thinkers, moved into this line of thinking, while other scientists like Einstein seemed reluctant to make these steps. At the moment, I’m with Einstein… not because I claim to really “know” anything, but I just haven’t been able to get my intuition around the quantum concepts, I guess.


Okay – if you’re a physics major or professional, you’re probably grinding your teeth at my mis-statements. I am trying to learn this, and am very interested in this sort of issue that gets to such a fundamental question.

Can anyone help? Or point me to a source that tries to better explain the whole concept here, or perhaps on that better summarizes the Copenhagen school of thought?

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