serious physics problem

Great Debates
1

I was wondering about the “inherently probabilistic” nature of certain particles as described by physicists. As I understand it, statistics (probability) is our method of estimating the likelihood of any given event given what we KNOW. However, there is a lot that goes on in any given event that we don’t know about, because of all the tiny particles bumping off each other and chaos theory and zillions of minutae. However, all these things are actually occurring, whether we know about them and can measure them or not.

So, are physicists waffling when they say “inherently probabilistic”? Is that code for “I can’t really figure out how the law governing this works exactly, given the limits of our current ability to measure” (since as Cecil once pointed out, the act of observing disturbs the observed)?

Also, if all these tiny things are happening, and in spite of the fact that we aren’t observing, everything is dutifully obeying the physical laws of their nature, then how can we talk about chance and randomness? Don’t all events that occur affect other events in a way that could not have happened differently, i.e., a sort of mathematical determinism? Is reality just a chain of p=1’s? Do philosophers or physicists have any plausible reasons for thinking that the human idea of “choice” in the literal sense is somehow exempt? This has been bugging me for pretty much all of my adult life, and I keep reading books on the subject but I can’t help but think people are just constrained by their comfortable little Universes, because all the physicists I’ve forced to answer this question shrug and say “ain’t my job” or get mystical on me. The philosophers do the same thing. Cecil is my only hope.

2

The Heisenberg Uncertainty Principle is not merely some problem with the accuracy of our equipment. It is fundamental to the universe that the more accurately you know a particle’s position, the less accurately you can know its velocity and vice versa. (You can never have a perfectly focussed laser beam since this implies a zero perpendicular velocity component - if you know that so accurately, the positions of the photons must become uncertain).

Now this only applies to the very small: the uncertainty of the position or momentum of even an atom (rather than an electron) is pretty much zero. So, in real life most of these uncertainties cancel out and things can be certain. However, where “real life” is directly dependent on this uncertainty (as in the laser beam example or the Schrodinger’s Cat thought experiment), real life is “inherently probabilistic”.

As for determinism and free-will, well, I believe that the brain is merely an enormously complex computing device having all kinds of input apparatus, memory levels, “random number generators” and feedback mechanisms and that free will is an illusion, but that’s just me.

3

Yes of course, the Heisenberg Uncertainty Principle. I took physics too. But again, this is about what we KNOW. Surely, electrons HAVE both a velocity AND a position (being they wavey or particular). The problem is in our ability to know what these are at the same time. That sits just fine with me.

Problem is, if even something as “predictable” as an atom is still made up of “probabilistic particles”, then you have a problem with perfect prediction, because if you add even the teeniest bit of uncertainty to your equation, all of a sudden you’re talking about butterflies flapping their wings and hurricanes in the Honduras.

Prediction, however, isn’t what this game is about, at least not yet. The bottom line problem is that even fundamental particles have gotta have physical laws that apply to them under various conditions. Particles do not “choose” which slit they feel like passing through in some of your classic experiments. They go through one or the other for a reason.

I am inclined to agree that free will is an illusion myself - and anyone who wanted to convince me otherwise would have to convince me of a few things:

  1. That fundamental particles do not obey physical laws
  2. That somehow this has a influence on the human brain when it comes to “choosing”.

I have no problem with the “lay” use of “choose”, as in “Prochoice” or “I choose chocolate over vanilla today.” Yet if I’m just a ticking machine and you knew everything there was to know about me, my brain, my DNA, everything everyone ever said to me and everything I ever thought about everything…you’d be able to KNOW which flavor I’d pick. I think.

What about string theory, does this help? Honestly I have no idea what this theory is about but I’m quite curious.

4

If it is, then the perception that your logic is valid is likewise an illusion. After all, it is also the function of input apparatus, memory levels, randon number generators and feedback mechanisms of which you speak. You may think that your logic is valid, but only because these mechanisms force you to think that way.

That’s why I’ve always found the statement, “Our brains are just complex mechanisms with random number generators in place of free will,” to be unsatisfying. If it’s true, then we have no reason to trust human logic – including the logic which tells us to trust our logic.

5

Only for chaotic systems, and certainly not true in general.

Consider a little girl on a playground slide. You might not know exactly where the child starts her descent, but you do know that she’ll wind up at the bottom. No great deal of uncertainty there.

Now, consider a marble perched on the apex of a cone. If it tilts slightly in one direction, it’ll roll down the cone’s surface. You might not know exactly where it’ll land, but if you know roughly where it starts to tilt, then you can establish its destination to within a few degrees.

Mind you, there are non-linear systems which exhibit chaotic behavior, but this certainly is not typical of physical phenomena in general.

6

No it doesn’t. Good luck understanding string theory, it’s a very complex subject. There are a few books out there that are easy to find if you’re interested. Just do some searching on Amazon.com.

Perhaps you would find some satisfaction with the Many Worlds hypothesis. In a nutshell, it says that all possible outcomes actually do occur, they just branch off into an infinite number of universes.

7

Indeed, but it may be the case that those laws are such that randomness is essential.However, it might not be so hopeless: your later allusion to string theory might have relevance here. Perhaps something is going on at some level, or in some dimension, which we have not yet got a “handle” on, which might somehow explain how this randomness comes about.

I think not, personally. Some of those inputs might very well be genuinely random, and the supercomputer required to untangle all of the “encrypted” memories might simply be unrealisable. But just because we can’t predict something, eg the weather, does not mean that it cannot be explained.
JT: Agreed, this thing called logic is just another epistemology when it comes down to it. But we do not quite have no reason to trust it. What we can say is that it seems to “work”, and that logic, mathematics and science make incredibly specific predictions which, astonishingly, are borne out against all the odds.

Yes, we may still be being deceived by Descartes Devil - we must trust that we are not. Logic, maths and science are what I place my trust in: that the universe is so, not some other way, and that the computer in my skull has “encoded” it largely as it is rather than as it is not.

8

Quite the contrary; if there is no free will, and if our brains are nothing more than complex computing machines with random number generators, then there is plenty of reason not to trust it. A computer can be programmed to produce bad results, as well as good one. Indeed, without deliberate, carefully tested and validated programming, it is far more likely to produce erroneous results.

In fact, different human brains have concluded different things regarding the existence of free will. Why should one trust the logic of someone who says, “Our brains are just complex computers!”, as opposed to someone who says, “That explanation is self-refuting and unsatisfactory.”

And where did you get this perception that your logic seems to work? From the very same computing machine of which you speak. In other words, your “logic” is what tells you to trust this logic, which is why that argument is invalid.

9

JT, we are merely arguing extent it seems. There are reasons to trust the computer, and reasons not to. There are reasons to believe Descartes Devil deceives us all, and reasons not to. As you say, the computer itself may be faulty, finding some reasoning convincing which is “really” nonsense.

However, not considering a brain to be a complex computer unfortunately provides no better answers. A “soul” with “free will” can still be deceived and fed with nonsense in the guise of “logic”. I do not understand why you feel such an explanation is any more satisfactory.

10

Nobody is trying to argue that our brains are perfect. We’re only trying to figure out whether anything other than a single outcome - on any scale - is physically possible. I think it isn’t possible.

Science talks a lot about “random” events and about “chance” and “probability”. What this may really mean is, “Well, since science is about replicating events and predicting their outcomes, and we can’t do that for this one, we have to resort to a language of uncertainty.” This is a good scientific stance.

Yet particles move because they have to. Some law somewhere is governing their motion. Maybe someday someone will be able to explain this to us. But unless someone wants to argue that there is NO REASON AT ALL why a particle just moved in a particular direction, then we are right back to the indefensible free-will argument.

I’d like to believe I have choices just as much as the next lass. I’d also like to believe physicists when they say that randomness exists, because it makes for a nice loophole. On the other hand, it seems like they’re saying that physical entities or phenomena behave without cause. Which seems like a waffle.

11

I submit that billions of years of evolution have produced an entity which interprets and analyzes the real world far better than any computer we have thus designed. Once you have accepted the proposition that there is a “real world”, evolutionary pressures will easily give you a being that deals best with it.

There’s nothing stopping you from thinking that, but if you were a brain surgeon, I’d rather you thought of my brain as a machine than a mystical object.

Someone who always doubted the source of their logic could think themselves out of dinner, of even out of their life, in the Stone Age.

Really, although the abstract concept perhaps are independent of the metaphysical configuration of the universe, the practical applications of them ARE dependent on its configuration. In other words, the reason I use logic, and math, and science, is because it works. If they cease to work, something else which gives better results will take their place.

12

I think you still don’t quite understand. Although a lot of people make the Uncertainty Principle into an issue of our disturbing the system, or of our ability to know position and momentum to a given degree, it cuts deeper than that. It’s not merely that we can’t know the position and momentum to arbitrary accuracy simultaneously. It’s that a particle cannot have a precisely defined position and momentum simultaneously, even if no sentientt being is trying to measure it. If the position is absolutely defined, the momentum id undefined, and vice-versa. This is why absolute zero is so hard to reach (particles frozen in place would have perfectly defined position and momentum), and why atomic nuclei are such weird places (position is tightly defined, so the momentum is hugely uncertain).

Weird world, quantum.
Between uncertainty, Sensitive Dependence on Initial Conditions and on the tiny effects of far-away objects (this isn’t a new topic – I can show you decades-old articles on it), and Godel’s theorem about incompleteness, there’s plenty of uncertainty to keep the world from being wholly predictable. Heck, even in the absence of these theorems and facts, the real world is a messy place full of overlooked influences, nonlinear laws, ans interactive effects that keep you from perfectly predicting what will happen at any time.

13

In any event, lack of free will makes for a perfectly logical brain. It makes everything we do/experience inherently logical, including all of our emotions, all of our fears, hopes, dreams, etc. It makes it logical when bugs annhiliate themselves on those bug zappers during the summer. Having a nice ticking mathematically determined brain makes everything you CAN do LOGICAL to do. Since you can’t really do anything else.

14

And yet you still have tremendous variety in the quality of the “logic” that people produce. While the human brain is a remarkable machine, the human capacity for logic is still spotty at best.

Look, we can all agree that the human brain is a remarkable thing. However, if you argue that the brain is nothing but a complex machine with some random number generators built in, then you have painted yourself into an untenable position. You can’t have it both ways. You can’t say, “I trust my logic because the human brain is a truly remarkable machine, with an incredible capacity for interpreting the world,” while simultaneously dismissing the people who disagree by stating, “Well, they’re wrong! Their logic is wrong! They’re wrong!”

Similarly, you can’t have it both ways with regard to free will and logic. You can’t say, “Well, free will is just an illusion,” while simultaneously insisting that your logical processes are not. Why shouldn’t the accuracy of your logic be illusory as well? You may choose to defend your logic, within your own mind, but even the correctness of your defense would be a mere illusion. You may as well be a complex computer that produces garbabe, but has been programmed to believe in its own correctness!

Again, if the brain is just a complex pre-programmed machine, and nothing more, then why can’t it be programmed to produce erroneous results? Heck, the fact that you and I disagree would clearly indicate that one of us is programmed incorrectly. This alone proves that the complexity of the brain–while remarkable indeed–proves nothing about the correctness of your own thinking processes.

15

The fallacy in the OP is the assumption that, below any ability of ours to percieve, that determinism reign’s supreme.

This is not the case.

Ray Hall of Fermilab explained it best during a seminar on quantum mechanics I once attended.

Remember that the electron shell is the only thing about the atom that really takes up any appreciable volume. The “shape” of the atom, thus the shape of any molecule that atom might be a part of, and thus the shape and properties of any material those molecules make up, is completely determined by the electron’s orbit.

Now let’s suppose that the electron has a definite position and velocity beyond our ability to percieve. The properties of the electron are present only at a specific place at a specific time.

That would mean that the way in which two atoms interacted chemically would be dependent upon what part of their orbit the electrons were in at the time of interaction. Chemistry would be a complete crapshoot, because there would be no way to get consistent observations of interactions. But in fact it this is not the case.

Uncertainty at the sub-atomic level is vital to certainty at the macroscopic level. It is only because of this built in uncertainty that the universe looks anything like it does.

The reason this is so hard to understand intuitively is because it defies analogy. Neither the wave or particle model is adequate to explain this behavior. Or as Hall put it: “This is the aspect of electron behavior that we don’t know how to think about.”

16

Yes, in evolution traits are passed on if you survive, not only if you positively advance toward a goal. But still, we are more logical than computers in dealing with the world as we perceive it.

It’s possible that both are wrong.

I never say that it is not, but until a better system comes along, that’s what I’m using.

There is perfectly good explanation for superstitious thinking. As long as superstitious thinking prevented more accidents than it caused, it will be selected for. Don’t eat the blue mushrooms: the Shasa-khaine God of Anger placed them here to kill us! As it so happens, the blue mushrooms are poisonous. Unfortunately, it also leads to thinking such as “last time, we sacrificed our firstborns and we beat our enemies: let’s do it again!” But if we were not so prone to superstitions we might be less conservative in our actions and die sooner.

So, how would you “prove” that your mind’s concept of dualism is not an illusion? Indeed, it doesn’t even have to be an evolutionarily harmful one: a being with feelings will probably be more motivated if he feels he has “free will”, rather than accept fatalism.

17

Like CalMeacham said, the problem is more fundamental than our not knowing. It is simply that the concept we have of particles in everyday life breaks down on the quantum scale…where they behave in many ways like waves. And, it should be noted that some people have tried to propose so-called “hidden variables” theories to explain things like the two-slit experiment, basically proposing that the particle has chosen a definite state but it just remains hidden from us. However, such theories lead to concrete predictions, such as certain inequalities, as Einstein and two other scientists pointed out (“EPR paradox”) and many experimental tests have now shown, I think fairly convincingly (although people always like to try to dream up new loopholes), that the inequalities implied by the hidden variable theories are not satisfied in the real world.

By the way, it is not really too difficult to understand where the uncertainty principle for position and momentum of a particle comes from once you understand:

(1) that a particle can be treated mathematically as a wave with the amplitude of the wave related to its probability of being in a certain position and the frequency of the wave proportional to the particle’s momentum.

(2) fourier analysis.

In particular, what you will learn in fourier analysis is that an infinite sine wave has a single frequency. However, if you want to make a “wave packet”, i.e., a sort of sign wave that oscillates but within a decaying envelope, you do this by adding together waves of various frequencies. The bigger your wave packet, the narrower the range of frequencies you need. The smaller (more sharply localized) your wave packet, the broader the range of frequencies you need.

So, recalling the idea that the amplitude of the wave at a point is a measure of the probability for the particle to be found in that particular position, what you have is that if the particle has a perfectly well-defined momentum, then the frequency of the wave associated with it is perfectly well-defined and thus it is represented by an infinite sine wave…which means its spread in position is infinite. Conversely, if you make the wavepacket very sharply localized, you now have a good handle on the particle position but you have a large spread of frequencies making up the wave-packet, and thus its momentum is not well-defined. Translating this into mathematics, one arrives at the mathematical statement of the Uncertainty Relation between a particle’s position and momentum.

18

I don’t understand your line of argument here. I understand it contains words like “force you to think” and “only because” and I understand sort of what you think you are saying, but it doesn’t really make sense when you bring it all together. Mechanistic motivations are not the same things as logical justifications, and even if we couldn’t trust our own logic, your implied conclusion is backwards: the fact that something would make us question the validity of our logical reasoning is not any sort of motive at all for us to doubt its truth.
Plus, your arguement is logical, and hence self-defeating. You can’t reason your way out of reason like that.

Furthermore, if you want to talk about “random number generators in place of free will” you are going to have to explain what free will is and how complex mechanisms and random number generators would have anything to do with replacing it. If you find something to be unsatisfying, please explain exactly WHAT the criteria are that we are supposed to be satisfying.

19

Quite the contrary. If something makes you question the validity of your reasoning, then you have plenty of reason to question whatever conclusions you derive from that reasoning! That is precisely the problem with insisting that the human brain is a purely mechanistic system.

Not true, because I don’t claim that the brain is just a complex, preprogrammed computer. Because I don’t make that claim, my argument is not self-defeating.

Pay close attention, Apos. If you claim that the human brain is just a complex computing machine, then your argument is self-defeating. However, if you are not limited to that claim, then your argument is not self-defeating. In other words, this is only a problem for those who insist on a purely mechanistic human brain – not for those who reject that tenet.

First of all, it’s disingenuous to insist that “Free will is just an illusion, generated by our computer minds,” while simultaneously insisting that other people should be the ones to define free will. If you insist on a definition, then this question should be directed to both camps – the ones who deny free will, and the ones who acknowledge it.

Second, we’ve been over this definition many times before, Apos. Free will is the ability to freely make moral choices, in a way that’s neither deterministic nor random. A tree which falls onto your car has no free will, since its behavior is purely deterministic. A computer with a random number generator has no free will, since its decision-making capability is, well, random. Only a fool would cast moral blame on a tree or a computer for whatever grievous damage they may cause. In order for someone to be morally accountable, that person’s decision-making capability has to come from themselves, in a way that transcends mere pre-programming and random number generation.

I have already explained this. Repeatedly, in fact. You cannot insist that free will is just an illusion generated by your brain, while simultaneously insisting that your logical processes are non-illusory. Both the perception of free will and the perception of logical correctness would be coming from the same brain, after all. If your so-called “free will” is just an artifact of the chemical processes within your brain, then why shouldn’t your perception of logic be a sham as well?

But for the sake of reason, let us assume that your grian is indeed nothing more than a complex machine, driven by some random number generators. If you wish, I am prepared to treat your brain in exactly that manner.

“So, Apos, you say that your brain is just a complex computing machine, with some random number generators to simulate the appearance of free choice. Is this what your brain tells you about itself? That’s interesting, since I have encountered a great many brains which say the exact opposite. Why should I have any particular faith that your computing processes are accurate, if these other marvelously complex computers are telling me otherwise?”

20

People here have done a good job dealing with the physics. Now let me clear up a bit the problem of “free will”–which really isn’t a problem at all.

First, it should be kept in mind that the problem of “free will” at first had nothing to do with deterministic physics. The question was whether God predestines our actions, whether he causes to do what we do, whether his knowledge of the future is equivalent to predestination, etc.

Those who believe in Christian-style monotheism can continue to worry about whether God predestines our actions. I don’t, and so I won’t.

But there is my argument. Our actual experience of choosing/willing is anterior to any verbal discussion of same. Likewise, first we see the color red, then we start to talk about that experience. We don’t first define a color and then debate whether we see it or not.

The medievals referred to this whole set of experiences as the “will.” Actually, they thought of it as a very clear-cut and easily identifiable function/factor of the human mind (and of God himself, for that matter). Today, things do not seem so simple. We know enough about consciousness and mind to know that we really know very little at all. Is the “will” one single function, a bundle of functions, or what? No one can answer this question.

In any case, first we have the experience of choosing/willing. Even if we were to discover that the universe is 100% deterministic, we still receive no new information about how we perceive our own choosing/willing. Likewise, if we find out that certain quantum phenomena are 100% random, we still get no new information.

Sure, we are forced to recognize, on a semantic/verbal level the compatibility of the two facts: “A) We perceive our choosing/willing to be thus AND B) the universe is deterministic/random.” But this is no more profound or useful than saying, “A) We perceive our choosing/willing to be thus AND B) Neptune is currently the outermost planet in the solar system.”

Nor does it make any sense to say, “Because the universe is deterministic, I could not have chosen otherwise.” The problem here is that we separate the “I” from the mental process of choosing/willing. We are those very mental processes.

Ultimately–and this is revealed by introspection, I believe–we do not choose what we want. We just want it. Sometimes we are on the verge of saying or doing something, and the thought pops up in our mind: Do you really want to say/do that? And yet we don’t choose to have that thought–it either comes or it does not.

Not to burst anyone’s bubble here, but no, we are not free. We have to eat, drink, sleep, etc. Our thoughts and will are ultimately constrained by the need to survive.

But here is the good news: orchestrating this symphony of thought and perception is our own little partition of the One, the Ultimate Reality–it is the true self. And once the symphony is tuned to this conductor–as ultimately it must become–then issue of freedom again becomes moot, but pleasantly so.