Is uncertainty ontological or epistemological (or both)?
May 2, 2011 7:37 AM Subscribe
I was wondering if there is any support in the natural sciences for uncertainty being ontological on a non-quantum level.
I've been reading today that there are two ways to think about uncertainty, one being realist, that there is an ontological risk 'out there,' and the second being subjective, that uncertainty is simply a condition of our limitations of knowledge - though these are not necessarily independent. However, I was wondering whether in the natural sciences there is any support for the ontological uncertainty outside of quantum effects - whether there is a general consensus that there is inherent uncertainty in interactions between 'things,' or rather had we all necessary information things would be deterministic, and it is just our knowledge that 'creates' uncertainty.
I've been reading today that there are two ways to think about uncertainty, one being realist, that there is an ontological risk 'out there,' and the second being subjective, that uncertainty is simply a condition of our limitations of knowledge - though these are not necessarily independent. However, I was wondering whether in the natural sciences there is any support for the ontological uncertainty outside of quantum effects - whether there is a general consensus that there is inherent uncertainty in interactions between 'things,' or rather had we all necessary information things would be deterministic, and it is just our knowledge that 'creates' uncertainty.
I suspect the general consensus is that above the quantum level, things are deterministic except for some fringe cases. If we had a perfect theory, perfect instruments with perfect precision, and a calculator bigger than the universe, we could predict the behavior of just about everything.
But, Henri Poincare effectively proved that while the three-body gravitational problem is theoretically deterministic, it's practically impossible to solve in the general case beyond a statistical approximation.
posted by KirkJobSluder at 7:59 AM on May 2, 2011
But, Henri Poincare effectively proved that while the three-body gravitational problem is theoretically deterministic, it's practically impossible to solve in the general case beyond a statistical approximation.
posted by KirkJobSluder at 7:59 AM on May 2, 2011
Response by poster: Thanks grizzled - I understood that this was the case, but I also thought (which may be incorrect) that this inherent uncertainty, for whatever reason, goes away/become irrelevant on the macro level.
So, for instance, when we flip a coin, is there a 50% chance of either outcome ontologically, or is it just that our lack of data in any coin flip makes it impossible to know, thus 'creating' the 50% probability. Given this is a generic example, would there be different categories of events for which the answer might be different?
posted by vckeating at 8:19 AM on May 2, 2011
So, for instance, when we flip a coin, is there a 50% chance of either outcome ontologically, or is it just that our lack of data in any coin flip makes it impossible to know, thus 'creating' the 50% probability. Given this is a generic example, would there be different categories of events for which the answer might be different?
posted by vckeating at 8:19 AM on May 2, 2011
Response by poster: Oops, got that out before the second reply. So the answer then is that uncertainty is epistemological on the macro level, but ontological/epistemological on the quantum?
posted by vckeating at 8:21 AM on May 2, 2011
posted by vckeating at 8:21 AM on May 2, 2011
FWIW (& IANAtoaotoP), some physicists do see scope for a completely deterministic physics.
posted by Gyan at 8:28 AM on May 2, 2011
posted by Gyan at 8:28 AM on May 2, 2011
Ah, the idea that if "we had all necessary information things would be deterministic" is called "hidden variables." Einstein was a fan.
You will probably find more to research if you use terms from physics rather than terms from philosophy.
posted by adipocere at 8:40 AM on May 2, 2011
You will probably find more to research if you use terms from physics rather than terms from philosophy.
posted by adipocere at 8:40 AM on May 2, 2011
I suspect the general consensus is that above the quantum level, things are deterministic except for some fringe cases. If we had a perfect theory, perfect instruments with perfect precision, and a calculator bigger than the universe, we could predict the behavior of just about everything.
This is not the general consensus - though it might have been 100+ years ago. "Uncertainty" appears to be a fundamental feature of nature. For the typical macroscopic systems, the quantum effects are simply too small for us to be able to notice them,which has led physicists and mathematicians of the past to believe that a classically deterministic description of nature was possible, given perfect instruments, etc... Nature does not yield itself to perfect measurements.
posted by aroberge at 8:52 AM on May 2, 2011
This is not the general consensus - though it might have been 100+ years ago. "Uncertainty" appears to be a fundamental feature of nature. For the typical macroscopic systems, the quantum effects are simply too small for us to be able to notice them,which has led physicists and mathematicians of the past to believe that a classically deterministic description of nature was possible, given perfect instruments, etc... Nature does not yield itself to perfect measurements.
posted by aroberge at 8:52 AM on May 2, 2011
I'm hardly an expert on this stuff, but I'll give some pointers here.
The sudy of flipping coins and how they behave is called statistical mechanics. the goal of this dicipline is to answer this and related questions: how do the quantum mechanical rules of the atomic and molecular scales relate to those of 10^26 molecules.
The heart of this problem is what's called the reversability paradox: given enough time, Poincaré proved in the 1890s that a statistical dynamical system can return to its original state. The problem with this is that this goes against what we understand of the second law of thermodynamics, that entropy is always increasing. What does time mean if the universe can "reset" periodically on the whole and locally?
One way out of this thicket is to presume that entropy is driven by the inherent uncertainty required by quantum mechanics. In this interpretation, the experience of time is, in fact, a result of quantum uncertainty.
It's important to note that this is an interpretation, which, though reasonable common, not a proven theory. It is consistant with known physical law (well-proven theory), but not required. There are other ways of interpreting what "entropy" is, for example, which don't use a link to the uncertainty principle. The "hidden variables" ones are some of others. As I say, I'm hardly an expert on this. I'm not trying to provide an answer here by any means, just a pointer to the broader fields of study.
posted by bonehead at 9:12 AM on May 2, 2011
The sudy of flipping coins and how they behave is called statistical mechanics. the goal of this dicipline is to answer this and related questions: how do the quantum mechanical rules of the atomic and molecular scales relate to those of 10^26 molecules.
The heart of this problem is what's called the reversability paradox: given enough time, Poincaré proved in the 1890s that a statistical dynamical system can return to its original state. The problem with this is that this goes against what we understand of the second law of thermodynamics, that entropy is always increasing. What does time mean if the universe can "reset" periodically on the whole and locally?
One way out of this thicket is to presume that entropy is driven by the inherent uncertainty required by quantum mechanics. In this interpretation, the experience of time is, in fact, a result of quantum uncertainty.
It's important to note that this is an interpretation, which, though reasonable common, not a proven theory. It is consistant with known physical law (well-proven theory), but not required. There are other ways of interpreting what "entropy" is, for example, which don't use a link to the uncertainty principle. The "hidden variables" ones are some of others. As I say, I'm hardly an expert on this. I'm not trying to provide an answer here by any means, just a pointer to the broader fields of study.
posted by bonehead at 9:12 AM on May 2, 2011
So the answer then is that uncertainty is epistemological on the macro level, but ontological/epistemological on the quantum?
IANAPhysicist, but I think you're making the mistake of assuming that quantum uncertainty only means anything on a very small scale.
One of the interpretations of quantum mechanics is the relational interpretation. In simple terms, anything that a particular observer has not observed is - in that observer's universe - like Schroedinger's cat in an unopened box, existing in a "smeared" state which is a superposition of all possible states. This is true on the microscopic level (has the atom in the box decayed?) and also on the macroscopic (is the cat alive?). It is only when the observer makes an observation that the superposition collapses and a single reality comes into being for that observer.
The relational interpretation sets hard limits on what it is possible for an observer to know (among other reasons, there are things that have happened elsewhere in the cosmos that it is not possible for us to know, even in theory, because there hasn't been time for light to travel from there to here and information can't travel faster than light). These are ontological limits because unobserved things simply do not exist in an uncollapsed state in the observer's universe.
To understand how this works with multiple observers, consider an extension of the cat thought experiment. Call it Schroedinger's Room: the cat is inside the box which is inside a room. From the point of view of an experimenter inside the room, the cat exists in a superposition of alive and dead until the experimenter opens the box. From the point of view of a person standing outside the door to the room, not only the box but also the whole contents of the room are in a superposition (of various states, including: live cat in unopened box, dead cat in unopened box, live cat in opened box, experimenter suddenly dead of natural causes etc) until someone opens the door.
Of course, the relational interpretation is only one of many (I like it partly because Greg Egan wrote a great novel about it, or at least about a similar interpretation) and I'm sleepy so I might not have got it right.
On the coin thing: flipping a coin is such a complex action, with so many possible variables, that it's practically impossible to understand the quantum events that lead to the coin being heads or tails except as an exercise in statistics (as bonehead says). Schroedinger's Cat was a thought experiment designed to eliminate all of that complexity and leave a macroscopic state at the mercy of a single quantum event: the decay of the atom. But if you were smart enough to understand the quantum events behind the coin flip, you could reduce that to quantum uncertainty as well.
posted by A Thousand Baited Hooks at 9:51 AM on May 2, 2011
IANAPhysicist, but I think you're making the mistake of assuming that quantum uncertainty only means anything on a very small scale.
One of the interpretations of quantum mechanics is the relational interpretation. In simple terms, anything that a particular observer has not observed is - in that observer's universe - like Schroedinger's cat in an unopened box, existing in a "smeared" state which is a superposition of all possible states. This is true on the microscopic level (has the atom in the box decayed?) and also on the macroscopic (is the cat alive?). It is only when the observer makes an observation that the superposition collapses and a single reality comes into being for that observer.
The relational interpretation sets hard limits on what it is possible for an observer to know (among other reasons, there are things that have happened elsewhere in the cosmos that it is not possible for us to know, even in theory, because there hasn't been time for light to travel from there to here and information can't travel faster than light). These are ontological limits because unobserved things simply do not exist in an uncollapsed state in the observer's universe.
To understand how this works with multiple observers, consider an extension of the cat thought experiment. Call it Schroedinger's Room: the cat is inside the box which is inside a room. From the point of view of an experimenter inside the room, the cat exists in a superposition of alive and dead until the experimenter opens the box. From the point of view of a person standing outside the door to the room, not only the box but also the whole contents of the room are in a superposition (of various states, including: live cat in unopened box, dead cat in unopened box, live cat in opened box, experimenter suddenly dead of natural causes etc) until someone opens the door.
Of course, the relational interpretation is only one of many (I like it partly because Greg Egan wrote a great novel about it, or at least about a similar interpretation) and I'm sleepy so I might not have got it right.
On the coin thing: flipping a coin is such a complex action, with so many possible variables, that it's practically impossible to understand the quantum events that lead to the coin being heads or tails except as an exercise in statistics (as bonehead says). Schroedinger's Cat was a thought experiment designed to eliminate all of that complexity and leave a macroscopic state at the mercy of a single quantum event: the decay of the atom. But if you were smart enough to understand the quantum events behind the coin flip, you could reduce that to quantum uncertainty as well.
posted by A Thousand Baited Hooks at 9:51 AM on May 2, 2011
I believe the point of the Schroedinger's Cat thought experiment is exactly this. In that thought experiment, you put a cat in a box with a vial of poison gas, and a trigger mechanism that can break open the vial if a radioactive atom decays. Now the box is sealed; we haven't yet observed the cat. It's indeterminate whether the atom has decayed, and thus it's uncertain whether the cat is still alive. When we open the box and observe the cat, we will cause the indeterminacy to resolve itself one way or the other. But which way it will go is not determined. Thus even if an omniscient being had complete information about the whole world up to the time we sealed the box, it still couldn't predict what will happen.
The thought experiment shows that indeterminacy at the quantum level can turn into indeterminacy at the macroscopic level.
(I am no physicist though.)
posted by LobsterMitten at 9:47 PM on May 2, 2011
The thought experiment shows that indeterminacy at the quantum level can turn into indeterminacy at the macroscopic level.
(I am no physicist though.)
posted by LobsterMitten at 9:47 PM on May 2, 2011
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posted by grizzled at 7:56 AM on May 2, 2011