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Quantum Epistomology

  1. Sep 17, 2003 #1


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    Assuming that the uncertainlty principle is a fact of the world, as many physicists firmly believe, how does this affect our deep undersranding of knowledge?

    In the Middle Ages the consideration of bodyless angels led to subtle considerations of what we can know and how we can know it. Monistic science has traditionally had only a naive approach to epistomaology. But I think that quantum constraints, like the angels of old, should return nuance to the field.

    What do you think?
  2. jcsd
  3. Sep 17, 2003 #2
    We are never sure of what we know.
  4. Sep 17, 2003 #3


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    Thats not completly true. I'm a lil fuzzy on the subject, so please slap lightly if needed.

    For instance, I know that I will be hungry in a few hours, and that I will probably eat a Mr. P's pizza, microwaved for 2 min and 50 seconds.

    In fact, now that I mention it, I am certain that I know this.

    But on broader topics, I can agree that it is difficult to know what we consider as true or fact might be changed. But seems like thats the point. Keep learning and refining so that we can be sure of what we know. 300 years ago, a person could not state with as much certainty what they would be eating in 2 or 3 hours. He couldn't tell you exactly how long it would take to cook it to perfection. (Yes, microwave is a form of cooking :)

    I've read a lil about quantum this and that. I understand the uncertainty principle to a point. My guess on the matter is that there is a certain level of certainty, especially when dealing with information. It may be that technology is not able to provide the certainty on the quantum level that we are used to in day to day life. I mean, there was a point in time where man was uncertain if he would still be alive after walking through a thick forest. Later, we've learned all there is to know about a forest, what dangers lie within, survival, etc, and now I can look at a thick patch of forest and know with some level of certainty that I will survive the trip.

    Like I said, don't kick me to hard, if I'm totally off base lemme know so I can sit back and learn something.
  5. Sep 17, 2003 #4
    In the Middle Ages and bodyless angels: there were heavy discussions (during decades) about ... the numbers of hairs on the heads of these angels! Strings. ;-)
  6. Sep 17, 2003 #5
    The uncertaintly principles demonstrates something that is rather obvious: that we can't know everything. This does not mean that we cannot be sure of anything, just that there are limits to the extent of our knowledge--in this case, the precision of measurements of velocity and position.
  7. Sep 18, 2003 #6
    How could we in fact know what we know, without the ability not to know? Where would the contrast be, and how would we be able to differentiate?
  8. Sep 18, 2003 #7
    Perhaps the uncertainty principle is due to the basic building blocks of our knowledge. An error which is carried through the information until we decide we need a result, only then does it become observable to us.

    Or (from Tim) we are simply not meant to know everything about the way things work. A safety catch built in to stop our heads exploding (either from pride at the ultimate achievement, or from all the knowledge acquired).

    Exactness is unachievable...
  9. Sep 19, 2003 #8
    Much nonsense is said about the uncertainty principle, when to me what it states is something far too simple to have any deep philosophical consequence. The fact is that velocity and position are mutually exclusive by definition. If "velocity" is defined as "change in position", how can you know "position" and "change in position" at the same time? Of course it's impossible but that has nothing to do with the nature of reality, it's just a question of logic and semantics.

    The whole problem arises from the misconceptions created by too much faith in abstract thinking. What I said above was obvious until calculus was invented. After that, the notion of "instantaneous velocity" gave rise to the idea that it was possible for an object to both be moving and have a well-defined position at the same time. Nonsense! That's not what "instantaneous velocity" was supposed to mean; "instantaneous velocity" is a limit, and limits only exist in abstract thinking. In reality, when it comes to making measurements you can't measure a limit, you can only measure a value that gets close to it.

    As to whether uncertainty is a basic principle of reality or not, it's also obvious that it has to be. If it weren't we wouldn't be asking the question to start with, we would know for sure that the answer would be negative.

    I would like to answer that question, but I'm not sure what a good answer would be :smile:
  10. Oct 1, 2003 #9
    map =/= territory

    the uncertainty is ours not the universe's. quantum mechanics reflects the limits of classical (human) precision. we only know what we measure, and there are limits to measurement. if there weren't then there would be no dimensions -- phenomena would be undifferentiated, knowledge would be impossible. uncertainty is inherent in knowing.
  11. Oct 2, 2003 #10


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    Re: map =/= territory

    This is not what quantum mechanics - and all the theories that flow from it - say. They say that uncertainty is in the world, that basic things about the world are not just known up to an uncertainty, but exist up to an uncertainty. And they have experiments to prove* it.

    * prove in the sense of demonstrate forcefully of course.
  12. Oct 4, 2003 #11
    really? and what experiments are those? it seems to me if one had only an uncertain reality with which to measure (prove?) the uncertainty of reality one would not even be able to make a measurement. perhaps you can explain it to me ...
  13. Oct 5, 2003 #12


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    IIRC, The usuals are:

    The various experiments relating to the bell inequality/EPR paradox.

    If we take uncertainty as just uncertainty in knowledge, there must be an absolute value of quantum variables that are measured imperfectly. So, if we separate an experiment such that we have two entangled particles(meaning that one is directly related to another without foreign influence. eg. with conservation of momentum, the sum of the two must equal a set value) that cannot possibly influence each other. We then measure a property of one, and measure a connected property of the other.

    If the uncertainty is merely knowledge, the distribution of the values of each should both be random, regardless of whether you measure A first and then B, or the other way round. With the quantum view, by measuring one you increase the uncertainty of the other, so there is a definite difference in the values you make in the sequence you use. This is put mathematically in the bell inequality, which experiments have violated, confirming the quantum view. The best one is probably the Aspect experiment.

    Another one is the twin slit experiment, where the uncertain wave nature of photons/electrons allow individual particles to show interference patterns.

    Another is quantum tunnelling, which depends on actual uncertainty to allow the penetration of particles through potential barriers.
  14. Oct 6, 2003 #13


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    Thos are good, and there are also

    - "Delayed choice" experiments

    - "Quantum Eraser" experiments

    - "safe bomb detection" experiments

    (Look them up) all of which go to show that the concept "this particle has a property" is much more dubious and nuanced than one would think. I don't think a philosopher would be wise to talk about reality without internalizing the content of these experiments.
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