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Is physics based purely on observation?

  1. Jan 18, 2012 #1
    Hello everyone, I recently had a debate with my philosophy teacher about physics, she was saying that physics is purely an observational science, I objected by saying that some areas of physics are based on reasoning and have no observable results to show, stating superstring theory as an example. Am I right? If I am, could you please state some theories based on reasoning and mathematical rigor rather than observation? Thank you in advance.
     
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  3. Jan 18, 2012 #2

    russ_watters

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    What does "purely observational" mean?
     
  4. Jan 18, 2012 #3

    sophiecentaur

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    On the other hand, Philosophy is not even based on observation - just a set of axioms that may or may not have any relevance to the world - depending on how eloquent the Philosopher happens to be.

    Science is all about trying to explain what we observe. Some explanations are more tenuous than others but I think you could say that all explanations / models are developed in the hope that someone, some day, can verify it experimentally. A Scientific Theory can only be such if it is 'disprovable'. Take Higgs Boson, for instance. That was postulated long before an experiment was even thinkable - but there's no point waiting until someone builds measuring gear just in case someone might want to use it for something - you'd be waiting for ever.

    So I think your Philosophy teacher was probably right but the word 'purely' seems too much of a quality judgement - reads like "only".
     
  5. Jan 18, 2012 #4

    Nabeshin

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    Your professor is correct. Physics must ultimately submit to experimentation, as that is the ultimate test of any theory. String theory is such a complex theory, we simply haven't worked out any testable predictions of it yet. It is the hope of all the string theorists that eventually we will figure out how to extract predictions from the theory, deciding the question of whether or not it matches up with physical reality. All the work in mathematics and reasoning that has gone into string theory up to the point is in order to get the physical predictions out.

    Now, there are mathematicians among us who couldn't care less whether or not string theory is actually a good description of our reality. They're simply interested in the logical structure of the theory of quantum vibrating strings! That's the distinction between physicists and mathematicians though. It's true, the line can seem a little blurry, but even in the most speculative theoretical physics papers, you'll find a short paragraph towards the end describing what things would be like IF the strange theory were true.
     
  6. Jan 18, 2012 #5

    russ_watters

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    The reason I asked what "purely" means is that the scientific method has 4 steps and only two of them are about observation.
     
  7. Jan 18, 2012 #6
    I've heard a lot of ways to divide the scientific method into steps, what are the steps you're talking about?
     
  8. Jan 18, 2012 #7
    I think your professor is right. Science is (best) defined by a measure of empiricism. Observation is the final arbiter of any and all scientific hypothesis and theories. If you are just sitting and thinking and coming to conclusions based off of some arbitrary system of logic you are not doing science. (you are doing maths or philosophy or something else)
     
  9. Jan 18, 2012 #8

    russ_watters

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  10. Jan 19, 2012 #9
    Physics may be purely observational. Physicists, not so much. If two theories are put forward to explain a particular phenomena physicists will gravitate toward the one that is more simple and elegant until observational data differentiates one from the other. For example, Newtons theory of gravity was originally disliked because it predicted elliptical orbits instead of the more simple and elegant circular orbits of previous theories.
     
  11. Jan 19, 2012 #10

    sophiecentaur

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    Philosophy is a very useful discipline to help in the scientific process because it insists on rigour in making the 'non-experimental steps'. But I have a real problem with the 'self important' stance that Philosophy takes about its own worth. It is 'great fun' to wring out every last aspect of an artificial model of society / religion / culture / the World and it does require a high level of ability. But when Philosophers try to apply their conclusions to the real world, they rely on force of personality and 'marketing skills' to justify applying those conclusions. There always seems to be some step which involves 'faith' where the Scientist makes the same step using 'experiment'.

    I guess there are more than one kind of reality and my personal reality is in contention with that of the Philosopher. Hence, 'they' tend to make me cross.
     
  12. Jan 19, 2012 #11

    sophiecentaur

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    Our posts crossed there.
    I should say that the rigour which is required in 'good' Philosophy should be applied when Scientists start to make arbitrary choices of model. The reductionist principle is pretty universal in Science and it can be justified (in the absence of experimental evidence in a particular case) on the grounds of experience (which is experimental in nature). Even Scientists (who are mostly human, after all) have emotional attachments to certain methods. Conservatism, for instance, is a very health influence of mainstream Science. Without it, we'd be on a random walk. Any worthwhile hypotheses will eventually find its way into general acceptance as a theory despite the influence of prima donna experts.
     
  13. Jan 19, 2012 #12

    micromass

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    I like this video:

    https://www.youtube.com/watch?v=EYPapE-3FRw
     
  14. Jan 20, 2012 #13
    As I understand it, modern physics is decades ahead of any experiments possible with todays technology..
    To that extent I'd say it's moving away from being purely obeservational

    However, it's roots are still solidly in observationalism, if that's the word you'd use.
     
  15. Jan 21, 2012 #14

    Pythagorean

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    I think feynman's scientific method is more accurate than the 4-step method; but still, not everybody does things in that order. Some people play first with their system and then hypothesize after they know their system. Or formulate the hypothesis as they write their paper (already knowing the system and what's novel having to make a story out of it).

    ie, the hypothesis can just as easily be the last step.
     
  16. Jan 21, 2012 #15
    You could just as easily argue that everything is based on observation, but physics is a science which means it deals with systematically cataloging and organizing data including such unobservable possibles as the Many World's theory. The only additional restriction with physics is that it must relate to fundamental physical properties.
     
  17. Jan 21, 2012 #16
    mrspeedybob, the observation of elliptical orbits preceded Newton. Tycho Brahe collected huge amounts of data on the orbit of mars by observation and passed that data down to Kepler, who spent years trying to make sense of it. Kepler was the first to realize the collected observations had to add up to an elliptical orbit, and he proposed that all orbits were elliptical.

    http://en.wikipedia.org/wiki/Kepler's_laws_of_planetary_motion

    This was old news by Newton's time. Newton's theory was actually liked because it explained how universal gravitation ought to result in elliptical orbits thereby complying with Kepler's laws and simultaneously explaining that the familiar force of gravity was behind it.

    With Newton specifically in mind, I think your teacher has no case. The Principia is about 2% observation and 98% reasoning to make sense of the observations. As you probably know, Newton coherently assembled all known physical laws for the first time, and bent classical geometry in strange ways to serve the purposes of calculus, in order to lay out his case for universal gravitation. Newton was prompted to explore the issue because of the observations, but he's certainly not merely describing things: he's rigorously reasoning things out mathematically. I think this is eminently typical: observations are often inexplicable, and physics seeks to rigorously reason out the explanation.
     
  18. Jan 21, 2012 #17

    sophiecentaur

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    I have great difficulty taking a lot of, even high powered, philosophy seriously. Every conclusion in a philosophical argument must start with an implicit or explicit "IF . . . .".
    In Science / Physics, conclusions have a much 'harder' input requirement - i.e. "This model explains the following observation. . . ".

    I remember listening to an interview with a prestigious Christian Philosopher about why one should believe in God. Her clinching (?!) remark was "If you are optimistic then you MUST believe in God". Now, there's a 'bootstraps' argument if ever I heard one.
     
  19. Jan 21, 2012 #18

    Pythagorean

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    Empiricism is a philosophy... IMO, THE most high powered philosophy.
     
  20. Jan 21, 2012 #19

    sophiecentaur

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    And is it not the same as Science?
     
  21. Jan 21, 2012 #20

    Pythagorean

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    No. It's the most likely philosophy a scientist would have, especially in the west. But science is a combination of philosophy and mathematics.

    Everyone has philosophical baggage though, when you start actually detailing their interpretations of the data. "empiricism" is a very broad, vague word: our miniature philosophies can be the most dangerous or enabling.
     
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