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Thread: Learning Physics?

  1. #46
    Quote Originally Posted by Mike Henderson View Post
    In physics thought experiments you're allowed to specify things that would be extremely difficult to produce in real life. The thought experiment is still valid because physics still has to apply even in extreme cases.

    Einstein and Feynman (among others) were great proponents of thought experiments. Schrödinger's cat is a thought experiment.

    Mike
    Yes, agreed 100%. In this case, though, it's an impossible situation. That impossibility is what insures the conservation laws will hold. It's sort of like saying "what do the laws of physics predict would happen if you could extract path information from the double slit experiment, yet maintain the interference pattern?" The problem is that the situation is impossible within the current framework of the physical laws so the laws don't apply anymore. In your case, setting up the perfect situation is impossible given the current framework, so analyzing it in the same framework gives results that no longer agree with experiment.

    The other way of looking at it is that the photon always ends up SOMEWHERE. It never goes poof. When you analyze it on a photon by photon basis, the conservation of energy becomes obvious. The photon goes somewhere. You never end up with no photon. It's only when you analyze it using a wave treatment that you have the problem of purely destructive interference, but then when you do that and take everything into account you find that it's impossible to actually setup a situation that gives you that pure destructive interference. it's not just a matter of technology or "hardness". It's a matter of there's no arrangement that's possible in the current framework that could ever give you that without also giving you enough constructive interference elsewhere to make up for it.

    Schrodinger's cat can, in principle, be setup. We can't really do it in real life right now, but presumably that's just a technological hurdle. The case you're trying to setup can't be setup even in principle, no more than a measurement could ever be taken that violates the uncertainty principle. It's deeply unsatisfying, and it was deeply unsatisfying to Einstein and Shrodinger himself as well, but that's all there is at the moment.

    BTW, I use this stuff everyday. Whenever my inlays don't fit perfectly, I always blame Heisenburg
    Last edited by John Coloccia; 08-30-2010 at 10:57 PM.

  2. #47
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    And to think....I just came to the Creek to learn to build furniture.....
    Ken

    So much to learn, so little time.....

  3. #48
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    Someone took my stapler...
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  4. #49
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    Maybe drop the thought experiments back a step perhaps

    you are traveling in your car at the speed of light, you turn on the headlights, what happens?

  5. #50
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    Boy, do I feel stupid.

  6. #51
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    Quote Originally Posted by Chuck Saunders View Post
    you are traveling in your car at the speed of light, you turn on the headlights, what happens?
    I blow a fuse because I installed the Taiwanese faster-than-the-speed-of-light bulbs incorrectly...
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  7. #52
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    My shop cat has started a collection to save Schrodinger's cat.

    Unfortunately all he's collected so far is a bunch of planer shavings and a catnip mouse.......Rod.

    P.S. Being in the elctrical field I've always used "j".....
    Last edited by Rod Sheridan; 08-31-2010 at 10:02 AM. Reason: Added Post Script

  8. #53
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    Rod,

    I need an address to make a contribution to your cat's efforts. Will I have to pay import/export fees on shavings going to Canada?
    Ken

    So much to learn, so little time.....

  9. #54
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    Quote Originally Posted by Ken Fitzgerald View Post
    Rod,

    I need an address to make a contribution to your cat's efforts. Will I have to pay import/export fees on shavings going to Canada?
    Ken, no import fees, we're all one happy family now with NAFTA

    Could I be so bold as to request something other than white oak? I seem to be swimming in that at present.

    Good thing that Diann's parents have a farm and their chickens need shavings for bedding.

  10. #55
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    I keep checking back on the updates to this thread because I have a school age children in college and high school. I have come to the conclusion that you guys are keeping this thread going just so I can come to the realization that I:

    A. Should have studied more in school.

    B. You're doing it just to make me realize how stupid/ignorant I really am.

    Keep it up though. You are never to old to learn.

  11. #56
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    John,

    Some of my favorite days are the ones that include technical discussions in the forums.
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  12. #57
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    I agree. It keeps my mind fresh and really makes me want to get out and learn more. When I was in school (high school and college), I wanted to get into physics and organic chemistry. They both really fascinate me to the extent that I thought about a career in one or the other. But the one small detractor was my lack of paitence and desire for math. Unfortunately, you can't eliminate the math from either career. College Calc was mind numbing for me.

  13. #58
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    Quote Originally Posted by Rod Sheridan View Post
    P.S. Being in the elctrical field I've always used "j".....
    I always liked you, Rod....
    Wood: a fickle medium....

    Did you know SMC is user supported? Please help.

  14. #59
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    Quote Originally Posted by Ken Fitzgerald View Post
    I would suggest as long as the resistor isn't a dead short, the battery terminals are 9 volts dc +/- with respect to the other terminal.

    In the case of the 1/4 wave dipole, I'd suggest at any one time, the voltage is 90º out of phase to the other end....could be leading or could be lagging depending on the reference.
    Well, having built more than one dipole antenna over the years, the 1/4 wave vertical is unique in that it works equally poorly in all directions.

    If the dipole is constructed in electrical multiples of 1/4 wave every thing is goodness and it radiates energy, and you have a voltage max at the tip of the antenna. Consider a sine wave that is only 90 deg. (You might ask what about the remainder of the sine wave? It's energy is radiated via radials mounted at the bottom of the antenna. Alternatively, the ground absorbs the energy.)

    BUT, What if the antenna isn't the correct length? You then have a problem. When the sine wave gets to the end of the antenna, it does not have a max or a min, and it is very unhappy and reflects some amount of the sine wave back to the source. This is expressed as a standing wave in antenna parlance. The EE will talk about +jwt, or -jwt. When jwt =0, everybody is happy and you have a condition known as resonance.

    Time to go to the store and maintain domestic tranquility.
    Best Regards, Ken

  15. #60
    Thanks for all the suggestions, sites, links, and recommendations!

    Just a side note, if you didn't click on Wayne's links, take a minute (or hours) and do so. It's an excellent site teaching just about anything.

    Thanks again all!
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