First Principles

Tomorrow in class, I plan to utter the words, “This is the most basic, fundamental concept in all of Nature.” I wonder if you’d agree. What would you call the most basic, fundamental concept in all of Nature? (Other than the Pirates will have a losing season, of course.)

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8 Responses to First Principles

  1. jwambaugh says:

    Conservation of energy? It’s underlies mechanics, relativity, and especially statistical mechanics, and follows from the invariance of time (a principle I like).

  2. brianbunton says:

    Yep, that’s it. I may have oversold it when I told them that this was the most important day of their lives.

  3. bmarts says:

    I would have said the most basic fundamental concept is that the laws of nature are constant in space and time.

  4. jwambaugh says:

    I don’t think everyone agrees that the physical laws have been constant for all of space and time: http://en.wikipedia.org/wiki/Cosmic_inflation

  5. bmarts says:

    John, I don’t see anything in that article that suggests the physical laws changing with time. The different behavior (early inflation) is a result of the different conditions of the early universe (it was small) and not different physical laws.

  6. jwambaugh says:

    You’re quite right, my fault. That article only explains that there is a missing mechanism behind inflation. I’ve seen a couple of papers that suggest that that mechanism could be variable physical constants, which I think of as being variable physical laws (though the forms might be fixed). This seems like an appropriate summary of that movement:
    http://www.physorg.com/news68967509.html

  7. bmarts says:

    This seems like the kind of thing that would be hard to nail down. You can have a philosophical discussion on whether a constant is a natural law. Unfortunately, you may have cases where what appears to be a constant based on today’s experiments really depends on something like the curvature of space, which doesn’t have to be constant.

    My original point though, is that one of the fundamental ideas of doing science is that I can do an experiment today in Florida and tomorrow in North Carolina and the results obey the same natural laws. If we believe that the natural laws are subject to change, even conservation of energy will go out the window too.

  8. brianbunton says:

    I’m wondering if this is a chicken-or-egg situation. Can they be cast as essentially the same thing? I’m thinking of the famous classical mechanics problem (side note: the first upper level class I’ll be teaching is classical, next spring) that Ronen wrote about deriving the Lagrangian of a free particle (m r’^2/2) from the isotropy of free space. Could one use the fact that energy is a constant to prove spacetime symmetry?

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