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Q & A: universal laws? chaos?

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Most recent answer: 07/11/2016
Q:
So, as a preface, I know next to nothing about physics, but one thing bothers me about "Laws of Physics". How can we know they are Universal laws, when we only know what the outcome of any given experiment is in our Gravity Well (I believe that would be the correct naming of the solar system). I do understand that under variables such as higher gravity, you could adjust the numbers to reflect, the differences. But, we the universe is not uniform and orderly, it is chaotic, correct? So, should "Laws" be emended to "Laws within the uniformity of our solar system", yes I understand that is a huge mouthful. At the same time what if sometime in the far future, if humanity somehow makes it to another star system, what if physics act differently due to a bigger or lesser concentration of matter/dark matter/anti matter? If there is an introductory book to physics that would explains these questions please point me to it so I can try to understand it myself.
- Matthew (age 36)
Springfield, Oregon
A:

Most beginning textbooks don't really deal at all with these philosophical issues, unfortunately. Most philosophical texts are too wordy. I recommend a little series of lectures by Richard Feynman, called The Character of Physical Law.

As for the specific issues you raise, it's very remarkable that we have laws of physics that are completely robust under those sorts of changes of conditions. We can detect signals from events happening under extremely different conditions (two black holes colliding, rotation of binary stars including an extremely dense neutron star, nuclear and chemical reactions in other star systems, radically different pressures and temperatures on earth,....) and they all still follow precisely the fundamental rules of physics. Amazingly, that's true even when the rules (like General Relativity) were based on very limited samples of the range of possible conditions. 

So this tells us something special about our universe (and maybe others)- underneath the complicated and often chaotic behavior lie some very general precise laws.  It does not tell us that our current laws will work under absolutely all conditions, however. In fact, our two deepest and most general laws (General Relativity and quantum field theory) cannot be combined self-consistently, so at least one will have to go at some point. We hope that it will be replaced by a more general law, becoming just a good approximation to that law under a broad range of conditions. That's what happened to Newtonian physics when relativity and quantum mechanics were discovered.

Mike W.


(published on 07/11/2016)

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