Darren New wrote:
> Paul Fuller wrote:
>> Several times, as carefully as I could I explained that angular 
>> momentum is conserved in a closed system.  That is a general principle 
>> that is apparently fundamental to the way the universe works. 
> 
> Well, it's not just random. All the "conservation" laws are based on 
> "symmetry" laws.  Conservation of energy is based on the premise that 
> what you do here will act the same as what you do there. Conservation of 
> momentum follows from the idea that an experiment you do now will give 
> the same results as an experiment you do later. Conservation of angular 
> momentum is based on the premise that an experiment you do facing this 
> way will give the same results as an experiment facing that way.
> 
> There are similar relationships in the quantum world like conservation 
> of spin and so on.
> 
> I.e., it's not just that it happens to hold. We know *why* it happens to 
> hold, and how to tell when we find a situation where it doesn't hold.
> 
> Which I personally find pretty cool to know. :-)
> 
I don't think I implied that it is random.  If so then let me clear that up.

What I said was 'apparently fundamental to the way the universe works'. 
    Just my choice over declaring it a 'law'.  Certainly not random or 
by accident.

We can understand that "you can't create something out of nothing" or 
"everything must be balanced".  Statements of principles that help us to 
investigate and understand everything else.

I don't think you can explain though why those principles are true 
without essentially coming back to restating them or observing that 
we've never seen them to be broken.  So I'll call them fundamental. 
They are the rules of the game.  The pieces follow the rules not because 
they want to but because there simply is no way not to.

Sure they match our sense of fair play.  Perhaps even our sense of fair 
play is based on the fundamental principle rather than the other way 
around ?

When you say the "Conservation of energy is based on the premise ..." 
and "Conservation of momentum follows from the idea ...", I would 
instead say that the premise and the idea are based on the fundamental 
principles.

And it is cool :)

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