On 3/2/2014 2:38 PM, LizR wrote:
On 3 March 2014 08:33, meekerdb <meeke...@verizon.net
<mailto:meeke...@verizon.net>> wrote:
I don't think Tegmark appreciates how much the "laws of physics" depend on
our
demands that the "laws" be invariant, e.g. conservation of energy is a
consequence
of requiring the lagrangian to be time-translation invariant.
That isn't a demand, it's an observation. (Made by Emmy Noether, IIRC.)
Noether observed the connection between continuous symmetry in a lagrangian and the
existence of a corresponding conserved quantity. But that a lagrangain (or theory in any
form) have that character is a "demand"; or at least a strong desiderata. Remember how
the neutrino was discovered. If some process seemed to not conserve energy, we'd just
look for something new we could count as the energy difference.
See Vic Stenger's "The Comprehensible Cosmos" for full development of the
idea that
all of physics can be seen this way. So the "laws" are the way they are
because we
make them up to fit the observations and we only want to make them up in
certain
ways that make them useful for prediction and explanation.
So are you saying that the conservation of energy is no more fundamental to physics than
the shape of Africa?
No, I'm saying it's so fundamental we'd reshape Africa to fit. It's almost essential to
having a theory that doesn't refer to a particular time, that applies equally at all times.
Brent
Sorry, I don't quite follow what you're saying here (it seems either trivially correct
or wrong but I can't tell which!)
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