On 1/16/2014 1:40 AM, LizR wrote:
On 16 January 2014 19:20, meekerdb <meeke...@verizon.net <mailto:meeke...@verizon.net>>
On 1/15/2014 7:44 PM, Stephen Paul King wrote:
But stop and think of the implications of what even Bruno is saying.
completely a construction of our minds.* _There is no 3,1 dimensional
manifold out there_. We measure events and our minds put those together into
tableaux that we communicate about and agree on, because our languages,
logical system, force the results to obey a set of implied rules. We
explanations, formulate models and look for rules that the models might
Hopefully we can make predictions and measure something...
Sure we create models like spacetime - BUT we can agree on them and they are
successful models both in prediction and in explanations leading to other
You write *like this a new discovery.* The set of rules isn't implied, it's
explicit: The model must be the same for everybody in every circumstance.
is intended to apply everywhere. That's why momentum and energy are conserved.
These models are our best guess about what's out there. So it makes no more sense to
say _"There is no 3,1 dimensional Riemannian manifold out there" _than to say
is no computer monitor in front of me." or "I'm a brain in a vat." or
"There is no
refrigerator in my kitchen."
If I remember correctly, momentum is conserved because space has no preferred
That's angular momemntum. Linear momentum is conserved because "space has no preferred
position". I put that last in scarce quotes because in the context of "why are the laws
of physics the way they are" it is an fundamental choice of our model that we don't want
any preferred position, so in a sense we pick out that characteristic as physics and lump
everything particular into geography.
Noether proved that if we wrote our laws to have a continuous symmetry (like translation
invariance) there would necessarily be a corresponding conserved quantity.
P.S. Do you know what conserved quantity corresponds to invariance under a
and energy is conserved because there is no preferred time. An insight we owe to one of
my heroes, the wonderful Emmy Noether, if I'm not mistaken.
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