On 23 May 2014 12:54, meekerdb <meeke...@verizon.net> wrote: > On 5/22/2014 4:16 PM, LizR wrote: > > On the other hand, I find arguments along the lines of "we generate > physics because we demand certain types of answer from nature" > unsatisfying, indeed they strike me as postmodernism in disguise, which I'm > personally averse to. > > Me too. But that's not what I (or Stenger said). What we said was that > we demand that our descriptions of nature apply in all circumstances in > order to count as "laws of physics". >
Oh well, I wouldn't argue with that. (Except if someone discovers that some constant of nature actual varies with time...but that would almost certainly point to something more fundamental that doesn't.) > What's surprising is how much you can get from this, as shown by Noether. > Just demanding translation invariance implies a conserved quantity we call > momentum. > Yes of course. Most of modern physics is based on symmetry principles. But it isn't "demanding" translation invariance, imho, it's observing it. One can imagine worlds in which physical properties vary with position, but we observe that we don't live in one of them. (Of course Max T gets this from his MUH, observing that lots of mathematical structures have built in symmetries .... though Garrett Lisi hasn't found the right one yet). > Look up Vic's book. > I have an awful lot of books on science floating around waiting to be read. Not to mention "Tronnies" :-) > As I say, I think he makes it sound better than it is because it's not > always to obvious what transformation relative to which we want to maintain > invariance. You have to know that you want make the speed of light > invariant in order to get conservation of 4-momentum. > I don't see the problem here. Measurements indicated something was weird with the speed of light, and that was followed up, resulting in special relativity. If you try to make something invariant that isn't, you will find your measurements give the wrong results, surely, and revise your assumptions? At least, eventually. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
