From: *Russell Standish* <[email protected]
<mailto:[email protected]>>
On Sun, Mar 11, 2018 at 01:24:19PM +1100, Bruce Kellett wrote:
> From: *Russell Standish* <[email protected]
<mailto:[email protected]>
> <mailto:[email protected] <mailto:[email protected]>>>
> >
> > On Sun, Mar 11, 2018 at 10:17:01AM +1100, Bruce Kellett wrote:
> > >
> > > My feeling is that we observe that the world has certain symmetries,
> > then we
> > > design our theories to reflect these symmetries, because
theories that
> > > incorporate the observed symmetries work better. Since the starting
> > point is
> > > observation, we have some prospect of learning something other
than the
> > > nature of our thought processes.
> > >
> > > Bruce
> >
> > My claim is that there are always symmetric theories. Assuming some
> > horrible
> > non-symmetric world, we can make a symmetric theory by a suitable
> > transformation of variables - in rather the same way we can see a
> > computation in a rock by a suitable transformation of variables.
>
> I think that in general it requires a little more than just a
transformation
> of variables. If we fail to see rotational symmetry in the world
around us
> (same laws in all directions), then we would have to postulate some
oriented
> field, or some interaction that depended on position and/or
direction. To do
> it by a transformation of variables you would require the variables
> themselves to reflect this non-symmetric field.
>
>
> > What do you say to the proposition that evolution might have equipped
> > us with the facility to see those symmetries "intuitively", since it
> > makes computing things about the world easier?
>
> I don't think that actually changes anything -- what that means is that
> those symmetries existed in the world, and evolution took place in the
> context of those symmetries. So it is anything but an arbitrary
imposition
> by our minds on a non-symmetric world.
Of course - I never claimed that. Just that the symmetries observed
tell us more about what we've evolved to see in our environment
rather than an intrinsic property of the environment.
If we have evolved to see it in our environment then it follows that it
was actually in the environment to be seen, and not merely a product of
evolution. Our eyes evolved to be sensitive to particular wavelengths of
light because they corresponded to wavelengths to which the atmosphere
was largely transparent so that there was a lot of radiation of these
wavelengths around. Evolution is an adaptation to the conditions of the
environment, not something that creates that environment. Or are you
saying that we see in the visible range rather than the IR (to which
some animals are sensitive) merely by chance? So that the symmetries we
observe are a chance selection from a much wider range of symmetries
that actually exist.
A lot of the symmetries that Lawrence is referring to when he talks
about wider symmetries are essentially abstract -- we do not immediately
see the SU(2) symmetry of isotopic spin, that is a construct of our
theories, as are most abstract gauge symmetries. Evolution did not equip
us with senses that intuitively see that protons and neutrons are
related by a symmetry transformation.
Bruce
--
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 [email protected].
To post to this group, send email to [email protected].
Visit this group at https://groups.google.com/group/everything-list.
For more options, visit https://groups.google.com/d/optout.
