Re: Symmetries of general relativity

[EMAIL PROTECTED] (Kevin A. Scaldeferri) wrote in message news:<[EMAIL PROTECTED]>...
> In article <[EMAIL PROTECTED]>,
> Lubos Motl  <[EMAIL PROTECTED]> wrote:
> >On 26 Nov 2003, Kevin A. Scaldeferri wrote:
> >
> >> Newtonian gravity is diffeomorphism-invariant (i.e. generally
> >> covariant).  If you find this, to use your own word, confusing, you
> >> can find it explained in depth in MTW.
> >
> >If the books like MTW are too difficult and contrived,
> 
> Certainly there is something "contrived" about this example.

I don't agree. Of course it is not as beautiful as GR, but the
generally covariant version of Newtonian gravity is surprisingly
elegant granted the existence of a "universal" time. 

> >I recommend you the Elegant Universe by Brian Greene to learn - in
> >laymen's terms
> 
> Why would I want to do that when the layman's explanation is a naive
> oversimplification?

To my amazement, many popularizations do contain silly statements
like this. It's interesting how many naive oversimplifications 
get petrified and handed down the generations of popularizers ---
the statement that the singularity in a black hole is at the
"center" is one of my favourites; another one is the idea that
we should expect the expansion of the universe to be slowing
down because of "gravitational attraction" [completely ignoring
isotropy]. I guess people like Greene are eager to get on to
the parts that really interest them, so they cut through the
old stuff with the aid of cliches handed down to them from
past efforts to explain GR.