Question on Time Reborn by Lee Smolin

roosh

Recently read Time Reborn by Lee Smolin and I was wondering about one particular aspect of the ideas put forward.

The book essentially challenges Einsteinian relativity, namely the relativity of simultaneity. In it, Smolin suggests an alternative that appears to require a "preferred family of observers" whose clocks measure "preferred global time".

I was just wondering if this was similar, if not the same, as LET after the adjustments made by Poincairé; where, according to the wikipedia entry:
most vestiges of a substantial ether had been eliminated from Lorentz's "ether" theory, and it became both empirically and deductively equivalent to special relativity. The main difference was the metaphysical postulate of a unique absolute rest frame, which was empirically undetectable and played no role in the physical predictions of the theory, as Lorentz wrote in 1909,[C 7] 1910 (published 1913),[C 8] 1913 (published 1914),[C 9] or in 1912 (published 1922).[C 10]"
https://en.m.wikipedia.org/wiki/Lorentz_ether_theory

It seems Smolin's preferred family of observers, with preferred global time, is very much akin to the absolute rest/reference frame of Lorentz.

Just wondering if this is the case, or is there something that distinguishes the two?

Morbert

The alternative that Smolin discusses in Chapter 14 (shape dynamics) is similar to LET insofar as there is a preferred frame of reference that measures the passage of global time. If you take LET to simply mean a commitment to a preferred frame of reference, then shape dynamics is a LET.

But shape dynamics doesn't postulate some ether-like medium. Instead it postulates a relativity of size. Different observers will disagree over the size (but not shape) of objects sufficiently far apart.

roosh

@Morbert Thanks.

Within shape dynamics, is there a reason for the disagreement in size of objects?

Morbert

Within shape dynamics, is there a reason for the disagreement in size of objects?

Do you mean is there something that motivates this particular formulism? Smolin likes the formalism because it is a good stage for loop quantum gravity, his preferred theory of quantum gravity. More generally, some people believe a global time parameter is easier to work with when combining quantum theory and theories of gravity.

If you are asking if there is some ontologically prior state of affairs responsible for relativity of size, I'm not aware of any. Smolin postulates it as a nomological property of the universe.

roosh

Morbert wrote: »

If you are asking if there is some ontologically prior state of affairs responsible for relativity of size, I'm not aware of any. Smolin postulates it as a nomological property of the universe.

I guess this. Not to oversimplify but, as in Einsteinian relativity, relative motion leads to length contraction and time dilation, is there anything similar that causes/leads to the relativity of size in shape dynamics?

Is it simply the topology of the universe that leads to this, does it only occur with relatively moving reference frames, is it simply (to borrow the physics lesson from father ted) bcos objects are "near/far away"?

Just encountering shape dynamics for the first time; I am going to have a scout around and read up what I can on it, but just had that question re:LET.

ban resistant recalcitrant debutant

Morbert wrote: »

...

But shape dynamics doesn't postulate some ether-like medium. Instead it postulates a relativity of size. Different observers will disagree over the size (but not shape) of objects sufficiently far apart.

I couldn't resist.

Like cows, is it?, some of which are near and some of which are far away?