The relativity of simultaneity is a direct consequence of Einstein's 1905 light postulate:
http://www.people.fas.harvard.edu/~djmorin/chap11.pdf
p. 9: "Consider the following setup. In A's reference frame, a light source is placed midway between two receivers, a distance L' from each (see Fig. 11.4). The light source emits a flash. From A's point of view, the light hits the two receivers at the same time, L'/c seconds after the flash. Now consider another observer, B, who travels to the left at speed v. From her point of view, does the light hit the receivers at the same time? We will show that it does not. In B's reference frame, the situation looks like that in Fig. 11.5. The receivers (along with everything else in A's frame) move to the right at speed v, and the light travels in both directions at speed c with respect to B (not with respect to the light source, as measured in B's frame; this is where the speed-of-light postulate comes into play). Therefore, the relative speed (as viewed by B) of the light and the left receiver is c+v, and the relative speed of the light and the right receiver is c-v."
If Lee Smolin, Julian Barbour, Craig Callender and others hate the relativity of simultaneity and dream of absolute simultaneity, they will have to analyse a text like the above one and admit that, with respect to B, the light does not travel in both directions at speed c. Rather, with respect to B, the light travels at c+v to the right and at c-v to the left. Then the relative speed (as viewed by B) of the light and the left receiver is c, the relative speed of the light and the right receiver is c again and ... ABSOLUTE SIMULTANEITY IS RESTORED:
http://www2.warwick.ac.uk/fac/cross_fac/ias/earlycareer/events/time/programme/julian_barbour.pdf
Aspects of Time, Julian Barbour, Warwick, August 24th 2011: "Was Spacetime Glorious Historical Accident? (...) ABSOLUTE SIMULTANEITY RESTORED!"
http://www.fqxi.org/community/articles/display/148
"Many physicists argue that time is an illusion. Lee Smolin begs to differ. (...) Smolin wishes to hold on to the reality of time. But to do so, he must overcome a major hurdle: General and special relativity seem to imply the opposite. In the classical Newtonian view, physics operated according to the ticking of an invisible universal clock. But Einstein threw out that master clock when, in his theory of special relativity, he argued that no two events are truly simultaneous unless they are causally related. If simultaneity - the notion of "now" - is relative, the universal clock must be a fiction, and time itself a proxy for the movement and change of objects in the universe. Time is literally written out of the equation. Although he has spent much of his career exploring the facets of a "timeless" universe, Smolin has become convinced that this is "deeply wrong," he says."
Pentcho Valev pvalev@yahoo.com
