Sorry typo that should be GRB not BRB!
On 11 January 2014 12:36, LizR <[email protected]> wrote: > On 11 January 2014 11:20, Stephen Paul King <[email protected]>wrote: > >> Dear LizR, >> >> I am trying to get a somewhat complicate question out and understood. >> Let me state it crudely: Given the infinite number of possible 1p content >> that the UD can "run", how do we obtain from the UDA or UD or UD* the >> situation that we believe to be true: that there exists a space-time that >> *contains* some huge number of observer -each with its own 1p- *and* the >> appearance of interactions among them *and* a set of physical laws, GR and >> QM that have a mathematical structure that prohibits the assumption of an >> absolute 1p that "could see everything all at once"? >> >> BTW, there are empirical reasons to strongly doubt that space-time has >> some form of granularity, as such would violate SR by making signal >> propagation velocities dependent on the energy of the photons. Ultra high >> energy and medium energy gamma rays have been observed to arrive >> simultaneously (modulo small error bars) from sources that are millions of >> light-years away. This makes the notion of "quantized" space-time dubious. >> >> Apparently the jury is still out on this - see the 4/1/14 edition of New > Scientist with the (typically non-sensationalist :) headline "BREAKING > RELATIVITY - The celestial signals that defy Einstein", which claims the > opposite - that BRB130427A (from a distance of some billions of light > years, redshift 0.34) had a delay of 100s of second between low and high > energy gamma rays. This is the most energetic event observed to date (on > 27/4/13). Also, on 30/6/05, the MAGIC telescope in the Canary Islands > detected a gamma ray burst from half a billion light years away with a 4 > minute delay between the low and high energy radiation. There is also some > data from the Ice Cube neutrino observatory that indicates hints of an > energy dependent time lag in neutrino bursts... > > But there are other observations that don't show these features, plus > there are some assumptions involved that may change how we interpret them, > and so on. What is needed of course is "more light!" - as observations > continue it should become clearer whether there is some dispersion (maybe > only at gamma ray energies that even GRBs struggle to reach very often, > which would indicate that the granularity of space-time is quite small) - > or not, in which case any granularity that exists would have to be very > small, even compared to the Planck length, > -- 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 http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.
