On Sunday, January 6, 2019 at 1:49:06 AM UTC-6, Brent wrote: > > > > On 1/5/2019 9:49 PM, [email protected] <javascript:> wrote: > > >> But is this consistent with https://arxiv.org/abs/1109.5191v2 which >> showed spacetime to be smooth down to 1/525 of the Planck length? >> >> Brent >> > > *If we can't measure a Planck length, how can we measure of fraction of > that value? How large are those tiles in relation to Planck length? AG* > > > By looking for the cumulative effect of the EM waves interacting with the > "graininess" of spacetime over very many grains. The idea is that photons > of wavelength very long compared to the grain size will just average over > them as though they were continua. But very high energy, gamma ray photons, > with much shorter wavelength, will experience the graininess and propagate > slightly slower, which over cosmological distances will produce a > difference in arrival time at our telescopes. Read the paper. > > Brent >
I don't know enough about the LQG mathematics to reconcile it with the result "Such limits constrain dispersive effects created, for example, by the spacetime foam of quantum gravity. In the context of quantum gravity, our bounds set M1c2 greater than 525 times the Planck mass, suggesting that spacetime is smooth at energies near and slightly above the Planck mass." But one thing may be happening is that LQG may model space as (Planck-sized) cells, so a single path from A to B through space would be jig-jaggy, but if multiple paths from A to B were "averaged", then a more continuous result would appear. - pt -- 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.
