On Wednesday, December 27, 2017 at 6:37:16 PM UTC-7, Brent wrote: > > > > On 12/27/2017 5:21 PM, agrays...@gmail.com <javascript:> wrote: > > > > On Wednesday, December 27, 2017 at 3:43:05 PM UTC-7, Lawrence Crowell > wrote: >> >> The CMB is composed of radiation with a black body distribution peaked at >> around 1000nm. The radiation is now in the microwave band at about 1 mm >> wavelength. The IR photons were spread by the expansion of spacetime by a >> factor of 1000, and the actual z factor for the CMB is z = 1100. With the >> exponential expansion of the universe this z will increase until the CMB is >> in the radio wave band > 1m wavelength, and then eventually expanded beyond >> the dimensions of any practical antenna. It will take about 10 billion >> years for that to happan. >> >> LC >> > > There's a huge difference between photons falling below our threshold of > detection, and those which can never reach us because they left their > source after it had crossed our event horizon. AG > > > Not really. From the event horizon they are redshifted to zero energy, > which is the threshold of detection. LC isn't talking about some current > technological limit on detection. > > Brent >
LC refers to a "practical antenna" so he must mean something related to our detection capabilities. Moreover, if a source of light is receding faster than c due to expansion, it must mean that photons leaving it will simply never reach us. Not a case IMO of being redshifted to zero energy. AG -- 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 everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
