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 > > > On Wednesday, December 27, 2017 at 2:17:49 PM UTC-6, [email protected] > wrote: >> >> Since galaxies were formed after the CMB came into existence about >> 380,000 years after the BB, and those far away will wink out as they cross >> the cosmic horizon, why doesn't the CMB also wink out? I know the latter is >> reddening as the cosmos expands, and is ubiquitous, but when the question >> was posed to me last night at a meeting in Pasadena with former JPL >> colleagues, I didn't have a good answer. TIA, 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 [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.
