On Wednesday, January 29, 2020 at 12:18:40 PM UTC-7, Brent wrote: > > The idea that some clocks run slower than others is a confusion. Talk of > clocks in general relativity always refers to ideal clocks that, by > definition, run at identical rates when compared at the same place. > "Running slow" really refers to taking a shorter path (less elapsed proper > time) thru spacetime, as reflected in the metric. As AG noted the "running > slow" relation is symmetric; so it can't be invariant. > > Using the CMB is an operational way to define a global time. It is the > same as co-moving coordinates in which matter is, on average, stationary. > But it is a good/useful coordinate system because it makes the > representation of an FLRW model simple. There's an implicit assumption > that the universe is homogenous and isotropic, which implies that it > satisfies an FLRW model. With that assumption a measurement of curvature > locally can be extended to infer the whole spacetime. Space can be flat > while spacetime is curved, so as to be open or closed. > > Brent >
Can you answer the question? If we have two clocks at the distant galaxy; some observer's clock which is running slower compared to a local clock in this galaxy, and the CMBR clocks at every location in the universe which are synchronized, what is the status of time dilation? Do it exist or not? TIA, AG > > On 1/29/2020 12:57 AM, Alan Grayson wrote: > > Considering the distant galaxies, they're receding at near light speed. So > according to SR, their clocks should be ticking at a much slower rates > than, say, a local clock in our galaxy. OTOH, there's a physical clock for > the entire universe; namely, the temperature of the CMBR. If we tell time > by this clock, all clock readings of all galaxies are identical. So which > is it? Are clocks in distant galaxies running slower than a local clock in > our galaxy, or are both clocks running at the same rate? 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] <javascript:>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/everything-list/5c5aa450-761d-4784-9ba3-f25085991a83%40googlegroups.com > > <https://groups.google.com/d/msgid/everything-list/5c5aa450-761d-4784-9ba3-f25085991a83%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > > -- 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 view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/6752836c-a025-4a21-b1e5-0a690c1f6576%40googlegroups.com.
