On Fri, Jan 31, 2020 at 3:04 AM Alan Grayson <[email protected]> wrote:
> > > On Thursday, January 30, 2020 at 10:37:13 PM UTC-7, Brent wrote: >> >> >> >> On 1/30/2020 5:37 PM, Alan Grayson wrote: >> >> >> >> On Thursday, January 30, 2020 at 6:29:18 PM UTC-7, Alan Grayson wrote: >>> >>> >>> >>> On Thursday, January 30, 2020 at 5:09:56 PM UTC-7, Brent wrote: >>>> >>>> >>>> >>>> On 1/30/2020 12:45 PM, Alan Grayson wrote: >>>> >>>> >>>> That's not it. I think the two observers, one in a galaxy far removed >>>> and one here, would read the same CMBR "time", regardless of the distant >>>> galaxy's speed of recession. But relativity says otherwise. This is what >>>> puzzles me. AG >>>> >>>> >>>> Ask yourself *when* do they read the same time. >>>> >>>> Brent >>>> >>> >>> I don't know if this helps. Since the temperature of the CMBR is the >>> same everywhere, at any time t, we can in principle determine if the two >>> measurements are simultaneous or not. AG >>> >> >> But regardless of simultaneity or not, there's no dilation of this clock! >> (And AE doesn't say what a clock is.) What the hell is going on? AG >> >> >> The clocks used in relativity examples are the whatever the most perfect >> and stable clock in existence are (in this case cesium atom clocks). They >> always measure proper time thru spacetime. The only reason that when >> compared they seem to register different durations is because they traveled >> different paths thru spacetime and these paths had different proper >> length. "Time dilation" is not some function of the clock...it's a >> function of the path the clock is measuring. Remember my odometer analogy? >> >> Brent >> > > Given that the temperature of the CMBR is the same for every location in > space-time > The same for every location in spaceTIME? That would imply that if you had one clock created at the big bang, and an observer next to that clock measured the local CMBR temperature when its own proper time showed an elapsed time of say 2 million years, and then if you had a second clock created at the big bang, and an observer next to that clock measured the local CMBR temperature when its proper time showed an elapsed time of 10 *billion* years, they would show the same temperature--which clearly isn't true. And as long as neither of those two clock readings occurs within the other's past or future light cone, you are perfectly free to construct a cosmological coordinate system where they are both simultaneous (both assigned the same value of the time-coordinate in that coordinate system), in relativity there is no coordinate system whose judgment about simultaneity is considered more objectively correct than any other (though some are certainly more *useful* than others in a pragmatic sense, the coordinate system where surfaces of constant CMBR temperature are also surfaces of simultaneity is widely used in cosmology for that reason). -- 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/CAPCWU3%2BBfbZ6h3TZJ6juC8yn3OmmGkJOsL7Uqc%2B_HH3gxZxdSQ%40mail.gmail.com.
