On Saturday, February 1, 2020 at 7:45:05 PM UTC-7, Alan Grayson wrote: > > > > On Saturday, February 1, 2020 at 3:04:16 PM UTC-7, Brent wrote: >> >> >> >> On 2/1/2020 12:11 PM, Alan Grayson wrote: >> >> >> >> On Saturday, February 1, 2020 at 6:49:40 AM UTC-7, John Clark wrote: >>> >>> On Sat, Feb 1, 2020 at 7:41 AM Alan Grayson <[email protected]> wrote: >>> >>> *>But what if the CMB is the local clock? * >>> >>> >>> I'm not sure what you mean by that, but if all the hemispheres of the >>> CMB look about the same to you then you'd know you're motion was about the >>> same as the average motion of matter in the universe, if the hemispheres >>> looked radically different then you'd know you were moving at a different >>> speed than most matter in the universe. But so what? If you and I want to >>> compare our local clocks the only relevant factors are our relative speed >>> (Special Relativity) and the relative gravitational fields (General >>> Relativity) we're in, how the CMB looks to either of us is irrelevant. As >>> Brent said "*it's called relativity theory for a reason*". >>> >>> Einstein and even Galileo said if you're in a sealed room moving at a >>> constant velocity you can't tell if you're moving or not, but you don't >>> need to invoke the CMB to know that if you look out a window on a moving >>> train you can see that there is a lot more stuff outside that window than >>> inside the train, and so you could determine you're moving relative to most >>> of the stuff around you. And if I was in a smaller train than you on a >>> parallel track that was moving even faster than you compared to most of the >>> stuff around us then the only thing you would need to know to figure out >>> the time dilation is our relative motion. And both of our local clocks will >>> be different not just from each other but also different from the clock on >>> the station platform. >>> >>> *> How could it manifest time dilation, compared to a clock in some >>>> moving frame, if its "clock" reading doesn't change? AG * >>> >>> >>> I don't understand the question. You never see your local clock rate >>> change, you observe other people's local clock rate change. Everything >>> always seems normal to you, it's other people's clocks that behave oddly. >>> >>> John K Clark >>> >> >> When you use the Lorentz transformation to calculate the slower clock >> rate in another frame, what you get is the real clock rate in that frame. >> It's what the other observer measures, even though that observer notices >> nothing different. IOW, the calculation of the other observer's clock rate >> is not just an appearance, but what is experienced by the other observer. >> Now suppose we have an observer moving wrt the CMB, and the other observer >> at rest wrt the CMB, what I was calling the local clock. The local clock >> rate never changes, but it should according to relativity, from the pov of >> the observer in motion wrt the CMB. AG >> >> >> I think it is unfortunate that the idea of time dilation and length >> contraction was ever introduced. Just compare time dilation to ordinary >> Doppler shift. We don't make a big deal of the oscillator appearing slower >> when it's going away from us. We didn't invent a "frequency contraction" >> and puzzle over it. We just see it is just a temporal-geometric effect and >> the oscillator didn't do anything, it didn't slow down or speed up. When >> someone measures the frequency of an oscillator they would never attribute >> the measured value to the oscillator without correcting for Doppler due any >> relative motion that was present. Relativistic effects should be looked at >> the same way. Time dilation is not a clock slowing down compared to your >> stationary clock. It is the relativistic Doppler effect due to the two >> clocks measuring time in different directions. It should not be attributed >> to the clocks, any more than Doppler shift is changing an oscillator. It's >> just the paths they take thru spacetime and each one correctly measures >> duration along their path. How one looks from a different frame is >> interesting from the standpoint of instruments and measurements, but that's >> so you can correct for the spatio-temporal effects of motion and curvature, >> or you can invert the relation and infer the motion and curvature from the >> effects. But it should be kept clear that the motion and curvature are not >> effecting anything locally, they are only a relative effect of the >> intervening space and motion. >> >> Brent >> > > But the doppler effect is apparent only; it's what the observer receiving > the signal measures or perceives; not what is reality for, say, the > engineer of the passing train. In contrast, IIUC, the LT tells us what the > observer in the transformed coordinate system actually measures, and > experiences. AG >
Another problem; using space-time paths, one gets the differential elapsed time for different paths, say for the TP. But the LT, gives the actual clock rate in the transformed frame. I don't think using space-time paths gives this information. 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 view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/1d993a42-cc3f-465f-81f0-3d19019329d1%40googlegroups.com.
