On Saturday, July 11, 2020 at 10:30:21 PM UTC-6, Alan Grayson wrote: > > > > On Saturday, July 11, 2020 at 10:20:54 PM UTC-6, Brent wrote: >> >> >> >> On 7/11/2020 9:00 PM, Alan Grayson wrote: >> >> >> >> On Saturday, July 11, 2020 at 9:49:31 PM UTC-6, Brent wrote: >>> >>> >>> >>> On 7/11/2020 8:07 PM, Alan Grayson wrote: >>> >>> >>> >>> On Saturday, July 11, 2020 at 8:41:21 PM UTC-6, Brent wrote: >>>> >>>> >>>> >>>> On 7/11/2020 4:29 PM, Alan Grayson wrote: >>>> >>>> >>>> >>>> On Saturday, July 11, 2020 at 5:05:02 PM UTC-6, Brent wrote: >>>>> >>>>> >>>>> >>>>> On 7/11/2020 12:54 AM, Alan Grayson wrote: >>>>> >>>>> >>>>> >>>>> On Tuesday, July 7, 2020 at 10:06:44 PM UTC-6, Alan Grayson wrote: >>>>>> >>>>>> >>>>>> >>>>>> On Tuesday, July 7, 2020 at 8:50:50 PM UTC-6, Alan Grayson wrote: >>>>>>> >>>>>>> >>>>>>> >>>>>>> On Tuesday, July 7, 2020 at 8:05:28 PM UTC-6, Bruce wrote: >>>>>>>> >>>>>>>> On Wed, Jul 1, 2020 at 4:18 PM Alan Grayson <[email protected]> >>>>>>>> wrote: >>>>>>>> >>>>>>>>> How, exactly, is the Principle of Equivalence used by Einstein to >>>>>>>>> develop GR? TIA, AG >>>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> This lecture by Sean Carroll should answer all your questions: >>>>>>>> >>>>>>>> URL: https://wp.me/p2WMeM-3vl >>>>>>>> >>>>>>>> Bruce >>>>>>>> >>>>>>> >>>>>>> I'll watch it tonight, but I think I've figured it out; >>>>>>> specifically, the EP implies space-time is curved by the presence of >>>>>>> mass/energy (and this is independent of the need to express the laws of >>>>>>> physics in a coordinate independent way via tensors). AG >>>>>>> >>>>>> >>>>>> Here's my reasoning regarding the EP; if an observer is in a box >>>>>> subject to uniform acceleration, a beam of light starting on the extreme >>>>>> left side (moving transverse or perpendicular to the acceleration >>>>>> vector), >>>>>> will hit a lower point on the right side, showing that uniform >>>>>> acceleration >>>>>> results in curved paths in space-time. But if this result is identical >>>>>> to >>>>>> gravity, locally, it means that curved paths in space-time are produced >>>>>> by, >>>>>> or are equivalent to gravity. >>>>>> >>>>> >>>>> That makes no sense. You're saying that because curved paths can be >>>>> produced two different ways then they must always be produced the second >>>>> way. >>>>> >>>>> >>>>> BUT gravity is only observed in the presence of mass/energy. ERGO, the >>>>>> EP implies mass/energy curves space-time. AG >>>>>> >>>>> >>>>> And that's not even true. Gravitational waves can propagate thru the >>>>> vacuum. The Schwarzschild solution is for empty space. De Sitter space >>>>> is >>>>> an empty cosmos. >>>>> >>>> >>>> Light can propagate through empty space, but it can't arise from >>>> nothing. Same presumably for gravitational waves. AG >>>> >>>> >>>> Are you going to say the same thing about matter? electric charge? >>>> >>>> Brent >>>> >>> >>> I'm not sure what your point is. All I was saying above is that >>> mass/energy causes curvature of space-time as per the EP. A gravitational >>> wave moving through empty space seems no different in principle than light >>> moving through empty space. In both cases there is a mathematical solution >>> for the wave motion, with the source of the wave left undefined. But every >>> wave motion must has a source. AG >>> >>> >>> And every source must have an origin? There is nothing in the equations >>> that says there must be a source. >>> >>> Brent >>> >> >> Can EM waves exist if there are no charges and currents? If you affirm, >> has this ever been observed? This result, if it is a result, is likely an >> artifact of the mathematics which has no basis in physical reality. Anyway, >> are you claiming that spacetime curvature can exist in the absence of >> matter/energy? Is this what the EP says? AG >> >> >> It's what the equations say. So if waves only exist due to matter >> sources that's a separate fact, not part of the theory. It seems just as >> plausible to me that fields existed first and "stuff" appeared as quantized >> waves in the fields. >> >> Brent >> > > What do you find erroneous in my interpretation of the EP? I never heard > it interpreted to mean that curvature of space-time is NOT caused by > gravity. AG >
Are you claiming that because there are gravitational wave solutions to GR in the absence of matter/energy, curvature of space-time isn't caused by, or is equivalent to gravity? But how can there be curvature of space-time in the absence of matter/energy since, in this case, we're dealing with SR, wherein space-time has no curvature? 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/3372804f-6bf6-44d4-9506-f73bf607e6e6o%40googlegroups.com >> >> <https://groups.google.com/d/msgid/everything-list/3372804f-6bf6-44d4-9506-f73bf607e6e6o%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/728ae500-7bf1-4574-bbd6-3a8dae1c1606o%40googlegroups.com.
