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 -- 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.
