On Saturday, July 11, 2020 at 5:29:03 PM UTC-6, 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 >
In a universe with no matter or energy, aren't we back to SR where there's no curvature and light travels in a straight line? So the gravitational waves you refer to don't take curved paths. AG > >> Brent >> >> >> For Bruce; so far I've gotten about two-thirds through Carroll's video. >> Will complete it this weekend. I sense a flaw in GR, suggested by the >> inclusion of G, the gravitational constant. How can a constant inferred >> from an approximate theory of gravity, Newton's Theory of Gravitation, be >> included in a presumed perfect theory of gravity, General Relativity? Don't >> you think something very subtle is awry here? 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/ffbbc9e9-1ba7-4410-8009-d76cf4ec12e6o%40googlegroups.com >> >> <https://groups.google.com/d/msgid/everything-list/ffbbc9e9-1ba7-4410-8009-d76cf4ec12e6o%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/c454baa8-bed9-4325-85ab-b6f1aec32474o%40googlegroups.com.
