On Monday, July 13, 2020 at 6:30:46 PM UTC-5, Alan Grayson wrote: > > > > On Monday, July 13, 2020 at 5:19:30 PM UTC-6, Lawrence Crowell wrote: >> >> On Monday, July 13, 2020 at 4:42:24 PM UTC-5, Alan Grayson wrote: >>> >>> >>> >>> On Monday, July 13, 2020 at 1:42:49 PM UTC-6, Alan Grayson wrote: >>>> >>>> >>>> >>>> On Monday, July 13, 2020 at 11:57:50 AM UTC-6, Brent wrote: >>>>> >>>>> >>>>> >>>>> On 7/12/2020 11:50 PM, Alan Grayson wrote: >>>>> >>>>> There can be because it's consistent with the equations. A black hole >>>>>> doesn't include any matter. General relativity is non-linear, that's >>>>>> why >>>>>> there can be non-flat cosmologies that contain no matter. Of course >>>>>> there >>>>>> may be some different, better theory in which spacetime can't be curved >>>>>> without matter...but it seems unlikely since we have good evidence that >>>>>> gravitational waves exist. >>>>>> >>>>>> Brent >>>>>> >>>>> >>>>> Yes, good evidence that gravitational waves exist, but as far I know >>>>> they're always associated with material interactions such as collisions >>>>> of >>>>> black holes. In the case of EM waves, I'd be more receptive of your claim >>>>> that they can exist independent of charges and/or currents, but as far as >>>>> I >>>>> know there's no evidence of that. AG >>>>> >>>>>> >>>>> But a collision of black holes does NOT involve matter. Black holes >>>>> (as far as the theory goes) are purely geometric things, i.e. made of >>>>> empty >>>>> space. >>>>> >>>>> Brent >>>>> >>>> >>>> How then does the BH at the center of our galaxy weigh in at 4 million >>>> solar masses? AG >>>> >>> >>> It's measured by observing the rotation rates of stars near the galactic >>> core, and not so small by comparison with other BH's at the center of >>> galaxies, called Super Massive BH's. AG >>> >> >> It is unfortunately apparent that you are pretty highly confused by some >> of this. You need to sit down and read a comprehensive book or text on GR >> and related subjects. It is not going to be possible to clear this up with >> dozens of email posts. >> >> LC >> > > About the EP; I merely stated that it demonstrates that acceleration is > locally indistinguishable from gravity, and then I stated what "locally" > means. This is what Wiki and other sources say. Yet you say I am confused. > How so? About masses of BH's, I watch documentaries which feature > astrophysicists offering their opinions, and they *uniformly* claim that > BH's have mass. How could it be otherwise if they're remnants of massive > collapsed stars? Not one makes Brent's claim, that they're just geometric > manifestations. AG >
Black hole mass is a pure spacetime physics. There is no material stuff anyone can get their hands on. With the tortoise coordinate the distant observer might say the matter-fields that made of a black hole exist, but if one tried to reach them they always recede away. Black holes do not have mass in a standard sense, though they have an ADM mass defined by the curvature of spacetime. LC -- 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/73eaaefd-b59a-4c4e-88bd-7b2aac7c1d0bo%40googlegroups.com.
