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 -- 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/4a13f56d-36a8-4711-b239-2c20da3ffec4o%40googlegroups.com.
