On Tuesday, July 14, 2020 at 4:34:00 AM UTC-6, Lawrence Crowell wrote: > > 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. >
Generally, what resides inside a BH interacts gravitationally with what's exterior and is the remnant of a Type 1A supernova. It's unreachable, but has some correspondence with normal mass, which is why its mass can be estimated by its exterior effects, say for the one residing at the core of the Milky Way. I don't know how their masses are estimated when they are cores of distant galaxies. AG > > 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/dbd39a41-410f-4a09-8e95-f45200d89c5eo%40googlegroups.com.
