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Groups > sci.physics > #714901
| From | Sergio <invalid@invalid.com> |
|---|---|
| Newsgroups | sci.physics |
| Subject | Re: Asymmetrical GRCs |
| Date | 2018-11-26 19:22 -0600 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <pti69i$jn9$1@gioia.aioe.org> (permalink) |
| References | <580f93c6-35d6-4da7-a2f7-29b7a49cdada@googlegroups.com> <ab3475b2-bc8c-1ba5-6024-3b251ba1bac5@PointedEars.de> |
On 11/25/2018 2:45 PM, Thomas 'PointedEars' Lahn wrote: > [The following is part of my preparing for the Astronomy test > on Tuesday. Do not expect this level of verbosity every time.] > > john wrote: >> [referring to “Asymmetrical Galaxy Rotation Curves” (GRCs), apparently; >> an acronym that apparently he has just invented] >> It is impossible for one side of a turning disc to be going faster than the other. > > Why do you think this would be claimed in the first place? > > A galactic rotation curve plots the orbital speed v of stars against > *their distance D from the center*. It typically looks as follows: > > [Use a fixed-width font for display; see also > <https://github.com/PointedEars/userscripts#ggformatteruserjs>] > > > v solid disc (v = ω D) > ^ . > : . __...---- observed > : . _.--'' > : . .-'-. __ > : ..' . |PE > : . . > : . . > :. ' . _ _ spiral > '-------------------------> D > > What would be expected from the luminous matter is the graph labeled > “spiral”: the orbital speed of stars should *go down* as their distance > from the galactic center increases. Because a spiral galaxy is NOT like a > solid disc, but a loose arrangement of stars and the interstellar medium (ISM). > > Instead, the orbital speed remains *approximately* *constant* as D increases > (“observed”). > > There is absolutely NO implication in such a diagram that one "side" of the > galaxy would rotate faster than another "side". > > If it helps you to see that, the other "side" is implied in the diagram: > > v solid disc (v = ω D) > . ^ . > ----...__ . : . __...---- observed > ''--._ . : . _.--'' > .-'-. . : . .-'-. __ > . `.. : ..' . |PE > . . : . . > . . : . . > _ _ . ' .:. ' . _ _ spiral > −D <-------------------------:-------------------------> D > galactic > center > _ > . ' ' . > ' . ' ' . ` > ' ' . . ` ' > . ' ' ` ' ^ .^ ^ ^ > ' ' . ' ' . ^ : : : : > . ' . ' . '^ : : : : : v > : : : : : : v C ^ : : : : : : > v : : : : : v. . _ . , ' > : : : :. v' ' . . ' ' . > v v v' v . '. .' . ' > . ' ' ' . . > . ` . . ' . __ > ` . _ . ' |PE > > > Motion of stars in a spiral galaxy: The length of the arrows indicate > how fast a star at this distance from the center (C) is orbiting around > the galactic center (its tangential/orbital/radial speed). > (The direction of the arrows indicate the direction of tangential motion.) > > Cf. > <https://en.wikipedia.org/wiki/File:Galaxy_rotation_under_the_influence_of_dark_matter.ogv> > > > Do you understand it now? > Excellent!
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Asymmetrical GRCs john <johnsefton288@gmail.com> - 2018-11-25 05:08 -0800
Asymmetrical GRCs john <johnsefton288@gmail.com> - 2018-11-25 05:28 -0800
Re: Asymmetrical GRCs moroney@world.std.spaamtrap.com (Michael Moroney) - 2018-11-25 14:10 +0000
Re: Asymmetrical GRCs Odd Bodkin <bodkinodd@gmail.com> - 2018-11-25 14:26 +0000
Re: Asymmetrical GRCs moroney@world.std.spaamtrap.com (Michael Moroney) - 2018-11-25 14:01 +0000
Re: Asymmetrical GRCs Odd Bodkin <bodkinodd@gmail.com> - 2018-11-25 14:26 +0000
Re: Asymmetrical GRCs moroney@world.std.spaamtrap.com (Michael Moroney) - 2018-11-25 14:53 +0000
Re: Asymmetrical GRCs john <johnsefton288@gmail.com> - 2018-11-25 09:03 -0800
Re: Asymmetrical GRCs moroney@world.std.spaamtrap.com (Michael Moroney) - 2018-11-25 17:37 +0000
Re: Asymmetrical GRCs Odd Bodkin <bodkinodd@gmail.com> - 2018-11-25 18:55 +0000
Re: Asymmetrical GRCs Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-11-26 22:14 +0100
Re: Asymmetrical GRCs john <johnsefton288@gmail.com> - 2018-11-26 15:29 -0800
Re: Asymmetrical GRCs Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-11-27 01:23 +0100
Re: Asymmetrical GRCs john <johnsefton288@gmail.com> - 2018-11-27 03:10 -0800
Re: Asymmetrical GRCs john <johnsefton288@gmail.com> - 2018-11-27 07:10 -0800
Re: Asymmetrical GRCs john <johnsefton288@gmail.com> - 2018-11-27 07:54 -0800
Re: Asymmetrical GRCs moroney@world.std.spaamtrap.com (Michael Moroney) - 2018-11-27 16:11 +0000
Re: Asymmetrical GRCs moroney@world.std.spaamtrap.com (Michael Moroney) - 2018-11-27 16:08 +0000
Re: Asymmetrical GRCs john <johnsefton288@gmail.com> - 2018-11-27 21:28 -0800
Re: Asymmetrical GRCs john <johnsefton288@gmail.com> - 2018-11-28 03:47 -0800
Re: Asymmetrical GRCs moroney@world.std.spaamtrap.com (Michael Moroney) - 2018-11-28 13:00 +0000
Re: Asymmetrical GRCs john <johnsefton288@gmail.com> - 2018-11-28 07:45 -0800
Re: Asymmetrical GRCs Odd Bodkin <bodkinodd@gmail.com> - 2018-11-28 17:20 +0000
Re: Asymmetrical GRCs moroney@world.std.spaamtrap.com (Michael Moroney) - 2018-11-28 17:55 +0000
Re: Asymmetrical GRCs moroney@world.std.spaamtrap.com (Michael Moroney) - 2018-11-28 12:54 +0000
Re: Asymmetrical GRCs Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-11-28 00:38 +0100
Re: Asymmetrical GRCs john <johnsefton288@gmail.com> - 2018-11-25 09:08 -0800
Re: Asymmetrical GRCs moroney@world.std.spaamtrap.com (Michael Moroney) - 2018-11-25 17:49 +0000
Re: Asymmetrical GRCs Odd Bodkin <bodkinodd@gmail.com> - 2018-11-25 18:55 +0000
Re: Asymmetrical GRCs Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-11-25 21:45 +0100
Re: Asymmetrical GRCs Sergio <invalid@invalid.com> - 2018-11-26 19:22 -0600
Re: Asymmetrical GRCs mitchrae3323@gmail.com - 2018-11-26 13:26 -0800
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