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Groups > sci.physics.relativity > #399445
| From | Steven Carlip <carlip@physics.ucdavis.edu> |
|---|---|
| Newsgroups | sci.physics.relativity, sci.physics |
| Subject | Re: This is your guru |
| Date | 2016-11-22 22:57 -0800 |
| Organization | A noiseless patient Spider |
| Message-ID | <o13ekb$5vp$1@dont-email.me> (permalink) |
| References | (11 earlier) <o0t19k$128b$1@gioia.aioe.org> <o0td2p$u15$1@dont-email.me> <o0v276$44d$1@gioia.aioe.org> <o10d8g$86o$1@dont-email.me> <o1179k$1f4h$1@gioia.aioe.org> |
Cross-posted to 2 groups.
On 11/22/16 2:39 AM, Maryann Tonn wrote:
> Steven Carlip wrote:
>>> On to the subject, gravity cannot possibly travel at any speed, since
>>> is a geometry, curvature in GR, hence similar to the projection of a
>>> shadow. No matter how fast or slow you shake your head, its shadow will
>>> never leave the association with your head. Your gravity "field" is to
>>> Matter/Mass what a Shadow is for an opaque object.
>> Not the best analogy, but it will do for a start. Suppose your head is
>> casting a shadow on a wall a meter away. When you move your head,
>> do you think the shadow moves instantaneously? Steve Carlip
> Nonsense. The point you fail to catch, is that the shadow, your head's
> projection, the geometry, NEVER leaves your head, as your Gravity "field"
> supposedly does by travelling "in waves" from your head to another head.
You want to change the subject again? OK, we can do that.
As I said, a shadow isn't the best analogy, but it will do. I notice
that you didn't answer my question, so let me answer it for you. If
your head casts a shadow on a wall a meter away and you move your head,
the shadow won't move instantaneously -- it will move about three
nanoseconds later. (The light that has already passed your head will
keep going, and will take about three nanoseconds to reach the wall;
it's only after that's happened that the shadow will move.)
So now, move your head and then quickly move it back again to its
starting position. One meter away, your shadow will be suddenly
wiggle three nanoseconds after you've moved your head, and then
return to its original position. Two meters away, your shadow will
be still for six nanoseconds, then suddenly wiggle, then return to
its original position. Three meters way, the same thing will happen
after nine nanoseconds. The wiggle in your shadow will continue to
propagate out at the speed of light as long as there's a shadow at
all.
You can say that the shadow is still attached to your head, and in
some sense that's true, but it's attached to where your head was
in the past, not to where it is now. Once the wiggle in your
shadow has started out, you can't call it back; you can make more
wiggles by moving your head more, but the original won't be affected.
The changing pattern of light that you initiated by wiggling your
head has escaped you, and is traveling off at the speed of light;
it's beyond your command.
Gravity is a little more complicated -- it takes more than one
number ("how much light") to describe spacetime curvature, and
there are conservation laws that come in, so you get things like
quadrupole radiation and velocity-dependent effects. But the
basic idea is the same.
As a matter of fact, this is not a bad analogy. I may use it the
next time I teach GR, probably next fall. If you give me your
real name, I'll be happy to credit you.
Steve Carlip
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This is your guru mlwozniak@wp.pl - 2016-11-16 00:09 -0800
Re: This is your guru Melzzzzz <mel@zzzzz.com> - 2016-11-16 10:52 +0100
Re: This is your guru mlwozniak@wp.pl - 2016-11-16 02:41 -0800
Re: This is your guru Melzzzzz <mel@zzzzz.com> - 2016-11-16 11:43 +0100
Re: This is your guru mlwozniak@wp.pl - 2016-11-16 03:49 -0800
Re: This is your guru Melzzzzz <mel@zzzzz.com> - 2016-11-16 13:18 +0100
Re: This is your guru mlwozniak@wp.pl - 2016-11-16 04:48 -0800
Re: This is your guru JanPB <filmart@gmail.com> - 2016-11-16 21:54 -0800
Re: This is your guru mlwozniak@wp.pl - 2016-11-16 23:19 -0800
Re: This is your guru JanPB <filmart@gmail.com> - 2016-11-16 23:32 -0800
Re: This is your guru mlwozniak@wp.pl - 2016-11-16 23:38 -0800
Re: This is your guru JanPB <filmart@gmail.com> - 2016-11-17 00:14 -0800
Re: This is your guru mlwozniak@wp.pl - 2016-11-17 00:38 -0800
Re: This is your guru JanPB <filmart@gmail.com> - 2016-11-17 10:37 -0800
Re: This is your guru mlwozniak@wp.pl - 2016-11-17 22:36 -0800
Re: This is your guru Tom Roberts <tjroberts137@sbcglobal.net> - 2016-11-16 10:26 -0600
Re: This is your guru Kieth Staudt <KiethS@StaudtInstitute.info> - 2016-11-16 18:12 +0000
Re: This is your guru Melzzzzz <mel@zzzzz.com> - 2016-11-16 19:28 +0100
Re: This is your guru JanPB <filmart@gmail.com> - 2016-11-16 21:57 -0800
Re: This is your guru mlwozniak@wp.pl - 2016-11-16 23:34 -0800
Re: This is your guru JanPB <filmart@gmail.com> - 2016-11-17 00:23 -0800
Re: This is your guru mlwozniak@wp.pl - 2016-11-17 03:37 -0800
Re: This is your guru JanPB <filmart@gmail.com> - 2016-11-17 10:39 -0800
Re: This is your guru mlwozniak@wp.pl - 2016-11-17 22:50 -0800
Re: This is your guru JanPB <filmart@gmail.com> - 2016-11-17 23:52 -0800
Re: This is your guru mlwozniak@wp.pl - 2016-11-18 00:53 -0800
Re: This is your guru JanPB <filmart@gmail.com> - 2016-11-18 12:28 -0800
Re: This is your guru Maciej Woźniak <mlwozniak@wp.pl> - 2016-11-19 10:07 +0100
Re: This is your guru Marion Vanriper <Marion@Vanriper.info> - 2016-11-26 09:30 +0000
Re: This is your guru Tom Roberts <tjroberts137@sbcglobal.net> - 2016-11-17 10:09 -0600
Re: This is your guru JanPB <filmart@gmail.com> - 2016-11-16 12:11 -0800
Re: This is your guru mlwozniak@wp.pl - 2016-11-16 23:14 -0800
Re: This is your guru JanPB <filmart@gmail.com> - 2016-11-16 23:35 -0800
Re: This is your guru mlwozniak@wp.pl - 2016-11-16 23:52 -0800
Re: This is your guru JanPB <filmart@gmail.com> - 2016-11-17 00:25 -0800
Re: This is your guru paparios <paparios@gmail.com> - 2016-11-17 03:59 -0800
Re: This is your guru "Dan S. MacAbre" <no@way.com> - 2016-11-17 12:12 +0000
Re: This is your guru Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-11-18 05:07 +0100
Re: This is your guru "Dan S. MacAbre" <no@way.com> - 2016-11-18 10:02 +0000
Re: This is your guru Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-11-18 22:13 +0100
Re: This is your guru "David (Time Lord) Fuller" <fuller.david@hotmail.com> - 2016-11-18 21:46 -0800
Re: This is your guru "Paul B. Andersen" <relativity@paulba.no> - 2016-11-19 09:30 +0100
Re: This is your guru Tom Roberts <tjroberts137@sbcglobal.net> - 2016-11-19 10:01 -0600
Re: This is your guru "David (Time Lord) Fuller" <fuller.david@hotmail.com> - 2016-11-19 08:07 -0800
Re: This is your guru Norberto Haman <norberman@norberman.info> - 2016-11-19 16:37 +0000
Re: This is your guru Steven Carlip <carlip@physics.ucdavis.edu> - 2016-11-20 09:37 -0800
Re: This is your guru Norberto Haman <norberman@norberman.info> - 2016-11-20 20:32 +0000
Re: This is your guru Steven Carlip <carlip@physics.ucdavis.edu> - 2016-11-20 15:54 -0800
Re: This is your guru Maryann Tonn <libradaz@libradazert.info> - 2016-11-21 15:00 +0000
Re: This is your guru Steven Carlip <carlip@physics.ucdavis.edu> - 2016-11-21 19:16 -0800
Re: This is your guru Maryann Tonn <libradaz@libradazert.info> - 2016-11-22 10:39 +0000
Re: This is your guru paparios <paparios@gmail.com> - 2016-11-22 03:16 -0800
Re: This is your guru Maryann Tonn <libradaz@libradazert.info> - 2016-11-22 11:24 +0000
Re: This is your guru Ned Latham <nedlatham@woden.valhalla.oz> - 2016-11-22 12:13 +0000
Re: This is your guru benj <benj@nobody.net> - 2016-11-22 17:37 -0500
Re: This is your guru Steven Carlip <carlip@physics.ucdavis.edu> - 2016-11-22 22:57 -0800
Re: This is your guru Dusty Kollman <uberdriver@uberdriver.info> - 2016-11-23 13:37 +0000
Re: This is your guru paparios <paparios@gmail.com> - 2016-11-23 06:04 -0800
Re: This is your guru Dusty Kollman <uberdriver@uberdriver.info> - 2016-11-23 14:27 +0000
Re: This is your guru paparios <paparios@gmail.com> - 2016-11-23 06:44 -0800
Re: This is your guru Dusty Kollman <uberdriver@uberdriver.info> - 2016-11-23 14:56 +0000
Re: This is your guru Steven Carlip <carlip@physics.ucdavis.edu> - 2016-11-23 10:46 -0800
Re: This is your guru Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-11-23 23:21 +0100
Re: This is your guru Bob Goodman <bobg@boobgodman.info> - 2016-11-23 22:58 +0000
Re: This is your guru Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-11-25 20:00 +0100
Re: This is your guru Bernardo Dearmond <bnard@dearmond.org> - 2016-11-25 21:46 +0000
Re: This is your guru Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-11-25 22:56 +0100
Re: This is your guru "David (Lord Kronos) Fuller" <fuller.david@hotmail.com> - 2016-11-23 20:13 -0800
Re: This is your guru Odd Bodkin <bodkinodd@gmail.com> - 2016-11-23 09:24 -0600
Re: This is your guru Dusty Kollman <uberdriver@uberdriver.info> - 2016-11-23 15:33 +0000
Re: This is your guru Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-11-23 23:23 +0100
Re: This is your guru "David (Lord Kronos) Fuller" <fuller.david@hotmail.com> - 2016-11-23 20:15 -0800
Re: This is your guru Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-11-25 20:05 +0100
Re: This is your guru "David (Lord Kronos) Fuller" <fuller.david@hotmail.com> - 2016-11-25 14:57 -0800
Re: This is your guru Dusty Kollman <uberdriver@uberdriver.info> - 2016-11-23 18:28 +0000
Re: This is your guru Poutnik <poutnik4nntp@gmail.com> - 2016-11-23 19:37 +0100
Re: This is your guru Dusty Kollman <uberdriver@uberdriver.info> - 2016-11-23 18:39 +0000
Re: This is your guru "David (Lord Kronos) Fuller" <fuller.david@hotmail.com> - 2016-11-21 22:40 -0800
Re: This is your guru Tom Roberts <tjroberts137@sbcglobal.net> - 2016-11-19 10:47 -0600
Re: This is your guru Norberto Haman <norberman@norberman.info> - 2016-11-19 17:20 +0000
Re: This is your guru mlwozniak@wp.pl - 2016-11-17 04:37 -0800
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