Mensaje del debate
Weird funky precession question
Path: g2news2.google.com!news1.google.com!border1.nntp.dca.giganews.com!border2.nntp.dca.giganews.com!nntp.giganews.com!backlog2.nntp.dca.giganews.com!news.giganews.com.POSTED!not-for-mail
NNTP-Posting-Date: Fri, 03 Jul 2009 11:56:51 -0500
From: Dave Typinski <möb...@trapezium.net>
Newsgroups: sci.astro.amateur
Subject: Re: Weird funky precession question
Date: Fri, 03 Jul 2009 12:56:54 -0400
Message-ID: <e0bs459udgfs8v3p166lj7ot94mhoni37e@4ax.com>
References: <d5do45l68hvnmeudanjvg5ede54t40c398@4ax.com> <73ee6c21-8573-4093-a963-9fa4116207ea@a37g2000prf.googlegroups.com>
X-Newsreader: Forte Agent 4.2/32.1118
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 8bit
Lines: 39
X-Usenet-Provider: http://www.giganews.com
X-Trace: sv3-PZoPa3FPaLWXH6SculDVzmMMF3vTdoyZznur1Bwjwx1UjjL7t8LqyLDAzhKGUQYzSs2b8pG85wPEw9w!/1qg2OFv1xJYnR/ernz8fjhpheNMbrd8aOWhtiK05sqoAr5i0SQkJ4YCEk9p+UpBC4GwEKt05A==
X-Complaints-To: abuse@giganews.com
X-DMCA-Notifications: http://www.giganews.com/info/dmca.html
X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers
X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly
X-Postfilter: 1.3.39
X-Original-Bytes: 2654
Quadibloc <jsav...@ecn.ab.ca> wrote:
>
>On Jul 1, 10:31 pm, Dave Typinski <möb...@trapezium.net> wrote:
>> Assuming an astronomical object is a member of a two-body system and
>> has a spin axis and an orbital plane, can the object's spin axis
>> precess around an axis /other/ than the normal to its orbital plane?
>>
>> Doesn't seem likely, not with only two bodies.
>>
>> Okay, add a few more bodies.
>>
>> Take the Moon, for example. Its spin axis precesses about the normal
>> to its orbital plane.
>>
>> Why couldn't its spin axis also precess around the normal to the
>> ecliptic?
>>
>> Or does it, but to a very much smaller degree?
>>
>> Is that what nutation is? A smaller and faster precession around some
>> other axis superposed on a somewhat larger and slower "main"
>> precession?
>
>To find out what precession can do, this Wikipedia article seems like
>a good one...
>
>http://en.wikipedia.org/wiki/Precession
>
>Since nutation, described on another Wikipedia article, is largely
>tied to the advance of the Moon's nodes, no doubt it is a response to
>the Moon's gravity even as ordinary precession is a response to the
>Sun's. It's probably simpler to combine the torques and get the
>resultant precession than to add precessions, though.
I'm 100% positive that's the simpler and better way to see it.
Sometimes, though, it can be illuminating--or at least amusing--to
look at things from a *coff* different angle. ;-)
--
Dave
|
