20120110, 23:31  #34  
Basketry That Evening!
"Bunslow the Bold"
Jun 2011
40<A<43 89<O<88
3×29×83 Posts 
Quote:
:P Last fiddled with by Dubslow on 20120110 at 23:33 

20120111, 04:13  #35  
Einyen
Dec 2003
Denmark
3176_{10} Posts 
http://en.wikipedia.org/wiki/Light_year
Quote:
Wikipedia has the exact current Julian lightyear while online conversion again rounds it. 

20120111, 17:49  #36  
Jul 2006
USA (UT5) via UK (UT)
2^{2}×59 Posts 
Quote:
Gareth 

20120111, 18:01  #37  
Bamboozled!
"πΊππ·π·π"
May 2003
Down not across
2^{2}×3×11×83 Posts 
Quote:
Quote:
Paul 

20120111, 18:06  #38  
Bamboozled!
"πΊππ·π·π"
May 2003
Down not across
2^{2}×3×11×83 Posts 
Quote:
As the mass isn't constant, at which date was the mass measured, or does it have another arbitrary value which may or may not match the true solar mass at least once? I'm nitpicking, of course, as the mass loss from EM and neutrino radiation and solar wind, offset by the mass gain from infalling matter such as comets is an exceedingly tiny fraction of a solar mass over reasonably short time scales. Much easier, IMO, would be to define the AU as a particular number of metres. Paul 

20120111, 20:50  #39  
Jul 2006
USA (UT5) via UK (UT)
2^{2}·59 Posts 
Quote:
is a derived constant, derived by multiplying one defining constant (c, the speed of light in a vacuum) by one primary constant (, the lighttime for unit distance). Gareth 

20120111, 21:04  #40 
Basketry That Evening!
"Bunslow the Bold"
Jun 2011
40<A<43 89<O<88
3×29×83 Posts 

20120113, 05:40  #41  
"Richard B. Woods"
Aug 2002
Wisconsin USA
7692_{10} Posts 
Quote:
The massless particle is not being held in circular orbit by gravity, so we're using a bit of magic rather than Gm_{1}m_{2} here. There may have been a moment when k = 0.01720209895 had a physical meaning, but it's just a defined constant now. Last fiddled with by cheesehead on 20120113 at 05:46 

20120113, 13:14  #42 
"Brian"
Jul 2007
The Netherlands
2·3·5·109 Posts 
By "massless" the definition presumably means that the mass of the orbiting body "tends to zero" so that only the sun's gravitational field should be considered. I guess there must be some complicating factor which would affect the orbital speed of a body of significant mass but I am unsure what this factor might be. Perhaps the definition is simply seeking to avoid the hypothetical situation where the body has comparable mass to the sun and then the two bodies are orbiting each other, complicating the measurements of radial speed? Or is there some other more subtle complicating effect if the orbiting body has significant mass?

20120122, 02:13  #43  
Aug 2003
Snicker, AL
3BF_{16} Posts 
Quote:
DarJones 

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