Darren New nous apporta ses lumieres en ce 2008/01/03 23:51:

>>   Not everything gets longer. Only intergalactic space, far away from
>> the galaxies, gets longer.
> 
> That's what has me curious.  How does space far from galaxies "decide" 
> to get larger while space between stars doesn't?
It don't decide to get larger far from galaxies, galaxies prevent it to get larger.
> 
>>>>   AFAIK space doesn't expand inside galaxies.
>>
>>> OK. More weirdness. Have you heard any postulates on why that would 
>>> be the case? Space only expands where the gravity is sufficiently low? 
>>
>> http://en.wikipedia.org/wiki/Hubble%27s_law
>>
>> "In using Hubble's law to determine distances, only the velocity due
>> to the expansion of the universe can be used. Since gravitationally
>> interacting galaxies move relative to each other independent of the
>> expansion of the universe, these relative velocities, called peculiar
>> velocities, need to be accounted for in the application of Hubble's
>> law. The Finger of God effect is one result of this phenomenon
>> discovered in 1938 by Benjamin Kenneally. In systems that are
>> gravitationally bound, such as galaxies or our planetary system, the
>> expansion of space is (more than) annihilated by the attractive force
>> of gravity."
> 
> OK. That still doesn't make sense to me. As space expands between two 
> stars within a galaxy, the gravity between those stars gets *weaker*, 
> meaning they orbit more slowly and are less likely to hold together. 
> Maybe that's why galaxies turn from globular clusters into spirals or 
> something, tho.
The concensus is rather that galaxies start as spiral and degenerate into 
globular clusters.
Usualy, spiral galaxies are relatively young, with lots of forming stars and 
interstellar gases. Globular galaxies are older, have very little or no new 
stars forming and almost to totaly lack interstellar gases.
> 


-- 
Alain
-------------------------------------------------
You know you've been raytracing too long when you've tried rendering hair with 
each strand as an object.
Quietly Watching

Post a reply to this message