How big do we need for comsological principle?

  • Context: Graduate 
  • Thread starter Thread starter skydivephil
  • Start date Start date
  • Tags Tags
    Principle
Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
Sign up Log in
3 replies · 2K views
skydivephil
Messages
470
Reaction score
9
When we say the universe is homogenous and isotropic . How many Mega PArsecs are we talking about? Preusmably we all agree its not homogenous or isotropic on small scales. So where is the border and how when was it established? Is the current estimate, whatever it is, as recent as Sloan Digital Sky survey or much older than that?
 

Discussion

Astronomy news on Phys.org
How many Mega PArsecs are we talking about?
There's a diagram on Ned Wright's site. It's a gradual transition - the larger the scale, the more homogeneous.
 
skydivephil said:
When we say the universe is homogenous and isotropic . How many Mega PArsecs are we talking about? Preusmably we all agree its not homogenous or isotropic on small scales. So where is the border and how when was it established? Is the current estimate, whatever it is, as recent as Sloan Digital Sky survey or much older than that?
Roughly 80Mpc or so.
 
Agh thanks for that, wanted it for my cosmology exams which was yesterday ,think I aced it and you guys have been enormous help in general, Physics forums rock