# Search results

1. ### Luminosity Distances

That is very clear and helpful, Thank you!
2. ### Luminosity Distances

Hey I'm getting very muddled with my units, and would really appreciate some clarity :-) I have angular distances between galaxies at some redshift, in arcseconds I want to calculate the distance in parsecs, taking into account the luminosity distance. In the equation; r =...
3. ### Using the RW Line element

Woops (!!) yes, I see. k does account for those cases. Thanks again! :-) (Sorry), but for the pressure.... These dark/normal matter and radiation contributions to the pressure are then denoted Omega_m and Omega_R? I promise that's my last question! :-D (Thankyou so much).
4. ### Using the RW Line element

Wowee! Thankyou :-) That's cleared it up significantly. May I ask one last thing? When you said : 'If you want to use a different distribution of matter' By different distribution of matter, is that regarding the open, closed and flat cases? And for the pressure 'P'; this is...
5. ### Using the RW Line element

Hello! :-) I've been thinking about the RW line element (c^2 d tau^2), and I understand that there is a term which describes the geometry of the Universe (d sigma^2) and then a term corresponding to the cosmic time (c^2 dt^2). The resulting (c^2 d tau^2 ) term would be the line measured by...
6. ### The formation of Galaxy Clusters from density fluctuations in the early Universe

Wow- that was brilliant. Thankyou so much. That is precisely where I was stuck :-) I rrreeeaally appreciate that, thanks :-)
7. ### The formation of Galaxy Clusters from density fluctuations in the early Universe

heh! You caught me! :O I presumed that it meant that the photons were travelling slower than the rate of expansion... D: Now I know..... :) So, given this new definition of 'decoupling' (thanks!).....as the "decoupling of light and matter....when the partially ionized (mostly hydrogen) gas...
8. ### The formation of Galaxy Clusters from density fluctuations in the early Universe

Hello!:wink: May I ask for a little assistance in filling in the gaps of my understanding? :S I understand that the current large scale structure of the Universe is thought to be the result of early fluctuations in density which have been stretched out in the expansion of the Universe. I...
9. ### Confusion with conversion for the Hubble Constant

Hah. I totally figured it out. I was confused originally because I did use that equation, but got h=h I thought h=70, rather than H0 = 70 :( So is 'h' basically just a fraction then? I understand now. Gah. Thanks
10. ### Confusion with conversion for the Hubble Constant

Hello! I want to get my data in terms of h70 -1 Sometimes the estimates are in terms of h50 or h70, and I know how to convert those just fine. However, sometimes they give H0 = 100 h Mpc-1 kms-1 instead..... My question is, what is this in terms of h? I know that the relation is...