I've noticed what it seems to be an error in Ned Wright's calculator(adsbygoogle = window.adsbygoogle || []).push({});

http://www.astro.ucla.edu/~wright/CosmoCalc.html

First off, I want to present a beautiful theorem that relates 3 of the more often used distances in astronomy. Is called Etherington reciprocity theorem (Etherington,1933). It can be found here

http://arxiv.org/PS_cache/gr-qc/pdf/9910/9910014.pdf [Broken]

and here

http://nedwww.ipac.caltech.edu/level5/Hogg/Hogg7.html

the theorem is

D_{L}=(1+z)*D_{S}=(1+z)^{2}*D_{D}

D_{L}is luminosity distance

D_{S}is angular size distance

D_{D}is angular diameter distance

If you go to the calculator, and introducing any value of redshift, you don't get the angular size distance, how is indicated, but the angular diameter distance! Just see the value of the luminosity distance and introduce it in Etherington theorem

I'm right in my claims?

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# A critizism to Ned's calculator

**Physics Forums | Science Articles, Homework Help, Discussion**