Tolman surface brightness test -

[_Andreas]

Tolman surface brightness test -- need help!

Richard Tolman derived that in an expanding universe with any arbitrary geometry, the surface brightness of a set of identical objects will decrease by (1+z)^4.

I have two questions:

1) The surface brightness is the same as the flux (W/m^2), right?
2) My understanding so far has been that the received flux decreases with the distance squared, so reading that it will decrease by a factor of (1+z)^4 is a bit confusing. Is it perhaps a factor that is ignored when the distance from Earth is relatively small (because z is so small)?

Need help urgently!

 

[_Andreas]

Oh, and another question. Some sources say the SB will decrease by (1+z)^2 instead of (1+z)^4 in an expanding universe. Which is correct?

 

[_Andreas]

I've received answers to the first two questions already, so no need for anyone to bother with them. The question in my second post is still unanswered, though.

 

[SpaceTiger]

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