Re: How is luminosity distance interpreted?



David Rutherford wrote:


Craig wrote:


2. If D_L is not considered to be the distance now, what is the
(mathematical) relationship between D_L and D_now, if any?



I'm not sure it makes sense to ask that question. By construction,
your "D_now" implies faster-than-light travel, which is not very
meaningful... The luminosity distance can be calculated based on the
redshift at time of emission, and the cosmological parameters of the
universe.


For a universe expanding at a constant rate (which I know is not the current view), the distance now should be derivable from the emission distance and the rate of expansion.

I'm trying to show that HST supernovae data is consistent with a constant (not accelerating) expansion rate, which would eliminate the need to invoke dark energy. You can see my progress so far at

http://www.softcom.net/users/der555/horizon.pdf

I'm having trouble, however, relating d_0 in my velocity/redshift/distance law,

v = c ln(1 + z) = H_0 d_0

where d_0 is my D_now, to D_L so that I can relate my model to the data.

I've revised the article, above, which you can see at the link

http://www.softcom.net/users/der555/horizon.pdf

I've corrected a misconception about the age of the CMBR (thanks to OG for pointing it out). I seem to have read it wrong. I had it as originating about 500 million years after the Big Bang, when in fact standard cosmology has it at about 500 _thousand_ years.

The result of correcting this misconception is that it may be possible to eliminate the epoch of the ``Dark Ages'' of cosmology, completely, and redefine the era and origins of the CMBR.

Dave

.

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