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The
In Euclidean space, such a ratio is straight-forward, but given
the universe's overall expansion and Curvature, and that
long-distance observations look backward in time, this function is
not so straight-forward and is of interest. Functions can be derived
for various Lambda-CDM model parameters and One strategy is to compare the brightness with the angular size of distant galaxies, e.g., by measuring the angular size of the brightest galaxies (Radio Galaxies are suitable) at various redshifts. Another is simply to observe brightness, size, and redshift. The models under consideration as well as observation indicate that beyond a certain redshift/distance, the angle no longer decreases with smaller with distance, but actually increases. While this is non-intuitive if your intuition takes Euclidean space as its basis, the universe was much smaller then, yet is spread over the entire celestial sphere, so objects must appear "larger". And despite appearing "larger" to us, they still appear dimmer with distance because their light broadcast in all directions must eventually span our current larger universe. astrophysics,cosmology,measure)https://ned.ipac.caltech.edu/level5/March02/Sahni/Sahni4_5.html Referenced by:
Redshift-magnitude Relation |