Test #4: Angular size versus redshift for galaxies and radio sources

This test predicts the most drastic difference between expanding and static models, since expansion requires a minimum angular size near roughly redshift z = 1.2, whereas static models usually predict no minimum in the observable range. The test is also the most observational-bias-free among the four classical tests. Results from observations of galaxy cluster radii, and (independently) from the sizes of brightest cluster members⁷, both disagree strongly with predictions of any form of the Friedmann expanding universe models since no such minimum angular size is seen, but agree reasonably well with static universe models. Results from the largest angular sizes of double radio sources are less consistent with static models, but still disagree strongly with all expansion models. Results showing a lack of small radio sources give cosmological parameters inconsistent with any of the preceding, but may themselves be explained by interplanetary scintillation effects.⁸

To defend expanding models it is necessary to postulate strong evolutionary effects, sometimes counter-intuitive ones. For example, the most powerful radio sources must also be the intrinsically smallest ones. It is also necessary to have little or no deceleration of the universe, or even an acceleration of the expansion; i.e., the universe must be strongly open; except for the small radio source observations, which seem to imply the universe must be strongly closed unless the lack of small sources is a scintillation effect. In most static models, redshift is not a distance indicator for radio sources such as quasars and most radio galaxies, so only the galaxy results (which agree) should be considered significant. Therefore three of four independent applications of this test, two of them strongly, favor static universe models over expanding models; and the fourth test is inapplicable to most static models.