Tolman’s Elegant Test
The cosmic characteristic most extensively described in the Bible is the ongoing expansion of the universe.1 No other holy book of the world’s religions describes this feature, nor was it anticipated by secular scholars before the development of Einstein’s theory of general relativity.2 Therefore, evidences for a continuously expanding universe provide an impressive tool for demonstrating the divine inspiration of the Bible. Such evidences just received a huge boost.
Many lines of proof exist for demonstrating that the universe is expanding. The velocities with which galaxies are moving away from each other, the verifications of general relativity, the relative age and crowding of galaxies seen at greater distances (thus farther back in time), the measurable cooling of the cosmic background radiation—these four offer a sampling.3 Richard Tolman of the California Institute of Technology proposed one of the best tests as early as 1930, a test involving measurement of galaxies’ surface brightnesses.4
Astronomers consider the Tolman test the most elegant of the expanding universe tests because of its independence from other cosmological parameters. Surface brightness is simply an object’s luminosity divided by its radius squared. Any adjustments required by geometric effects such as space curvature would impact the luminosity and radius squared identically. Thus, all such effects would simply cancel out each other.
The Tolman test is elegant for a second reason. It predicts an enormous difference in results between an expanding universe and a non-expanding universe. Specifically, the surface brightness of identical objects in an expanding universe decreases by (1 + z) quadrupled, whereas the surface brightness of identical objects in a non-expanding universe would decrease by just (1 + z). The “z” in each case represents the amount of “redshift,” or shifting of spectral lines toward longer, redder wavelengths.5
The Tolman test has been difficult to apply, however, for both technological and practical reasons. Developing the instruments and techniques to select identical galaxies took decades. Not until 1990 was the test even possible, and even then its success was limited by the imprecision of ground-based measurements.6 The desire to carry out a truly robust Tolman test gave impetus to development of the Hubble Space Telescope (HST).7
Ironically, by the time the HST went into orbit, other tests of cosmic expansion had been so successfully run that the Tolman test fell far down on the HST’s priority list. Earlier this year, though, the opportunity to apply the test finally came. Lori Lubin of Caltech and Allan Sandage of Carnegie Observatories teamed up, using the 400-inch Keck telescope to measure nearly a thousand galaxies’ redshifts and the 94-inch HST to measure those galaxies’ surface brightness. Instead of photographic plates, they used the much superior “charged coupled” devices. Their results convincingly demonstrated that the universe is indeed continuously expanding.8
The Tolman test provides yet one more proof that the Old Testament prophets saw thousands of years ahead of their time, supernaturally far ahead. They were correct in predicting that Earth resides in a “stretching” cosmos (Isaiah 42:5). This solid evidence for cosmic expansion represents just one more tool for demonstrating the inspiration and accuracy of the Bible.
- Hugh Ross and John Rea, “Big Bang—The Bible Taught It First!” Facts for Faith (Q3 2000), 26-32.
- Hugh Ross, The Fingerprint of God, 2d ed. (Orange, CA: Promise, 1991), 19-59.
- Hugh Ross, The Creator and the Cosmos, 3d ed. (Colorado Springs: NavPress, 2001), 32-63.
- Richard C. Tolman, Relativity, Thermodynamics, and Cosmology (Oxford, UK: Oxford University Press, 1934), 467.
- Allan Sandage and Lori M. Lubin, “The Tolman Surface Brightness Test for the Reality of the Expansion. I. Calibration of the Necessary Local Parameters,” Astronomical Journal 121 (2001): 2271.
- Allan Sandage and Jean-Marc Perelmuter, “The Surface Brightness Test for the Expansion of the Universe. I-Properties of Petrosian Metric Diameters,” Astrophysical Journal 350 (1990): 481-91; Allan Sandage and Jean-Marc Perelmuter, “The Surface Brightness Test for the Expansion of the Universe. II-Radii, Surface Brightness, and Absolute Magnitude Correlations for Nearby E Galaxies,” Astrophysical Journal 361 (1990): 1-20; Allan Sandage and Jean-Marc Perelmuter, “The Surface Brightness Test for the Expansion of the Universe. III. Reduction of Data for the Several Brightest Galaxies in Clusters to Standard Conditions and a First Indication that the Expansion Is Real,” Astrophysical Journal 370 (1991): 455-73.
- Allan Sandage, Large Space Telescope: A New Tool for Science, ed. P. F. Simmons (New York: AIAA, 1974), 19.
- Allan Sandage and Lori M. Lubin, 2271-88; Lori M. Lubin and Allan Sandage, “The Tolman Surface Brightness Test for the Reality of the Expansion. II. The Effect of the Point-Spread Function and Galaxy Ellipticity on the Derived Photometric Parameters,” Astronomical Journal 121 (2001): 2289-300; Lori M. Lubin and Allan Sandage, “The Tolman Surface Brightness Test for the Reality of the Expansion. III. Hubble Space Telescope Profile and Surface Brightness Data for Early-Type Galaxies in Three High-Redshift Clusters,” Astronomical Journal 122 (2001): 1071-83; Lori M. Lubin and Allan Sandage, “The Tolman Surface Brightness Test for the Reality of the Expansion. IV. A Measurement of the Tolman Signal and the Luminosity Evolution of Early-Type Galaxies,” Astronomical Journal, 122 (2001): 1084-1103.