Reasons to Believe

Bulk Flow Galaxy Test Affirms the Big Bang

Why do scientists repeatedly test whether the big bang model for the origin of the universe is correct? Efforts to escape the Christian implications of the big bang—namely, that the universe has continually expanded under unchanging laws of physics from a beginning of all matter, energy, space, and time—explain its persistent and exhaustive testing. So far, the model has convincingly passed every devised test for which adequate measurements exist. Now, a new study has yielded yet another success.

Three decades ago, astronomers determined that an early, brief episode of cosmic hyper-expansion, known as inflation, was needed for the big bang to produce—at the right time and place—the stars and planets necessary for life. Recently, measurements made by the Wilkinson Microwave Anisotropy Probe (WMAP) and Planck satellites confirmed that a cosmic inflation episode indeed occurred.

Cosmic inflation, in the context of the big bang model, predicts that coherent, large-scale, peculiar motion of matter in the universe, known as the “bulk flow,” will be negligible. Since 1994, nine different astronomy research teams have observed a variety of galaxies to test whether or not a bulk flow exists. Three of these studies claimed to have found a small bulk flow. One yielded ambiguous results. Five reported no evidence for a bulk flow.

Now, Princeton University mathematician Krishnan Mody and University of Toronto astronomer Amir Hajian have both proposed and performed a robust test for the bulk flow.1 They point out that an independent measuring method based on substantially larger size scales can be achieved through utilizing the Sunyaev–Zel’dovich effect. In 1980, Russian astronomers Rashid Sunyaev and Yakov Zel’dovich explained how high-energy electrons would distort the cosmic background radiation (remnant radiation from the cosmic creation event) in such a way as to yield the signature of future dense clusters of galaxies.

Mody and Hajian built a full-sky kinetic Sunyaev–Zel’dovich template and proceeded to fit it to the latest WMAP data. They compared this fit to X-ray-detected galaxy cluster catalogs based on the deepest map of galaxy clusters to date. The team confidently reports that they “find no significant detection of the bulk flow”2 and conclude, “Our results are consistent with the ɅCDM prediction.”3 The ɅCDM (Lambda Cold Dark Matter) cosmic model is the “standard model” and the most successful of the big bang models.

Thanks to Mody and Hajian’s work, Bible believers can be gratified that a book written thousands of years ago described (and in this way, “predicted”) a scientifically tested model for the origin of the universe. This predictive power firmly establishes the divine inspiration, reliability, and trustworthiness of Scripture.

Subjects: Big Bang

Dr. Hugh Ross

Reasons to Believe emerged from my passion to research, develop, and proclaim the most powerful new reasons to believe in Christ as Creator, Lord, and Savior and to use those new reasons to reach people for Christ. Read more about Dr. Hugh Ross.

1. Krishnan Mody and Amir Hajian, “One Thousand and One Clusters: Measuring the Bulk Flow with the Planck ESZ and X-Ray-Selected Galaxy Cluster Catalogs,” Astrophysical Journal 758 (October 10, 2012): 1–6.

2. Ibid.,1.

3. Ibid.