One might think that scientific evidence long ago debunked the idea that Earth resides at the center of the universe. Beginning with Nicolaus Copernicus in 1543, the heliocentric (sun-centered) model gradually replaced the Ptolemaic (Earth-centered) model. Yet scientists continue to propose models that place Earth in such a special location in order to explain astronomical observations.
One model places Earth at near the center of a large void. This idea seeks to explain away the proposed dark energy and the extraordinary fine-tuning it implies. Fortunately, a steady stream of data provides astronomers the means to test whether these void models offer the best explanation.
Edwin Hubble discovered in the 1920s that the universe expands. Since then, astronomers have sought to measure the history (approx 13.7 billion years) of the universe’s expansion in greater and greater detail. Using Type Ia supernovae, two different teams stumbled on a remarkable find a decade ago. Distant supernovae (exploding stars) were dimmer than expected, implying that the expansion of the universe started accelerating around five billion years ago. However, the most obvious mechanism to explain this acceleration, namely some form of dark energy or space-energy density, requires extreme fine-tuning in order for the universe to be habitable.
But, in order to escape the implications of a Creator’s involvement in such fine-tuning, alternatives exist. The most popular model posits that the solar system resides near the center of a humongous region of low density in the universe. Outside this void, the added density would exert a gravitational attraction that explains the supernovae results (that they appear dimmer). However, if dark energy exists, it also affects the clustering of galaxies across the universe as well as the ripples in the cosmic microwave background (CMB) radiation––leftover radiation from the beginning of the universe.
A team of Canadian scientists investigated whether void models could account for these additional data.1 They found that it was possible to construct void models that matched the CMB and supernovae data but only for highly constrained conditions in the early universe or for Hubble values (expansion rates) that have already been ruled out. When they included the galaxy clustering data, the constraints essentially eliminated any reasonable void model.
This research highlights two important points. First, cosmology exhibits a high degree of integrity by considering these void models. Although most scientists find the idea that Earth resides in some special location repulsive, they let the data decide which models are best. Second, these results strengthen the body of evidence that the universe is designed to support life and, thus, the case for a supernatural Creator.
- James P. Zibin, Adam Moss, and Douglas Scott, “Can We Avoid Dark Energy?”, Physical Review Letters, 101 (December 19, 2008): 251303.