Astronomers and cosmologists largely accept the reality of dark matter and dark energy. However, many recent creationists oppose both dark matter and dark energy, though it is not clear why. I propose a review of the evidence for dark matter and dark energy, a survey of creationists’ responses to both, and recommendations of how we ought to view dark matter and dark energy.
There are three lines of evidence for dark matter:
- Rotation curves of spiral galaxies
- Dispersion velocities of galaxy clusters
- Gravitational lensing of distant galaxies and quasars by closer galaxy clusters
The evidence for dark matter goes back to 1933, but astronomers did not readily accept dark matter – it took decades. Once astronomers came to accept the reality of dark matter in the 1980s, invocation of dark matter in the origin and maintenance of galactic structure gradually came about. This was followed by the inclusion of dark matter into big bang cosmology by the late 1990s. Since gravity is thought to be the dominant force in cosmology, inclusion of dark matter into cosmological models originally was motivated by the desire to have more realistic models. However, dark matter soon became a free parameter that could be manipulated within the big bang model to resolve issues with the model.
Meanwhile, in the 1990s, astronomers were using type Ia supernovae to extend the Hubble relation to great distances. The expectation was that gravitational deceleration would have resulted in an upward inflection in the Hubble relation at great distance. However, in 1998 it was discovered that at great distance the Hubble relation has a downward inflection, indicating that the expansion of the universe is accelerating. This seemed to be a return of the cosmological constant (λ) that Einstein had introduced in 1917 but was rejected a decade later because of discovery of the Hubble relation. Rather than being a constant repulsion term in the universe as the cosmological constant was, cosmologists today entertain the possibility that the repulsion in the universe may change over time. Hence, cosmologists chose a new term, dark energy, in comparison to dark matter, though the two terms have nothing in common. Both dark matter and dark energy are now incorporated into the standard (λCDM) cosmology.
Many recent creationists reject both dark matter and dark energy, though the reasons are not clear. Much of the criticism of dark matter coming from recent creationists tends to focus on two fronts:
- Treating dark matter as a rescuing device for the big bang and other evolutionary ideas
- The negative results of the tests of different theories of the identity of dark matter particles
However, these discussions do not properly handle the facts. The evidence for dark matter preceded dark matter’s inclusion in the big bang model and ideas of galactic evolution by many decades. Furthermore, the evidence for dark matter is based upon operational science, the study of how the world operates today. In contrast, inclusion of dark matter into the big bang model and for the origin and maintenance of galactic structure are historical science. Creationists ought to be aware of this distinction, but alas, many them don’t appear to be. The null results of tests of dark matter candidates are disproof of particular models of dark matter, not disproof of the existence of dark matter.
Similarly, recent creationists tend to view dark energy as a rescuing device for the big bang model. The reality is that dark energy is the best interpretation of the downward inflection of the Hubble relation at great distance within the big bang model. That is, dark energy is based upon real data that is interpreted in terms of an evolutionary model. Simply dismissing dark energy out of hand is tantamount to dismissing the data. What the downturn in the Hubble relation might mean in a creationary cosmology model must await the development of such a model.