The physical universe teems with questions. The more we learn about it the less we seem to understand. In poetic perfection, the light of science is finding its latest mystery in the world of dark matter.
Dark matter is a term used to describe the missing matter needed to model rotation of galaxies or clusters of galaxies. Following the well-substantiated laws of gravitation and rotational motion, the rotation velocities of the stars in a typical spiral galaxy should fall off as the square root of the distance to the star from the center of the galaxy. As you move out into the spiral, the stars should be moving slower. However, observations show that the “curve” that describes this relationship is actually flat (see chart). The possible explanations for this inconsistency are (1) the laws of gravity are wrong or (2) the amount of mass in the galaxy has been substantially miscounted. Since throwing out the law of gravity makes physicists just a little queasy, the favorite explanation is that there is a large amount of extra mass that simply has not been observed. The “dark matter,” called such because if it were luminous we should be able to see it, could correct the calculation and bring the galaxy into harmony once more. How much matter are we missing? On the galactic scale, estimates are something like 50%. On larger scales, the problem gets worse, with estimates usually upwards of 90%.
After the initial knee-jerk reaction (“We’re missing 90% of the universe?!”), this isn’t an altogether unreasonable proposal. Why should we believe that we are able to see all the matter that is floating around in space? It is almost certain that we are missing things, maybe a lot.
But what sorts of things are we missing? Popular candidates include MACHOs (MAssive Compact Halo Objects … no really, that is what they are called) which could be anything from dim brown dwarf stars to the invisible abyss of black holes. More exotic candidates include WIMPs (Weakly Interacting Massive Particles … seriously, I’m not making this up) which could be rare non-baryonic particles like neutrinos or even undiscovered varieties.
What is the relevance of dark matter to a Christian apologetic author like me? The dark matter mystery speaks directly to the fact that beneath the facade of a well-ordered cosmological model, scientists still have massive (pun intended) problems modeling the universe.
On the one hand, the University of California Santa Cruz issued a press release titled “Scientists Release Most Accurate Simulation of the Universe to Date”1, an article that would lead the reader to believe that we have solved the biggest of all mysteries:
The Bolshoi supercomputer simulation, the most accurate and detailed large cosmological simulation run to date, gives physicists and astronomers a powerful new tool for understanding such cosmic mysteries as galaxy formation, dark matter, and dark energy.
The simulation traces the evolution of the large-scale structure of the universe, including the evolution and distribution of the dark matter halos in which galaxies coalesced and grew. Initial studies show good agreement between the simulation’s predictions and astronomers’ observations.
On the other hand, the Harvard-Smithsonian Center for Astrophysics issued a press release only two weeks later titled “Dark Matter Mystery Deepens”2, which states the following about their study analyzing the dark matter distribution in two Milky Way neighbors:
“After completing this study, we know less about dark matter than we did before,” said lead author Matt Walker, a Hubble Fellow at the Harvard-Smithsonian Center for Astrophysics.
… Cosmologists use powerful computers to simulate this process. Their simulations show that dark matter should be densely packed in the centers of galaxies. Instead, new measurements of two dwarf galaxies show that they contain a smooth distribution of dark matter. This suggests that the standard cosmological model may be wrong.
“Our measurements contradict a basic prediction about the structure of cold dark matter in dwarf galaxies. Unless or until theorists can modify that prediction, cold dark matter is inconsistent with our observational data,” Walker stated.
The simple truth is that science knows less about the overall structure and evolution of the universe than some would like to acknowledge. Furthermore, do not think for a moment that this is a rare fact. Dark matter is not the most disconcerting problem in modern astrophysics. Other larger scale issues result in the belief of “dark energy,” another “fix” for models gone awry (but more on that another time).
If you cannot explain the universe’s structure, then you cannot explain the universe’s history. If you cannot explain the universe’s history, then you cannot explain the universe’s source. Science is no closer to producing an entirely materialistic model of the universe than they ever have been. Each new discovery creates a plurality of new mysteries. Without the willingness to consider the Divine Creator, the universe remains as dark as the matter needed to explain it.