Reasons To Believe has cataloged a large number of fine-tuned aspects of the universe, all of which make it fit for life. A recent article in New Scientist highlights one particular parameter, namely the ratio of dark matter to normal matter (electrons, protons, neutrons, etc.). Changes to this ratio affect the habitability of the universe by changing the amount of large-scale structures like clusters of galaxies.
A habitable galaxy must reside in a small cluster with an abundance of smaller dwarf galaxies. These small galaxies provide the fuel for star formation that leads to stars with a large enough metal concentration to support life. However, galaxies in large clusters experience collisions with other such structures. They also exhaust their star-forming fuel too rapidly. A greater fraction of dark matter compared to normal matter would inhibit the formation of any large-scale structures. A smaller fraction would tend to produce only large galaxy clusters. The Milky Way Galaxy lives in a just-right cluster.
Although the exact nature of dark matter remains elusive, scientists are confident that the processes that produced dark matter differ from those that produce normal matter. Consequently, there is no reason to expect that these different processes would generate a ratio of dark matter to normal matter conducive to life. Yet they did.
As research reveals the extent of fine-tuning that makes this universe habitable, the options for explaining that fine-tuning decrease. Traditionally, many philosophers and scientists have argued that any real cosmic fine-tuning derives from a Designer. However, some scientists argue that the design we see is only apparent. Such a claim requires an adequate explanation for the data.
The most popular rationalization relies on the existence of a vast multitude of universes known as the multiverse. In fact, Nobel laureate Steven Weinberg maintains,
If you discovered a really impressive fine-tuning…I think you’d really be left with only two explanations: a benevolent designer or a multiverse.
Another well-known cosmologist, Bernard Carr echoes that sentiment:
If there is only one universe you might have to have a fine-tuner. If you don’t want God, you’d better have a multiverse.
I would argue that the “God or multiverse” choice is a false dichotomy. First, in past TNRTBs I have shown that the multiverse does not help the naturalist eliminate God. In fact, in a strictly naturalist worldview, the multiverse adversely affects the scientific enterprise. Second, I see no inherent problems with God using a multiverse to create a place where Earth life, especially humanity, could grow and thrive.
It is uncertain whether the multiverse will ultimately prove true. However, the fact that so many prominent scientists see it as a potential explanation for the fine-tuning observed in this universe highlights the strength of evidence backing the inference that a Designer fashioned this universe.
If you would like to see a question about the multiverse addressed in this forum, send it to firstname.lastname@example.org.