Today’s New Reason To Believe

by Jeff Zweerink

Does the universe end at the farthest reaches we can observe? If it doesn’t, then what characteristics does this realm beyond the observable universe exhibit? While science fiction authors have written in depth about alternate universes, many scientists want to bring these questions into their arena. To do so, they must posit explanations that account for existing data and predict what future experiments and observations might reveal. The most expedient avenue for such investigations involves inflation and its effect on the cosmic microwave background (CMB) radiation .

A team of Caltech cosmologists recently developed an inflationary model that predicts that the universe is far larger than the region we can see (a Level I multiverse in more technical lingo). Their research seeks to explain a possible asymmetry of the amplitudes of the CMB fluctuations observed by WMAP. Hailed in the popular press as chance to “glimpse before the big bang”, this model makes predictions that will allow cosmologists to better understand the mechanism responsible for the important inflationary era early in the history of the universe.

The pertinent feature of their model utilizes two different scalar fields, instead of one, during the inflationary epoch. One field, the inflaton, drives the inflationary expansion. A second field called the curvaton produces the density fluctuations. Using a two-field approach allows the model to explain the possible asymmetry in the fluctuation amplitudes without disrupting the uniformity seen in the CMB.

Large-scale modes of the curvaton extend beyond the region that inflated to become our observable universe. Thus, different sections of the observable universe can have different values for the curvaton field. These variations lead to different amplitudes for the CMB fluctuations. If this model proves true, it implies that our observable universe represents a small fraction of the total size of the universe. More importantly, this model makes detailed predictions that will be tested by future measurements of the CMB by missions like Planck.

In an earlier TNRTB, I described another piece of data that indicates the universe is much larger than what we can see. Exciting times lay ahead as scientists try to find out just how big the universe is. Regardless of what future results reveal about the physical extent of the universe, RTB expects those results to also provide further demonstration that a supernatural Creator stands as the ultimate cause of this universe.

If you would like to see a question about the multiverse addressed in this forum, send it to multiverse@reasons.org.

by Jeff Zweerink

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 multiverse@reasons.org.

by Jeff Zweerink

History disfavors any theory placing Earth in a geometrically special location. Early scientists, such as Ptolemy of ancient Greece, thought Earth resided at the center of the solar system. However, geocentric cosmology eventually gave way to heliocentrism most notably associated with Nicolas Copernicus. Since Copernicus’s time extensive observations have demonstrated that the Sun does not reside at the center of the Milky Way Galaxy (MWG). Nor does the MWG reside at the center of the Local Group of galaxies or the universe. Scientists refer to the fact that Earth is not in a central, specially favored position as the Copernican Principle.

Although this view provides a foundation of cosmological research, scientists don’t simply accept the Copernican Principle. They continue to test it.

One area of research particularly suited to testing is the universe’s mysterious dark energy. The first need to invoke dark energy to explain features of the universe arose as astronomers tried to understand observations of distant Type Ia supernovae. The supernovae appeared dimmer than expected and the simplest explanation was that dark energy was causing the expansion of the universe to accelerate. However, dark energy is not the only explanation.

The same supernovae data would arise if the MWG resides at the center of a large region (something similar in size to the observable universe) with a lower density than that of the surrounding regions. However, placing the solar system (located within the MWG) at the center of such a special region clearly violates the Copernican Principle. Nevertheless, scientists do not simply reject the low density region, also called the void model. They seek to test its validity.

In a previous TNRTB I highlighted one test of the void model that used the cosmic microwave background. Now scientists have developed another test using supernovae data. Reseachers started by characterizing void density profiles that could explain the supernovae data. Then they modeled in detail how the supernovae data would appear with a much larger sample than currently exists. They found that with a sufficient sample of supernovae data from a specified distance, the void model produced different results when compared to dark energy models. Observations over the next few years should definitively tell which model is correct.

If dark energy models prevail, cosmologists will continue to face the great challenge of trying to understand what it is and why it exhibits such extraordinary fine-tuning in order for this universe to support life. If the void models prevail, a guiding scientific principle will need revision. Either way, exciting times lay ahead.

If you would like to see a question about the multiverse addressed in this forum, send it to multiverse@reasons.org.