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Multiverse Musings: How Does Inflation Lead to a Multiverse?

Not to beat a dead horse, but one final issue regarding inflation needs clarification. I made this statement in a past TNRTB: “The issue of whether inflation models also produce a multiverse and, if so, does that multiverse argue against a Christian worldview are separate issues.” I have written a number of articles articulating that many multiverse models fit comfortably within a Christian worldview and that multiverse research strengthens the cosmological and teleological arguments for Christianity. However, I have not addressed the issue of how inflation leads to multiverse models.

First, one must remember that inflation does not imply a change in the laws of physics. Rather, the universe resided in a “higher potential” state that caused a rapidly expanding space-time (inflation). As this potential decayed to a lower energy state, the universe heated up and transitioned to the expansion rate we see today. Multiverse models arise as cosmologists seek to understand this transition in more detail.

The transition from inflation to expansion must occur in such a fashion so as to produce the extreme homogeneity of the universe reflected in the cosmic microwave background (CMB). But the rapid expansion of space in the high potential and the fact that various regions of space decay to the lower potential at different times make the homogeneity feature difficult to produce. Even with all the issues that inflation solved, it did not gain acceptance for many years because of this “graceful exit” problem. 

Physicist Alan Guth provided an interesting solution to this problem nearly two decades ago, but it changed the way cosmologists thought about the created realm. Most people not trained in cosmology typically think about the universe development in this progression:

  • Space-time created as the start of the big bang.
  • The universe expands, undergoing a period of inflation in the first fraction of a second. During this inflationary epoch, the universe expands by an enormous factor (25 to 100 orders of magnitude) in a time less than 10-34 seconds.
  • The inflation potential decays (throughout the observable universe) to give the expansion rate seen today.
  • The universe cools down, eventually emitting the cosmic microwave background radiation and forming stars and galaxies. Almost 14 billion years later, human beings arrive on planet Earth.

Currently, all scenarios following this progression suffer from the graceful exit problem and cannot be reconciled with the CMB measurements. Guth’s solution proceeds along this line:

  • Some preexisting “überspace” continually undergoes inflation.
  • The inflation potential decays in some particular region of this überspace, signifying the start of our universe.
  • If viewed from the outside, this bubble-region (our universe) where inflation ceased grows larger as time progresses. The boundary between the inflating region outside the bubble and the non-inflating region inside the bubble represents the big bang. Regions inside the bubble cannot see out; regions outside the bubble cannot see in.
  • The region inside the bubble cools down, eventually emitting the cosmic microwave background radiation and forming stars and galaxies. Almost 14 billion years later, human beings arrive on planet Earth.

These newer inflationary models inevitably produce a Level I multiverse (unless space exists in some bizarre topology). Furthermore, the chance is beyond small that a single location of this inflating überspace decays. Consequently, these types of inflationary models also produce Level II multiverses.

Even though these inflationary models dramatically change our view of our universe’s place in creation, it does not mean it undermines the Christian faith. It bears highlighting that even these inflationary multiverse models still require a beginning and, therefore, a Beginner.

If you would like to see a question about the multiverse addressed in this forum, send it to [email protected].