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Multiverse Musings – Introduction

Since joining RTB in August 2005, I have devoted a fair bit of time trying to understand the latest ideas on the multiverse and how it impacts our apologetic arguments. I find it fascinating and complex and worthy of the effort to begin understanding the important issues—especially since the multiverse garners a lot of publicity.

Because of its popularity and its impact on RTB’s apologetics, I decided to devote one TNRTB a month to articulating and examining the multiverse idea. My intent is to lay out what I believe to be the most exciting, difficult to understand, and apologetically impactful issues in a clear and concise way. While I believe there are significant issues in multiverse models (described in coming articles), they are not inherently antibiblical. While it certainly affects the advancement of various arguments, the multiverse concept dramatically expands our view of reality and, I will argue, ultimately strengthens the case for the God of the Bible as Creator.

It would be hopeless to try covering all aspects of this complex topic in one sitting. So to get the ball rolling, some terminology is critical. The term “universe” describes all the space-time that exists whether—in principle—we could ever see it. In contrast, the “observable universe” contains only those regions of the universe where emitted radiation can reach some specified location—typically Earth. With a universe about 14 billion years old and our best measurements of its expansion history, our observable universe presently spans about 50 billion light-years. Inflation currently conceives of our universe existing within an inflating bubble of an “überspace.” If other bubbles exist containing other universes, these I will refer to as “bubble universes.” For most people, the “multiverse” refers to the ensemble of all bubble universes, although scientists use the term more broadly.

With this terminology, Max Tegmark’s multiverse overview provides a nice framework for further discussion. He organizes all multiverse models into four different levels, with higher-numbered levels being more speculative than lower-numbered levels.

Level I: There exist regions, beyond our observable universe but similar in size, which exhibit the same laws of physics but start with different initial conditions. Basically, this affirms that the universe does not end just beyond the most distant regions we can observe. The only controversial issue at this level pertains to the size of the region beyond our observable universe. If the universe is closed, the geometry of the observable universe (very close to flat) provides a minimum size for the whole universe of a few thousand times our observable universe. However, if the current formulations of how inflation works contain any truth, these models generically predict that the spatial extent of the universe is infinite.

Level II: There exist other bubble universes that obey the same equations of physics but with different fundamental constants, particles, and dimensionality. This level differs from Level I in that many universes (not just the one where we reside) actually exist inside their own inflating bubbles. Whereas all the regions outside our observable universe in Level I obey the same laws of physics with the same fundamental constants, each Level II bubble universe obeys the same laws of physics but the fundamental constants assume different values than those from our universe.

Level III: This level corresponds to the many-worlds interpretation of quantum mechanics put forth by Hugh Everett. The relevant feature of this level pertains to the physical basis for quantum events. When determining what happens at the quantum level, the best one can do is assign a probability for each of multiple different outcomes. Basically, the many-worlds interpretation says that for each quantum event, a “history” or “world” actually exists where each of the possible outcomes is realized.

Level IV: This level posits that any mathematically coherent structure defines a physical reality. Obviously, this leads to universes with completely different laws of physics. No Level V can exist because Level IV encompasses all possibilities.

Most of the scientifically and apologetically pertinent points arise in the Level I and Level II multiverses, so the bulk of what I discuss here will generally center on these two levels. Next time I will focus on how a Level I multiverse impacts probability-based apologetic arguments.