The Biggest Big Question of All

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Why is there something rather than nothing? There are at least ten answers to this, arguably the biggest Big Question of all time.
 
1. God

The theist’s answer to the question is that God existed before the universe and subsequently brought it into existence out of nothing (ex nihilo) in a single creation moment as described in Genesis. But the very conception of a creator existing before the universe and then creating it implies a time sequence. In both the Judeo-Christian tradition and the scientific worldview, time began when the universe came into existence, either through divine creation or the Big Bang. God, therefore, would have to exist outside of space and time, which means that as natural beings delimited by living in a finite universe, we cannot possibly know anything about such a supernatural entity. The theist’s answer is an untestable hypothesis.
 
2. Wrong Question

Asking why there is something rather than nothing presumes “nothing” is the natural state of things out of which “something” needs an explanation. Maybe “something” is the natural state of things and “nothing” would be the mystery to be solved. As the physicist Victor Stenger notes in his forthcoming book, Why is There Something Rather Than Nothing?: “Current cosmology suggests that no laws of physics were violated in bringing the universe into existence. The laws of physics themselves are shown to correspond to what one would expect if the universe appeared from nothing. There is something rather than nothing because something is more stable.”
 
3. Grand Unified Theory

In order to answer the question, we need a comprehensive theory of physics that connects the subatomic world described by quantum mechanics to the cosmic world described by general relativity. As the Caltech cosmologist Sean Carroll notes in his book From Eternity to Here: “Possibly general relativity is not the correct theory of gravity, at least in the context of the extremely early universe. Most physicists suspect that a quantum theory of gravity, reconciling the framework of quantum mechanics with Einstein’s ideas about curved spacetime, will ultimately be required to make sense of what happens at the very earliest times. So if someone asks you what really happened at the moment of the purported Big Bang, the only honest answer would be: ‘I don’t know.’” That grand unified theory of everything will itself need an explanation, but it may be explicable by some other theory we have yet to comprehend out of our sheer ignorance at this moment in history.

4. Boom-and-Bust Cycles

Sean Carroll also suggests that our universe may be just one in a series of boom-and-bust cycles of expansion and contractions of the universe, with our universe just one “episode” of the bubble’s eventual collapse and re-expansion in an eternal cycle, and therefore “there is no such thing as an initial state, because time is eternal. In this case, we are imagining that the Big Bang isn’t the beginning of the entire universe, although it’s obviously an important event in the history of our local region.”

 5. Darwinian Multiverse

According to the cosmologist Lee Smolin, in his book The Life of the Cosmos, our universe is just one of many bubble universes with varying sets of laws of nature. Those universes with laws of nature similar to ours will generate matter, which coalesces into stars, some of which collapse into black holes and a singularity, the same entity out of which our universe may have sprung. Thus, universes like ours give birth to baby universes with those same laws of nature, some of which develop intelligent life smart enough to discover this Darwinian process of cosmic evolution.
 
6. Inflationary Cosmology

In his 1997 book The Inflationary Universe, the cosmologist Alan Guth proposes that our universe sprang into existence from a bubble nucleation of spacetime. If this process of universe creation is natural, then there may be multiple bubble nucleations that give rise to many universes that expand but remain separate from one another without any causal contact between them.
 
7. Many-Worlds Multiverse

According to the “many worlds” interpretation of quantum mechanics, there are an infinite number of universes in which every possible outcome of every possible choice that has ever been available, or will be available, has happened in one of those universes. This many-worlds multiverse is grounded in the bizarre findings of the famous “double-slit” experiment, in which light is passed through two slits and forms an interference pattern of waves on a back surface (like throwing two stones in a pond and watching the concentric wave patterns interact, with crests and troughs adding and subtracting from one another). The spooky part comes when you send single photons of light one at a time through the two slits—they still form an interference wave pattern even though they are not interacting with other photons. How can this be? One answer is that the photons are interacting with photons in other universes! In this type of multiverse you could meet your doppelganger, and depending on which universe you entered, your parallel self would be fairly similar or dissimilar to you, a theme that has become a staple of science fiction (see, for example, Michael Crichton’s Timeline).
 
8. Brane-String Universes

A multi-dimensional universe may come about when three-dimensional “branes” (a membrane-like structure on which our universe exists) moves through higher-dimensional space and collides with another brane, the result of which is the energized creation of another universe. A related multiverse is derived through string theory, which by at least one calculation allows for 10^{^500} possible worlds, all with different self-consistent laws and constants. That’s a 1 followed by 500 zeroes possible universes (recall that 12 zeroes is a trillion!). In his book The Unconscious Quantum, Victor Stenger published the results of a computer model that analyzes what just 100 different universes would be like under constants different from our own, ranging from five orders of magnitude above to five orders of magnitude below their values in our universe. Stenger found that long-lived stars of at least 1 billion years — necessary for the production of life-giving heavy elements — would emerge within a wide range of parameters in at least half of the universes in his model.
 
9. Quantum Foam Multiverse

In this model, universes are created out of nothing, but in the scientific version of ex nihilo the nothing of the vacuum of space actually contains the theoretical spacetime mishmash called quantum foam, which may fluctuate to create baby universes. In this configuration, any quantum object in any quantum state may generate a new universe, each one of which represents every possible state of every possible object. This is Stephen Hawking’s explanation for the fine-tuning problem that he himself famously presented in his 1996 book (co-authored with Roger Penrose) The Nature of Space and Time: “Quantum fluctuations lead to the spontaneous creation of tiny universes, out of nothing. Most of the universes collapse to nothing, but a few that reach a critical size, will expand in an inflationary manner, and will form galaxies and stars, and maybe beings like us.”
 
10. M-Theory Grand Design

Stephen Hawking has continued working on this question, and this month, he and the Caltech mathematician Leonard Mlodinow present their answer in a book entitled The Grand Design. They approach the problem from what they call “model-dependent realism,” based on the assumption that our brains form models of the world from sensory input, that we use the model most successful at explaining events, and that when more than one model makes accurate predictions “we are free to use whichever model is most convenient.” Employing this method, they write, “it is pointless to ask whether a model is real, only whether it agrees with observation.” The dual wave/particle models of light are an example of model-dependent realism, where each one agrees with certain observations but neither one is sufficient to explain all observations. To model the entire universe, Hawking and Mlodinow employ “M-Theory,” an extension of string theory that includes 11 dimensions and incorporates all five current string theory models. “M-theory is the most general supersymmetric theory of gravity,” Hawking and Mlodinow explain. “For these reasons M-theory is the only candidate for a complete theory of the universe. If it is finite — and this has yet to be proved — it will be a model of a universe that creates itself.” Although they admit that the theory has yet to be confirmed by observation, if it is then no creator explanation is necessary because the universe creates itself. I call this auto-ex-nihilo.
 
Most of these ten explanations are testable. The theory that new universes can emerge from collapsing black holes may be illuminated through additional knowledge about the properties of black holes. Other bubble universes might be detected in the subtle temperature variations of the cosmic microwave background radiation left over from the Big Bang of our own universe. NASA's Wilkinson Microwave Anisotropy Probe spacecraft is collecting data on this radiation. Another way to test these theories might be through the Laser Interferometer Gravitational Wave Observatory (LIGO) that is designed to detect exceptionally faint gravitational waves. If there are other universes, perhaps ripples in gravitational waves will signal their presence. Maybe gravity is such a relatively weak force (compared to electromagnetism and the nuclear forces) because some of it “leaks” out to other universes. Maybe.
 
In the meantime, in answer to the question Why is there something instead of nothing?, it is okay to say “I don’t know” and keep searching. There is no need to turn to supernatural answers just to fulfill an emotional need for certainty and comfort. Science’s uncertainty is its greatest strength. We should embrace it.
 
Michael Shermer is the publisher of Skeptic magazine, a monthly columnist for Scientific American, and an adjunct professor at Claremont Graduate University. His books include The Science of Good and Evil, Why Darwin Matters, and The Mind of the Market. He can be reached at mshermer@skeptic.com.