The origin of the universe is one of the most difficult realities we ponder.
It bends our logic, straining the words we have to describe it. If one is to say the universe started at the Big Bang some 13.8 billion years ago, the immediate reaction is: "But what came before that? What caused the Big Bang?"
This is the issue of the "first cause" — the cause at the beginning of the causal chain that caused all else but was itself not caused — that has plagued and inspired philosophers for millennia.
Before philosophy, religions across the globe dealt with the same issue by positing the existence of deities that are beyond the laws of cause and effect. By existing beyond space and time, deities are, by definition, immune to the shortcomings of being human. They can be the first cause.
Scientists tend to prefer other kinds of explanation about the world, including those that deal with issues of origins. But when it comes to the Big Bang, our theories hit a hard wall. Readers may enjoy this video featured in Aeon magazine, where philosopher Tim Maudlin from New York University addresses some of the difficulties.
Despite what physicists like Stephen Hawking and Lawrence Krauss say, we are far from understanding the physics of the Big Bang. In fact, it isn't even clear that we can provide a complete scientific explanation of the origin of the universe.
Every scientific theory is built upon a set of concepts. For example, we use what we call the laws of nature, which are statements of regularities that we find in the behavior of physical systems, such as the conservation of momentum and energy. It's hard to imagine how to construct a theory of the origin of everything that doesn't make use of such laws. Yet, a theory describing the origin of the universe should, as a matter of principle, also explain the origin of the laws of nature.
Can we conceive of a science capable of doing that? There is no a priori reason we can't. However, current ideas about there being a multiverse, a collection of universes of which ours is one, will not help on this front. They still use a conceptual structure derivative of present-day physics.
What seems to be needed is a new way of depicting the laws of nature not as static truths about the world but as emerging behaviors that unfold and take hold as time elapses. Physicist Lee Smolin and philosopher Mangabeira Unger hint at this in their book, but don't offer a working approach. (Who can blame them?)
Still, any explanation needs to start from something. How can we explain everything without appealing to something? Why the universe? It may be one of those questions that will keep tying us in knots for a very long time.
Marcelo Gleiser is a theoretical physicist and cosmologist — and professor of natural philosophy, physics and astronomy at Dartmouth College. He is the co-founder of 13.7, a prolific author of papers and essays, and active promoter of science to the general public. His latest book is The Island of Knowledge: The Limits of Science and the Search for Meaning. You can keep up with Marcelo on Facebook and Twitter: @mgleiser.