I have edited and paraphrased this article, for brevity's sake, but you can read the full-length original, by Amanda Gefter, in New Science Magazine.
Cosmologist George Ellis, from the University of Cape Town, South Africa, is regarded as one of the world's leading experts on general relativity. Ellis is one of many theorists who has been contemplating what he considers a dangerous idea: the suggestion that our universe is but a tiny part of an unimaginably large and diverse multiverse. To the dismay of Ellis and many of his colleagues, the multiverse has developed rapidly from being a speculative idea to a theory verging on respectability. Several strands of theoretical physics—quantum mechanics, string theory, and cosmic inflation—seem to converge on the idea that our universe is only one among an infinite and ever-growing assemblage of disconnected bubble universes. The main cause for alarm is the fact that it postulates the existence of a multitude of unobservable universes, making the whole idea untestable. If something as fundamental as this is untestable, says Ellis, the foundations of science itself are undermined. Raphael Bousso of the University of California, Berkeley, has also been grappling with the multiverse, and in the past few months has found a way round the troubling problem of unobservable universes. At a stroke, he has transformed the multiverse from a theory so problematical that it threatens to subvert science, into one that promises predictions we can test. His insights are steering physicists along the path to their ultimate goal of uniting quantum mechanics and gravity into one neat theory of everything. The trouble is that in an infinite multiverse, everything that can happen will happen—an infinite number of times. In such a set-up, probability loses all meaning. "How do you compare infinities?" asks Andrei Linde of Stanford University in California. Two events that are simultaneous for me are not simultaneous for you, so there are an infinite number of ways you can slice up the multiverse. None is more "true" than any other, so there's no reason to choose one time slicing over another—and different slices can yield dramatically different results.
Quantum mechanics tells us that the vacuum of space is not empty; instead, it crackles with energy. It also tells us that, sooner or later, any given universe will decay spontaneously into another one with lower energy. Indeed, most cosmologists envisage our big bang as precisely such an event, during which the vacuum we live in emerged from a higher-energy vacuum that constituted a universe before ours. What matters here, though, is that there are a plethora of possible universes that can be produced in this way, each with its own probability.
Bousso's work, combined with a totally different view researched by Alexander Vilenkin of Tufts University in Boston, arrive at similar conclusions. Both suggest that the holographic principle is profoundly significant, and could lead us to a theory of quantum gravity—the long-sought theory of everything that mirrors the dynamics of the multiverse. As it turns out, everything we need to know about the multiverse might be right here in our own universe.
What I find interesting about all this—not being a physicist myself, but a metaphysicist—is that everything we know about the way consciousness itself works points to the reality of a multiverse, or a hugely extended "reality," or expanded consciousness, in which all realities coexist and are possible. Not everything has to be tested and defined by the mind, which craves measurement; there are experiences of truth that inhere in our nature and need not even be sought because they are so intimately known. I find it fascinating that science continually approaches what we, as meditators and metaphysicians, know about the principles of awareness.
I also find it interesting that scientists would panic because something might be untestable, and thus might put an end to science. I believe science is a subset of metaphysics, that eventually we will all need to put away our proof-addicted minds and dive directly into the experience of oneness and the multitudinuous potentials of our higher identity as mini-gods within the greater God-force. Perhaps science will one day end up stopping at the gate where Mind May Not Enter. For after all, is it possible, or even necessary, to describe everything??