Last month, a team of researchers based in Antarctica announced they’d detected gravitational waves, faint echoes from the first moments of the Big Bang. This discovery has enormous implications for cosmology, the world of physics and even our understanding of the future of our universe. My recent post about the BICEP2 project (A Window on the Universe’s Distant Past and Future) explored some of these, as does my upcoming article about cosmic inflation for The Futurist. (July-August 2014)
These writings gave me a lot to think about regarding the origins of our universe. Invariably, when explaining the early evolution of the cosmos, one particular question always comes up: where did the singularity that started the Big Bang come from? For some time, many physicists and cosmologists have said it could be possible for our universe to have actually started from nothing – as wild and counterintuitive as that sounds. But without proof this seems like a statement of faith, impossible to prove or disprove and therefore outside the purview of true scientific discussion. Ever since Popper, we’ve said that falsifiability is the demarcation between what is scientific and what is not. It felt like this might be the point where the scientific method would have to give way to the origin stories of myth.
Or perhaps not.
Last week saw the publication of a paper that may be as important to our understanding of the Big Bang as was the detection of gravitational waves. A team from the Wuhan Institute of Physics and Mathematics in China has made the first rigorous mathematical proof that the Big Bang could have spontaneously generated from nothing. The Wuhan team, led by Qing-yu Cai, developed new solutions to the Wheeler-DeWitt equation, which sought to combine quantum mechanics and general relativity in the mid-20th century.
According to Heisenberg’s uncertainty principle, quantum fluctuations in the metastable false vacuum – a state absent of space, time or matter – can spontaneously give rise to virtual particle pairs. Ordinarily these pairs self-annihilate almost instantly, but if these virtual particles separate immediately, they can avoid annihilation, creating what physicists call a true vacuum bubble. The Wuhan team’s equations show that such a bubble has the potential to expand exponentially, causing a new universe to appear. All of this begins from quantum behavior and leads to the creation of a tremendous amount of matter and energy during the inflation stage. (Note that as stated in this paper, the metastable false vacuum has “neither matter nor space or time”, but is a form of wavefunction, referred to as “quantum potential.” While most of us wouldn’t be inclined to call this “nothing”, physicists do refer to it as such.)
This description of exponential growth of a true vacuum bubble corresponds directly to the period of cosmic inflation resulting from the Big Bang. (The inflation epoch is thought to have occurred 10-36 – or a trillion trillion trillionth – of a second after the Big Bang.) According to this proof, the bubble even stops expanding – or else it may continue to expand at a constant velocity – once it reaches a certain size. Nevertheless, this is a very different version of inflation than those proposed by Guth, Linde and others, in that it doesn’t rely on scalar fields, only quantum effects. Still, this work dovetails well with that of the BICEP2 team, both discoveries having significant implications for our understanding of the universe and our future should they be stand up to further inquiry.
Given the quantum behavior of virtual particles in a vacuum as put forth in this paper, it’s reasonable to assume this hasn’t happened only this once, but many, potentially even an infinite number of times. The idea of a multitude of multiverses being generated by processes similar to those that gave rise to our own universe is not new. But this is the first time we’ve actually identified the mechanisms that may have been involved. In discussing this with one of the proof’s authors, Qing-yu Cai said he thinks their work “supports the multiverse concept.” Whether this process would result in the exact same physical laws that we see in our own universe remains to be determined, since according to these equations only limited conditions could result in an exponentially expanding true vacuum bubble.
Another idea that’s been discussed in the past is whether or not we could ever create new universes ourselves, perhaps using something like the Large Hadron Collider (LHC). However, as Qing-yu Cai observed, “space-time of our universe is a whole, it cannot be divided into small parts arbitrarily, even at LHC.” Therefore, “it seems impossible to create new universes ourselves.”
Ultimately, this mathematical proof needs to be checked out by others and ideally put to some yet-to-be-determined tests. In the end, the work may or may not be accepted. That is, after all, how the scientific method operates. But if this proof should stand up to scrutiny, it will most certainly give us considerable new insights into the mechanisms that gave birth to our cosmos. The news of this past month demonstrates that the field of cosmology remains vibrant, with new ideas and discoveries regularly being made. Our universe and the physics at its foundation are incredibly complex and will continue to yield new knowledge about our past, present and future for a long time to come. Perhaps until the end of time.