Given the time of the year, it's hard not to go back to some of our perennial questions about beginnings; in our case here at 13.7, I'm talking about the beginning of nothing less than everything, the origin of the universe.
Here is one place where the boundaries between scientific and religious narratives sometimes get blurred. Not because the two are doing the same thing, for they clearly aren't; but because the question is essentially the same: we want to know how everything came to be. Otherwise, our own story is incomplete, given that we are, at the most fundamental level, creations of this universe.
Many people of faith are often puzzled by claims that modern science can say things about this issue. And there is no question that progress in cosmology and astronomy have brought us a remarkable narrative of the universe's earliest history, that we now know started around 13.8 billion years ago: like you and me, the universe also has a birthday.
Things quickly get complicated if we persist with this b-day analogy: you and I had parents, and they had parents, and so on. There is continuity in this story, that we can trace back to the first living entity. Once we get there, we find another tough wall: how did the first living entity come to be, if there was nothing alive to birth it? Presumably, and this is the only acceptable scientific explanation, life came from non-life, from the increasing complexity of chemical reactions between the biomolecules present on primordial Earth, some 3.5 billion years ago, or perhaps even earlier.
What about the universe? How did it come to be if there was nothing before?
If the origin of life is mysterious, the origin of the universe is much more. After all, the universe, by definition, includes all there is. How can everything come from nothing? The prerogative of science is to develop explanations without the recourse of divine intervention. We play the game of nature within nature, that is, using the laws of nature as our blueprint.
And here is the rub, the source of the conceptual challenge: science operates within clear conceptual boundaries, and these are a precondition to construct a scientific explanation. To explain the origin of everything science needs to explain itself. And to do this, we need to develop a new mode of scientific explanation.
Let me explain. Current descriptions of the origin of the universe use the two pillars of 20th century physics, general relativity — Einstein's theory where gravity is due to the curvature of space caused by the presence of mass — and quantum physics, describing the world of atoms and subatomic particles. Combining the two is quite reasonable, given that in its infancy the whole universe was small enough so that quantum effects had to be present. Models make use of the bizarre effects from quantum physics to explain what seems to be unexplainable. Explain to a point, that is.
The same way that a radioactive nucleus spontaneously decays, the entire cosmos could have emerged from a random energy fluctuation, a bubble of space that appeared from nothing, the quantity physicists usually call the vacuum. The interesting thing is that this bubble could have been a fluctuation of zero energy, due to a clever compensation between matter's positive and gravity's negative energy. This is why many physicists writing for general audiences confidently state that the universe came from nothing. And proudly declare that the case is closed. If only things were so simple.
This nothing, the vacuum of physicists, is far from a metaphysical notion of complete emptiness. In fact, the vacuum is an entity filled with activity, where particles can come into and out of existence like bubbles in a boiling caldron. To define the vacuum we need to start from many fundamental concepts, such as space, time and fields. We need to rely on a series of natural laws that have only been tested for situations far removed from the extreme environment of the primordial universe.
We extrapolate what we know to energies 15 orders of magnitude above what we can test (that's a thousand-trillion times), hoping that things will make sense because we can't predict any stumbling blocks in between. However, these predictions are based on what we can measure and from current models of high-energy physics, which also based on what we can measure and on what we consider reasonable extrapolation. This is fine, and is a necessary approach to push the boundaries of knowledge into realms unknown. But at no moment we should forget the limits of this framework and claim that we know how to conceptualize the origin of the universe. Bringing in the multiverse and stating that it is eternal, and that our universe is a sprouting bubble from it doesn't bring us closer to a solution.
It doesn't seem to me that science, as formulated nowadays, can come up with a solution to the question of the origin of the universe.
It can furnish models describing possible scenarios, and those are excellent tools to push the boundaries of knowledge to earlier and earlier times, in the hope that observations and data will guide us further. However, this is different from explaining the origin of life through complex chemistry. To explain the origin of everything we need a science capable of explaining itself, the origin of its laws, a theory that explains the origin of theories. A multiverse is not a way out, given that we would still need the whole apparatus of space, time and fields to describe it. We also can't make heads nor tails of how the laws of nature may vary between its different branches.
The infinite, and its opposite, nothingness, are essential but very dangerous concepts: labyrinths where it is easy to get lost, as Jorge Luis Borges reminds us in his Library of Babel.
Now, to identify a conceptual difficulty is often blamed as a defeatist position. Should we give up then? Of course not. Knowledge only advances if we push it forward and take risks to do so.
What is at fault here is not our drive to make sense of a deep mystery through reason and scientific methodology. This is what we do best and is the only way to push forward. What is at fault is to claim that we know much more than we do and that we have understood things that, at a moment's reflection, we are clearly far from understanding.