Geraint Lewis and Luke Barnes’s lucid, fast-paced, and funny new book might best be summed up in their own words: “Our conclusion is that the fundamental properties of the Universe appear to be fine-tuned for life.” As the authors carefully explain in A Fortunate Universe: Life in a Finely Tuned Cosmos, it doesn’t matter whether other kinds of life are out there. It’s enough that there is life here on Earth to raise the question of why the universe is the way it is, seemingly fine-tuned to allow for life. After all, in the vast parameter space of hypothetical universes, life is a tight fit. Change the fundamental constants, or the basic laws of physics, or the low-entropy, free-energy-rich initial state of the universe, and the story on Earth would have been radically different. Life has very little wiggle room.
The fine-tuning problem tends to elicit strong responses. Some physicists are casually dismissive, claiming it’s a nonproblem: What else could the fundamental constants be? They are what we measure them to be, period. Others extrapolate beyond current experimentally validated theories. Multiple universes may exist in addition to ours, and in them the values of the fundamental constants might differ. If many other universes exist, it’s not so surprising that in one or a few, the values will conspire to be what they are here. After all, sooner or later someone wins the lottery. We could be a rare statistical fluke in a vast landscape of potential universes. (But how can we know how rare?)
Lewis and Barnes lay it bare for anyone who wants to understand what’s at stake. They find inspiration in this quote from Albert Einstein:
I would like to state a theorem which at present cannot be based upon anything more than faith in the simplicity, i.e., intelligibility, of nature: there are no arbitrary constants . . . that is to say, nature is so constituted that it is possible logically to lay down such strongly determined laws that within these laws only rationally determined constants occur.
That is Einstein’s dream, the ultimate triumph of theoretical physics: a metatheory that explains why the fundamental constants appear to be fine-tuned to have the values we measure them to have. No coincidences or unknowables allowed, only certainty.
Consider, though, that even if scientists were one day to be in possession of such a metatheory, one could ask why nature operates by that metatheory and not another that predicts different outcomes. We end up mirroring the original fine-tuning problem one step removed.
Lewis and Barnes are entirely open about the potential pitfalls of speculative theories. They argue, quite correctly, that we only find if we look, and that’s what we should be doing. Their tone is optimistic and validating. Let’s push current theories as far as possible and see where they lead us, they say. Fill those dustbins with fake universes.
The authors end the book with a theological discussion on the nature of God and on naturalism versus theism. That path may be a turnoff for those with little patience for religious arguments, but it is entirely justifiable given the ontological nature of the fine-tuning problem. When it comes to fundamental questions of existence—in this case, the existence of our universe and its properties—we humans are like a fish in a bowl trying to figure out the nature of the ocean. It’s wiser to accept our ignorance with humility and embrace uncertainty than to claim certainty with blind arrogance and risk future embarrassment.
To make predictions with physical theories, scientists must be able to measure initial conditions of the system under examination: positions and velocities of particles, temperatures and pressures, density profiles and energy levels. But deriving the reasons why the fundamental laws of nature are what we observe them to be seems beyond the scope of what current science can do. Theories depend more on subjective experiences than most of us are willing to admit. As Werner Heisenberg once wrote, “What we observe is not Nature itself but Nature exposed to our methods of questioning.” Try as we may, we can’t jump out of the fishbowl.
Marcelo Gleiser is the Appleton Professor of Natural Philosophy and a professor of physics and astronomy at Dartmouth College, where he directs the Institute for Cross-Disciplinary Engagement. His latest book is The Simple Beauty of the Unexpected: A Natural Philosopher’s Quest for Trout and the Meaning of Everything (ForeEdge, 2016).
