The conjecture of "fine-tuning"...and "cosmopsychism"?

            A persistent claim in what one might call the philosophy of cosmology is the supposed “fine-tuning” of the constants of physics to conditions we consider suitable for sustaining living things. Consider, as a representative example, the introduction to a recent essay by Philip Goff in Aeon:

In the past 40 or so years, a strange fact about our Universe gradually made itself known to scientists: the laws of physics, and the initial conditions of our Universe, are fine-tuned for the possibility of life. It turns out that, for life to be possible, the numbers in basic physics – for example, the strength of gravity, or the mass of the electron – must have values falling in a certain range. And that range is an incredibly narrow slice of all the possible values those numbers can have. It is therefore incredibly unlikely that a universe like ours would have the kind of numbers compatible with the existence of life. But, against all the odds, our Universe does.

            Goff goes on to interpret this “fact” of fine-tuning as support for “…the idea that the Universe is a conscious mind that responds to value.” In his view, the Universe has a clear telos – the production of intelligent life. Given how central “fine-tuning” is to Goff’s claim, one might be forgiven for more closely examining the basis for his probability argument – the likelihood of a given universe having physical constants compatible with intelligent life.

            Probability, in its simplest form, is a calculation of the likelihood of a particular outcome given the range of possible outcomes. If, for simplicity, we assume that all potential combinations of the physical constants are equally likely, then the probability of getting a universe that can support intelligent life is a simple ratio: the number of possible universes that we judge could potentially support such life, divided by the number of possible universes. To get to Goff’s conclusion that this outcome is “incredibly unlikely,” we have to know both how many possible universes there are, and how many of them could support intelligent life. In terms of the constants in the laws of physics (those parameters that must be measured empirically, rather than calculated from theory), we need to know what range of variation is possible for each constant, and how much of that variation is compatible with intelligent life. This is where we get Goff’s basic claim of “fine-tuning” - “that range [of values of physical constants] is an incredibly narrow slice of all the possible values those numbers can have.”

            A crucial assumption in this view is that physical constants could potentially vary at all. Goff argues, for example, that we are fortunate that the parameter 𝛆 - representing the efficiency of the fusion of hydrogen to helium - has the value 0.007, since a universe where 𝛆 was slightly larger or smaller would have either very little or only hydrogen. However, the fact that we can simply substitute other values of 𝛆 in our equations hardly demonstrates that other values are actually possible. Further, nothing in our actual experience suggests that 𝛆 can vary; in fact, it seems to be the same everywhere in the universe (the fact that we can observe stars across vast separations in distance and time being but one example). Taken from another perspective, it would be truly remarkable if a parameter like 𝛆 could have a range of values yet somehow always turn up with the same value whenever we measure it. To claim “fine-tuning” is to claim that some entity could adjust the value of parameters like 𝛆; it takes a remarkably imaginative line of thinking to argue that our base assumption about a parameter should be that it is a variable, when all our experience suggests it is a constant.

            This is not new territory, either. In the late 17^th and early 18^th centuries, ingenious observations of Jupiter’s moon Io by Ole Rømer – and conversions to absolute distances by Christian Huygens – showed that the speed of light in a vacuum was both finite and quite fast – about 220,000 km/s, as compared to the modern value of 299,792 km/s. One could have wondered why the speed of light had that particular value…until around 1864, when James Clerk Maxwell calculated what the speed of light had to be if it were an electromagnetic wave. The only speed compatible with mutual electric and magnetic induction – and with the conservation of energy – was remarkably close to the observed results. Before Maxwell, one could have imagined light having many potential speeds and wondered about their consequences, but after Maxwell those flights of imagination were simply implausible. Physics explained why light had one particular speed – the speed toward which experimental measurements were rapidly converging.

            Even if we were to grant that the constants could vary, it is rather difficult to determine how much variation “fine-tuning” advocates think is possible. A factor of two? An order of magnitude? Any number we can imagine? A statistical estimate of variation relies on measuring a value many times in a sample to determine how much variation is likely. To estimate potential variation the physical constants, we must measure each of those parameters in many different contexts and calculate a value and uncertainty. For the gravitational constant – which is notoriously variable in its measured value – the variation in modern measurements is on the order of 10^-4, or one part in ten thousand. For the mass of the electron, the uncertainty derived from measurement is on the order of 0.1 parts per billion (depending on which units one uses to express the mass). In that light, considering universes where the electron is 2.5 times as massive (as Goff does) is utterly hypothetical. Or, to put it another way, we have no reason to think that the physical constants themselves could vary outside a remarkably tiny range of values, and that range itself is likely a product of the uncertainty of our measurements. The careful reader might fairly object that this is simply a restatement of the remarkable constancy of the measured parameters in physics. That is precisely the point.

            Thus the denominator in Goff’s hypothetical probability calculation – the range of possible combinations of the physical constants – is actually quite tiny; from an empirical point of view, only a minuscule range of the values we can imagine correspond to observations of the actual Universe. If the constants are truly constants, the denominator is simply one – ours is the only possible version of the current laws of physics. But what of the numerator – the portion of possible universes compatible with intelligent life? Here again, proponents of fine-tuning are rather vague on their probability assessments for a rather simple reason: we have almost no grounds to evaluate what kinds of universes could support intelligent life in principle, because we cannot possibly imagine all the ways intelligent life could arise. When we think of life in other universes (or even on other planets), “suitable for intelligent life” is usually shorthand for “suitable for life that uses solar energy to convert carbon dioxide and water to oxygen and carbohydrate, later releasing energy in the oxidation of that carbohydrate; most likely using a particular set of nucleotides to encode information and translate that information into protein macromolecules; organizing independent subunits (cells) into hierarchies which can specialize to the degree that a complex internal model of the outside world is represented inside the resultant organisms.” In other words, we are quite good at enumerating the requirements for the intelligent life we know best (humans), but our particular case does little to delimit the range of possible ways to get intelligent life in principle. To do so, we would have to have “comprehensive imagination,” a complete understanding of all the possible ways intelligent life could arise in a variety of possible universes. Our track record of predicting where relatively familiar life might be found on Earth is rather poor (e.g. hydrothermal vent communities); there is no reason to expect our imagination to be any less myopic when conceiving of ways unfamiliar life could arise or produce intelligence.

            In sum, an estimate of the probability of getting a universe that can produce intelligent life (the estimate Philip Goff characterizes as “incredibly unlikely”) relies both on estimating the actual range of possible universes and the number of those universes compatible with intelligent life. Fanciful speculation aside, we have no empirical reason to think that the constants of the physical universe could be anything else but the ones we know. Further, only an excess of hubris could lead us to think that we are able to comprehensively imagine all the ways intelligent life could arise in a given universe. As a result, we can only conclude that “fine-tuning” is a speculative story, and any assessment of its probability is groundless. If a scholar like Goff wants to postulate a “cosmopsychic” hypothesis of the “Universe [as] a conscious mind that responds to value,” he is more than welcome to do so. Offering that hypothesis as an solution to a problem – the popular metaphor of “fine-tuning” physical constants – only works if we have good reasons to think there is a problem at all. 

Trying to see beyond the telos...

I just finished reading Jim Holt's "existential detective story" Why Does the World Exist?. It's a fun romp through a variety of answers to the ultimate question in philosophy; particularly striking (to me, at least) is the way so many of the answers end up projecting our human desires onto the universe rather than examine the universe on its own terms. From the infinitely good creator of Richard Swinburne who nonetheless acts very much like a human parent, to the "ethical need for a universe...full of happiness and beauty" of John Leslie, human values and analogies pepper many of the expeditions searching for some ultimate telos (Aristotle's term for the final cause or purpose) for the universe. But should we really expect the existence of the immense universe of which we are but a tiny part to be explained in terms of human values and characteristics?

Aside from the really absurd notions such as strict creationism, the best current example of this philosophical narcissism has to be the notion of the Strong Anthropic Principle. This line of thinking extrapolates from the rather obvious assertion that we must be living in a universe that is compatible with our survival (the "weak" anthropic principle) to a full-blown assertion that the universe was set up with the purpose (telos again!) of producing intelligent beings like us. There is more to the Strong anthropic principle than just the bald assertion, of course; the key point is the supposed "fine-tuning" of the constants of the physical universe to the conditions of human existence. There are 25 physical constants in the Standard Model of quantum mechanics (add another for the cosmological constant so we can use gravity). The value of these constants are not defined by theory; instead, they must be measured experimentally. Small changes in most of those constants would result in radically different universes, many of which look to be incompatible with the survival of any of the living things we know. Advocates of the Strong Anthropic Principle claim that those constants must have been carefully adjusted to the values we measure to produce a world in which humans could live. Put simply, the Strong Anthropic Principle claims that the universe was literally set up to suit us.

The claim of fine-tuning does, however, have some serious shortcomings. Statistically, it cannot be evaluated; our sample set of possible universes includes exactly one, which means we have no way to judge how much the physical constants can vary among possible universes, or if they can vary at all. While there is some intriguing evidence suggesting that the fine-structure constant shows very small variations in time and space within our universe, we are still stuck with a sample of one. In other words, we currently don't know whether there is a knob for fine-tuning, say, the strong nuclear force attached to our universe, and the metaphor of an entity carefully adjusting these 25 physical constants is completely hypothetical.

Since we have not observed variation in the constants, we are left with evaluating the plausibility of fine-tuning. An advocate of the idea could do pretty well sticking with the existing Standard Model of quantum mechanics, arguing that there are quite a few (25 is a lot) fundamental quantities that are not defined but merely measured. Within the mathematical framework of the Standard Model, nothing prevents us from adjusting the charge of the electron to a different value and working out how the universe might look; in general those changes produce hypothetical universes where atoms disintegrate, stars fail to form, hydrogen is fused to helium far too rapidly to allow life to evolve, etc. In other words, if we assume that constants not defined by our physical theories are free to vary, then it can seem very fortunate for us that our universe includes values for those constants that allow our species to survive.

That is, however, a big assumption. There is no particular reason to assume that a quantity that must be measured rather than defined by theory has an arbitrary value. Indeed, the history of science suggests that things which could only be measured at first were later defined by theory. One can recall, for example, the huge number of undefined values in the ancient Earth-centered cosmos, from the distance to the stars, Moon, Sun, and other planets, to all the various mathematical devices like the epicycle used to calculate their complex apparent movements. Compare that multitude of observed properties to Kepler's Sun-centered laws of planetary motion, which define the positions and movements of objects in the Solar System much more precisely, with far fewer values simply measured from observation. Another great example is the periodic table in chemistry. Before the periodic table, it might be easy to marvel that iron has the particular chemical properties it does, making possible, for example, the ability of red blood cells to bind oxygen from air in the lungs. Those properties (atomic weight, valence, etc.) could be measured, and one could argue that it was extremely fortunate for living things that iron was present on the earth with precisely those chemical properties. After the periodic table, however, the properties of iron (and all the other chemical elements) are not arbitrary or fortuitous, but rather part of a systematic series, the result of atoms formed with equal numbers of electrons and protons (and later, with quantum theory, neutrons which are compatible with a stable nucleus). The alchemist's pure empiricism, with lost of characteristics of elements to remember, is replaced with a model which predicts many of those characteristics, as well as the characteristics of elements not yet discovered in nature. There is no reason to assume that the Standard Model is the last word in physics, either; its limitations (like its incompatibility with general relativity) are well-known. If the history of science has anything to tell us, it is that the theory that replaces the Standard Model is likely to define many more of the constants that can currently only be measured. Just as we no longer marvel that potassium has exactly 19 electrons, we may find the particular value of many of the constants in the Standard Model to be predictable in a future theory.

Let's grant the big assumption, however, for the sake of argument. What if the constants could vary? Then we should feel either very lucky that they took the values they did, or we should be grateful for the supreme being that fine-tuned them to suit us so well. Otherwise there wouldn't be any intelligent life, and the universe would be a pretty desolate place...right?

If we're wedded to the idea that intelligent life should look like us, perhaps. It would be tough for life as we know it to exist with very different values for the constants (although not, as Victor Stenger and Fred Adams have shown, for all such changes). Note the phrasing: life as we know it. We know a lot about the range of life forms that have flourished based on organic chemistry, a phospholipid bilayer membrane, and a nucleic-acid genetic system on one rocky planet orbiting a small main-sequence star. Are we really so arrogant as to think we know all about how intelligent life can form in general? We can say with some certainty that the examples of life we are familiar with could not tolerate big changes in the constants, but we cannot seriously think that our imaginations are fertile enough to deduce all the forms life could take, and rule them out in all the hypothetical universes created by varying the physical constants.

This kind of provincial thinking - that if we cannot imagine something, it must be impossible - is common enough to have a name: the philosopher's error. It is a product of extrapolation, of projecting the way we work and think onto the world beyond us. When we think of life on other worlds, we tend to think of it in ways remarkably similar to ours (for instance, our obsession with liquid water on Mars). Even on Earth, we can be surprised by life harvesting chemical energy from hydrothermal vents on the ocean floor (rather than from sunlight). We should be more honest with ourselves about the limits of our imagination.

Finally, we need to understand that life as we know it isn't some fixed entity that could only match certain physical conditions. Life evolves to better fit its physical environment. We could imagine a narcissistic fish contemplating how well-designed the ocean is to flow over its gills; how well-suited the viscosity of water is to flow smoothly across those gills; how well-balanced the salinity of the ocean is with that of the fish's blood. Imagine the fish's shock when we explained that the fish itself had evolved to better match the characteristics of the ocean! Douglas Adams came up with an excellent metaphor for the problem, published in his posthumous work The Salmon of Doubt:

This is rather as if you imagine a puddle waking up one morning and thinking, 'This is an interesting world I find myself in — an interesting hole I find myself in — fits me rather neatly, doesn't it? In fact it fits me staggeringly well, must have been made to have me in it!'

Not only could life plausibly exist in many more ways than we can imagine, it could likely evolve in many more ways to fit its environment, whatever that environment might be.

The thinking behind the Strong Anthropic Principle is just one striking example of the pervasive anthropomorphic strain in human thought. We take concepts that work quite well in human social relations (such as the concept of the purpose of a person's actions) and apply those concepts to the universe far beyond that social context. Nevertheless, humanity has managed to move, in the last five hundred years, from a cosmos centered on us, to a cosmos centered on the Sun, to a cosmos with no particular center. Knowing that our planet orbits one of a hundred billion stars in one of roughly five trillion galaxies (in the visible universe), shouldn't we finally have the humility to realize that the universe is not constructed around our needs? Can we finally stop projecting our human concepts on the universe, and instead accept it on its own cosmic terms?