21 October 2006

Scale confusion

The View From the Centre of the Universe: Discovering Our Extraordinary Place in the Cosmos, by Joel Primack and Nancy Ellen Abrams

Let’s try an experiment. Take a piece of chalk and draw a circle around yourself on the ground. Think of something else for a minute. Now look down. You’re in the middle of a circle! Doesn’t that make you feel special?

This is the recommended therapy for people suffering from a kind of transgalactic ennui. Blame scientists. Ever since they showed that the Earth goes round the sun and not vice versa, humans’ place in the universe has seemed increasingly marginal. As the cosmologist Carl Sagan put it: “We live on a hunk of rock and metal that orbits a humdrum star in the obscure outskirts of an ordinary galaxy comprised of 400 billion stars in a universe of some hundred billion galaxies …” How insignificant we are, on the vast scales of space.

Such is the received wisdom and, like all received wisdom, it is worth challenging. Husband-and-wife team Primack, an astrophysicist, and Abrams, a philosopher of science, understand our pain. They know the temptation of what they call “the existential alternative”, as exemplified by Sagan. They give the feeling a rather beautiful name: “cosmic homelessness”. And they promise to prove, using the latest cosmological discoveries, that the idea is wrong. Science itself, they say, demonstrates that we are actually central to the universe.

The book is a superb pop-science primer on current cosmology. There are gorgeously clear explanations of relativity, dark matter (which Primack was one of the first to propose, and the existence of which seems more likely after recent observations of two distant galaxies colliding), the stages of the universe after the Big Bang and so on. The language is imagistically immediate – “violently relaxed halos of dark matter” – and there are some fruitfully head-spinning thought experiments about reality on galactic scales.

But whenever the authors move from scientific exegesis to the deduction of our centrality, the philosophical rabbit they pull out of their hat crumbles to bits – becomes, as it were, a dust-bunny. We are, for example, said to be at the centre of the “cosmic spheres of time”. It turns out that it just means that we are at the centre of a time diagram, drawn around planet Earth, now. Well, yes, by definition we are. Along the way there have been some striking concepts, such as this one: “Light and other forms of information are already travelling towards Earth and will arrive in 10 years, a hundred years, a million years from now. That information has been on its way for possibly billions of years. Much of our future already exists – it just hasn’t gotten here yet.” That is a pleasingly illuminating thought, but it doesn’t prove our centrality to anything except our own viewpoint.

Another argument goes like this: we are all made mostly from stardust – heavy atoms produced in the nuclear furnaces of stars. But actually the vast majority of stuff in the universe is not like us: it’s dark matter, or dark energy, or interstellar gas. This means that we are at the top of the “cosmic density pyramid”, represented by a shining eye. Why are we at the top of this pyramid? Well, just because the authors have drawn it that way. They could equally have inverted the pyramid and put us at the bottom; or represented our form of matter as a mouldy spot on the surface of a Krispy Kreme doughnut. But that would not have been so inspirational.

There is a kind of promiscuously New Age bent to the book. A whole section considers ancient creation mythologies; there is talk of the Kabbalah, reference to the Norse sagas and speculation about contact with wise aliens who “may have nurtured themselves over millions of years without depending on material growth, instead powering their culture largely by creativity and shared commitment”. Do not wonder, please, how the wise aliens invented radio and space travel while avoiding the vice of “material growth”.

One of the authors’ best examples is the surprising fact that human beings are roughly in the middle of all possible sizes of anything, from the quantum scale to superclusters of galaxies. This, too, is made distractingly fey by drawings and chatter about a cosmic uroboros, a snake eating its tail. Even so, it provides one of the book’s most interesting and useful ideas, that of “scale confusion”. The authors explain how in physics, for example, the strong atomic force is irrelevant outside the nucleus, and gravity is irrelevant at tiny distances (until the very smallest). Things in general are only important at certain scales. Thus the question “Does God exist?” is an example of scale confusion, because “existence” only really means anything at our own size. “On a small scale, do electrons exist? [...] there is no solid thing, only a ‘probability cloud’ [...] In the same way, very large-scale things [such as galaxy clusters or constellations] can only metaphorically be said to ‘exist’.”

Scale confusion reappears in the book’s final section, which seeks to apply our new cosmic insights to life right here, right now. “Since civilisations cannot behave like individuals and vice versa,” the authors argue, “to describe individual acts as civilisational may be a kind of scale chauvinism (the logical fallacy in which a favourite size-scale is considered more fundamental than the others).” Politicians are incontinent scale chauvinists, always muddling concepts of individuals, families, nations and civilisations to deleterious effect. This is a useful observation, well expressed. Other applications of science to society are less persuasive, for example that a mixture of “circular” and “random” motion could help us withstand the “gravity” whereby wealth inevitably clumps together in the hands of a few. The scientific metaphors do not add much to the laudable social concern.

It becomes clear, indeed, that the motivation for making all the dubious claims about our centrality to the universe has really been political. The authors at last confess: “There is nothing in modern cosmology that requires the existential view, nor anything that requires the meaningful view.” But isn’t talk of the “meaning” of the universe analogous to scale chauvinism, a kind of category mistake? To ask what is the meaning of the universe is like asking what is the angular momentum of Much Ado About Nothing. None the less, the authors fear that giving in to “cosmic homelessness” may induce apathy or amorality, so we must adopt the view of universal meaning. In one sense this is like the way proponents of “intelligent design”, because they think that evolutionary theory has eroded our basis for morality, demand that religion in pseudoscientific disguise be taught instead. Of course, Primack and Abrams do not lie about the science: they are on science’s side, and narrate its discoveries brilliantly. But their warm and fuzzy interpretations of it are, finally, a matter of choice and mood. If you feel peckish, there is even a recipe for a chocolatey Cosmic Dessert, which sounds delicious.