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Hunting Down the Universe by Michael Hawkins
Robert Taylor describes astronomer Michael Hawkins and his quest for dark matter.
Imaine you’re on board an aeroplane at night. You look down and see nothing, just darkness and occasional tiny points of light, some on their own, some in clusters. From this perspective, what could you work out about the sources of the light, the buildings, streets and cities? Now reverse the perspective and look up at the night sky. You see tiny points of light, some in clusters, etc. What can you assume about the sources of these lights? This is how Michael Hawkins describes the problem of being an observational astronomer. In both cases, one can observe, map and correlate, but the picture that is built up may in fact be fundamentally distorted.
Perhaps because of this uncertainty, Michael Hawkins is an astronomer with a strong philosophical interest. His book, mainly a personal account of his astronomical work, sets out to demonstrate the importance of philosophy to modern science. There can’t be many modern scientists who would describe the methodology of 20th century science in terms of the work of Plato and Aristotle, but that is typical of Hawkins’ unconventional, acerbic approach. He points out that Nobel Prizewinning work on cosmic background radiation was actually done by two Bell telephone engineers and also accuses the multi-billion pound Hubble Space Telescope of producing little more than pretty pictures. Hawkins explains with a vigorous relish how science is a human process, driven by ambition, bitterness and PR, as often as high-minded ideals.
Philosophically, he focuses on the debate between Empiricism (which he takes as deriving from Aristotle) and Rationalism (derived from Plato). Science is generally taken to be empirical – its knowledge is based on experiment or observation and anything which cannot be accounted for directly cannot be proved to exist. However, Hawkins argues that Rationalism (which says that ‘real’ or fundamental knowledge cannot be discovered by observation) is often significant in science, because science is based on theories, not observations. Hawkins is very much against this domination of theory. He takes the now-dominant idea that the Universe began at a single point and has been expanding ever since – the Big Bang theory – and examines its origins. Initially, he says, the Big Bang theory offered very little advantage over the Steady State theory (which presumes the Universe to be static and infinite). In particular Big Bang was based not on positive observational data, or even observational failure of the Steady State theory, but on purely theoretical developments. Really then Big Bang versus Steady State is a debate about metaphysics as much as science. Hawkins points out that different conceptions of religion have inclined astronomers toward the Steady State or the Big Bang pictures of the Universe.
Throughout the book one can sense Hawkins’ combative, argumentative personality. The jacket explains that he is one of the few people to survive both a plane crash and a lightning strike (presumably not at the same time). And although a ‘Big Bang believer’, he attacks the adoption of Big Bang purely on faith. He points out that although it did not have any significant observational support for over ten years, in that time it became accepted and grew to dominate the scientific establishment to such an extent that once-influential astronomers, opposed to Big Bang, were forced out of the profession, unable to obtain research time or academic positions.
The problem is that at the Big Bang, all matter was compressed into a single point. The Universe then began to expand, and as the matter in it is stretched out over a greater and greater area, so its density decreases. However the Universe as we know it has achieved some kind of balance between expansion and density that stops either the expansion overcoming the density (sending all matter flying off into infinity), or the density overcoming the expansion (pulling all matter back into a singularity). So the Universe is at a critical balance. Working out precisely what these proportions are has been extremely difficult. The rate of expansion, average density and age of the Universe are all linked. Unfortunately the age of the Earth according to the geological record has often been much greater than the age of the Universe predicted by astronomers. Furthermore if the Universe is as incredibly old as is now suggested (up to 18 billion years old), then its average density would not be enough to balance the expected rate of expansion ? the Universe should have been much bigger by now.
Astrophysicists have struggled for years to factor in a purely theoretical ‘cosmological constant’ to restore the balance. Another suggestion is that there is much more matter in the Universe slowing down the rate of expansion. This ‘dark matter’ is non-atomic, non-reactive stuff and impossible for us to experience.
This is where Hawkins’ own work came in. Or rather didn’t, because although he was aware of the difficulties in balancing the Universe his own work was, as one might expect, in a much more observational area, far removed from speculation about unknowable realities. He was measuring the observed variation of light from incredibly distant, incredibly bright bodies known as quasars and concluded that although the variation couldn’t be explained as intrinsic to the quasars, yet there was nothing in their path to us that could account for it, either.
Over a period of seventeen years and without any idea of what he was looking for he became convinced that this ‘missing dark matter’ did exist and was causing the variation in light from the quasars in an effect known as ‘gravitational lensing’. Basically these dark bodies were so dense that they were bending light around them – causing the variations.
Philosophically, this is interesting because it shows the Popperian model of theories tested by experiment is not always accurate. Hawkins was not testing a theory – he didn’t know what he was looking for and didn’t realise the significance of what he found.
“There was no specific theoretical prediction that primordial black holes existed in abundance …. Therefore the implications of my discovery came as a complete surprise.”
This is also philosophically interesting because it opens up the ancient rationalist /empiricist debate, at the heart of a new, original scientific theory. Hawkins’ philosophical preoccupations are much more than idle speculation; they have significant effects on his astronomical work. Hawkins is at heart an empiricist, he styles himself as an observational astronomer and he clearly admires Wittgenstein and the positivist quantum theorists. Yet if he follows this line all he can say is that certain light sources have been observed to have a certain variation. He can’t say anything about what he believes to be the cause of this variation and his work can’t have much effect on solving the ‘balance of the Universe’ problem. To have that effect he has to suppose that the Universe is mainly composed of black holes that are fundamentally unknowable; non-atomic and non-reactive, one can only make assumptions about them based on their absence from the atomic world. This seems frighteningly ‘Platonist’: the Universe is really organised in a way we can know only in theory.
Michael Hawkins’ book tells a wideranging and extremely absorbing story, in a way that’s sometimes serious sometimes sarcastic but always readable. I’d recommend it to anyone with an interest in contemporary astronomy and philosophy of science.
© Robert Taylor 1998
Robert Taylor has a BA in Philosophy and an MSc in Logic and Scientific Methods. He earns a living as a television script-writer and is currently writing episodes of the cult BBC 1 children’s show ChuckleVision.
Hunting Down the Universe by Michael Hawkins is published by Little, Brown and Company; price £18.99