Core changes

Scientific breakthroughs result from seeing the world in a completely new light: take Newton's theory of gravity, for example. But, says Peter Atkins, a lot of cherished notions can be swept aside in the process

The most exhilarating progress in science has come from standing ideas on their head. There's hardly a major idea that has not arisen from thinking inside out. Indeed, the Hungarian-American biochemist, Albert Szent-Gyorgi, made the well-known remark that discovery consists in seeing what everyone else has seen and thinking what no one else has thought.

On the whole, we inhabit the farmyard of experience: progress in understanding involves burrowing beneath the surface and nosing around in the underworld of phenomena. What our noses usually discover is a topsy-turvy word, a world in an intellectual looking-glass, a world with the skin on the inside.

Aristotle, deep thinker that he was, was a farmer when it came to observation. He saw oxen struggling to pull their cart through mud, and concluded that all motion had to be sustained by virtual oxen. He was briefly stumped for an explanation of an arrow's flight, for where were the oxen? He concluded that vortices in the air behind the arrow would act as aerial oxen and sustain its flight, and concluded that an arrow in a vacuum would flop to the ground.

Of course, we now know – through Galileo's more percipient eyes and Newton's astounding power of analysis – that exactly the opposite is true: an arrow is impeded by the vortices it spins off, not impelled.

There are many more subtle examples of inversion giving rise to elucidation. Physics is thick with them, and it is unnerving to consider the likelihood that in some future development of the subject, our currently most cherished concepts will also be inverted. A fine example of the overthrow of cherished concepts is the Second Law of Thermodynamics, which states, broadly speaking, that "no engine can convert heat completely into work". Now, I'm aware that the mere mention of the Second Law is generally held to be the epitome of scientific scariness. Yet CP Snow held it up as the litmus test of scientific and, indeed, general literacy, remarking that not knowing the Second Law is like never having read a work by Shakespeare.

When presenting thermodynamics to my own students, I try to unglaze their eyes by remarking that no other scientific law has contributed more to the liberation of the human spirit. They snigger, but I mean it. For my present purpose, though, I shall avoid that flight of heartfelt passion, and use the Second Law merely as an example of being inside out. In fact, the Second Law gives us a double dose of inside-outery. When you look at a steam engine, the crucial parts are obvious: there is the boiler and the bits involving a piston. A great deal of thoughtful design goes into both, for the aim is to achieve economy and efficiency. It comes as a complete surprise, perhaps, that when scientific eyes are directed at this elaborate contraption, they identify the undesigned as the bit that really counts.

Szent-Gyorgi's Victorian predecessor, William Thomson (Lord Kelvin), saw what everyone else had seen but no one else had thought, and realised that no steam engine could operate without an outside world to dump waste heat into. His version of the Second Law is that every steam engine must discard some heat: it isn't the flow of heat into the engine that drives it, it's the flow of heat out of it that does so.

The second revolution illustrated by the Second Law is that it dashes the illusion that things get better. I can accept that in today's global climate, few people consider that the world is getting better; but I mean something more than that. It's undeniable that some things do seem to get better: plants grow and come into flower; children eat and grow; we perform actions, such as sculpting a great statue; and we form opinions. More globally, evolution has brought us from less than a single cell of yestergigayear to the awesomely complex assembly of a hundred trillion cells that constitutes each of us today. In that sense, the sense of abating chaos and resulting in complex structure, the world certainly seems to be getting better.

But that is an illusion: it is getting worse. And what underlies that remark is once again the Second Law, for that law exposes to us the spring of creation. We see through its eyes that the world is driven forward by the collapse of matter and energy into ever greater chaos. However, and this is the crucial point, that collapse is not uniform. The world is a web of interactions, an elaborate network of intermeshing gears, so that although there is an overall purposeless, the intermeshing is such that, here and there, as at you and me, there are local abatements of chaos where temporary local structures – proteins, houses, symphonies, wars, carrots, opinions, whole biospheres – are formed.

Inversion of the obvious has also occurred in biology. The most relevant to this year's celebration of the anniversary of the discovery of the structure of DNA in 1953 is the realisation that DNA had anything at all to do with replication and inheritance. At the beginning of the 20th century, proteins were all the rage, and as their structures became clear – a literature spun from 20 amino acid "letters", much as the whole of boundless English literature is spun from 26 letters – people were convinced that proteins held the key to inheritance, for only they seemed potentially rich enough in information.

Lurking in the background of studies of the protein-rich cell nucleus was another substance, a nucleic acid of unknown overall structure but of apparently much more limited variety of composition, made up of only four units rather than the 20 of proteins. It was presumed that this nucleic acid was a mere structural component of the nucleus, rather like the even more boring cellulose of plants.

Then, slowly, it was revealed as the supermolecule of modern times. In a series of experiments culminating in the work of Watson and Crick, one of these nucleic acids, deoxyribonucleic acid, DNA, emerged into the world as the most important molecule of all, the depository of the human race. The revolution that began when proteins were found to be but worker molecules to this queen, is with us still: it has made biology a rational subject, brought it into the orbit of the physical sciences, and promises to do the same for medicine and agriculture.

Albert Einstein also turned physics on its head, most famously with his theory of gravitation, general relativity. His was the most elegant revolution of all, for his theory of gravitation was to eliminate it. Perhaps all great progress in science is the elimination of questions by looking at them from a new perspective. Isaac Newton had established gravitation as a universal force emanating from massive bodies, but had felt uncomfortable at its mysterious action at a distance. We all know the fact of its local existence, as we struggle with it every time we stand up and relax into it when we sit down. But we have taken the farmyard view: Einstein indulged in inside-outery on a grand scale, and said that universal gravitation is an illusion: there is no such thing as gravity.

Instead, there is "curved spacetime". What we see as bodies – us, projectiles, planets – moving in curved space under the influence of gravitation is actually the motion of bodies in straight lines through spacetime that has been warped and twisted by matter. His other great achievement was to calculate the warping of spacetime and to relate it to the matter it contained.

There is a similar process of replacing the obvious to achieve ultimately a greater simplicity (which, after all, is what fundamental science is all about) currently under way. We farmers all know that we inhabit four-dimensional spacetime, with three dimensions of space and one of time the arena for all our actions.

But the view is emerging that even that is an illusion. The universe is a simpler place to describe, in the sense that the particles and the forces holding them together are fewer in number, if we adopt the view that there are actually 11 dimensions of spacetime, and that at the event that we call "the creation", seven of them did not wake up in time and were left tightly furled, leaving us with the illusion that there are only four.

Scientists are hewers of simplicity from complexity. They seek the simplest possible view of creation in all its wondrous forms, the minimalisation of concepts but with the retention of the potential for unbounded complexity. If that involves overturning our most cherished concepts based on coarse observation of the everyday, so be it. True understanding is worth any cost in comfortable familiarity.

Peter Atkins is professor of chemistry at Oxford University and a Fellow of Lincoln College, Oxford. His book, 'Galileo's Finger: The Ten Great Ideas of Science' is published this week by OUP (£20)