It was once possible to do basic science with an absolute minimum of means.

For instance, Archimedes discovered the law of buoyancy, which led to the whole science of hydrostatics, while supposedly watching the water level as he climbed into his bath. Galileo made the fundamental discovery that the period of a pendulum does not depend on the size of its swing by observing a hanging lamp in a church and timing its movements, using his own pulse. Newton founded the whole science of optics with little more than a glass prism, a few pieces of cardboard, and sunlight. The technology needed for each of these advances was minimal, which is just as well, because what was available was primitive.

Over the centuries, the dependence of scientific discovery on supporting technology steadily increased. It is still true that occasional major advances are made with little help from instruments. For instance, we have Alexander Fleming, whose observation in 1928 of the effect of a wind-blown mold on bacteria in a Petri dish led to the whole field of antibiotics. Earlier, in 1896, Henri Becquerel discovered radioactivity through the chance placement of a film plate close to uranium salts.

However, such strokes of luck (and associated genius) are relatively rare. Most advances in science today depend on advanced technology. The science of modern astrophysics would not exist without the spectroscope and the cyclotron, while molecular biology is close to unthinkable without powerful microscopes, X-ray crystallography, and a large array of chemical tools. Conversely, most of today's scientific instruments make use of science that was unknown a century ago.

Science and technology go hand in hand, and progress in one is often impossible without some prior advance in the other. But that is a generality, and rather than working in those terms I thought that I would take a major recent discovery in science, and sketch out, extremely briefly, the widening net of sciences and technologies on which it depends.

Last year, astronomers found evidence that distant galaxies are receding from us, and doing so at an accelerating rate. The idea that the universe is expanding is not new. In 1928, Edwin Hubble proposed that idea, based on the fact that the light from fainter galaxies is shifted toward the red end of the spectrum. In turn, the notion that the whole universe could be expanding grew from the highly abstruse theory of general relativity, devised by Einstein and published in final form in 1916. The question that astronomers were asking from about 1930 onward was, will the expansion continue, or slow down and stop, or even at last reverse and become a contraction? I think it is fair to say that accelerating expansion was a surprise to everyone.

And how was evidence of that acceleration discovered? It came from observations of very distant and very faint stellar explosions known as supernovas. To see such faint objects, large telescopes are needed. The first simple telescopes came into use almost four hundred years ago, when Galileo used one built with his own hands to discover mountains on the Moon and the satellites of Jupiter. However, today's large instruments are anything but simple. They call for their operation on a variety of technologies: precision measuring devices (today we use lasers) to ensure that the telescope mirror is of exactly the right shape; special materials that combine strength with lightness; drive mechanisms that keep the telescope pointed at precisely the right target; and, in the case of spaceborne telescopes like the Hubble, elaborate computer software to schedule experiments, plus communications equipment to send observed data back to Earth.

Many ground-based telescopes depend on the same technologies. The image of the patient astronomer, observing night after night whenever weather and spouse permit, remains true for many amateurs, and a lot of valuable astronomy is performed in that way. However, the big telescopes necessarily operate quite differently. In many of them an actual "observer" is nowhere to be seen. In place of the human eye the telescopes have at their focal plane an array of sensors highly sensitive to light, known as charge coupled devices. Such sensors, focused for hours on a single target, reveal objects far too faint to be seen by any human.

And what is the pedigree of these devices? Like all electronics, they derive from the discovery of the electron, in 1897, by J.J. Thomson. However, that discovery drew on the abstract theories of electromagnetism developed by James Clerk Maxwell in the 1860's and published in 1873.

And how did that scientific theory arise? It grew in turn out of experiments made in the 1830's by Michael Faraday. He used the simplest of means, working with magnets, iron filings, hollow metal cans, and rotating copper disks. However, from those experiments, from Maxwell's theories, and from practical uses of the electron, grew all the supporting technology needed to make today's delicate observations with large telescopes.

Of course, observations in this case are not the end of the story. Massive amounts of calculation were needed to reduce and make sense of the data. That could not be done without computers, themselves another line of descent from Faraday, Maxwell, and Thomson.

The sequence sketched out here, of a scientific observation or experiment leading to a new theory, which leads to a new piece of technology or makes possible a new and more delicate experiment, is absolutely typical of the way that science and technology interact, each one leapfrogging over the other to provide advances. This strong inter-dependence is the reason why most crank ideas in science are doomed to fail. They seek to reject some single basic notion of science, but do not recognize that such a rejection affects everything else. All the sciences and the technology derived from them are inextricably linked together.

In some academic (but non-scientific) circles, it has been popular in recent years to suggest that modern science is "just one more way of looking at the world," with no more validity than any other point of view. Anyone promoting such ideas ignores two basic facts. First, technology based on science undeniably works, to the point where we take it for granted as part of our everyday life in everything from televisions to toasters. And second, you simply cannot divorce the technology from the science that underpins it, and conversely. You can't have one without the other.

This is not to suggest that all science is good, or even that everything which claims to be science is real science. There's plenty of junk science around, and you don't have to look hard to find it. More on that next week.

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