The description of new discoveries in science is often stated in terms of overturning old ideas or worldviews. Copernicus and Galileo, we often say, overturned Aristotle’s views of the universe with the earth at its centre. Einstein overturned Newton’s laws of motion. This gives the misleading impression that all scientific knowledge, understanding and theories are unstable, and may be overturned in the next century. As a result, scientific ideas, even solid ones, are mistrusted in today’s climate of uncertainty, conspiracy theories, postmodern distrust of authority and truth, and the popularized view that science equates to an atheist agenda (backed up by fundamentalists on both sides).
I stated in my book (page 53) that, although there is the potential to debate any scientific description of the universe or part thereof – science is open, not closed – in practice, almost all advances in science have changed parts of our previous understanding and not the whole. Scientific thought in the popular media at one time appeared to swing wildly between whether eating cholesterol, sugar or fat was good or bad for your health. However, the research kept refining the debate in terms of where the cholesterol comes from, how much sugar, and what sort of fats may be good or bad for you, and the specific health effects involved. Thus the scientific debate progressively narrowed, defining the situation in more and more detail. People now rarely debate whether fats are good or bad for you, but more specific questions – e.g. whether omega-3 fatty acids protect against heart disease, and if so how much is beneficial. Has the idea that eating fats is bad for your health been overturned?
In short, no. We have long known that we need fat in our diet, and the real questions are how much and what sort. The earlier crude debate (as pitched by the media) had no simple answer, and so in those days experts could quite rightly be quoted as giving evidence that fats were good for you (some are in certain quantities) and the media could find others who proved that they were bad for you (some are, in excess). Meanwhile, researchers focused on the details in the biology of fats. But the layperson could be excused for thinking that scientists “could not agree”, and conclude that science was not to be trusted in giving you advice about what to eat. They said fats were bad for you, and now a few years later they are saying some fats are good for you, while my doctor says I am eating too much fat. Trust your grandmother’s advice, or alternative authorities – people who seemed to be more confident of their advice than the scientists.
Karl Giberson, in his excellent book The Wonder of the Universe, states that “The most difficult part of science for an outsider to navigate is scientific controversy.” He also points out that “overturning” previous ideas is an exaggerated figure of speech. When we say that Copernicus and Galileo “overturned” Aristotle’s view of the universe, we are not saying that all of a sudden people realized the earth was round not flat, or bigger than they had thought, or that they described different seasons for the first time, or that they came to believe that sunrise was in the East. The one critical thing Copernicus and Galileo suggested was that the sun was the centre of the planetary orbits, rather than the earth. Most other ideas did not change at all. For instance the earth had been known to be spherical since the Greek astronomers, and its circumference was calculated at the equivalent of about 40,000 km by Eratosthenes, two centuries before Christ. None of this was called into question by Copernicus and Galileo. The sphericity and circumference of the earth stood the test of time, and still does so.
Now of course we have refined Eratosthenes estimate to 40,075.017 km (at the equator), and 40,007.86 km at the meridian, and we can see from those figures that the earth is not a perfect sphere as thought at one time, but is wider at the equator and flattened (by a few kilometres) at the poles.
Have we, by refining the measurement and the shape, “overturned” Eratosthenes? To all intents and purposes, no. The few kilometres difference in distance, and the slightly less than perfect spherical shape made absolutely no difference to them, or to most of us. If you were trying to decide whether you could walk around the earth, or take a ship or even a plane, there would be far more uncertainty in your route, because of land and sea, and currents, winds and storms, not to mention riots and wars and airspace permits, than from the few kilometres difference between Eratosthenes’ estimate and ours. Only when you consider global satellite positioning systems, and detailed geophysics and astronomy measurements, does the difference become really critical.
In a similar way, Copernicus’s and Galileo’s calculations were refined by Kepler; the understanding of the planetary orbits were refined by Newton; Newton’s laws of motion and gravity refined by Einstein to adjust for extreme speeds and energies. The 19th century naturalists’ understanding of development of species, was refined by Darwin, whose ideas have been subsequently refined by the discovery of genes, DNA and mutations. The 18th-19th century geologists’ estimates of the great age of the earth have been refined by radio-isotope dating methods, which agree with cosmological estimates of the age of the solar system.
Science is open, and can change, but change in overarching explanatory theories is slow and requires a change in consensus. In medieval times questions about the world were answered by appeal to logical proofs, to authority (such as that of Aristotle, or the Bible) and to common sense experience. That worked up to a point but it did not have a mechanism for correcting persistent misconceptions or for breaking new ground, and developing new technology. It’s hard to show new findings – Jupiter’s moons, for instance – to Aristotle and see whether he would change his opinion, so we are stuck with what he said and thought in his lifetime. Logic, authority, and common sense, on their own, tend to close ranks and prevent new ideas and observations from progressing understanding.
These days logical deductions and calculations provide hypotheses rather than proofs, and are tested by observation or experiment. Einstein’s special theory of relativity was logically and mathematically beautiful, but few took it to represent reality until a key prediction – the bending of passing starlight by the sun’s gravity – was confirmed during an eclipse. Now also, authority has been replaced by constant peer review and critique in an open scientific community – consensus, rather than pronouncement has become crucial. And whereas common sense plays a part in scientific ideas, it is more important that new ideas make sense of the world in a more complete and integrated way than the old. Common sense might reject the stretching of time in Einstein’s special theory of relativity, and the action at a distance implied by quantum theory but these theories have made sense of thousands of new observations in situations where Newton’s laws (and common sense) are inadequate. Although Einstein’s theories and quantum mechanics have become well-accepted, physicists acknowledge that they are not perfect and are in need of refinement themselves, because they cannot be readily reconciled with each other.
The proof of the pudding is in the eating. New technology provides solid evidence that science is on the right track, even when that science is rough and ready and in need of refinement. We have proved Eratosthenes by round-the-world plane travel, proved Copernicus and Galileo by the success of the Gregorian calendar, and successful Voyager images of the planets, earth and sun taken from the outer solar system, proved Newton’s laws of motion in almost every transport and ballistic system devised, and proved Einstein in the adjustments in clock speed necessitated by relativity for GPS satellite systems. Similarly we have proved the relationship between species not just at the body shape level, but at a biochemical level, by the successful use of animal proteins, such as insulin (produced by animal genes) to substitute for human insulin, and many others. Even fish and invertebrates produce insulin. Further, we can now successfully manufacture human insulin and other proteins in organisms as different from us as yeast, bacteria and Safflower plants, because their gene and protein making processes are virtually the same as ours. Such practical technologies would have seemed ridiculous and may not have occurred without pursuing Darwin’s and others’ ideas about the relationship between all species.
Giberson states that modern scientific ideas come to be accepted in the end based on what they achieve in predictions, explanations and viable technology, rather than on endless debate about the ideas themselves or what they will mean for philosophy or theology (contrary to the belief of some, they are not preferentially accepted in order to disprove God’s existence).
Thus, almost all changes refine, rather than truly overturn previous ideas. We don’t often think about it but much of our current scientific understanding of the world has not changed since ancient times and is unlikely to do so. A rock dropped from your hand will still go down, and one thrown up and away will follow a curve, observations on which the lives of our prehistoric ancestors depended and which they knew well, even if we, their descendants, can calculate the curve, speed and impact of our ballistic missiles more accurately, and can send them further and with more destructive results.