Notes from Under Sky

How Wrong is Wrong?

Everything you know is right again—sort of

Something happened recently that reminded me of one of my pet peeves—in science in general, but in astronomy in particular. I'll open with a quote from Isaac Asimov, from an essay of his called "The Relativity of Wrong" (an F&SF essay), which ought to be required reading in schools. (It ought to be, but it sure isn't.) He wrote:

"He [John Campbell, his editor at Astounding] also told me that all theories are proven wrong in time.
"My answer to him was, 'John, when people thought the Earth was flat, they were wrong. When people thought the Earth was spherical, they were wrong. But if you think that thinking the Earth is spherical is just as wrong as thinking the Earth is flat, then your view is wronger than both of them put together.'"

That, in a nutshell, is my pet peeve: the contention that what we know today will surely be proven wrong tomorrow, because that's what happened yesterday. That contention relies on the proposition that if something isn't totally right, then it must be wrong. That's not true. There is, as Asimov puts it, a relativity of wrong.

Thus, for example, Einstein showed that Newton's rules of mechanics are inaccurate for large masses and high speeds. Does that mean that Newton's rules aren't taught today in classrooms? Of course not. Einstein's rules are also taught today, but Newton is taught before them. Einstein's theories of relativity are considered by many to be revolutionary, but if so, they are philosophically revolutionary, not quantitatively so. They do not invalidate Newton's rules, and they shouldn't be expected to. Almost everything in our experiences is captured very well indeed by Newton.

In turn, Newton, in his Principia Mathematica (and in De Motu Corporum before that), based his theory of gravitation on the empirical laws of planetary motion put together by Johannes Kepler. Kepler stated three laws, which are, briefly:

  1. Planets travel in elliptical orbits, with the Sun at one focus.
  2. Planets in their orbits sweep out equal areas in equal times. (In modern language, angular velocity is conserved.)
  3. The cube of a planet's orbital period is proportional to the square of its mean distance from the Sun (its semi-major axis, that is).

But Newton showed that planets do not exactly travel in elliptical orbits. Instead, the other planets perturb those orbits, causing the planets to speed up at some points, slow down in others, and thereby change the shape of the orbits, however minutely. Does this mean that Kepler's laws are not taught? Of course not. Kepler's laws are taught in any course where planetary orbits are examined in any significant detail. That's because they are pretty darned effective.

Kepler, of course, obtained his rules in attempting to validate both his idea that the spacing between orbits is determined by Platonic solids (which did turn out to be wrong), and the Copernican system. Kepler showed that the Copernican system, with its circular orbits, its equants, and its epicycles, was wrong. Does that mean that the Copernican system is not taught at all? Of course not. Our earliest exposure to the solar system (at age eight, say) shows it to be an orderly system, with the Sun in the center, and the planets—including the Earth—travelling in circular orbits around the Sun. We don't teach the epicycles and equants anymore, because Kepler showed them to be an inaccurate portion of the Copernican theory. But the central insight—that the Sun is the center of the aptly named solar system, that the planets travel around it, and that the Earth is just one of them—is retained, and rightly so.

Furthermore, these theories—Copernicus, Kepler, Newton, and Einstein—are taught in roughly that order (although Kepler may be taught more as an aside, sadly). We learn Copernicus in primary school, Kepler and Newton in secondary school, and Einstein (seriously, not as a sampler item) in college. Still furthermore, they are not taught as theories that demolish the preceding theory and supplant it utterly, but as successive refinements. Copernicus's theory is accurate to degrees, Kepler's to arcminutes, Newton's to arcseconds, and Einstein—well, we haven't yet found an inaccuracy in Einstein. That doesn't mean one won't be found, of course, but if and when it is, that won't necessarily make Einstein wrong. It will probably mean that some refinement to his theory has been found that is almost undetectably small under most circumstances.

Nor is this sequence isolated in the history of science. The central insight of Darwinian evolution—that the mechanism of evolution is natural selection—is retained today in education. Does that mean that Darwin (and Wallace) had it right in every detail? No. They could not benefit from most of the observations and investigations conducted over the 20th century and into the 21st. There is today considerable dispute over many details of evolution, over which there may be no consensus for some time. But despite how the situation is often portrayed in the media, natural selection as the predominant mechanism is in little danger of falling by the wayside. It will be taught in schools for as long as we can foresee.

Scientific theories are built like cities, with most structures remaining in place, perhaps being updated while new ones are created around them. Ever so rarely is an entire city simply razed to the ground and created anew, like Troy.

That this is so frequently misunderstood is, I think, a consequence of the uneasy relationship most of the public has with science. They appreciate its results, but they are reluctant to get their hands dirty with the process. Instead, they let the media interpret the process for them. Given that scenario, it would be unexpected if misconceptions didn't arise all the time. But things don't have to be that way, and that's why I may seem so aggressive in explaining matters—here, and elsewhere.

Copyright (c) 2003 Brian Tung