The AP discussion to which tsaeb refers is
here, on the subject of biological evolution, which began with Paul quoting an assertion by a political columnist that evolution must be accepted on faith because it occurs too slowly to be observed. I noted that there is abundant scientific evidence to support it, but that most of this evidence is, of necessity, "indirect" rather than "direct."
Now, this dichotomy between direct and indirect is somewhat arbitrary and artificial. In other words, "directness" of evidence is a fuzzy concept that would seem to defy classification. Some examples might help.
If you and I go to a pistol range and you see me shoot at a tin can, you will observe that I aim the gun at the can, pull the trigger, you hear a bang, and (if I'm a good shot) see the can fly off its perch at just the same moment. Most of us would hypothesize that the can was knocked off by a bullet from the gun. But did you actually see the bullet fly through the air? Of course not. Is that direct or indirect evidence?
Could the can have been rigged with a hidden string, pulled at just the same moment that I fired a blank from the gun? This would be an elaborate hoax, but still a credible hypothesis. Suppose later examination reveals bullet holes in the can not previously there, in support of the original hypothesis of the flying bullet. Is
that direct or indirect evidence? We judge the observations on their merits, and whether we classify them as direct or indirect is beside the point.
"Seeing is believing," many would say. An extremist philosophy might hold that reality can only be trusted to man's five senses (and his ability to reason logically, of course). The ancients had little else to go on. Once the telescope was invented, were Galileo's observations of heavenly bodies valid extensions of the visual sense, or were they in some sense more artificial and less convincing? Were those observations of Saturn's rings direct or indirect? You see how slippery the concept is when you try to pin it down.
So now we have our mass spectrometers, gas chromatographs, atomic clocks, etc. We can find a fossil embedded in a sedimentary rock, measure various radioactive decay products in those rocks, measure very similar rocks (found in the same position within the familiar column of geologic strata) from all over the world, and make inferences about when those rocks were originally laid down. This in turn allows us to make inferences about when the creature whose fossilized remains we hold must actually have lived. Direct or indirect?
We can examine the light from a star by passing it through a spectroscope. We can match its spectral lines with those produced by particular atoms at particular energies in a lab here on earth, and find that they match perfectly (much as the rifling marks on bullets can be matched to others fired from the same gun in a ballistics lab), except that the spectra are red-shifted a measurable amount. We understand the Doppler effect, and can infer that the star must be moving away from us at a speed that we calculate from the red shift. Direct or indirect?
We can't see atoms or molecules with our naked eyes. We can't see them in a microscope, either. We can't even see them with an electron microscope at a magnification of over one million. Yet there is abundant evidence that matter is composed of atoms and molecules, going back many centuries. Direct or indirect?
The most "indirect" of scientific evidence always rests on earlier observations, which in turn rest on even earlier ones, forming a long chain of evidence that ultimately stretches back to the most basic, elementary, and "direct" evidence that was established decades or centuries ago. And these are long and thick chains indeed. That's how can we know things like the age of the universe, or what the earth looked like half a billion years ago, or that whales evolved from land creatures, or how many water molecules are in that bottle of Evian. Scientific knowledge is in a sense indistinguishable from the history of science.
Young children are taught science as rote facts, and we ask them to accept these facts as true, just as they accept arithmetic, history, geography, and spelling. At a later stage of education, however, no knowledge of science is complete until the student learns not just what we know, but
how we came to know it. This is absolutely essential for establishing the reality of science, as well as for developing critical thinking skills to navigate our complex world of facts, guesses, myths, urban legends, hoaxes, and delusions.
And this is what is most urgently lacking in practically all of science education: not just what we know but how we know it.
My fingers are tired of typing.
Now let's hear from others.
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