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I love sobering thoughts. Here’s one. Around the year 1900, Charles Darwin’s (and AR Wallace’s) theory of variation and selection was virtually forgotten. What is today hailed (rightly) as the greatest intellectual achievement of 19th century science was all but discarded by the beginning of the 20th century.
Why? Because given the world as it was known then, it couldn’t have worked.
I often encounter natural selection described as a beautiful, simple idea. “How could I have been so stupid not to think of it myself,” is the sentiment described. The fact that no one, not Newton, not Descartes, not Aristotle nor Galileo nor Hypatia nor Euclid, thought of it first indicates that it’s not so simple. The fact that the beautiful, simple idea was later discarded is even better evidence.
These days there’s an evangelical named Ray Comfort who is criticizing evolution with what he thinks is a simple, beautiful argument. He’s right; it is simple and beautiful, but also wrong. It is wrong because the facts of the real world take us somewhere else. It is wrong in the same way the rejection of natural selection by 1900 was wrong. It is wrong because it is ignorant of another simple, beautiful idea. Genes are lumpy.
Comfort’s argument goes like this. “Evolutionists” say that elephants evolved from non-elephant ancestors. But the first elephant (for Comfort the first is always a male) had to find a wife. Isn’t it an odd coincidence that just when the male elephant came along, a female elephant evolved, too? But if not, with what creature did the elephant mate?
If you don’t know anything about genetics, this might be a convincing answer. And in fact it was (in different form) the argument that in part caused the rejection of natural selection the first time around.
To choose another example, suppose a white moth were to appear in a population of black moths. That white moth would have to mate with a black moth. If (as was believed at the time) inheritence is blended, their offspring would be grey. These grey moths in turn would overwhelmingly mate with black moths, resulting in even darker offspring, and so on. In this way, any unique traits would disappear almost as soon as they arose.
Ah, but genes don’t blend in this way. Instead, here’s what might happen. A white moth mates with a black moth. Their offspring are ALL BLACK! White has disappeared, not over several generations, but instantly. But isn’t this a backwards step? Patience, grasshopper.
Now the all-black moths mate. Occasionally, two black moths that each have a white parentwill mate. In this cross, one out of four of their offspring will be white! The white trait, hidden in the first generation of offspring, reappears in the second.
If you’ve taken a biology class, you probably recognize this. It’s a common piece of pedagogery, and reveals the pea plant experiments of Gregor Mendel, a contemporary of Darwin whose work was forgotten in his lifetime. Big deal, right?
The big deal (so often missed in introductory material on this subject) is that this discovery, that genes are discrete (I prefer the word “lumpy”), gave natural selection the tool it needed to work! The result is the world you see around you. Because unique traits could survive as discrete lumps of genetic material, even hiding in generations, all manner of variability could eventually appear, spread, and fluorish.
So what does all this have to do with Comfort and his elephants? The point is that Comfort would be right – if inheritance blended. But it doesn’t. Genes are lumpy. An elephant ancestor needn’t be an elephant to carry elephant traits. It can carry genes for elephant-like traits, and those genes can hide within the genome. When those genes come together in the right individual, the traits (completely accidentally) can make that individual more likely to survive, and so the traits are passed on. Eventually, the traits become common in the population, and you have elephants.
The point is not so much that Comfort and the 1900-era biologists were wrong. Being wrong is part of learning. The point is that scientists, by working out sometimes simple, beautiful relationships, such as Gregor Mendel and his peas, can reveal not just a deep truth, but can show us just how and why it is true. This knowledge, gained through long, hard, arduous work, is now available to everybody. You can know things that Aristotle never could have imagined, not because you’re smarter, but because you are alive, here and now, in a world positively brimming with simple, beautiful, and true ideas.
Now that’s a sobering thought.
As I often do, I am listening to a science book on CD as I drive to and from work. Yes, I’m falling behind on all the important politics and news of Britney Britney and Menudo, but for me those few minutes of audio immersion in science are some of the best of my day.
It struck me today as I listened, though, how none of it really mattered, and that it was great. The speaker was talking about the invention of things like the steam engine, the airplane, and the automobile, and how little role science or scientists played in those inventions. Later on, of course, that changed, as inventions like nuclear reactors, the transistor, and the laser were driven almost entirely by science. It would be ridiculous to look around at the modern world and deny the role of science.
Yet most people have no idea how a nuclear reactor, a transistor, or a laser works. Some, like doctors, may need to know what a laser does, but knowing the science behind it is virtually irrelevant to actually using the thing. And here’s my point: for most people, the science behind the thing doesn’t matter.
There are things that do matter. I’m in the process of selling my house. I have to know things, like what an interest rate is, how to negotiate a selling price, how to read and sign my name. I’m working on various grants at work. I have to know how to spell, how to talk to people without making them dislike me, how to answer e-mail. I’m trying to sell a new book. I have to know how to write a cover letter, how to look for an agent, and how to accept rejection. But for none of these things does science matter. Yes, if I were a working scientist, science would really matter. But if I were a working auto mechanic, then auto mechanic-y stuff would really matter. If I were a baker, then . . . etc. etc.
Educators make a huge mistake when they try to convince their learners that science is Important, that it Matters. No it doesn’t. It’s wonderful and exciting, but it doesn’t matter in the same way that knowing how to read, count, or talk to people matters. If you’re trying to find the right combination of ingredients to make a room temperature superconductor, then science matters. But for most of us, science doesn’t matter, not really, and that is wonderful. It frees us up to just have fun, to know science for what it is – a grand exploration of the world, for no better reason than the world exists and is begging to be explored.
Let’s see what we can discover next!
Something I heard shook me. There are 60 billion neutrinos from the Sun passing right through your thumbnail every second.
Neutrinos are one of my favorite topics. They say something about science and what we know. Here’s the story.
Alpha decay and beta decay are both types of radioactivity. Other than that, they’re about as different as two processes can be. Alpha decay involves the ejection of an alpha particle, really a helium nucleus. Alpha particles are two protons and two neutrons, and throwing them around is the equivalent of tossing bowling balls around in the subatomic world.
Beta decay involves the ejection of an electron (or a positron in special circumstances). Compared to an alpha particle, a beta particle – an electr0n – is just a bit of fluff. Though they usually penetrate deeper than alpha particles, they don’t carry nearly the oomph.
That’s the obvious difference between the two. But there’s a more subtle difference, beautiful and deep. Alpha decay is, for any particular decay of an isotope, always exactly the same. If you get an alpha from U-238, the energy of that alpha is always the same. There are some isotopes that can decay in different modes; yet even so, the emission spectrum is always discrete, like the light from a laser, rather than continuous, like a light bulb. If you know where an alpha particle came from, you know its energy.
Beta decay isn’t like that. The spectrum of electron energies from beta decay is more like the spectrum from an incandescent bulb. There’s an upper limit, but between that limit and zero, the electrons take on all sorts of values.
This bothered scientists when they discovered it. Why should beta decay have this strange property? Where did the extra energy go (or, alternatively, where did it come from)? Given this evidence, some scientists were prepared to give up the conservation of energy.
A desperate alternative was tried instead. Perhaps, it was suggested, an invisible, electrically neutral, non-reactive particle came flying out of beta decay along with the electron. This invisible particle could carry that extra energy. Voila! The conservation of energy was saved!
Enrico Fermi named the particle “neutrino”, Italian for “little neutral one.” Cute.
It seemed like a trick, fixing the books. We can’t find the extra energy? Fine, we’ll just make up a story. Here it is, in a place we can never find it. Quite convenient, and also not very scientific.
So things stood for decades. Physicists had a neat solution, but also a big problem. Where was the evidence for the neutrino? There was none. The calculated properties of the neutrino meant that a single particle would, on average, travel through several light years of solid material before interacting. Hence the 60 billion through your thumb every second. Even if you’re exceptionally odd, your thumb is nowhere near as thick as a light year, so you have little chance of stopping any particular neutrino.
Ah, but the power of large numbers means that with lots and lots of neutrinos, occasionally a few will do something unusual. Just as the average U-238 atom will last 4.5 billion years, but some are always defying the odds and decaying anyway, a few neutrinos will also defy the odds and get absorbed, even in relatively small amounts of matter.
But how do you know that you’ve caught a neutrino?
In 1955, two scientists named Fred Reines and Clyde Cowan decided to try it. They filled a tank with cadmium chloride and surrounded the tank with detectors. They were looking for two gamma rays flying away in opposite directions. This would indicate that an electron and positron had been annihilated. And that would mean that a proton had just absorbed a neutrino, in the process shooting off a positron and turning itself into a neutron.
The details aren’t that important, though they are fascinating and maybe I’ll write about them later. The important point is that Reines and Cowan found the neutrino. It was really there!
This is astonishing. First, scientists noticed something that they didn’t expect – the continuous spectrum of beta decay. The observation violated one of the physicists’ most cherished ideas, the conservation of energy. To fix it, they created out of wholecloth this invisible particle with virtually no properties. But then, their patch turned out to be a real thing! This, to me, shows that physics has in some sense found out something true about the universe.
Science isn’t just observation and classification. As this example shows, science can actually touch on something we might call truth. The neutrinos point the way. The truth is out there. Think about that next time you gnaw on your thumbnail.