Discovering infrared radiation

 THOUGHT OF THE DAY:     
"Nothing great was ever achieved without enthusiasm." - Ralph Waldo Emerson, from Circles
I suppose, although I would soften the "nothing" and doubt this was worth saying.

I think your instinct is right. Emerson's “nothing” is doing more work than the proposition can support.

Enthusiasm certainly helps explain many great achievements: it supplies persistence, energy, and the willingness to keep going when the undertaking becomes tedious or difficult. But “great” achievements have also come from duty, discipline, necessity, obsession, curiosity, calculation, or simply being the person who happened to be there when circumstances made something possible.

And I suspect there's a deeper problem with the aphorism: enthusiasm is easier to notice in retrospect than it is to distinguish from the achievement itself. We tend to call someone enthusiastic because they devoted enormous effort to something we now regard as important. If the undertaking had failed, we might have called the same behavior stubbornness or eccentricity.

So I'd probably revise Emerson mentally to something like: “Nothing great is easily achieved without sustained interest and effort.” Less memorable, unfortunately—but considerably harder to argue with.

As for whether it was worth saying: Emerson was a professional producer of sentences that sound as though they ought to be carved over a doorway. Some deserve the doorway. This one perhaps belongs on a motivational poster in a high-school gym.

There is the story of the discovery, I think by Newton but would appreciate correction, of the rather accidental discovery of infrared radiation, simply because of having proper controls on an experiment and then being ready to understand an unexpected result.

Yes—and you remembered the important part correctly, although it was William Herschel, not Newton, in 1800.

Herschel was investigating something quite ordinary: whether the different colors in sunlight carried different amounts of heat. He passed sunlight through a prism to make a spectrum and put thermometers in the different colors. Crucially, he used other thermometers as controls, so he could distinguish the heating caused by the spectral radiation from ordinary changes in room temperature.

Then came the lovely accident. The thermometer got hotter beyond the red end of the visible spectrum than it did in the red itself. There was apparently nothing there—the region was dark. Herschel realized that something invisible was carrying heat. We now call it infrared radiation.

And this is a particularly good example of why I think your objection to Emerson's aphorism is apt. Herschel wasn't necessarily operating with tremendous enthusiasm. He was doing something much more prosaic and scientifically valuable: he had designed an experiment in which an unexpected result could not easily be dismissed as an experimental nuisance, and he was paying attention when it occurred.

There's an even nicer wrinkle. Herschel initially got the physics partly wrong. He regarded the heat-producing rays as fundamentally different from the visible light rays, rather than as another part of the same electromagnetic spectrum. Yet the observation was sound and enormously fruitful.

So perhaps a better aphorism would be:

Great discoveries often come not from enthusiasm but from careful measurement, good controls, and the willingness to take an inconvenient result seriously.

That's rather less suitable for an inspirational calendar, of course. But considerably more interesting.

The idea of waves of light we cannot see requires a conceptual link; I remember a rather heated conversation with my grandfather about radio waves.  He thought some skulduggery was going on.

Yes. And your grandfather's reaction is actually quite understandable. There is a conceptual leap there that we now take almost completely for granted.

“Herschel found invisible heat beyond red” is one thing. But “there are waves propagating through space that nobody can see, and they can carry information” is another order of weirdness entirely. Radio makes the weirdness impossible to ignore: you can have a box sitting in your house apparently doing nothing, and somewhere else someone moves a piece of metal, and music comes out of the box.

Before Maxwell, the connection wasn't obvious. Light was known as a phenomenon of optics; electricity and magnetism were treated as rather different phenomena. Maxwell's great achievement in the 1860s was to show mathematically that changing electric and magnetic fields can propagate as waves, and that the calculated velocity was remarkably close to the measured velocity of light. His conclusion was essentially: light itself is an electromagnetic wave.

That immediately opened the door to a much larger spectrum. If light is an electromagnetic wave, there is no reason the spectrum should stop at what our eyes happen to detect. Infrared and ultraviolet had already demonstrated that. Radio waves were simply enormously longer-wavelength electromagnetic waves.

But I think your grandfather's “skulduggery” gets at something philosophically important. Invisible entities are easy to accept when we have learned to recognize their effects, but that doesn't make the conceptual step trivial. We can't see radio waves any more than Herschel could see infrared. We infer them from what they do.

And there's a wonderful progression:

visible light → invisible infrared → invisible ultraviolet → electromagnetic theory → radio waves → radio communication.

At each step, something that initially looks like an entirely new kind of phenomenon turns out to be part of a larger pattern.

In fact, your grandfather's skepticism is rather close to the position a scientifically sophisticated person could reasonably have taken in the nineteenth century. The remarkable thing isn't that people initially found radio waves hard to believe. It's that physics eventually produced one conceptual framework in which visible light, heat radiation, radio, microwaves, X-rays, and gamma rays all became manifestations of the same thing.

That's one of those occasions where the universe turns out to be considerably more economical than human intuition.