William Herschel's greatest triumph was discovering a new planet — Uranus. His greatest folly was as egregious as his scientific triumph was great. But it was a beautiful folly, and so let's pay tribute to the cultured lunar civilization he was sure he had discovered.
When William Herschel, a professional music teacher and amateur astronomer, presented to the Astronomer Royal his findings that a new planet seemed to be orbiting the sun, he was met with skepticism. He had a powerful telescope, but no formal training, which meant he still identified stars by referring to a sketched star map. He worked occasional evenings out of the back of his house, with only his sister to check his nightly findings. He'd also written a paper the year before that seemed to be the work of an educated lunatic. Herschel was privately convinced of, and utterly obsessed with, finding evidence of civilized life on the Moon.
In the late 1700s, alien hunting was as keenly pursued as it is today. Although it was assumed that the universe was only a few million miles wide, astronomers were sure that the "thousands" of stars hosted tens of thousands of planets, many of which were as filled with life as the Earth was. As telescopes got more powerful, it was supposed that, fairly soon, Earthlings would find their neighbors. Herschel built the biggest, baddest telescope ever yet made, and when he used it to look at the Moon, he saw clear signs of life.
Although it had already been revealed that the Moon had no atmosphere to speak of, he insisted that he saw forests on the moon, in the stippled marks on its surface and climbing its rough mountains. The knowledge of the day said that the Earth was only a few thousand years old, and the universe not much older. All species, from trees to humans, were contemporaries. If another world had any kind of life on it, it probably, astronomers thought, had intelligent life.
But Herschel didn't just see trees on the Moon. He saw circuses. In this case, "circus," means a structure built in a circle. There were many small circles on the Moon. Herschel was seeing craters. No one had seen them in such detail before. Their perfect symmetry convinced Herschel that they couldn't possibly be natural. He believed that the lack of atmosphere on the surface made Lunarians build their towns in circles as a way of catching the light.
"There is a reason to be assigned for circular-Buildings on the Moon, which is that, as the Atmosphere there is much rarer than ours and of consequence not so capable of refracting and (by means of clouds shining therein) reflecting the light of the sun, it is natural enough to suppose that a Circus will remedy this deficiency, For in that shape of Building one half will have the directed light and the other half the reflected light of the Sun. Perhaps, then on the Moon every town is one very large Circus?"
Although he never released his theories about Lunarian circuses, his musings were found in his notes, well after his death. He lamented the fact that others weren't watching the moon as closely as he was, since the appearance of a new small "circus" would mean the Lunarians were building a new town and thus prove that they were up there. Herschel was sure, in fact, that all planets in the solar system, and the entire Universe, were inhabited by some form of intelligent life. He was a keen extraterrestrial searcher, checking out every known planet, but nearest was dearest, and he never stopped watching, with fascination, the lunar towns that he saw, waiting for some kind of signal.
Today, we're in much the same boat as those eighteenth century astronomers were. After a time spent sure that either life was infinitely rare, or just so far away as to never be discoverable by humans, we're back to thinking that, perhaps in just a few years, we'll find extraterrestrial life somewhere. It might be a distant planet or under the ice caps of some nearer planet's moon, but the discovery again seems to be just within temporal reach. As we look forward to it, maybe we can give a quick sigh that it isn't within contemporary spacecrafts' distance. As wonderful as any discovery of alien life would be, I think we'd all love to take a stroll along a Lunarian Circus.