Hale-Bopp // Credit: Michael Stecker
My book, Comets: Visitors From Deep Space
, will be published this fall by Cambridge University Press. Here’s a taste of a historical chapter centering on observations by the Roman philosopher Seneca . . .
The Roman philosopher Lucius Annaeus Seneca, aka Seneca the Younger (ca. 4 B.C.
65), summarized the early take on comets — as opposed to the always visible parts of the heavens, the Sun, Moon, etc. — in one of his writings. “No man is so utterly dull and obtuse,” he penned, “with head so bent on Earth, as never to lift himself up and rise with all his soul to the contemplation of the starry heavens, especially when some fresh wonder shows a beacon-light in the sky. As long as the ordinary course of heaven runs on, custom robs it of its real size. Such is our constitution that objects of daily occurrence pass us unnoticed even when most worthy of our admiration. On the other hand, the sight even of trifling things is attractive if their appearance is unusual. So this concourse of stars, which paints with beauty the spacious firmament on high, gathers no concourse of the nation. But when there is any change in the wonted order, then all eyes are turned to the sky. . . . So natural is it to admire what is strange rather than what is great.”
“The same thing holds in regards to comets,” continued Seneca. “If one of these infrequent fires of unusual shape have made its appearance, everybody is eager to know what it is. Blind to all the other celestial bodies, each asks about the newcomer; one is not quite sure whether to admire or fear it. Persons there are who seek to inspire terror by forecasting its grave import. And so people keep asking and wishing to know whether it is a portent or a star.”
Seneca wrote about comets and much more in his famous work Natural Questions
, in Latin), written about the year A.D.
63. And he wrote about them under considerable pressure from Emperor Nero (A.D.
37–68), who had begun his life of wretched excess, total immorality, and criminality — and who had already arranged for the deaths of his mother, his wife, and his stepbrother. An imperial advisor, Seneca was accused of embezzlement and wrote in a manner of bald flattery toward the emperor.
Seneca mentioned recent comets, recalling “one which appeared during the reign of Nero Caesar — which has redeemed comets from their bad character.” He later referred to “the recent one which we saw during this joyous reign of Nero.” The flattery worked only for a short time. Accused of complicity in the Pisonian conspiracy, a plot to kill Nero, Seneca was forced to commit suicide. Nonetheless, his writings about comets published in Natural Questions
continued to influence thinking about the celestial visitors for many years to come.
Seneca believed that comets were not fiery apparitions but permanent creations of the natural world that would last and be seen for short periods because of their movements. He mentioned the observation of a comet during a solar eclipse and therefore believed many comets may move close to the Sun in the sky and be hidden by its glare. Impressively, Seneca proposed that comets move in circular orbits and travel around the sky, becoming invisible when they move behind planets. One of the chief arguments for comets being atmospheric, and not distant celestial bodies, came from the fact that their appearances and motions differed greatly from stars and planets.
For this, however, Seneca had a rational retort. “Nature does not turn out her work according to a single pattern,” he wrote. “She prides herself upon her power of variation. . . . She does not often display comets; she has assigned them a different place, different periods from the other stars, and motions unlike theirs. She wished to enhance the greatness of her work by these strange visitants whose form is too beautiful to be thought accidental.”
Seneca then looked forward to a distant future, realizing that understanding would deepen over the ages. “The day will yet come when posterity will be amazed that we remained ignorant of things that will to them seem so plain. . . . Men will some day be able to demonstrate in what regions comets have their paths, why their course is so far moved from the other stars, what is their size and constitution. Let us be satisfied with what we have discovered, and leave a little truth for our descendants to find out.”
As Roman philosophers went, Seneca was an impressive scientist in the making. He stood up for careful, analytical observations, and even though his conclusions were primitive, the analytical part was a big step forward. In fact, his belief in the periodic orbiting of comets caught on, finally, with Edmond Halley — more than 16 centuries after Seneca’s death.