Apr 8, 2021
Image: Halley's original observations of his comet in 1682. The observations of September 4, 1682, with their reductions, occupy the left-hand page. The right-hand page contains notes on the parabola. - nature.com
The work of decoding the cosmic traveler has surprising relevance right now according to scientificamerican.com.
This seems like a good moment to speak to the idea of uncertainty. Our world appears to be in a perpetual state of it. We have recently experienced rising global temperatures, melting glaciers, floods, wildfires and record-breaking hurricanes. And now a worldwide pandemic rages as humanity races to protect itself against a virus that has already claimed millions of lives.
Throughout history, science has been our species’ hedge against the uncertainties of our world. It is an organized attempt to move us beyond simply reacting to the marvels (and terrors) we perceive and experience. And that remains its role now, as thousands of researchers join forces in a collective mission: to better know SARS-CoV-2 and to rend that virus’s complexities into a blueprint to plan its containment and control.
But if we follow science’s trajectory backward in time, we can see that our first attempts to decode and classify natural phenomena came not from the study of our illnesses but from the movements of the heavens. Some of the first foreign invaders to infect humanity’s attention on a global scale were comets.
Reaching back more than 2,000 years, our historical record crackles with the palpable fear of these celestial bodies. In 1921 the American Catholic Quarterly Review summed up the collective disquiet around comets from a deep reading of past poets, playwrights and historians:
They were javelins, sabres, swords of fire, horses’ manes, dragons’ mouths, bleeding crosses, flaming daggers or decapitated heads with hair and bristling beard. They shone with the red light of blood, yellow or livid, like that of which the historian Josephus speaks, which showed itself during the terrible siege of Jerusalem.
History’s scribes documented the world’s unmitigated terror at the seemingly random appearance of these frightful “apparitions” (a term they often used), from the reigns of the ancient Greeks through the Dark Ages. What finally changed the general narrative was the advent of the Age of Enlightenment. Reason and logic, channeled through the minds of the likes of Isaac Newton, Galileo, John Locke, Gottfried Leibniz, and others, vied for the space previously occupied by superstition and religion.
The intellectual taming of comets began with Edmond Halley (with an assist from Newton) in the late 17th and early 18th centuries. In the April 11, 1908, supplementary edition of Scientific American, astronomer S. I. Bailey wrote, “Before Halley’s time comets had been regarded as chance visitors to our solar system, except when they were looked upon as special messengers of divine wrath.”
Halley used insights gleaned from Newton’s Philosophiae Naturalis Principia Mathematica (which he fronted Newton the cash to publish) to calculate the orbits of 24 comets in total. These included the comet of 1682, which both Newton and Halley observed directly. The reason it bears Halley’s name is that he used its arrival to see into its future.
“Halley noticed that [comets] recorded by Appian in 1531, by [Johannes] Kepler in 1607, and by Halley himself in 1682, seemed to return after a period of seventy-five or seventy-six years,” wrote astronomer J. E. Gore in a 1909 Scientific American article entitled “Edmund Halley: The Man Who Dispelled Cometary Superstitions.” These calculations led Halley to predict the comet’s return on “about the end of 1758 or beginning of 1759,” Gore added. Its next arrival was first glimpsed in March 1759.
Halley did not live to see his prediction borne out: he had died 17 years earlier. But he is forever immortalized for allowing us to look at these cosmic visitors as part of a system that can be observed, studied and at least partially drained of its uncertainty.
The story of Halley’s Comet also offers us a warning, especially meaningful in this moment of global uncertainty. We are living amid a human-made “infodemic” of misinformation surrounding the novel coronavirus and the vaccines we have created to hold the pathogen at bay. It is helpful to know that even in 1910, when Halley’s Comet returned—and was known to be an astronomical body orbiting in our solar system—there were those who saw it as an agent of our civilization’s demise. They were convinced that chemicals from the comet’s tail would seep into our atmosphere and kill us all.
Halley’s Comet’s warning is that science’s work is never done. No matter how much uncertainty we calculate away from our lives, there will be people who refuse those learnings and turn away from research and reason. The challenge for us as a species, as we wait with anticipation for the comet’s return in 40 years, is to move humanity forward collectively, despite the holdouts.
Comets such as Halley’s remind us that we must always keep asking questions. They provide an opportunity for reflection and a reminder of how much more we still have to learn. What if we had never asked ourselves, thousands of years ago, what that flaming streak in the sky actually was? What if we had never questioned the idea that this apparition was sent by a god to bring downfall to a civilization? If we had not done so, perhaps we would have blamed the coronavirus pandemic on Comet NEOWISE, which passed through our skies this past summer.
Halley’s Comet’s visit is a once-in-a-generation tradition that spans from a time before the dawn of humans. Its return gives us a reason to look up and wonder about the universe’s mysteries, regardless of all the fears and uncertainties on our own planet.
Ultimately, no matter what we do, the gears of the wider universe will keep spinning, and Halley’s Comet will be back. It will be up to us how we greet our returning visitor, however. Will we push science to new heights and let this celestial body teach us about our surrounding universe? Or will we succumb to our own vices and conflicts—and, in 2061, look up at Halley’s Comet’s pale streak and wonder why we didn’t do more?
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