Earth’s nearest neighbor


By Tom Burns - Stargazing



This year, we celebrate the 50th anniversary of the Apollo 11 moon landing on July 20. Much has been made of our failure to return to our nearest neighbor ­— our co-planet really — after Apollo 14 in 1974.

However, human landings have little scientific value, and the novelty of being the first and only nation to land on Luna wore off quickly. Our rather chauvinistic concern was to beat the Russians. After we did that, other political issues rose to greater importance. It is only now, when our political dominance is being challenged around the world, that politicians are again talking of lunar landings and even a permanent presence on the moon.

The fact is that more than sufficient science can be done without human hands to do the work. We have mapped its surface and explored its composition thanks to quite a number of unmapped, robotic orbiters and even landers.

Thanks to those landers and a new generation of enormous telescopes, humans think they know a lot about the moon and the universe these days. However, nothing is truly certain in astronomy and science in general. Understanding comes in small increments, slowly and arduously gained from painstaking research.

Thus, every discovery about the universe is incorrect to some degree. We must take comfort in the assumption that each new assertion seems a little less incorrect than the one before.

As late as 100 years ago, humans knew practically nothing about Earth’s nearest neighbor, our only natural satellite, the moon. Based on the best available evidence, even the brightest astronomers made lunar claims that seem in retrospect to be exceedingly weird.

If you don’t believe me, grab a small telescope and look at the crater Eratosthenes. (A detailed moon map will help you here.) Look first for the Apennines mountain range, a long, curved chain visible just north of the moon’s center. The Apennines act as the southeastern boundary of the large, dark, mostly empty splotch called Mare Imbrium, the “Sea of Rain.”

Punctuating the western end of the mountain chain is one of the moon’s most perfect craters. Exquisitely round with high terraced walls, Eratosthenes is small at only 38 miles wide. Its gorgeous central mountains look very much like a dimple in a small telescope. Here we see the imprint of the massive impact of some minor asteroid on an unsuspecting moon a long time ago.

Eratosthenes would be just another impact crater except for the work of William Pickering, the most respected lunar and planetary observer of the beginning of the 20th century. Pickering worked at the prestigious Harvard College Observatory. Among his accomplishments were the discovery of Phoebe, Saturn’s most distant moon, a detailed set of lunar photographs, and careful, groundbreaking observations of Mars.

In 1919, 100 years ago, Pickering took his telescopes to Jamaica, an island paradise where skies are often exceedingly clear. (Astronomy can be a tough job sometimes.) He paid particular — even obsessive — attention to the rather minor crater in question.

Did such close scrutiny of the moon make one crazy? Folklore seemed to suggest so. On the scientific level at least, Pickering was already a “lunatic” of the first order. His Jamaican observations of Luna sealed the deal.

What he found deep in the Eratosthenes crater could have changed the world. Or it was positively nuts. What was it?

Night after night, he observed it and began to notice an odd pattern. Over the course of a monthly lunar cycle, a number of strange, dark patches seemed to move in a regular pattern over the crater’s floor.

Earlier, Pickering had persuaded himself on very tenuous evidence that the moon not only had an atmosphere but patches of vegetation. He had also studied the earthbound movements of the giant buffalo herds across the American west and the migrations of the fur-bearing seals of the Pribilof Islands. He suggested that an astronomer on the moon would see the same kind of dark patches if he or she were watching those migrations on Earth.

According to Pickering, the dark patches on the crater floor moved about 20 miles and completed their motion in 12 days. The movement, he argued in a 1924 paper, “involves an average speed of six feet a minute, which … implies small animals.”

Some sort of insect seemed to be the most likely solution. These lunar moths, or whatever they were, traveled regularly between their breeding grounds and the large expanses of vegetation nearby.

Pickering’s reputation as a careful observer was so well established that other astronomers were forced to take his insect theory seriously, but in the end, no one could replicate his observations. Despite the skepticism of his colleagues, Pickering held fast to his views until his death in 1938.

Of course, we now know with certainty that the moon has neither atmosphere nor liquid water to support even the simplest form of life.

Neil Armstrong and Buzz Aldrin found no migrating moon moths. Sorry.

What was Pickering seeing on Luna? Nobody knows. Let’s just say that the word “lunatic” arises from the supposition that staring too long at the moon will cause you to become unhinged.

Perhaps at the dawn of the 22nd century, people will look back 100 years and chuckle at the odd claims of those crazy astronomers who live now. Or perhaps they will honor them the same way we revere Edwin Hubble, who worked around the same time as Pickering and altered our view of the universe enough to get a space telescope named after him. Only 100 years of tireless research and many returns to the moon yet to come will tell the tale.

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By Tom Burns

Stargazing

Tom Burns is the former director of the Perkins Observatory in Delaware.

Tom Burns is the former director of the Perkins Observatory in Delaware.