Peering at the same stars, through different lenses

A day in the life of two astronomers, one from the 15th century, the 20th

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Sitting at his desk, pen in hand, Paolo paused to consider his message carefully. There was reason not to be impetuous. Paper was expensive, and his letter to Johannes Regiomontanus in Nuremberg would take days to reach its destination. His German counterpart was almost the only colleague who could appreciate his observations, but Paolo would be lucky to have a reply in a month.

For the past several nights, Paolo had been recording positions of the bright comet that had appeared unexpectedly in the constellation Gemini. He used a string lined up on two bright stars to establish a line through the comet, and then the intersecting line from a second pair enabled him to pinpoint the comet's position. Many people

watched the fearsome apparition, wondering what dreadful consequences would ensue, but almost no one made careful measurements. Little did he guess that his comet would reappear 75 years later, and eventually would bear the name of a 16th-century English astronomer, Edmond Halley.

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The letter finished, Paolo turned to his most precious possession, his sole astronomical volume. It was handwritten, on parchment, and consisted of a group of small works bound together. One was on the astrolabe, a brass instrument more useful for simplifying mathematical calculations than for observing. Another was Sacrobosco's Sphere, now too elementary for Paolo, but remembered fondly from his days at the university.

More useful were the Alfonsine Tables, which enabled him to compute the positions of the sun, moon, and planets. The procedure was tedious, and it took Paolo several hours to get the planetary positions for the following week. Those would help him decide if there was a propitious time to take a bath. He was completely unaware that north of the Alps, in Mainz, the Bible had been printed in multiple copies by means of movable type, and he could hardly guess that before a score of years had passed, Regiomontanus would print a few hundred copies of the daily planetary positions for 30 years, saving other astronomers untold hours in calculating time.

Paolo's computations were interrupted by the arrival of two advanced students, who had come for their weekly tutorial on the casting of horoscopes. A great nuisance, Paolo thought, for today would soon be gone, but he needed their small fees for his livelihood.

Cambridge, Mass., Sept. 10, 1999

Sitting in front of his computer screen, Paul perused an e-mail that had arrived from a collaborator in Tel Aviv while he had been lecturing at the Science Center. It was Friday afternoon, and the sun had already set in Israel. So, his response would not get read until the next evening, after Shabat ended. The prospect of a 24-hour delay was frustrating.

Three days ago, he had returned from two nights with one of the twin 10-meter Keck Telescopes in Hawaii. He had not actually seen the world's largest telescopes, perched at 14,000 feet on Mauna Kea where the air is too thin to think properly, but had worked from a bank of computer screens at Keck Headquarters, well below the summit. He controlled the spectrograph remotely as the operator on the mountain moved the telescope from one star to another, all candidates for having planetary companions.

Each observation would give another point on the graph, but it would take repeated visits to establish the small velocity shifts that would reveal the presence of any unseen companions. He had carried away two tapes with about 3 gigabytes of digital data, but at home, it had taken three days to overcome the intense jet lag and to catch up on the accumulated paperwork.

Manipulating the data with a computer took place in small intervals between other responsibilities, which also involved sitting before the computer screen. There were papers sent electronically from the journals to be refereed. There were proposals to write to win more observing time at the Keck as well as with the 6.5-meter telescope at the Whipple Observatory in Arizona. And there were e-mail messages from collaborators in Switzerland and in Chile who had just received duplicate data tapes rushed onward by Federal Express.

Paul has numerous colleagues in the same building. He meets them at lunch-time colloquia, or sometimes in small seminars in his office where they discuss a paper in the current Astrophysical Journal. They will all have read the paper in an electronic version on their computer screens, but these sessions do offer a brief respite from life in front of a computer.

Afterward, there is time to download a data set from the European Hipparcos satellite for comparison with the Keck observations. He is hot on the trail of another planet orbiting a distant star. Another planet, and maybe another potential home for life in the universe. But then there is a letter of recommendation to write for a postdoc desperately seeking her next research position. What a shame, he thought, that these bright young astronomers have to struggle so hard to find a permanent position, and with no guarantee of success.

It's after 8 before Paul heads home. His wife will have to endure another late dinner, but that letter was important. For these young people, he mused, are the future of the community.

(c) Copyright 1999. The Christian Science Publishing Society

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