UP AND AWAY.(The Talk of the Town)

Beate Liepert is an atmospheric physicist at Columbia University. She has trouble telling left from right--a result, she thinks, of being forced, as a young girl in Bavaria, to write with her right hand. Now she's ambidextrous, and can read backward, although she used to have a problem with certain word pairs: she'd call sugar salt or a table a chair, and would insist, after being corrected, that she'd been misheard.

Liepert mentioned all this near the end of a drive the other day from upper Manhattan to an airfield in western New Jersey, where she was to embark on a flight in a hot-air balloon. A passenger's initial unease over the balloon flight--"We go up to six thousand feet," Liepert had said, "and we have no safety equipment"--had been displaced by that of riding in a rickety convertible driven by an absent-minded academic. Crawling along in the fast lane on I-78, Liepert tried, in a sturdy German accent, to explain her research.

"We try to see how much air pollution is locally emitted and how much goes around the world," she said. To that end, she (and her colleague Steven Chillrud, who was both afraid of heights and on vacation) had been measuring particles and light transparency in the air column over New York City in recent months. Liepert had been analyzing climate satellite data for NASA, but she wanted to gather more nuanced information. "Within a balloon, you are part of the air," she said. This was her eighth and final flight.

Liepert was one of the early proponents of the idea that air pollution blots out the sun--that the emissions that cause global warming can also mask its effects. This politically charged observation has led some to suggest that we should pollute the air on purpose. Liepert, for her part, is squarely in favor of producing fewer particles, not more. At any rate, she was particularly interested in the boundary layer between the low-lying Northeast Corridor pollution--the gray haze over New York and Philadelphia--and the globe-trotting stuff way up there, which can be less visible but more insidious. On an earlier flight, she had detected particles from a forest fire in Alaska.

The first balloon aeronauts, in 1783, were a sheep, a duck, and a rooster. For this particle-measuring flight, a sunset cruise, the ...