Eifelheim - Michael Flynn [68]
Tom nodded vigorously. “A measurement is defined by the operations performed to produce it. So different methods give different numbers. It’s even worse in cliology—”
“Right.” She stopped him before he could hijack the celebration. “Partly, the trend was due to physicists discovering more accurate methods. Galileo used shuttered lanterns in two towers a mile apart, and concluded that light speed was infinite. But clocks weren’t precise enough back then and his baseline was way too short. Using stellar aberration, the mean value was 299,882 kilometers per second. But the mean value using rotating mirrors—”
“Michaelson and Morley!”
“Among others. Light speed using rotating mirrors was 299,874; using geodimeters, 299,793; using lasers, 299,792 kiss. But method changes took place sequentially; so how much was due to the method, and how much to the thing being measured?”
Tom said, “Ummm …” which was all he really could hope to say at that point.
“From 1923 to 1928, the five published determinations alternated between the stellar aberration method and polygonal mirrors, with averages of 299,840 and 299,800, respectively.”
Tom was deep into MEGO by then. My Eyes Glaze Over. Normally, he was fascinated by matters statistic, but look up “fascination” someday. His “ummm” had turned into “unh-huh.”
“But there are little hints,” Sharon bubbled on. “Van Flandern—Naval Observatory—saw a deviation between the moon’s orbital period and atomic clocks, and claimed atomic phenomena were slowing down. But he was called a crank, and no one took him seriously. Maybe the moon was speeding up. Even allowing for all that, there seems to be a monotonically decreasing series whose asymptote is the Einsteinian constant.” She beamed in triumph, even thought she had discovered only a curiosity and not an explanation.
Tom had finished imitating a fish. “Umm. Correct me if I’m wrong, but aren’t there good reasons why light speed is supposed to be constant? That Einstein guy? I mean, I don’t know much about it, but I grew up believing in motherhood, apple pie, and the constancy of c.”
“Question of scale,” Sharon explained, waving an impaled cucumber at him. “Duhem wrote that a law satisfactory to one generation of physicists may become unsatisfactory to the next, as precision improves. The slope falls within the band of measurement error, so c is constant ‘for all practical purposes.’ Hell, for most practical purposes, we can still use Newton … But if we go back to the Big Clap and arm wrestle with flatness, or the horizon problem … You know,” she said, making a sudden conversational right turn, “Dirac almost found the same thing, but from a different direction.”
“Wouldn’t that be a different Diraction?”
Sharon really was a somber sort of creature and Tom’s bent to spontaneous low humor could rub her the way cat fur rubbed amber. “Be serious, would you,” she said. “Dirac found that the ratio of the electric force to the gravitational force of an electron-proton pair is roughly equal to the ratio of the age of the universe to the time it takes light to traverse an atom.”
Tom laughed. “I’ll take your word on that one.” He filled both their wineglasses again. “Okay, but the age of the universe isn’t a constant. It’s increasing….”
“At the rate of one second per second. Who says time travel’s impossible? It’s the speed and direction that’s a problem.” Sharon did have a sense of humor. It was more deadpan than Tom’s. The Marx Brothers were more deadpan than Tom. The wine was warming her quite nicely. If Tom was a bumbler, still he meant well, and there were too many who did not to remain angry at one who did. “Have some more fish,” she said. “It’s brain food.”
“Two helpings, then …”
They had not laughed together in several weeks, and the release was palpable. Problems could be obsessive, but worse, they could be solitary. It was good to connect again.
“So, there’s only one point in time when Dirac’s ratios could be equal,” he prompted.
She nodded. “Coincidence is the usual explanation. The