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It was the best of times; it was the worst of times. It was a time of revolution; it was a time for resolution. It was a time for precision; it was a time for speculation. It was a time for caution; it was a time for risks.
It was a time for map-makers.
Those themes, played out by real characters worthy of a Dickens novel, pervade two new books about the surveying of two planets: Earth at the end of the eighteenth century and Mars at the beginning of the twenty-first.
The circumference thus determined would become the basis of a world-wide standard of measurement in the new, rational, democratic order, the metric system. The standard of length would no longer be based on local custom or one royal's body part. It was to be exactly one ten-millionth of the distance along a meridian from the North Pole to the Equator of everyone's Earth.
So Jean-Baptiste-Joseph Delambre headed north toward Dunkirk, while his south-going partner, Pierre-Francois-Andre Mechain, set off for Barcelona. The task, though demanding, should have been completed in months, but it took seven years.
The setbacks were sometimes due to political turmoil, geography, or weather. More often, Mechain's melancholy and his perfectionist streak caused complications. So did some locals who impeded the work because standards of measure would lead to both taxation and loss of control over the local economy.
The heart of this story lies in discoveries from Mr. Alder's research, done largely by bicycling the route of the two geodesers. He found a cache of their private letters, still under the seal that Delambre had affixed not long before his death -- secrets he deemed best left for posterity.
Mechain, it turns out, believed he had made a critical error while determining the latitude of the southern endpoint. He covered it up, hoping to be able to repeat the measurement. In his three-volume account of the mission, Delambre chose not to reveal Mechain's deception. A universally accepted standard meter and Mechain's reputation were more important than whether the polar quarter-circumference was exactly ten million meters.
By modern measurements, that arc is 10,002,290 meters long, but the difference has more to do with Earth itself than with error -- hidden or otherwise -- in the geodesers' logs. And as for the discrepancy that so haunted Mechain, there's an irony that is too delicious for a reviewer to reveal.
Before telescopic photography, astronomers viewing Mars would sketch what they saw, trying to be faithful yet burdened with the human gift of interpretation. In 1877, Giovanni Schiaparelli saw and drew many actual geographical features; but some, particularly the canali (channels), were artifacts of his perceptual system.
It was natural for his brain to connect the dots. It was equally natural to imagine that the channels carried water, especially since the planet's seasonal color changes suggested that it supported vegetation.
Twenty years later, Percival Lowell drew his own maps and his own conclusions. In his mind, channels became canals, engineered by a civilization desperate to sustain itself on a dying world. His vivid descriptions captivated average citizens, angered skeptical scientists, and inspired science fiction writers.
Spacecraft of the 1960s and 1970s produced images with greatly improved resolution, sniffed the planet's atmosphere, analyzed its soil, and changed both maps and stories. Mars became a geologically inactive, cratered desert, lifeless now and always.
New stories arose with new champions, proposing affordable technologies that will enable people to establish Mars bases, then colonies, then a planet engineered to sustain an Earth-like ecosystem. Imagine the maps those pioneers will draw, Mr. Morton says, and imagine the stories those maps will tell.