The Day the World Discovered the Sun Read Online Free Page B

regions of the city.
    The crumble of icy gravel beneath the sleds’ runners came to a final stop at the governor’s residence. The foursome, whose wobbly legs reacquainted themselves with steady ground beneath their feet, climbed down.
    The governor’s eldest daughter approached Chappe and kissed his hand. Unsure how to respond, Chappe learned by the time the third daughter took his hand that he was expected to mirror her gestures and make the same kissing motions simultaneously. The governor told Chappe, through the interpreter, that he’d begun to worry that the team would not make it before the spring thaw, when travel slowed or ceased entirely.
    But worries could now rest, Chappe explained. The best observers—and instruments—this region had seen had now arrived. And all that remained was to find a suitable location for an observatory. Then, with an enlisted crew of local laborers at hand, the Frenchman only needed to build.
    Chappe located a hilltop three-quarters of a mile from Tobolsk and, with just twenty-six days till the transit, set out to create the site where he hoped to make history. No one suffered for daylight in this northern latitude. In early May, the sun rose at 5:30 AM and set at 9:30 PM . By transit day, June 6, daylight would trim the night by another hour on either end. Chappe unpacked and tested his equipment: the quadrant for measuring angles on the sky, his telescopes and the elaborate mechanical mounting that kept them trained on the same star or planet even as the earth’s rotation made it “move” through the sky throughout the night.
    Chappe supervised construction during long stretches of the day while fixing his instruments after their 3,400-mile marathon of gear-grinding and lens-scratching shocks and bumps. Chappe also had plenty of business to attend to in the build-up to the Venus transit. The astronomer had set up his clocks in the observatory building and tuned their accuracy down to the second. He further tested that his telescopes and quadrants could detect and precisely track a small shadow crossing the sun’s surface.
    Chappe also needed an exact fix on his observatory’s latitude and longitude. To find Tobolsk’s latitude (the number of degrees from the equator), Chappe measured the angle between the horizon and the sun at its highest position in the sky: noon. 18 He performed similar “altitude” measurements for the well-known stars Mizar and Caph when they crossed the same meridian line at night.
    Measuring such angular distances involved using an instrument as commonplace as the compass on a ship: the quadrant. Named after the portion of a full circle that it subtends (one-fourth of a circle or 90 degrees), the quadrant was like a protractor for the sky. Measuring altitudes with a quadrant—or its cousin, the sextant, which using a clever set of mirrors enabled measuring distances up to 120 degrees—involved first pointing the viewfinder at the horizon. Then holding the right side of the instrument in place (typically using a stand), one swung the viewfinder up to find the sun or star being sited. An arm extending down from the viewfinder pointed to a semicircle hanging beneath the finder containing hash marks that read out exactly how many degrees separated the two. (Like an hour, each degree is subdivided into 60 minutes of arc, or “arc minutes,” each of which is divided into a further 60 arc seconds.)
    So, for instance, Chappe observed with his quadrant on May 27 that Mizar—the second star from the end of the Big Dipper—was 87 degrees, 57 arc minutes, 15 3/4 arc seconds from the horizon. His starcharts told him (with some additional calculations) what Mizar’s altitude would be if he were at the equator. His latitude was then the additional degrees, minutes, and seconds between Mizar at the equator and Mizar’s altitude in Tobolsk. 19 The Mizar and Caph measurements both told him his