The Perfect Theory by Pedro G. Ferreira Read Free Book Online Page A

degree, or 1.7 arcseconds, it would be just as Einstein claimed. Such a clear and simple goal.
    It wasn’t actually that simple. The few places on the Earth where one could witness the total eclipse were remote and far apart. The astronomers would need to travel quite far, in a world that had just come out of a devastating war, to set up their equipment. Eddington, along with Edward Cottingham from the Greenwich Observatory, set up shop on the island of Príncipe. A backup team of two astronomers, Andrew Crommelin and Charles Davidson, was dispatched to a village called Sobral in the interior of the Brazilian Nordeste, a poor, dusty region near the equator.
    Príncipe is a small island in the Gulf of Guinea, a Portuguese colony known for its cocoa. A lush green island, hot, humid, and periodically peppered with tropical storms, it had a few large
roças,
or plantations, spread out where a few Portuguese landowners used the local inhabitants to farm the land. For decades it had supplied the cocoa beans to the Cadbury corporation. At the beginning of the twentieth century the cacao plantations were accused of using slave labor and lost their contracts, destroying Príncipe’s economy. When Eddington arrived, the island was slipping into oblivion.
    Eddington set up his apparatus in a remote corner at the Roça Sundy, where he was looked after by the landowner. Between daily tennis matches on the only court on the island, he waited for the day of the eclipse, praying that the recurring rainstorms and gray skies wouldn’t sabotage his mission. Cottingham primed the telescope, hoping that the heat wouldn’t distort the images.
    On the morning of the eclipse, it rained heavily and the sky was completely impenetrable until, less than an hour before totality, it started to clear. Eddington and Cottingham caught their first glimpse of the eclipse that was under way with part of the sun already obscured. By 2:15 in the afternoon, the sky was clear and Eddington and Cottingham could take their measurements—sixteen photographic plates of the sun with the Hyades cluster lurking in the background. By the end of the eclipse, the sky was beautiful, clear of any cloud. Eddington telegraphed a message to Frank Dyson:“Through cloud. Hopeful.”
    The cloudy start to the experiment in Príncipe may have saved the day. In Sobral in the Brazilian Nordeste, there was a perfectly clear and hot day on which the eclipse could be followed right from the very start. Crommelin and Davidson were surrounded by the jubilant locals to witness the historic event and were able to take nineteen plates to complement the sixteen taken by Eddington and Cottingham. Exultant, they also telegraphed back:“Eclipse Splendid.” At the time, they didn’t realize that the good viewing conditions and hot clear weather in Brazil had sabotaged their main experiment. The heat had warped the apparatus so much that the measurements on the photographic plates were rendered useless. It was only with backup observations with a smaller telescope that the expedition to Sobral was able to contribute data to the experiment.
    The astronomers were unable to return home quickly, and it was only in late July that the various photographic plates began to be analyzed. Of the sixteen plates that Eddington had recorded, only two had enough stars to measure the deflection properly. The value they got was 1.61 arcseconds with an error of 0.3 arcseconds, consistent with Einstein’s prediction of 1.7 arcseconds. When the plates from Sobral were analyzed, the results were worrying. The value measured was 0.93 arcseconds, far from the relativistic prediction and very close to the Newtonian prediction, but these were the same plates that had been deformed by the heat. When the backup observations from Sobral, undertaken on the smaller telescope, were analyzed, the deflection came out at 1.98 arcseconds with a very small error of 0.12 arcseconds.