Scientists had been suspecting for a long time that auroras were symmetrical relative the equator, but they could not confirm that experimentally. They had some cues: James Cook traveling in the Southern Hemisphere observed an aurora borealis on September 16, 1770, while the documents recently found in China recorded an aurora polaris on that day. The hypothesis was confirmed on October 22, 2001: the Polar probe of the National Aeronautics and Space Administration of the United States recorded auroras that appeared simultaneously in both hemispheres. They turned out to be mirror interreflections.