From ancient times, comets had always been regarded as heralds of disaster. ...Calixtus III, who was Pope from 1455 to 1458, and was greatly perturbed by the Turkish capture of Constantinople, connected this disaster with the appearance of a great comet, and ordered days of prayer that "whatever calamity impended might be turned from the Christians and against the Turks.”
Source: Religion and Science, 1935, chapt. 1.
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