Great Comet of 1577
...that the passing of the Great Comet of 1577 caused almost century-long debate, during which Galileo argued that comets were merely optical illusions?
...that the passing of the <b id="mw8A"><a href="./Great_Comet_of_1577" id="mw8Q" rel="mw:WikiLink" title="Great Comet of 1577">Great Comet of 1577</a></b> (<i id="mw8g">pictured</i>) caused almost century-long debate, during which <a class="mw-redirect" href="./Galileo" id="mw8w" rel="mw:WikiLink" title="Galileo">Galileo</a> argued that comets were merely optical illusions?