{"id":3475,"date":"2013-12-23T16:00:19","date_gmt":"2013-12-23T04:00:19","guid":{"rendered":"https:\/\/blogs.otago.ac.nz\/emxphi\/?p=3475"},"modified":"2013-12-20T10:48:06","modified_gmt":"2013-12-19T22:48:06","slug":"halleys-comet-and-christmas-day","status":"publish","type":"post","link":"https:\/\/blogs.otago.ac.nz\/emxphi\/halleys-comet-and-christmas-day\/","title":{"rendered":"Halley\u2019s Comet and Christmas Day"},"content":{"rendered":"

Kirsten Walsh writes…<\/em><\/strong><\/p>\n

Hello Readers!<\/p>\n

Since this is our last post for the year, and the holidays are almost upon us, I thought I\u2019d tell you a Christmas story:<\/p>\n

On Christmas day in 1758, Johann Georg Palitzsch<\/a>, a German farmer and amateur astronomer, became the first person to witness the return of, what would become known as, Halley\u2019s comet.<\/p>\n

Halley\u2019s comet is the only short-period comet (i.e. comet that completes an orbit in under 200 years) that is visible with the naked eye.\u00a0 It has featured in astronomical reports since at least 240 BC.\u00a0 However, it wasn\u2019t until 1705 that it was recognised as the same object.\u00a0 That year, the English astronomer Edmund Halley<\/a> determined the periodicity of the comet, writing about it in his Synopsis Astronomia Cometicae<\/em>. \u00a0With the help of Newton\u2019s theories of elliptical orbit, Halley had studied the data of the comets that had appeared in 1531, 1607 and 1682, and recognised that they all followed similar paths.\u00a0 He made a rough estimate that the comet would return in 1758.<\/p>\n

Halley died in 1742, and so he never saw the return of the comet.\u00a0 But Palitzsch\u2019s Christmas day observation confirmed his claim that, indeed, there was <\/em>a comet, visible by the naked eye, that had period of approximately 76 years.\u00a0 It was the first time anything other than a planet had been shown to orbit the earth.\u00a0 In 1759, the French astronomer Nicolas Louis de Lacaille<\/a> named the comet after Halley.<\/p>\n

This prediction counts, not only as a confirmation of Halley\u2019s theory, but also of Newtonian physics, and of the mathematico-experimental method more generally.\u00a0 It seems fitting that this confirmation happened on the 116th<\/sup> anniversary of Newton\u2019s birth!*<\/p>\n

We at Early Modern Experimental Philosophy wish you a happy holiday.\u00a0 We look forward to hearing from you in 2014!<\/p>\n

 <\/p>\n

*Actually, Newton was born in England on 25 December 1642, but Palitzsch saw Halley\u2019s comet in Germany on 25 December 1758.\u00a0 Until 1752, England used the Julian (\u2018Old Style\u2019) calendar, whereas Europe had adopted the Gregorian (\u2018New Style\u2019) calendar much earlier.\u00a0 There is a 10-day difference between the two calendars, so Newton\u2019s birthdate adjusts to 4 January 1643 on the Gregorian calendar.\u00a0 So while both events happened on Christmas day, they happened on different Christmas days.\u00a0 (Also, I hope you will forgive me for this picture, that I couldn\u2019t resist posting!)<\/p>\n

\"\"<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Kirsten Walsh writes… Hello Readers! Since this is our last post for the year, and the holidays are almost upon us, I thought I\u2019d tell you a Christmas story: On Christmas day in 1758, Johann Georg Palitzsch, a German farmer […]<\/p>\n","protected":false},"author":4582,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[113],"tags":[16413,16414],"class_list":["post-3475","post","type-post","status-publish","format-standard","hentry","category-ideas","tag-christmas","tag-halleys-comet"],"_links":{"self":[{"href":"https:\/\/blogs.otago.ac.nz\/emxphi\/wp-json\/wp\/v2\/posts\/3475","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.otago.ac.nz\/emxphi\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.otago.ac.nz\/emxphi\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.otago.ac.nz\/emxphi\/wp-json\/wp\/v2\/users\/4582"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.otago.ac.nz\/emxphi\/wp-json\/wp\/v2\/comments?post=3475"}],"version-history":[{"count":0,"href":"https:\/\/blogs.otago.ac.nz\/emxphi\/wp-json\/wp\/v2\/posts\/3475\/revisions"}],"wp:attachment":[{"href":"https:\/\/blogs.otago.ac.nz\/emxphi\/wp-json\/wp\/v2\/media?parent=3475"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.otago.ac.nz\/emxphi\/wp-json\/wp\/v2\/categories?post=3475"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.otago.ac.nz\/emxphi\/wp-json\/wp\/v2\/tags?post=3475"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}