{"id":457,"date":"2012-05-31T16:14:17","date_gmt":"2012-05-31T21:14:17","guid":{"rendered":"http:\/\/blog.richmond.edu\/physicsbunn\/?p=457"},"modified":"2012-05-31T16:14:17","modified_gmt":"2012-05-31T21:14:17","slug":"watch-out-for-andromeda","status":"publish","type":"post","link":"https:\/\/blog.richmond.edu\/physicsbunn\/2012\/05\/31\/watch-out-for-andromeda\/","title":{"rendered":"Watch out for Andromeda"},"content":{"rendered":"<p>There&#8217;s something I&#8217;ve <a href=\"http:\/\/blog.richmond.edu\/physicsbunn\/2009\/01\/14\/collision-course\/\">wondered about <\/a>for years. Astronomers always say that the Andromeda Galaxy (also known as M31) is going to collide with our own. After all, we measure the galaxy&#8217;s velocity via the Doppler effect, and we find it&#8217;s moving towards us. But the Doppler effect only lets you measure the radial component of the galaxy&#8217;s velocity &#8212; that is, how fast it&#8217;s moving towards or away from us, but not how fast it&#8217;s moving laterally. How do we know that Andromeda isn&#8217;t moving sideways at a high enough speed to miss us?<\/p>\n<p>Well, it <a href=\"http:\/\/www.nature.com\/news\/andromeda-on-collision-course-with-the-milky-way-1.10765\">turns out <\/a>not to be moving sideways very fast at all, so it is going to hit us. Good to know I guess. I&#8217;m just glad to see that this question I&#8217;ve been wondering about for so long is a legitimate question: I&#8217;ve seen so many mentions of the impending collision, with no reference at all to the lateral-velocity question, that I was wondering if I was missing something obvious.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>There&#8217;s something I&#8217;ve wondered about for years. Astronomers always say that the Andromeda Galaxy (also known as M31) is going to collide with our own. After all, we measure the galaxy&#8217;s velocity via the Doppler effect, and we find it&#8217;s moving towards us. But the Doppler effect only lets you measure the radial component of &hellip; <a href=\"https:\/\/blog.richmond.edu\/physicsbunn\/2012\/05\/31\/watch-out-for-andromeda\/\" class=\"more-link\">Continue reading <span class=\"screen-reader-text\">Watch out for Andromeda<\/span><\/a><\/p>\n","protected":false},"author":12,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-457","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/blog.richmond.edu\/physicsbunn\/wp-json\/wp\/v2\/posts\/457","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.richmond.edu\/physicsbunn\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.richmond.edu\/physicsbunn\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.richmond.edu\/physicsbunn\/wp-json\/wp\/v2\/users\/12"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.richmond.edu\/physicsbunn\/wp-json\/wp\/v2\/comments?post=457"}],"version-history":[{"count":0,"href":"https:\/\/blog.richmond.edu\/physicsbunn\/wp-json\/wp\/v2\/posts\/457\/revisions"}],"wp:attachment":[{"href":"https:\/\/blog.richmond.edu\/physicsbunn\/wp-json\/wp\/v2\/media?parent=457"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.richmond.edu\/physicsbunn\/wp-json\/wp\/v2\/categories?post=457"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.richmond.edu\/physicsbunn\/wp-json\/wp\/v2\/tags?post=457"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}