{"id":2262,"date":"2016-08-24T18:00:21","date_gmt":"2016-08-24T23:00:21","guid":{"rendered":"http:\/\/blogs.ams.org\/blogonmathblogs\/?p=2262"},"modified":"2016-08-24T18:00:21","modified_gmt":"2016-08-24T23:00:21","slug":"its-not-a-trick-its-an-illusion","status":"publish","type":"post","link":"https:\/\/blogs.ams.org\/blogonmathblogs\/2016\/08\/24\/its-not-a-trick-its-an-illusion\/","title":{"rendered":"It&#8217;s Not a Trick, It&#8217;s an Illusion"},"content":{"rendered":"<p class=\"p1\"><span class=\"s1\">I\u2019ve stumbled on the <a href=\"http:\/\/illusionoftheyear.com\/\"><span class=\"s2\">Best Illusion of the Year Contest<\/span><\/a> a few times, but this is the first year I\u2019ve thought about the illusions mathematically.<\/span><\/p>\n<span class=\"embed-youtube\" style=\"text-align:center; display: block;\"><iframe loading=\"lazy\" class=\"youtube-player\" width=\"640\" height=\"360\" src=\"https:\/\/www.youtube.com\/embed\/oWfFco7K9v8?version=3&#038;rel=1&#038;showsearch=0&#038;showinfo=1&#038;iv_load_policy=1&#038;fs=1&#038;hl=en-US&#038;autohide=2&#038;wmode=transparent\" allowfullscreen=\"true\" style=\"border:0;\" sandbox=\"allow-scripts allow-same-origin allow-popups allow-presentation allow-popups-to-escape-sandbox\"><\/iframe><\/span>\n<p class=\"p1\"><span class=\"s2\"><a href=\"https:\/\/divisbyzero.com\/2016\/07\/05\/sugiharas-circlesquare-optical-illusion\/\">Dave Richeson wrote two<\/a><\/span><span class=\"s1\"> <a href=\"https:\/\/divisbyzero.com\/2016\/07\/06\/make-a-sugihara-circlesquare-optical-illusion-out-of-paper\/\"><span class=\"s2\">posts about this illusion<\/span><\/a> by Kokichi Sugihara, one of the top illusions from this year. In it, (topological) cylinders appear to have either square or circular cross-sections depending on what angle you view them from. He used Geogebra to show how to derive a curve that has the requisite properties and made a template so you can put your own deceptive cylinder together.<\/span><\/p>\n<p class=\"p1\"><span class=\"s1\">Naturally, Richeson\u2019s posts led me down an illusive, illusory, illustrative, or perhaps just illusional, rabbit-hole. The illusions on the contest website highlight various perceptual habits most people\u2019s brains share\u2014our <a href=\"http:\/\/illusionoftheyear.com\/2015\/06\/ambiguous-garage-roof\/\"><span class=\"s2\">preference for right angles<\/span><\/a>, the way we infer motion from changes in light, and the importance of context in identifying shade\u2014but not so many of them have obvious mathematical connections. Then I got to a color illusion that really grabbed me.<\/span><\/p>\n<span class=\"embed-youtube\" style=\"text-align:center; display: block;\"><iframe loading=\"lazy\" class=\"youtube-player\" width=\"640\" height=\"360\" src=\"https:\/\/www.youtube.com\/embed\/n_5g9URYGo4?version=3&#038;rel=1&#038;showsearch=0&#038;showinfo=1&#038;iv_load_policy=1&#038;fs=1&#038;hl=en-US&#038;autohide=2&#038;wmode=transparent\" allowfullscreen=\"true\" style=\"border:0;\" sandbox=\"allow-scripts allow-same-origin allow-popups allow-presentation allow-popups-to-escape-sandbox\"><\/iframe><\/span>\n<p class=\"p1\"><span class=\"s1\">In June, Vi Hart, mathemusician and virtual reality researcher, posted a <a href=\"http:\/\/elevr.com\/philosophy-of-color\/\"><span class=\"s2\">long, interesting rabbit-hole of a post about color perception<\/span><\/a> on the <a href=\"http:\/\/elevr.com\/\"><span class=\"s2\">eleVR<\/span><\/a> blog. It starts with that late-night dorm room question \u201cis my red your red?\u201d and considers how our color perception might influenced or be influenced by virtual reality. What color effects will we be able to learn about and play with as VR gets better and more widespread?<\/span><\/p>\n<p class=\"p1\"><span class=\"s1\">The mathematics of color is fascinating and perplexing to me. I was strongly indoctrinated into the red-blue-yellow primary paint color paradigm as a child, and it\u2019s been hard to unlearn that enough to understand how we actually see color in light. Nick Higham, applied mathematician at the University of Manchester, has a <a href=\"https:\/\/nickhigham.wordpress.com\/2015\/09\/14\/mathematics-in-color\/\"><span class=\"s2\">post about mathematics and color<\/span><\/a> that explains some of the nuances.<\/span><\/p>\n<p class=\"p1\">To me, the most astonishing\u00a0thing about these illusions is that even when you know the mathematical and perceptual reasons you see what you do, you can&#8217;t help but see it. Right now I&#8217;m stuck on these drifting Gabors.<\/p>\n<span class=\"embed-youtube\" style=\"text-align:center; display: block;\"><iframe loading=\"lazy\" class=\"youtube-player\" width=\"640\" height=\"360\" src=\"https:\/\/www.youtube.com\/embed\/Jri0del_6t4?version=3&#038;rel=1&#038;showsearch=0&#038;showinfo=1&#038;iv_load_policy=1&#038;fs=1&#038;hl=en-US&#038;autohide=2&#038;wmode=transparent\" allowfullscreen=\"true\" style=\"border:0;\" sandbox=\"allow-scripts allow-same-origin allow-popups allow-presentation allow-popups-to-escape-sandbox\"><\/iframe><\/span>\n<div style=\"margin-top: 0px; margin-bottom: 0px;\" class=\"sharethis-inline-share-buttons\" ><\/div>","protected":false},"excerpt":{"rendered":"<p>I\u2019ve stumbled on the Best Illusion of the Year Contest a few times, but this is the first year I\u2019ve thought about the illusions mathematically. Dave Richeson wrote two posts about this illusion by Kokichi Sugihara, one of the top &hellip; <a href=\"https:\/\/blogs.ams.org\/blogonmathblogs\/2016\/08\/24\/its-not-a-trick-its-an-illusion\/\">Continue reading <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n<div style=\"margin-top: 0px; margin-bottom: 0px;\" class=\"sharethis-inline-share-buttons\" data-url=https:\/\/blogs.ams.org\/blogonmathblogs\/2016\/08\/24\/its-not-a-trick-its-an-illusion\/><\/div>\n","protected":false},"author":61,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[9],"tags":[609,84,83,608],"class_list":["post-2262","post","type-post","status-publish","format-standard","hentry","category-recreational-mathematics","tag-dave-richeson","tag-math","tag-mathematics","tag-optical-illusions"],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p3tW3N-Au","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/blogs.ams.org\/blogonmathblogs\/wp-json\/wp\/v2\/posts\/2262","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.ams.org\/blogonmathblogs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.ams.org\/blogonmathblogs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.ams.org\/blogonmathblogs\/wp-json\/wp\/v2\/users\/61"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.ams.org\/blogonmathblogs\/wp-json\/wp\/v2\/comments?post=2262"}],"version-history":[{"count":1,"href":"https:\/\/blogs.ams.org\/blogonmathblogs\/wp-json\/wp\/v2\/posts\/2262\/revisions"}],"predecessor-version":[{"id":2263,"href":"https:\/\/blogs.ams.org\/blogonmathblogs\/wp-json\/wp\/v2\/posts\/2262\/revisions\/2263"}],"wp:attachment":[{"href":"https:\/\/blogs.ams.org\/blogonmathblogs\/wp-json\/wp\/v2\/media?parent=2262"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.ams.org\/blogonmathblogs\/wp-json\/wp\/v2\/categories?post=2262"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.ams.org\/blogonmathblogs\/wp-json\/wp\/v2\/tags?post=2262"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}