{"id":3080,"date":"2008-10-24T09:44:57","date_gmt":"2008-10-24T09:44:57","guid":{"rendered":"http:\/\/scienceblogs.com\/principles\/2008\/10\/24\/dark-matter-doesnt-exist\/"},"modified":"2008-10-24T09:44:57","modified_gmt":"2008-10-24T09:44:57","slug":"dark-matter-doesnt-exist","status":"publish","type":"post","link":"http:\/\/chadorzel.com\/principles\/2008\/10\/24\/dark-matter-doesnt-exist\/","title":{"rendered":"Dark Matter Doesn’t Exist?"},"content":{"rendered":"

Claims of the non-existence of dark matter are a staple of astro-kookery, but Physics World<\/cite> today has a news story with the provocative title “Galaxy survey casts doubts on cold dark matter<\/a>,” which makes it sound like people from reputable collaborations are questioning the existence of dark matter.<\/p>\n

So what’s the deal? Well, here’s the explanation of the results, which come from a survey of 200-odd galaxies identified by both radio and visible telescopes:<\/p>\n

\n

Using data from both telescopes, the team classified the galaxies in terms of six independent properties. These were two optical radii (which define the sizes of the regions of a galaxy that emit 50% and 90% of the object’s light); the luminosity; the mass of neutral hydrogen in the galaxy; the dynamical mass (which includes dark matter); and the colour of the galaxy. The team then carried out a statistical analysis of the data and found five correlations between these six properties — leading them to conclude that the structure of these galaxies is controlled by just one parameter. Although the team was unable to conclude exactly what this parameter is, Disney says that it seems to have a strong relationship with the mass of the galaxies.<\/p>\n

Disney argues that the team’s finding is at odds with the hierarchical theory of galaxy formation, according to which the structure of a galaxy would be strongly influenced by the nature of the collisions that formed it. “If this were the case we would have expected to see 4-5 independent parameters”, he says. And because the hierarchical theory has CDM at its root, Disney believes that the team’s survey provides strong evidence that CDM does not exist. “Maybe our observations could be explained by CDM, but I wouldn’t bet on it”, he said. <\/p>\n<\/blockquote>\n

That sounds a whole lot squishier than the title would make you think. A complicated statistical analysis suggests that there are correlations between a bunch of parameters, which might invalidate a model of galaxy formation that might predict less of a correlation, and because that model involves cold dark matter, it might invalidate the CDM hypothesis. That’s a lot of mights.<\/p>\n

I’m not really in a position to evaluate this, though. One of my colleagues at work probably is, but I’m not going in today, so I’ll throw this out to my astro-savvy readers: what do you make of this story?<\/p>\n","protected":false},"excerpt":{"rendered":"

Claims of the non-existence of dark matter are a staple of astro-kookery, but Physics World today has a news story with the provocative title “Galaxy survey casts doubts on cold dark matter,” which makes it sound like people from reputable collaborations are questioning the existence of dark matter. So what’s the deal? Well, here’s the… Continue reading Dark Matter Doesn’t Exist?<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"1","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[10,33,11],"tags":[],"class_list":["post-3080","post","type-post","status-publish","format-standard","hentry","category-astronomy","category-in_the_news","category-science","entry"],"_links":{"self":[{"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/posts\/3080","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/comments?post=3080"}],"version-history":[{"count":0,"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/posts\/3080\/revisions"}],"wp:attachment":[{"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/media?parent=3080"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/categories?post=3080"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/tags?post=3080"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}