{"id":1798,"date":"2008-07-24T09:27:23","date_gmt":"2008-07-24T14:27:23","guid":{"rendered":"http:\/\/blogs.discovermagazine.com\/cosmicvariance\/2008\/07\/24\/arxiv-find-stars-in-other-universes\/"},"modified":"2008-07-24T09:27:23","modified_gmt":"2008-07-24T14:27:23","slug":"arxiv-find-stars-in-other-universes","status":"publish","type":"post","link":"https:\/\/preposterousuniverse.com\/blog\/2008\/07\/24\/arxiv-find-stars-in-other-universes\/","title":{"rendered":"arxiv Find:  Stars in Other Universes"},"content":{"rendered":"<p>Fred Adams wonders whether we could still have stars if the constants of nature were very different.  Answer:  very possibly!  It&#8217;s in <a href=\"http:\/\/arxiv.org\/abs\/0807.3697\">arxiv:0807.3697<\/a>:<\/p>\n<blockquote><p>Motivated by the possible existence of other universes, with possible variations in the laws of physics, this paper explores the parameter space of fundamental constants that allows for the existence of stars. To make this problem tractable, we develop a semi-analytical stellar structure model that allows for physical understanding of these stars with unconventional parameters, as well as a means to survey the relevant parameter space. In this work, the most important quantities that determine stellar properties &#8212; and are allowed to vary &#8212; are the gravitational constant $G$, the fine structure constant $alpha$, and a composite parameter $C$ that determines nuclear reaction rates. Working within this model, we delineate the portion of parameter space that allows for the existence of stars. Our main finding is that a sizable fraction of the parameter space (roughly one fourth) provides the values necessary for stellar objects to operate through sustained nuclear fusion. As a result, the set of parameters necessary to support stars are not particularly rare. In addition, we briefly consider the possibility that unconventional stars (e.g., black holes, dark matter stars) play the role filled by stars in our universe and constrain the allowed parameter space.<\/p><\/blockquote>\n<p>I&#8217;ve never thought that our knowledge of what constituted &#8220;intelligent life&#8221; was anywhere near good enough to start making statements about the conditions under which it could form, apart from fairly weak stuff like &#8220;life probably can&#8217;t exist if the universe only lasts for a Planck time.&#8221;  So when anthropic arguments start to hinge on thinking that fractional changes in the mass of this or that nucleus would result in a universe with no observers, it seems more prudent to admit that we just don&#8217;t know.  But putting any anthropic considerations aside, it&#8217;s still interesting to ask what the universe would look like if the constants of nature were completely different.  How robust are the starry skies?<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Fred Adams wonders whether we could still have stars if the constants of nature were very different. Answer: very possibly! It&#8217;s in arxiv:0807.3697: Motivated by the possible existence of other universes, with possible variations in the laws of physics, this paper explores the parameter space of fundamental constants that allows for the existence of stars. [&hellip;]<\/p>\n","protected":false},"author":4,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[11,28],"tags":[],"class_list":["post-1798","post","type-post","status-publish","format-standard","hentry","category-arxiv","category-science"],"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/preposterousuniverse.com\/blog\/wp-json\/wp\/v2\/posts\/1798","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/preposterousuniverse.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/preposterousuniverse.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/preposterousuniverse.com\/blog\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/preposterousuniverse.com\/blog\/wp-json\/wp\/v2\/comments?post=1798"}],"version-history":[{"count":0,"href":"https:\/\/preposterousuniverse.com\/blog\/wp-json\/wp\/v2\/posts\/1798\/revisions"}],"wp:attachment":[{"href":"https:\/\/preposterousuniverse.com\/blog\/wp-json\/wp\/v2\/media?parent=1798"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/preposterousuniverse.com\/blog\/wp-json\/wp\/v2\/categories?post=1798"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/preposterousuniverse.com\/blog\/wp-json\/wp\/v2\/tags?post=1798"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}