{"id":1154,"date":"2019-11-27T14:34:35","date_gmt":"2019-11-27T01:34:35","guid":{"rendered":"https:\/\/blog.waikato.ac.nz\/physicsstop\/?p=1154"},"modified":"2019-11-27T14:38:21","modified_gmt":"2019-11-27T01:38:21","slug":"when-you-are-your-own-opposite","status":"publish","type":"post","link":"https:\/\/blog.waikato.ac.nz\/physicsstop\/2019\/11\/27\/when-you-are-your-own-opposite\/","title":{"rendered":"When you are your own opposite"},"content":{"rendered":"<p>I was reading in a physics magazine earlier in the week about the nature of neutrinos. These are extremely numerous elementary particles, but only interact very weakly with anything.\u00a0 Around a million billion pass through you each second, almost all originating from our sun, but few of them are likely to interact with you enroute. A typical neutrino will travel through space for many many lightyears before it interacts with anything.\u00a0 Consequently studying neutrinos is pretty tough science. There are a few experiments in the world to detect neutrinos, such as the <a href=\"https:\/\/icecube.wisc.edu\/about\/overview\">IceCube detector<\/a> at the South Pole (Don&#8217;t you love the name?) Here&#8217;s Jenni Adams from the University of Canterbury talking about what it takes to detect them.<\/p>\n<div class=\"video-container\"><iframe loading=\"lazy\" title=\"A mountain-sized telescope, under a mile of ice | Jenni Adams | TEDxChristchurch\" width=\"1170\" height=\"658\" src=\"https:\/\/www.youtube.com\/embed\/PYYyRjTaypI?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" allowfullscreen><\/iframe><\/div>\n<p>I first came across neutrinos in my undergraduate studies in a Particle Physics course. Here they were discussed in terms of beta-decay, <a href=\"https:\/\/www.khanacademy.org\/science\/in-in-class-12th-physics-india\/nuclei\/in-in-nuclear-physics\/a\/radioactive-decay-types-article\">one of the more common forms of radioactive decay.<\/a> We see beta-decay for example with the element yttrium (I love that name too). The particular isotope of yttrium with 39 protons and 51 neutrons in its nucleus is unstable &#8211; a neutron is able to change to a proton and emit an electron (the &#8216;beta particle&#8217;) and an anti-neutrino.<\/p>\n<p>While I knew about protons, neutrons and electrons, the neutrino (or in this case, anti-neutrino) was something new.<\/p>\n<p>Now, we don&#8217;t know much about neutrinos, really, because they are so hard to observe. We know there are three types of them, and that they have a very small mass (though what the possible values of mass are is only partly known), that they have no electric charge, and they have a <a href=\"https:\/\/www.space.com\/39152-weird-quantum-property-of-spin.html\">&#8216;spin&#8217;<\/a> of 1\/2.\u00a0 And we know that a neutrino must have an &#8216;opposite&#8217; version &#8211; an anti-neutrino, because that&#8217;s how stuff works in this universe. <a href=\"https:\/\/www.livescience.com\/32387-what-is-antimatter.html\">Anti matter<\/a> is much the same as matter, it&#8217;s just an &#8216;opposite&#8217;. If we bring together a particle and its antiparticle, they can annihilate each other in a puff of energy.\u00a0 It&#8217;s a staple of science fiction stories, but it&#8217;s also highly useful science fact &#8211; for example, anti-electrons (positrons) are produced during positron emission tomography (the &#8216;PET&#8217; scan now commonly found in hospitals).<\/p>\n<p>But, what I found out while reading my physics magazine earlier in the week, was that no-one is yet sure whether or not a neutrino is its own antiparticle. That is, there&#8217;s the possibility that a neutrino and an anti-neutrino are actually the same thing. This isn&#8217;t crazy, for example a photon (a &#8216;particle&#8217; of light) is its own antiparticle. If this is the case, a neutrino would be the first and probably only example of an elementary particle being a<a href=\"https:\/\/en.wikipedia.org\/wiki\/Majorana_fermion\"> &#8216;Majorana particle&#8217;<\/a> &#8211; a particle of non-integer spin being its own antiparticle.<\/p>\n<p>There is a potential way of finding out. There are some elements that undergo,very occasionally, <a href=\"https:\/\/en.wikipedia.org\/wiki\/Double_beta_decay\">&#8216;double-beta&#8217; radioactive decay<\/a>, where two neutrons change to protons and emit electrons and anti-neutrinos simultaneously. Now, if the neutrino is its own antiparticle, two anti-neutrinos could annihilate each other. Thus, if one observes double-beta decay without any neutrinos one can conclude that they are their own opposite. <a href=\"https:\/\/neutrinos.fnal.gov\/sources\/beta-decay\/\">It&#8217;s an extremely hard experiment to do<\/a>, but there are research groups trying just that.<\/p>\n<p>In practical terms, it&#8217;s unlikely to mean very much to our daily lives, but for our understanding of the universe it would be very significant indeed.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>I was reading in a physics magazine earlier in the week about the nature of neutrinos. These are extremely numerous elementary particles, but only interact very weakly with anything.\u00a0 Around a million billion pass through you each second, almost all originating from our sun, but few of them are likely to interact with you enroute. [&hellip;]<\/p>\n","protected":false},"author":20,"featured_media":1162,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[7,52,51,40],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v22.3 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>When you are your own opposite : Physics Stop<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/blog.waikato.ac.nz\/physicsstop\/2019\/11\/27\/when-you-are-your-own-opposite\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"When you are your own opposite : Physics Stop\" \/>\n<meta property=\"og:description\" content=\"I was reading in a physics magazine earlier in the week about the nature of neutrinos. These are extremely numerous elementary particles, but only interact very weakly with anything.\u00a0 Around a million billion pass through you each second, almost all originating from our sun, but few of them are likely to interact with you enroute. 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