| Supersymmetry - the end of the line | Jon Butterworth and Herbi Dreiner Just before this blog moved to the Guardian, I wrote about a supersymmetry meeting I attended. Now my theory pal who organised it chips inIn case you missed it, I wrote about a conference on supersymmetry I went to last week, just before this blog moved home. I also gave some reasons why supersymmetry might, or might not, be seen as an attractive extension of the Standard Model of particle physics, given that there is no experimental evidence for it yet.Now my theory friend Herbi Dreiner, who I used to work with when I was a student and who organised the Bonn meeting, has given his view. Since I know there are heaps of supersymmetry fans out there, I thought I should bring it to your attention:The conference on "Supersymmetry and the Unification of Fundamental Interactions", which my colleagues and I organised in Bonn, finished yesterday. The entire week I was thinking I would drop into bed and sleep for a full day. But oddly, I feel quite refreshed. It was great fun listening to the talks and discussing with so many friends and colleagues, despite all the organisational headaches. The conference dinner was on an elegant boat which in an earlier life was used for the signing ceremony of the Schengen agreement. (For us mainland Europeans this is a big deal.)Supersymmetry seems alive and well and ready to face the challenge from the LHC. But what is supersymmetry? And what is so super about it? Why are we so taken with it, even though there is as yet no experimental evidence it actually exists? There are two main arguments. First, it is a solution to the "hierarchy problem". I will save this for a potential second post, if Jon invites me back. The other is indeed an aesthetic argument related to the "Coleman-Mandula theorem".Now, I tell myself every morning in front of the bathroom mirror that aesthetics is for wimps, but it is all the same an interesting argument.Symmetries have become a central pillar of our understanding of nature. A sphere is symmetric in the sense that if you leave me in a room with the sphere and come back in, you cannot tell if and by possibly how much and about which axis I have rotated the sphere. The sphere is highly symmetric. This, however, also makes a sphere kind of boring, since because it has to be the same in every direction it has no structure. If the sphere has a pattern on it, like for example an old black and white football, only very specific rotations are still undetectable. This is the remaining, reduced symmetry.It turns out that in the world of elementary particles there are two types of symmetry. One kind is internal symmetries. These govern the forces of nature like the electromagnetic force. Here a hidden, internal property of particles is changed. The other kind we call external symmetries and they affect the way particles fly through space and time. The appropriate external symmetry is described by special relativity, invented by Einstein in 1905. The undetectable transformations are called Lorentz transformations. In this case the laws of nature are unchanged if we look at the particles for example on a stationary train or one moving with constant velocity (and on smooth tracks!).Now how about Coleman and Mandula? They showed that in fact the Lorentz symmetries are the maximal external symmetry allowed in nature. If you were to introduce a larger more extensive symmetry the world would become so boring that particles could no longer interact. They would just fly around freely in space not knowing about each other. However, in their argument Coleman and Mandula neglected one external property of particles, their spin. This is a peculiar quantum property: they behave as if they had a small internal magnet. In specific units all the matter particles we know, e.g. the electron and the quarks, have spin 1/2. The force carriers like the photon have spin 1. Spin is an external property, which is affected by rotations in space. Now if we extend Coleman and Mandula and allow for discrete changes of spin by half a unit, we find a new maximal external symmetry of nature. This is supersymmetry. It is super because it goes beyond the previous external symmetries. If nature is supersymmetric the electron must have a partner with spin 0 and the photon a partner with spin 1/2 and all with many interactions.However, if this symmetry were at all extended (now also taking spin into account, of course) the resulting world would be boring and trivial with no interactions. Since we have now used up all external particle properties we believe this is the end of the line. This is what makes supersymmetry so special ... and to some beautiful.Of course, the data from the LHC over the next months and years, but also from precision measurements of certain particle properties, will decide whether any of this is real.Jon Butterworthguardian.co.uk © Guardian News & Media Limited 2010 | Use of this content is subject to our Terms & Conditions | More Feeds guardian.co.uk |
Harrabin's Notes Roger Harrabin on the impact of "sit-stand" flights bbc.co.uk |
UK Centre for Intelligent Design claims it will focus on science, not religion The newly opened Centre for Intelligent Design aims to start a debate in the UK that's not about religion but about evidenceIn 2006 Elanor Taylor wrote that it was time for the UK to wage war on intelligent design, saying that while it and creationism used to be regarded like line dancing and SUVs – "peculiarly American phenomena" – they were now taking root in British life. The last few years have led to more debate about creationism and intelligent design, especially their classroom presence, due in part to Darwin's bicentenary celebrations and the continued, sometimes acrimonious, discussion about the relationship between science and religion. Creationism in this country has its cheerleaders in museums, schools and zoos, but what of intelligent design? In Glasgow, a new institution hopes to fill that gap.The Centre for Intelligent Design features a video introduction from Dr Alastair Noble, who has argued that ID should not be excluded from the study of origins. He says, among other things, that he is part of a network of people who are "dissatisfied with the pervading Darwinian explanation of origins and are attracted to the much more credible position of intelligent design" and criticise the "strident strain of science" that says the only acceptable explanations are those depending on "physical and materialistic processes".The small print of the website says the centre's activity "is organised under a charitable trust governed by the laws of Guernsey, Channel Islands". The centre receives funding from individuals and organisations who support its aims, according to the website, and its launch has earned plaudits from the Discovery Institute which says the centre returns ID to its roots: "Some of the best known pioneers of modern science did their work in Britain and Europe in the conviction that they were exploring a universe that really was designed."In a telephone interview, Noble denies that the centre is a British branch of Discovery: "We are friends with Discovery and we talk to them, but we are not formally linked. We would be interested in developing links with Europe. We don't get money from America – it is funded from Britain. We don't have huge amounts of money. We will have a series of projects and will raise funds as and when needed."According to Noble, what separates the Centre for Intelligent Design from other bodies engaged in the evolution argument is its emphasis on science: "There are various organisations that debate the faith issue around origins, but what we will be trying to do is open a debate around the scientific issue. ID is consistently misrepresented as a religious position. The debate about ID is quite difficult to elevate to a civilised conversation. It's not about religion, it's about evidence."The network of people supporting the centre's activities numbers between 50 and 100. Among them is its president Professor Norman Nevin, emeritus professor of medical genetics, Queens University, Belfast, and its vice-president Dr David Galloway, who is also vice president of the Royal College of Physicians and Surgeons, Glasgow. In its FAQs, the site lists the UK scientists "who are brave enough to make their support for intelligent design public. There are many more who are not willing to risk their careers by making their objections to evolution known."Blogger and anti-Creationist campaigner Naon Tiotami notes that the support of "prominent academics" suggests "they may stand a fighting chance at being taken seriously by the media, something that Truth in Science hasn't accomplished," before adding: "All we can do at the moment is hope that this new project crash-lands before it even properly gets its feet off the ground."Next month the centre hosts Professor Mike Behe on a national lecture tour.I asked Michael Reiss professor of science education at the Institute of Education in London what he thought about the Centre for Intelligent Design. He replied: "In a free society it is important that organisations that do not accept the scientific theory of evolution are allowed to exist and to proclaim their message. However, the overwhelming scientific consensus is that the arguments against the theory of evolution put forward by creationists and those who advocate intelligent design (ID) are invalid."In a school setting this means that while teachers of science are perfectly at liberty to address creationist and ID issues, should they so wish, students must not be given the impression that there is a scientific controversy over whether the Earth is very old (about 4.6 billion years old) or whether all species descend from very simple common ancestors."For now, the Centre for Intelligent Design is nothing more than a website and an office. What it achieves will depend on how much appetite there is in the UK for intelligent design and what resistance is mounted to its message.EvolutionBiologyControversies in scienceCreationismReligionRiazat Buttguardian.co.uk © Guardian News & Media Limited 2010 | Use of this content is subject to our Terms & Conditions | More Feeds guardian.co.uk |
Private spaceship makes first solo glide flight By 2010-10-11T03:51:23ZMOJAVE, Calif. (AP) -- Virgin Galactic's space tourism rocket SpaceShipTwo achieved its first solo glide flight Sunday, marking another step in the company's eventual plans to fly paying passengers.... hosted.ap.org |
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