----- Original Message ----- From: "Robert Seeberger" <[EMAIL PROTECTED]> To: "Brin Mail List" <brin-l@mccmedia.com> Sent: Saturday, September 15, 2007 7:20 PM Subject: Mirror particles form new matter
> http://news.bbc.co.uk/2/hi/science/nature/6991030.stm > > > Fragile particles rarely seen in our Universe have been merged with > ordinary electrons to make a new form of matter. > Di-positronium, as the new molecule is known, was predicted to exist > in 1946 but has remained elusive to science. > > Now, a US team has created thousands of the molecules by merging > electrons with their antimatter equivalent: positrons. > > The discovery, reported in the journal Nature, is a key step in the > creation of ultra-powerful lasers known as gamma-ray annihilation > lasers. > > "The difference in the power available from a gamma-ray laser > compared to a normal laser is the same as the difference between a > nuclear explosion and a chemical explosion," said Dr David Cassidy > of the University of California, Riverside, and one of the authors > of the paper. > > "It would have an incredibly high power density." > > As a result, there is a huge interest in the technology from the > military as well as energy researchers who believe the lasers could > be used to kick-start nuclear fusion in a reactor. > > Mirror world > > Di-positronium was first predicted to exist by theoretical physicist > John Wheeler and its component atoms - positronium - were first > isolated in 1951. > > These short-lived, hydrogen-like atoms consist of an electron and a > positron, a positively charged antiparticle. > > Antiparticles are the mirror image of ordinary particles. > > There is an antiparticle for each type of particle in the Universe. > For example, a positively charged proton has a corresponding > negatively charged antiproton. > > Conventional thinking states that both antimatter and matter should > have been created in equal quantities at the birth of the Universe. > > The dominance of matter in our world is one of science's most > enduring mysteries. > > Antimatter only makes fleeting appearances in our Universe when > high-energy particle collisions take place, such as when cosmic rays > impact the Earth's atmosphere. They are also made in the lab in > particle accelerators such as Europe's nuclear research facility, > Cern. > > These appearances are always short lived because antiparticles are > destroyed when they collide with normal matter. The meeting leaves a > trace, often as high energy x-rays or gamma-rays. > > These emissions are used today in PET (positron emission tomography) > scanners to study activity in the brain. > > Short lives > > The transient nature of antiparticles has made creating and studying > di-positronium problematic. > > "We've known about this molecule; we're not surprised that it exists > but it's taken us more than 50 years to create it in the lab," said > Dr Cassidy. > > To make the molecule, Dr Cassidy and his team used a specially > designed trap to store millions of the positrons. > > A burst of 20 million were then focused and blasted at a porous > silica "sponge". > > "It's like having a trickle of water filling up a bath and then you > empty it out and you get a big flush," said Dr Cassidy. > > As the positrons rushed into the voids they were able to capture > electrons to form atoms. Where atoms met, they formed molecules. > > "All we are really doing is implanting lot of positrons into the > smallest spot we can, in the shortest time, and hoping that some of > them can see each other," said Dr Cassidy. > > By measuring the gamma-rays that signalled their annihilation, the > team estimated that up to 100,000 of the molecules formed, albeit > for just a quarter of a nanosecond (billionth of a second). > > Laser beam > > Dr Cassidy believes that increasing the density of the positronium > in the silicon would create an exotic state of matter known as a > Bose-Einstein condensate (BEC). > > BECs are usually produced by supercooling atoms so that they merge > and begin to behave like one giant atom. > > They have been used in many experiments such as the 2003 Harvard > study in which scientists were able to trap light. > > "At even higher densities, one might expect the material to become a > regular, crystalline solid," wrote Professor Clifford Surko, of the > University of Californian, San Diego, in an accompanying article. > > Taking it one step further, scientists could use the spontaneous > annihilation of the BEC, and the subsequent outburst of gamma-rays, > to make a powerful laser. > > "A gamma-ray laser is the kind of thing that if it existed people > would find new uses for it everyday," said Dr Cassidy. > > He highlighted an experiment at the National Ignition Facility (NIF) > in the US where scientists are using 196 lasers to heat a fuel > target to try to kick-start nuclear fusion. > > "Imagine doing that but you no longer need hundreds of lasers," he > said. > > > > xponent > > A Step Maru > > rob > > _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
