Sunday, May 29, 2011

Scientists Discover Electron's Spherical Shape

The most accurate measurement yet of the electron has been made by a team of European researchers, and the results reveal it is surprisingly spherical.

Illustration of this article

Writing in the journal Nature, the researchers from Imperial College London in the United Kingdom present their findings following an experiment that lasted over a decade.

The results reveal how the electron just misses being categorised as perfectly round by less than 0.000000000000000000000000001 cm. The team ascertain that if we were able to magnify an electron to the size of the solar system, it would appear perfectly spherical to the human eye within the width of a human hair.

The team of physicists carried out the study by looking at the electrons inside molecules called ytterbium fluoride. They used a very precise laser to take measurements of the motion of these electrons.

The scientists were able to detect that the electrons were round since if an electron is not spherical in shape its motion will exhibit a distinct wobble that contorts the shape of the rest of the molecule, much like an unbalanced spinning top. As the team witnessed no wobbling they concluded that the electrons were round in shape.

Dr Jony Hudson, one of the study's authors from the Department of Physics at Imperial College London, says: 'We're really pleased that we've been able to improve our knowledge of one of the basic building blocks of matter. It's been a very difficult measurement to make, but this knowledge will let us improve our theories of fundamental physics. People are often surprised to hear that our theories of physics aren't 'finished', but in truth they get constantly refined and improved by making ever more accurate measurements like this one.'

This study moves forward one of the biggest remaining mysteries in physics: getting to the bottom of how and why there is a predominance of matter over antimatter. The current accepted school of thought among physicians is that during the Big Bang as much antimatter was created as ordinary matter. But since the existence of antimatter, an elusive substance that behaves in the same way as ordinary matter except that it has an opposite electrical charge, was first predicted by the scientist Paul Dirac in 1928, it has only been found in tiny amounts from sources such as cosmic rays and some radioactive substances.

Working out where, and indeed if, any deposits of antimatter exist that have until now gone undiscovered is the main aim of research in this field. Scientists are trying to explain this lack of antimatter by searching for tiny differences between the behaviour of matter and antimatter that no one has yet observed.

As the antimatter version of the negatively charged electron is the positively charged anti-electron, also known as a positron, by understanding the shape of the electron better the scientists from Imperial College London hope this knowledge will lead them in turn to a better understanding of how positrons behave and how antimatter and matter might differ. This will be the focus of the next stage of their research.

Study co-author Professor Edward Hinds, Head of the Centre for Cold Matter at Imperial College London, commented on the implications of their work: 'The whole world is made almost entirely of normal matter, with only tiny traces of antimatter. Astronomers have looked right to the edge of the visible universe and even then they see just matter, no great stashes of antimatter. Physicists just do not know what happened to all the antimatter, but this research can help us to confirm or rule out some of the possible explanations.'

The team are now developing new methods to cool their molecules to extremely low temperatures in order to help improve their measurements of the electron's shape, and to control the exact motion of the molecules. This will enable them to study the behaviour of the embedded electrons in much greater detail than ever before.

Had the researchers found that electrons are not round it would have provided proof that the behaviour of antimatter and matter differ more than physicists previously thought. This would have explained how all the antimatter disappeared from the universe, leaving only ordinary matter.

Imperial College London

Citation: Hudson, J.J., et al. (2011) Improved measurement of the shape of the electron. Nature. DOI: 10.1038/nature10104.

1 comment:

  1. Would the apparent similarity in physical shape between the electron and positron support an argument for some form of yin-yang symmetry between matter and antimatter after the Big Bang?