Scientists
have made the first ever accurate measurements of the properties of
antihydrogen – an atom comprising of an antiproton and positron. The explanations
match those of an ordinary hydrogen atom. Even though this was what theorists
had expected, it leaves unresolved one of physics' greatest mysteries, which
we'd have been on the way to answering if the results had been different.
In most
ways, antimatter is like a spitting image of matter, with identical mass but
opposite electric charges and some other vital aspects, a phenomenon known as
symmetry. We have studied antimatter formed in particle accelerators and by
cosmic rays, but as an antimatter particle annihilates on encountering matter,
they do not generally last very long, so calculations of how different
antimatter particles interact with each other have been scarce.
Professor Jeffrey Hangst of Aarhus University and colleagues have started calling this, detecting
the radiation emitted when a positron in antihydrogen changes energy levels. In
Nature, they describe the energy levels are within 2 percent of those in
hydrogen if there is any change at all. The calculations cover what is known as
the Lamb shift, a change in the energy levels of two excited electron states,
which were once estimated to be same. The Lamb shift's discovery in 1947 stimulated
the development of quantum electrodynamics.
One of the
toughest things to clarify about the universe is why there is so much matter,
and so less antimatter. Models of the Big Bang propose equal amounts of each
should have been produced, leaving the apparent question of where all the
antimatter went.
Physicists
believe the near-absence of antimatter shows symmetry cannot be perfect – in
some way we don't yet realize why the properties of antimatter don't precisely
reflect those of matter. It was expected reviewing the transitions between
energy levels for a proton might give a clue of these deviances.
A universe
with equivalent amounts of matter and antimatter would not be a secure place to
have a planet, if one could even form while continuously endangered by
annihilation. Researchers, however, find “it's necessary for life” a very
unsatisfying clarification for why the universe has the structure it does. Thus
far, however, we haven't found anything more conclusive.
http://alpha.web.cern.ch/news-investigation-fine-structure-antihydrogen
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