The online news portal of TV5 PARIS -- In the late eighth
century, Earth was hit by a mystery blast of cosmic rays,
according to a Japanese study that found a relic of the powerful
event in cedar trees. Analysis of two ancient trees found a
surge in carbon-14 -- a carbon isotope that derives from cosmic
radiation -- which occurred just in AD 774 and AD 775, the team
report in the journal Nature on Sunday. Earth is battered by
protons and other sub-atomic particles which are blasted across
space by high-energy sources. The particles collide with the
stratosphere and react with nitrogen to create carbon-14, which
is then absorbed into the biosphere. A team led by Fusa Miyake
of Nagoya University found that levels of carbon-14 in the two
cedars were about 1.2 percent higher in 774 and 775 compared to
other years. This may not sound much, but in relation to
background concentrations of carbon-14, the difference is huge.
One source of cosmic rays is the Sun, whose activity varies in
phases called Schwabe cycles. O