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2001: Scientists discover why we are here
A Californian University has thrown more light on why the Big Bang works after nearly 40 years of world-wide research.

Most scientists accept that the universe began with the Big Bang and the existence - in equal amounts - of matter and anti-matter.

The theory has been complicated by the fact that if matter and anti-matter were present in equal amounts they would cancel each other out and there would not be a universe.

Experiments by Stanford University's international team of physicists have provided the most substantial proof yet that matter and anti-matter decay at different rates and this explains the continued predominance of matter.

Charge-parity explained

This process is called charge-parity (CP) violation and derives from research in the 1950s and 1960s by theorists like Andrei Sakharov.

The evidence for CP has rested solely on - increasingly accurate - measurements of the different decay rates of the sub-atomic particle, neutral K meson and its anti-particle.

Now the team working at the Stanford Linear Accelerator Center (Slac) has observed CP violation in a heavier particle/anti-particle pair related to B meson.

They made their discovery using a 1,200 tonne detector called Babar, designed, built and operated by 600 scientists and engineers, many from the UK.

Babar forces particles to crash into each other and simulate the effects of the Big Bang deep under the Californian landscape.

The findings of the Slac team will be published in the journal Physical Review Letters.

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Microwave map of the cosmos
Microwave map of the cosmos

Facts of the anti-matter
The idea of anti-matter has been around since 1928 when British physicist Paul Dirac suggested the existence of atoms with negatively charged anti-protons at the centre and positively charged electrons - positrons - orbiting them. Ordinary atoms consist of a positively charged nucleus surrounded by negatively charged electrons.
It is very difficult to make anti-matter and requires powerful particle accelerators like Babar.
Scientists estimate that around 20kg of anti-matter like anti-hydrogen - first produced in Switzerland in 1997 - could power a spaceship across the galaxy.
Over the past 10 years particle physicists in Europe, the US and Asia have put together plans for a gigantic, 3bn particle accelerator that they hope to be switched on by 2011.
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