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This text courtesy of CERN's Microcosm exhibit.

The power of the Weak Force


Why does the Sun shine?

Why are we made of stardust?

Why do some fundamental particles change from one kind into another?

Because of one of Nature’s forces: the weak force.

The weak force causes nuclear fusion in the Sun, starting a chain of reactions which makes it burn and pour out the radiant energy that supports life.

Stellar burning also cooks up heavier elements from lighter ones. These are hurled into space by supernovae - giant explosions of dying stars - to become the stuff we are made of.

If the weak force were stronger, the Sun might have burned out before life on Earth could evolve.

In 1896, Henri Becquerel discovered ‘beta radioactivity’. In 1932, Enrico Fermi suggested that it was due to a new, weak force; he was right. Today beta radioactivity is explained by weak interactions which change a ‘down’ quark into an ‘up’ quark inside a neutron, or vice versa inside a proton.

The Weak Force

In the 1860s, James Clerk Maxwell showed that electricity and magnetism were two aspects of a single force, electromagnetism. In the 1960s, Sheldon Glashow, Steven Weinberg and Abdus Salam produced a unified ‘electroweak’ theory describing electromagnetism and the weak force in the same equations. They won the 1979 Nobel physics prize.

The range of the weak force was known to be extremely short. So, following the Uncertainty Principle, the new theory had very massive bosons, the charged W+ and W- and neutral Z. To provide their mass, another hypothetical and novel particle was needed, the Higgs boson, named after one of its inventors.

Unlike all other known forces, the weak force is biased. It distinguishes between clockwise and anticlockwise, right and left, particles and antiparticles. If the Big Bang initially produced as much antimatter as matter, the weak force could be responsible for the lack of antimatter today.

Next: Massive Bosons
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