Astronomy Jargon 101: Weak Force

In this series we are exploring the weird and wonderful world of astronomy jargon! You’ll be surprised by the power of today’s topic: the weak force!

The weak nuclear force doesn’t get a lot of love. Even though it was discovered before its sibling, the strong force, it got stuck with a much less impressive name. Physicists in the 1930’s realized that the force must exist when they were trying to understand a process called beta decay, where a neutron inside an atomic nucleus will spontaneously decide to become a proton, and in the process an electron shoots out of the nucleus.

The weak force has a very short range, less than the width of atomic nucleus, and only operates rarely. But it does have a hidden superpower that no other force is capable of: it can transform one kind of particle into another.

Every proton and neutron is made of smaller, more fundamental particles called quarks. A single proton is really two up-quarks and one down-quark glued together, while a neutron is two down-quarks and a single up-quark.

The weak nuclear force is capable of switching the identities of the quarks. In the case of beta decay, the weak force transforms one of the up-quarks in a proton into a down-quark, turning it into a neutron.

The weak force has three carriers, called the W+, W?, and Z bosons. Each one of those carriers plays a different role, depending on the charges of the other particles involved.

The weak nuclear force has one other extremely weird feature. It’s the only one of the four forces to violate something called the symmetry of parity. In almost all physics, any interaction among particles looks like the same when viewed in the mirror. But not the weak force – it looks different.

So even though it doesn’t have an exciting name, it turns out to be perhaps the strangest of the forces.