THE PARADIGM PREPARES TO SHIFT:

The 2012 discovery of the Higgs boson secured the 2013 Nobel Prize in Physics for Peter Higgs and Belgian physicist François Englert, one of the others to have had much the same idea at the same time. But it was not the start of a new field of research so much as the end point of an existing one. The Higgs particle was the last remaining piece of a puzzle called the Standard Model, which brings together all the known fundamental particles and forces that make up the physical world (with the exception of gravity, a notoriously difficult phenomenon to fit into the microscopic picture of physics). With the discovery of the Higgs, that framework was finished and consistent--there is no place in it for anything else.

Yet the Standard Model doesn't explain everything we know about the world of particles and forces. One major remaining puzzle is dark matter: a hypothetical substance that seems to interact with known particles and light only via its gravitational effect. Because dark matter is seemingly immune to all other forces, it can pass ghost-like through ordinary matter. We can only infer its existence at all from its effects at astronomical scales: it is needed to explain why galaxies don't simply spin apart, and why light seems to get bent by otherwise empty space. But we have no idea what dark matter is. There are no particles in the Standard Model to account for it, and despite decades of searching, no other candidate particles have ever been detected. Some physicists suspect "dark matter" might not be some undiscovered particle at all, but rather that some other law (such as a modification to the theory of gravity) is needed to explain its apparent effects.

The Standard Model does not, meanwhile, explain why the amount of ordinary matter in our universe seems greatly to exceed that of its opposite, antimatter. Every known particle has an antimatter sibling: they are mirror images, rather like left and right. The negatively charged electrons that are constituents of all atoms, for example, have an antimatter partner with a positive charge, called the positron. When matter and antimatter meet, they annihilate one another in an outburst of energy. Our physical theories suggest they should have been formed in equal amounts in the Big Bang--so why were they apparently not?

The Standard Model also fails to explain how three of the fundamental forces at work in the universe--electromagnetism and the strong and weak forces that operate inside the atomic nucleus--might have once been one single force very early in the universe, just instants after the Big Bang. It is widely believed that this unity of forces existed: it has already been shown to be the case for the electromagnetic and weak forces, which were once a single "electroweak" force. The leading theories that describe this unification of forces imply the existence of a property called supersymmetry, which is not included in the Standard Model. Supersymmetry predicts that every particle has a "supersymmetric" partner. The existence of such supersymmetric particles could explain why the Higgs boson is not even heavier than it is, as the Standard Model seems to imply it should be.

Supersymmmetry looks to many physicists like a very enticing idea. Yet no evidence for it has ever been found. 

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