Have We Hit Bottom Yet?

Most physicists believe we have already discovered the smallest particles that exist, the basic building blocks of nature. However, this isn’t the first time scientists thought they’d reached bottom, the ultimate limit of minuteness.

This visual representation shows a proton-proton collision that may have created a Higgs boson within the ATLAS detector. The bulls-eye in the center is the tube the proton beams shoot through. The red and blue lines shooting away from the proton beams represent 4 electrons created by the collision — which is what physicists expect to see when a Higgs boson is created. (Photo courtesy of CERN)

The ancient Greeks believed everything was made from four constituents: air, water, fire, and earth. How primitive.

Later, people believed everything was made of atoms of 92 different elements.

Then science discovered atoms had two parts: nuclei surrounded by electrons.

After that, we learned that nuclei were made of protons and neutrons. And even later, physicists decided those were probably made of “up” and “down” quarks.

But more particles were discovered, ultimately leading to a final tally of 16 “fundamental” particles that comprise nature’s irreducible pieces that are believed to have zero size and no internal structure. Everything else we see around us is made of combinations of these fundamental particles.

Oops, with the discovery of the Higgs boson, let’s make that 17 fundamental particles. Oh, and 12 of the 17 particles have corresponding antiparticles; the other 5 are their own antiparticles.

To recap: in 25 centuries of peeling layer after layer of the cosmic onion, we’ve gone from 4 basic building blocks, to 92, to 2, to 3, and finally to 17+12. Great progress! (?)

But are we really smarter than the ancient Greeks? Maybe not.

Perhaps, some theoretical physicists say, the 16 17 fundamental particles are actually made of “+” and “0” preons (and two antipreons: “-” and “0”). They say “+” preons have an electric charge of +⅓, and “0” preons have zero charge.

The compositions and masses of some known particles are:

One might ask how the preon idea explains the enormous range of masses. If three “0” preons (e-neutrino) have zero mass, mustn’t each “0” preon have zero mass? If so, the two “+” preons in the up quark should each have a mass of 2, which would make the W+ mass 6 instead of 157,339. And how can nine preons (proton) weigh 86 times less than six preons? A person who would ask such questions hasn’t met any theoretical particle physicists, who are unsurpassed at mathematical crazy glue and duct tape. The more forthcoming ones say if this “seems like a bit of hand waving, it is.”

Of course, what is shown above isn’t the only alternative. In fact, there are more versions of preon theory than there are preon theorists.

I should mention one minor detail: all experiments to detect preons have come up empty. Anything made of something else can’t have zero size. While it’s impossible to prove that the size of anything is exactly zero to a zillion decimal digits, we do know that quarks are no larger than 1/5000th of the size of a proton, which has the smallest measured size. Theorists aren’t worried that there’s no evidence for their ideas, that just a reason to build bigger accelerators.

As an experimental physicist, I am innately skeptical of the latest theory-du-jour. Less than 1% of such whimsies are ultimately confirmed experimentally. But even the most skeptical must admit that progress in science, and ultimately for society, has often come when crazy ideas were proven true. Nothing shocked the sensibilities of the physics world more than Einstein’s revolutionary ideas. His success will provide cover for countless off-the-wall theories for centuries to come.

Indeed, the great physicist Wolfgang Pauli once said: “There’s no question this idea is crazy. But, is it crazy enough to be true?”

If preons are eventually discovered, the next question will be: “What are preons made of?”

Author- Dr. Robert Piccioni.

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