Physics in a Nutshell

Spin!

Spin is angular momentum, quantized into discrete units such as +1 and -1. In the original Karate Kid movie, the kid who wants to learn karate is frustrated by his teacher’s insistence that he spend his time painting fences and waxing cars. Only later is it revealed that the student had learned the fundamental moves without realizing it, blocking punches with “wax on, wax off.” Similarly, the deepest mysteries of physics are taught in Physics 101, but they’re hard to…

Gravitons

Sesame Street has a learning game that goes with the jingle “One of these things is not like the other. One of these things just doesn’t belong.” Can you find which one is different? If you’ve read anything about the kinds of physics we do at Fermilab, you’ve heard lots of words ending with “on” – words like proton, neutron, gluon, photon, boson, fermion and on and on and on. One of the words you might have encountered is the…

A leptoquark would be a strange amalgam of familiar leptons and quarks, the way that a platypus has features of both mammals and birds. Image from Charles Baker, Animals, Their Nature and Uses (1877) All of the atoms in our bodies are made of electrons, protons and neutrons, and the protons and neutrons can be further decomposed into quarks. At the bottom level, then, we are made of only two types of particles: electrons and quarks. But what do these…

If neutrinos are Dirac particles, their matter and antimatter versions are very different. If they are instead Majorana particles, the matter and antimatter components are the same thing. The neutrino is one of the most mysterious particles in the Standard Model. The original idea of neutrinos was formulated in response to a problem in beta decay, in which a neutron converts into an electron and a proton. (Historically, the electron in this kind of decay has been called a beta…

Antimatter can be found in science fiction and in fact. It both powers fictional starships and is associated with one of the most perplexing mysteries in modern physics. Since our theories suggest that matter and antimatter should have been made in equal quantities, yet we observe only matter, this mystery is really quite fundamental: Why are we here at all? View a video on antimatter. Star Trek taught us that if we want to go blasting all over the galaxy,…

One type of decay in the subatomic realm occurs when an existing object simply fissions into two smaller objects. In this case, the makeup of the initial particle and decay products are just moved around, as when a column breaks into pieces. One example is when a uranium nucleus breaks into thorium and helium nuclei. Decay evokes a lot of images, from jumbled piles of stone that once composed breathtaking examples of architecture to the dank smell of a damp…

Like supersymmetry, most snowflakes are nearly, but not exactly, symmetric. Image: SnowCrystals.com At its smallest scale, nature is highly symmetric. There are many different kinds of symmetries among particles — for instance, matter and antimatter are identical except for charge, like an image in a mirror that is the same as its object, but reversed. There are three generations of each type of matter (and antimatter) that are identical but for mass: small, medium and large. Photons of the electromagnetic…

Interaction? Collision? Event? Physicists use many words to describe what you are seeing here. Today’s column helps sort out those confusing terms. Those of you interested in the sorts of physics pursued by scientists working on the Fermilab Tevatron or CERN’s Large Hadron Collider may hear scientists casually toss around words that all seem to mean the same thing – interaction, collision, beam crossing or event. If you get confused when you hear a physicist talk about these things it’s…

A “Where’s Waldo?” snapshot typifies the situation in a high-luminosity, high-interaction, environment. If these people arrived one at a time, were separated by larger distances or were more distinct, we could see them more easily. Similarly, scientists have to clarify the particle collision picture to cope with high luminosity. After reading a recent Nutshell article about the Intensity Frontier, an inquisitive reader wanted to learn about how we cope with very bright beams. After all, the point of lots of…

While the laws of physics set limits on what is possible, our universe could have evolved in different ways. Or could it? Studying the Cosmic Frontier teaches us about the history of the cosmos. Combined with information gained at particle accelerators, we can try to find out if the basic structure of our universe was inevitable. Perhaps that is one of those “duh!” questions. After all, humans have wondered about the cosmos for all of recorded history and no doubt…