Fermilab Today

Fourteen billion years ago, when the hot, dense speck that was our universe quickly expanded, all of the matter and antimatter that existed should have annihilated and left us nothing but energy. And yet, a small amount of matter survived.

We ended up with a world filled with particles. And not just any particles — particles whose masses and charges were just precise enough to allow human life. Here are a few facts about the particle physics of you that will get your electrons jumping.

The particles we're made of
About 99 percent of your body is made up of atoms of hydrogen, carbon, nitrogen and oxygen. You also contain much smaller amounts of the other elements that are essential for life.

While most of the cells in your body regenerate every seven to 15 years, many of the particles that make up those cells have actually existed for millions of millennia. The hydrogen atoms in you were produced in the big bang, and the carbon, nitrogen and oxygen atoms were made in burning stars. The very heavy elements in you were made in exploding stars.

The size of an atom is governed by the average location of its electrons. Nuclei are around 100,000 times smaller than the atoms they're housed in. If the nucleus were the size of a peanut, the atom would be about the size of a baseball stadium. If we lost all the dead space inside our atoms, we would each be able to fit into a particle of lead dust, and the entire human race would fit into the volume of a sugar cube.

As you might guess, these spaced-out particles make up only a tiny portion of your mass. The protons and neutrons inside of an atom's nucleus are each made up of three quarks. The mass of the quarks, which comes from their interaction with the Higgs field, accounts for just a few percent of the mass of a proton or neutron. Gluons, carriers of the strong nuclear force that holds these quarks together, are completely massless.

If your mass doesn't come from the masses of these particles, where does it come from? Energy. Scientists believe that almost all of your body's mass comes from the kinetic energy of the quarks and the binding energy of the gluons.

—Ali Sundermier

Photos of the Day

Rusty hues

This old control box, located over by the Lederman Science Center, holds its own in the fall scenery. Photo: Jamieson Olsen, AD

Many colors greet passengers on Kautz Road. Photo: Jonathan Edelen, AD

nature, fall, Wilson Hall, trees, landscape

The trees have fallen into shadow. Photo: Valery Stanley, WDRS

In the News

A neutrino in a haystack: Brookhaven's contributions to the MicroBooNE neutrino experiment

From Brookhaven National Laboratory, Nov. 2, 2015

In the time it takes you to read this sentence, trillions of neutrinos will fly through your body.

Did you feel them? Probably not. That is because, despite their abundance, neutrinos rarely interact with matter; a neutrino can pass through a light-year of lead — about six trillion miles — without disturbing a single atom. And yet physicists are captivated by these tiny, subatomic particles. As the Nobel Committee recently observed in awarding the 2015 Nobel Prize in physics for neutrino experiments, discoveries about the "deepest secrets" of neutrinos "are expected to change our current understanding of the history, structure and future fate of the universe."

Physics in a Nutshell

Getting to higher energies

We can explore new territories of the subatomic realm by using more powerful accelerators. But how do we go about building these high-energy machines? Image: Angela Gonzales

In past columns we have investigated the fundamental principles of accelerators. One might naturally ask about accelerators of the future: How will they work? After all, in an early column I described how higher energies produce information at smaller distance scales, allowing us to investigate the fundamental building blocks of the universe. So how do we make accelerators that will get us to energies even higher than we can attain now?

A seemingly obvious way to accomplish this goal is to simply do what we have done in the past: Make ever larger accelerators that allow us to bend the beams in a larger circles, perhaps with improved magnetic fields in the magnets. Clearly, this is a brute force method, and it would be costly. At the same time, it could be straightforward. After all, this strategy has been used in the past. Consequently, we might be tempted to conclude that the problem could be solved simply by extending known technologies to larger scales.

However, the problem is not that simple. The amount of stored energy in the beam becomes a serious problem when the beam has to be aborted or is lost in the magnets: Major parts of the accelerator could be destroyed. In the past I impressed visitors to the Fermilab by telling them there was a megajoule of energy stored in the Tevatron beam, pointing out that this is the amount of energy in a stick of dynamite. With the operation of the LHC, we are already in an entirely new ballgame. The energy stored in the LHC beam is more than 350 megajoules. This is roughly the energy of a large aircraft carrier moving at a few miles per hour. I will leave it to the reader to figure out how many sticks of dynamite this represents.

The challenge of safely storing energy is not the only problem we will face in going to higher energies. Beams give off synchrotron radiation. Charged particles radiate photons — particles that carry electromagnetic energy, including in the form of light — when they are accelerated or bent by a magnetic field. The more lightweight the particle, the more radiation is emitted. Electrons make fantastic light sources for many different kinds of research. However, the fact that electrons radiate also makes them very difficult to accelerate to high energies: A very large quantity of power must be added to the beam to make up for the energy that is radiated by the electrons.

The synchrotron radiation can also do severe damage to the vacuum chamber and other accelerator components. Although this has not been a problem for proton accelerators up to this point, it becomes a problem for the next generation of higher-energy accelerators, because protons at high enough energy also radiate away much of their energy, potentially damaging magnets and other components. We would also have to supply more and better accelerator cavities to make up for the energy that is lost in each turn by the protons around the accelerator due to the synchrotron radiation emitted by the protons.

Accelerator scientists are beginning to think about how to solve these difficult problems. Perhaps the solution lies in a different type of acceleration, one in which a second beam is used to accelerate the primary beam over shorter distances to higher energies. One such method is called wakefield acceleration. Scientists are exploring this possibility, though they will need to overcome many difficulties to realize an accelerator of this type.

One thing is clear: To get to higher energies, we will need further significant accelerator research — and energy to match the effort!

—Roger Dixon

In Brief

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In the News

Tackling the Large Hadron Collider's big data challenge

From Scientific Computing, Nov. 4, 2015

At CERN's Large Hadron Collider (LHC), the world's most powerful particle accelerator, scientists initiate millions of particle collisions every second in their quest to understand the fundamental structure of matter.

With each collision producing about a megabyte of data, the facility, located on the border of France and Switzerland, generates a colossal amount of data. Even after filtering out about 99 percent of it, scientists are left with around 30 petabytes (or 30 million gigabytes) each year to analyze for a wide range of physics experiments, including studies on the Higgs boson and dark matter.