Content area
Full text
The "neutral" part of the atom is far more than buffer or ballast - when viewed at the correct scale
The atom is made up of three types of particles. There are the negatively charged electrons that zip around the core of the atom at speeds up to 10 percent of the speed of light. Their orbits remind us of planets; their motions are dynamic and exciting. There are also the protons, massive particles that sit at the atom's core and, by the strength of their attractive positive charges, hold the meteorlike electrons in orbit. These two types of particles determine the atom's shape, chemistry and dynamics. And then there is the neutron. It is neutral. It is a nonparticipant in the atomic dance where the protons swing their electron partners widely. It appears to be a spectator in the atom, a microscopic pebble. However, the neutron really does have its own life. Its surface is boiling with new particles, and its heart is alive with even tinier particles such as quarks and gluons. In the last dozen years we have developed a clearer view of this active particle. Before, when we have looked at the atom, we were viewing this world at the wrong magnification to see the really vibrant neutron.
To understand the neutron, we need to look at a scale 100,000 times smaller than the atom. To get a feel for that size, consider this: A red-blood cell is about 0.00001 meters across, about 100,000 times smaller than a human being. An atom is 100,000 times smaller than a blood cell, and a neutron or proton is about 100,000 times smaller than an atom. The diameter of these particles is a femtometer (10^sup -15^ meters, or a quadrillionth of a meter), but in the language of particle and nuclear physics, it is usually referred to as a fermi (named for Enrico Fermi, a physicist prominent in the building of the first nuclear reactor). Still, 100,000 is a hard number to visualize. To give a scaled-up example, if an atom were the size of Rhode Island, the nucleus would be the size of a person wandering around inside that state, and except for the electrons orbiting along the border, the rest of...