Quantum Theory Cannot Hurt You_ A Guide to the Universe - Marcus Chown [77]
ELECTRIC FIELD The field of force that surrounds an electric charge.
ELECTROMAGNETIC FORCE One of the four fundamental forces of nature. It is responsible for gluing together all ordinary matter, including the atoms in our bodies and the atoms in the rocks beneath our feet.
ELECTROMAGNETIC WAVE A wave that consists of an electric field that periodically grows and dies, alternating with a magnetic field that periodically dies and grows. An electromagnetic wave is generated by a vibrating electric charge and travels through space at the speed of light.
ELECTRON Negatively charged subatomic particle typically found orbiting the nucleus of an atom. As far as anyone can tell, it is a truly elementary particle, incapable of being subdivided.
ELEMENT A substance that cannot be reduced any further by chemical means. All atoms of a given element possess the same number of protons in their nucleus. For instance, all atoms of hydrogen have one proton, all atoms of chlorine have 17, and so on.
ENERGY A quantity that is almost impossible to define! Energy can never be created or destroyed, only converted from one form to another. Among the many familiar forms are heat energy, energy of motion, electrical energy, and sound energy.
ENTANGLEMENT The intermingling of two or more microscopic particles so that they lose their individuality and in many ways be-have as a single entity.
EVENT HORIZON The one-way “membrane” that surrounds a black hole. Anything that falls through—whether matter or light—can never get out again.
EXOTIC MATTER Hypothetical matter with repulsive gravity.
EXPANDING UNIVERSE The fleeing of the galaxies from each other in the aftermath of the Big Bang.
FERMION A microscopic particle with half-integer spin—that is, 1/2 unit, 3/2 units, 5/2 units, and so on. By virtue of their spin, such particles shun each other. Their unsociability is the reason that atoms exist and the ground beneath our feet is solid.
FRAME DRAGGING The dragging around of space-time by a massive rotating body. The effect is very small—though potentially measurable—in the vicinity of Earth but enormous near a fast-rotating black hole. Such a black hole sits at the eye of a tornado of whirling space-time.
FUNDAMENTAL FORCE One of the four basic forces that are believed to underlie all phenomena. The four forces are the gravitational force, electromagnetic force, strong force, and weak force. The strong suspicion among physicists is that these forces are actually facets of a single superforce. In fact, experiments have already shown the electromagnetic and weak forces to be different sides of the same coin.
FUNDAMENTAL PARTICLE One of the basic building blocks of all matter. Currently, physicists believe there are six different quarks and six different leptons, making a total of 12 truly fundamental particles. The hope is that the quarks will turn out to be merely different faces of the leptons.
FUSION See Nuclear Fusion.
GALAXY One of the basic building blocks of the Universe. Galaxies are great islands of stars. Our own island, the Milky Way, is spiral in shape and contains about 200,000 million stars.
GAS Collection of atoms that fly about through space like a swarm of tiny bees.
GENERAL THEORY OF RELATIVITY Einstein’s theory of gravity that shows gravity to be nothing more than the warpage of spacetime. The theory incorporates several ideas that were not incorporated in Newton’s theory of gravity. One was that nothing, not even gravity, can travel faster than light. Another was that all forms of energy have mass and so are sources of gravity. Among other things, the theory predicted black holes, the expanding Universe, and that gravity would bend the path of light.
GEODESIC The shortest path between two points in warped, or curved, space.
GRAVITATIONAL FORCE The weakest of the four fundamental forces of nature. Gravity is approximately described by Newton’s universal