FJ: What does your typical creative day look like?
JM: The alarm clock rings. Kathy and Jim send Pooka the Border collie to wake up Christopher, the eleven-year-old (my son, Kathy’s stepson). Kathy makes Chris’s breakfast. Jim takes Amtrak the Doberman for a walk, a process that usually yields at least two good ideas—a line of dialogue, a juicy metaphor, a structural tactic—for that day’s scene.
Chris eats breakfast while reading the funnies. Jim, Kathy, Chris, and Pooka walk a quarter-mile to the bus stop. (For reasons not worth explaining, the best way for my son to get to school is on a public bus.) While Kathy and Chris ride downtown together, Jim heads for home with Pooka. He typically gets two or three more good ideas along the way.
The rest of the day is a dance among competing obligations. Jim tries to get a load of dishes washed … to have at least one nourishing conversation with Kathy … and to jog twice around the block. But mostly he writes and writes and writes. It’s an addiction.
FJ: Did you ever write a line that you’re especially proud of—that is, a line in which you managed to capture your worldview in epigrammatic fashion?
JM: In Towing Jehovah, my heroine says to a friend, “That maxim, ‘There are no atheists in foxholes,’ it’s not an argument against atheism—it’s an argument against foxholes.”
* * * *
Faith L. Justice is a self-styled science geek and history junkie. Before becoming a freelance writer, she worked as a lifeguard, paralegal, college professor, and business consultant. She has published numerous science fiction and fantasy short stories and poems since co-founding a writer’s group twelve years ago. Faith lives with her husband, daughter, and cat in New York.
Bose-Einstein Condensates
By Marissa K. Lingen
12/10/01
In our daily experience, most of us deal with three phases of matter: solid, liquid, and gas. A fourth, high-energy phase of matter, plasma, occurs in high energy processes as near as a fire or as far away as the core of a star. For decades, the existence of a fifth, low-energy form of matter, known as Bose-Einstein Condensates (BECs), was only a theoretical possibility. In 2001, the Nobel Prize for Physics went to Eric Cornell, Wolfgang Ketterle, and Carl Wieman, who used lasers, magnets, and evaporative cooling to bring about this fascinating new phase of matter.
BECs have strange properties with many possible applications in future technologies. They can slow light down to the residential speed limit, flow without friction, and demonstrate the weirdest elements of quantum mechanics on a scale anyone can see. They are effectively superatoms, groups of atoms that behave as one.
The theory of BECs was developed by Satyendra Nath Bose and Albert Einstein in the early 1920s. Bose combined his work in thermodynamics and statistical mechanics with the quantum mechanical theories that were being developed, and Einstein carried the work to its natural conclusions and brought it to the public eye. At the time, none of the necessary technology was available to make BECs in the lab: cryonics were extremely limited, and the first laser wasn’t even built until 1960. The fine control allowed by modern computers was also a prerequisite. Because of all of these technological hurdles, it wasn’t until 1995 that experimenters were able to force rubidium atoms to form this type of condensate.
Phases of Matter
We can distinguish among the phases of matter in several ways. On the most elementary level, solids have both fixed volume and fixed shape; liquids have fixed volume, but not fixed shape; and gases have neither. Solids have stronger intermolecular bond structure than their corresponding liquids, which in turn have stronger intermolecular bond structure than gases. We can also differentiate between phases of matter by considering energy levels. Solids have the lowest energy levels (corresponding with the lowest temperatures), while liquids and gases have increasingly higher levels. At the top end of this scale, we can add plasmas, which are energetic enough to emit all kinds of energy in the form of heat and photons.
Bose-Einstein Condensates represent a fifth phase of matter beyond solids. They are less energetic than solids. We can also think of this as more organized than solids, or as colder—BECs occur in the fractional micro-Kelvin range, less than millionths of a degree above absolute zero; in contrast, the vacuum of interstellar space averages a positively tropical 3 K. BECs are more ordered than solids in that their restrictions occur not on the molecular level but on the atomic level. Atoms in a solid are locked into roughly the same location in regard to the other atoms in the area. Atoms in a BEC are locked into all of the same attributes as each other; they are literally indistinguishable, in the same location and with the same attributes. When a BEC is visible, each part that one can see is the sum of portions of each atom, all behaving in the same way, rather than being the sum of atoms as in the other phases of matter.
Wavefunctions and Quantum Spin
At the very beginning of the study of quantum mechanics, it was discovered that light could behave either as a wave or as a particle, when before it had only been treated as a wave. This discovery led Pierre de Broglie to theorize that perhaps matter could be treated as a wave, and not just as a particle. This theory was tested and found to be true: matter behaves as both a wave and a particle, depending on how it is observed.
Each atom has a wavefunction that describes its behavior as a wave. This wavefunction can be used to determine the probabilities that the atom will be in a given place or have a certain momentum or other useful properties. Each particle can also be determined to have a spin. While many physics terms mean something other than their everyday usage, “spin” seems to be a behavior that acts just as if the particle is spinning around an axis.
The amount of spin a particle can have depends on the type of particle. Fermions (like electrons) can have spin values that are +/- 1/2, +/- 3/2, +/- 5/2, etc.; bosons (like some isotopes of hydrogen and helium) have spin values that are whole numbers. Fermions obey the Pauli Exclusion Principle, whereas bosons do not. Bosons and fermions can both be composite particles; they don’t have to be “indivisible” particles. The same physics will hold for bosons such as photons and K mesons as will hold for hydrogen and helium atoms, as long as the atoms are close to their ground state.
The Pauli Exclusion Principle (which was determined experimentally) states that no two fermion particles can occupy the same state at the same time. They must have some way of being distinguished, whether by location, spin state, or some other property. That means that if one fermion is in a local ground or minimum energy state, the next fermion in the area must be in a higher energy state. For bosons, however, the Pauli Exclusion Principle is irrelevant by definition—so all of the bosons can be in the same state at the same time. They don’t have to be distinguishable from each other. When this happens, a Bose-Einstein Condensate is created.
Creating a Condensate
Because of the specialized conditions under which they can exist, Bose-Einstein Condensates have only been created in laboratories. First, an experimenter takes bosons that have been purified of other elements and puts them in a vacuum. Popular choices for these bosons include specific isotopes of atoms of helium, sodium, rubidium, and hydrogen. Not all isotopes are bosons, and only bosons can form a BEC. The initial method of making a rubidium condensate is the most straightforward, and further methods have been refinements of the same general principles of cooling.
The atoms are first cooled to fractions of a degree Kelvin. They need to be virtually motionless in order to stay in the BEC ground state. Then they are put into a magnetic trap, keeping them in a limited area. The magnetic trap is arranged with eight magnets in what is known as a quadrupole configuration. The magnets we are most familiar with in daily life are dipole magnets: a two-ended field of magnetization with one polarity at one end and the opposite polarity at the other end. A quadrupole configuration looks more like a plus sign, with the opposing points having the same polarity.
When the atoms are in a quadrupole magnetic trap, the way they interact is primarily through their spin; higher order considerations such as magnetostatic interactions are limited by the trap. A laser with a precisely calculated wavelength shines on the atoms, and as the light scatters off the atoms, it takes with it more energy than it brought into the process. The Doppler shift from the higher energy atoms is calculated so that they “see” the laser of the right color, and the atoms that are already lower energy stay unexcited. The energy state of the atoms is, of course, directly related to how quickly they are moving, so the first wavelength used is selected for the fastest atoms present.