Princeton University - Council of Science & Technology

POPE PRIZE

Essays 1 & 2
The Buzz on James Gould
Mission to Mars
Natalie R. Ram

Essays 3 & 4
Powering Princeton
Academics as Outlaws?
David Robinson

Essay 5
How Does Your Garden Grow?
Alexis Schulman

Essays 6, 7 & 8
Killing Cancer at its Root
Backpacking with Lee Silver
Avocado
Lauren C. Turner

Essay 9
Not with a Bang, but a Whimper
Joshua D. Younger

The Buzz on James Gould

They have six legs, they buzz, and they sting. Yet, they also dance – in flower petals, on air, and, most significantly, in their hives. Inflection is shaded into every motion; every wiggle means something. Theirs is the language of the honeybee, very nearly the most complex animal language in existence. Only the human language surpasses that of the bee in complexity. It is this language, hidden in dance, that captured the passion of an undergraduate student at the California Institute of Technology in 1969. His name was James Gould and his goal was nothing less than to prove, once and for all, that the dance language really existed. Karl von Frisch first proposed the idea of a dance language in bees more than 50 years ago. After noticing that one bee’s discovery of plentiful food could soon draw hundreds of others, von Frisch set up a glass hive to find out how information was passed around. On the basis of his observations, he postulated the dance language. Sometime in the interim, however, the idea of a dance language fell out of favor. Instead, parts of the scientific world claimed that bees homed in on target flowers by odor. This faction denied the existence of a complex insect language. By 1967, this schism had become the “Bee Controversy.” Science magazine, the premiere scientific journal, covered the controversy with two papers addressing the two sides of the dispute. And it is at this time that James Gould accepted the assignment that would make him legendary in the community of animal behaviorists. Professor Gould’s story begins, however, long before his foray into the bee world. Growing up in Oklahoma, James knew that he wanted to study science before he even reached high school. Although “there was no defining moment on the road to Damascus,” he says of his first realization of his love for the scientific world, “it was in 8th grade: my science teacher that year was a former headmaster of a school in Cuba (and on Castro's death list), and the first to spark an interest.” Later, Gould remembers being fascinated by experimentation and working in the laboratory. When he left for college, he left for one of the nation’s most prestigious scientific institutions: the California Institute of Technology, or Caltech. Caltech is known for breeding some of the world’s best scientists, particularly in physics. Introductory courses are designed with this in mind. Less fanatic physicists are “weeded out” of the program into majors like chemistry or biology. James Gould was no different: “Alas, I titrated from physics to chemistry and then to biology.” He settled into the molecular biology program and he might have stayed there if a change in location hadn’t shaken things up. In 1967, Gould was drafted to the U.S. Army Signal Corps. For the next year, he was stationed in Germany. And while he was there he picked up a book that changed his academic path – King Solomon’s Ring, by Konrad Lorenz. Although Lorenz is probably most famous for his work with ducklings – in which he “tricked” a nest of hatchling into believing he was their “mother” – his research spanned a much broader path in the science of animal behavior. Lorenz helped establish a new field of science – ethology, or the study of animal behavior. King Solomon’s Ring was Lorenz’s tribute to his animals, his explanation of their behaviors. When James Gould picked up the book, he found himself drawn into the world of animal behavior. What struck Gould most about the book were the illustrations. “Lorenz' drawings are striking,” he said, “because they are a wonderful mixture of science and whimsy, and give the reader a sense of the author's vision that neither words nor photos can adequately transmit.” But it was Seymour Benzer back at Caltech who “turned [the seed of interest in animal behavior] into a rampant weed.” Benzer was well known for his work with fruit flies, behavior, and genetics. Gould enrolled in his animal behavior course upon returning from Germany. Intrigued by what he had seen and read in Konrad Lorenz’s book, Gould wanted to know more. What he got was a chance to do groundbreaking science. As a final project, Benzer presented his students with the point-counterpoint arguments of the bee controversy. Nothing his colleagues could come up with had laid the arguments over a bee language to rest, so he assigned the problem to his undergraduate students – as if third-year students could accomplish what their tenured professors could not! Benzer told his scholars to design experiments of their own, experiments that would clearly show the presence or lack thereof of communication in the dance of the bee. James Gould brainstormed and planned, and when he submitted his proposal Benzer was so pleased that he sent him to try it out. The trick, Gould explains, was that he “forced the bees to lie.” The bee dance postulated by von Frisch coded information for both distance and direction into the dance. The number of tail waggles the bee performed communicated distance. Bees “calculated” their angle of flight from the path of the sun and communicated that information to their fellows by dancing on a line with that angle, even in the relative darkness of the hive. In order to sense with such precision the location of the sun, bees have three, highly light sensitive, “tiny little eyes” called ocelli in addition to their compound eyes. Gould painted over these eyes and rendered his subjects a good deal less light sensitive. This proved to be the keystone of the experiment. Gould was able to fool his “dimmer” bees into lying for him by changing the position of the sun – or, rather, the “really bright light” the bees now recognized as the sun. With his new “sun” in position, Gould then provided the bees with sweet nectar and pollen. When these hoodwinked bees returned to the hive, they must have danced the location of this abundant food source relative to their fake sun. They must have communicated their location because new bees, unaffected, unpainted bees, left the hive and headed immediately for where food should have been – relative to sun, not the awfully bright light. They didn’t find what they were looking for. If the painted bees had clued their sisters in to the location of the sweet food by odor, as the dance language opponents had suggested, the new bees would have found the food and not been fooled. But because precise – but incorrect – directions were supplied via the dance language, Gould got the results he wanted. The dance language had to exist. It appeared that Gould had done what his professors and their colleagues could not. Gould says those first experiments “attracted a lot of attention.” They also won him Caltech’s Green Memorial Award for the best undergraduate research. Gould continued working with bees as a graduate student at Rockefeller University. On the strength of that research – which laid to rest any lingering doubts about bee language – Gould earned himself a position in the Princeton University Department of Ecology and Evolutionary Biology directly after finishing his post-doctorate work. His supervisor called it “‘a pretty good first job.’” He has been at Princeton ever since. Gould might have continued working on bees, had it not been for his misfortune of developing an allergy to them. And while he continued his bee work – he says he finds them “endlessly fascinating” – even after the allergy developed, he claims that his wife put her foot down when she learned that his allergy medication wasn’t entirely fool proof. According to Professor Gould, Carol Gould told her husband that she wouldn’t allow him to continue putting himself directly into harm’s flight path. Carol Gould doesn’t quite agree with her husband’s assessment of the situation. True, she may have factored into the decision to suspend working with bees – after all, she says, “we had two small children that I was quite unwilling to raise alone!” – but there were other considerations as well. Carol Gould explains by email that “there were increasing problems from government officials who were averse to the sort of cross breeding and genetic fiddling Jim needed to do for the next step in understanding bee communication and navigation systems, so the best thing seemed to be to switch animals. I didn't make him quit – honest!!” So he turned his attention to different animals. Over the course of his career, Gould has worked not only with insects, but also with pigeons, whales, and fish. His favorite project, he recalls, while focused once again on bees, also involved tests with several other species as well. Gould wanted to explore how bees in particular, and other homing species – animals who come equipped with internal Global Positioning Systems – in general, sense the Earth’s magnetic field. In their search for rich flowers, bees often meander from flower patch to field and back. Yet once they find what they’re looking for, they turn tail and fly directly back to the hive in a “bee-line.” Gould wanted to know how, after so many twists and turns, bees still know exactly where they are in relation to their hive. It is a talent – the ability to home in on their exact location and the location of their target – that not even humans possess. What Gould found was magnetite, a metal highly sensitive to magnetic forces. In fact, he found magnetite “in humongous amounts.” Further investigation with other homing species such as homing pigeons – the animal that, “given all the money in the world and time enough,” Gould would study – and whales revealed that they all had extraordinarily high levels of magnetite. Gould was able to conclude that magnetite was “the major way animals sense things.” He was among the first people to investigate the idea. Professor Carol Gould joined her husband on many of his forays into the wild to study his subjects – once even traveling as far as Patagonia to observe whales. Mrs. Gould first met her husband during their graduate studies, hers in Victorian literature and his in biology. Of their early expeditions, Carol says that she “hadn't realized that if you marry a field biologist, you must be a bit flexible if you ever want to see him or her. I certainly didn't want to be a drag on the expedition, so I tried hard to learn the work.” Over the years, the work of husband and wife came closer together. Carol Gould, herself a Ph.D., became a lab associate in her husband’s lab analyzing data. Today, the professors Gould continue their close work. A majority of the books published by Professor Gould are also credited to his wife. He does the science; she does the writing. On the science of writing, Carol Gould said that she and her husband “found we could have fun putting the book together. I got better at writing and editing, and my experience in the field and in the lab helped. Many people were amazed that we could work together, but we always loved it. I am terrible about taking criticism, so Jim learned early to be really diplomatic.” Their joint writing continues, although today the writing tends to be more even handed – Carol revealed that James “actually did most of an article for [Princeton Alumni Weekly] on my biographical research that I didn't have time to do.” Despite his forays into science writing, his first love is still the lab. Professor Gould’s current research concerns the mosquito fish, a species in which the females have unconscious biases for what they like in their mates, but never express these likes and dislikes in mating. Unexpressed preferences are a puzzle of evolution, and this is one that Gould is trying to solve. He thinks that while the females’ preferences are not displayed in mate selection, they may play a part in helping to recognize sick fish and avoid them. This work is ongoing. On the surface, Professor James Gould’s career has been marked by a series of significant changes in direction – Gould moved from physics to biology, and worked with a whole array of species in the animal kingdom. But, on closer inspection, what is really most striking about Gould’s career is his consistency. From his first experiments to his current work, Gould has explored the various facets of one theme – communication. Communication among animals, by bee dances, bird song, or bound words, has shaped the whole of Professor Gould’s work. His excitement at the richness of communication in the natural world is what he imparts to his readers and his students. That is what he communicates to them.

Mission to Mars

The red soil crunches underfoot, while in the sky two speckled orbs shine with an unearthly light. There is no sound other than the low, shallow breath of a man in a new world. Turning his face towards the proud, majestic vehicle that has carried him so far from home, he utters words he has waited his whole life to deliver: “That’s one small step for man, one giant leap for mankind… again!” You may now sigh with regret as you return to reality. Humanity isn’t going to Mars anytime soon. In fact, with current technology, in order to travel only one way to Mars, that proud spaceship would have to be entirely filled with a propellant like gasoline. At most, living quarters might occupy a measly 3 percent of the total spacecraft volume. In other words, our spaceman might have the room to lie prostrate for his months long trip to the red planet. And besides, no first mission would want to go only one way. Yet, while current technology can’t move a rocket fast or efficiently enough to get us to Mars anytime soon, a new long-range rocket design may be just a few years away from completion. It is called the Lithium Lorentz-Force Accelerator (Li-LFA), and its description calls forth images of Star Trek and science fiction. Perhaps this is because both the Li-LFA and the Trekkie Warp drive rely on what could be called a plasma drive. It is this “plasma drive” that may soon be able to propel a rocket so quickly and efficiently that Mars will no longer be a question of “if,” but of “when.” The Lithium Lorentz Force Accelerator isn’t exactly a new idea. Lorentz Force thrusters and their predecessors, the Magneto Plasma Dynamic (MPD) thrusters, are already in place on many of today’s satellites and space probes. Even the use of Lithium in these thrusters is nothing new. What is new is the use of this kind of technology for long-range missions rather than minute adjustments. Updating and improving the Li-LFA for these far-reaching goals is the job of scientists at Princeton University, the Moscow Aviation Institute, and NASA’s Jet Propulsion Lab. Traditional space thrusters rely on burning fuel (a chemical reaction) to propel the spacecraft forward. As long as spacemen were only traveling short distances, say from Earth to the Moon, these chemical thrusters could serve well enough. But for longer manned missions, like a trip to Mars, using traditional chemical thrusters isn’t practical. Enter the plasma drive, which relies on electric power instead of combustion. According to Dr. Edgar Choueiri, a Professor of Mechanical and Aerospace Engineering at Princeton University and the head of the Princeton team of the Li-LFA project, the prospect of a mission to Mars forced scientists and engineers to “forget about combustion altogether.” There are several factors that make plasma highly advantageous compared with chemical propellants. Just as water changes from ice to liquid water to water vapor under heat and pressure, certain elements, when heated still further, break up into charged particles, or ions. This electrically charged mess is the plasma. Because it is electrically charged, plasma can carry electric current. It also responds to magnetic fields. It is this pair of characteristics that makes plasma the magical propellant. People familiar with electro-magnetic theory know that electric currents generate magnetic fields. Since plasma responds to both electric and magnetic fields, driving a strong electric current through a plasma will create a magnetic field. The plasma responds to this field by pushing against it (this push is called the Lorentz force). Effectively, the plasma creates the field it propels against. It produces the means of its own ejection. The explanation for why this propulsion system is so much more efficient than the combustion system lies in the relationship between exhaust speed and rocket speed. The speed of the rocket changes relative to the speed at which the propellant is pushed from the thrusters (known as the exhaust velocity). As the exhaust velocity increases, forward velocity also increases. According to Dr. Choueiri, current technology with chemical thrusters simply can’t push a rocket fast enough to make it to Mars and back – and the Li-LFA thruster can. In fact, he claims that the Li-LFA thruster can propel its rocket almost four times as fast as a combustion thruster. With exhaust and forward speeds that high, that amazing voyage to Mars becomes that much more possible. However, not everything about Li-LFA engines is so positive, or they would have been built a long time ago and Mars would be no great feat for us now. Indeed, one of the reasons why plasma thrusters haven’t been used over long distances is that they wear out so fast. Erosion of one of the most vital parts of the thruster, the cathode, happens so quickly that no current thruster could survive for as long a trip as the mission to Mars. Better design of this part and the use of lithium as the plasma of choice have greatly extended the life of the thrusters. By combining these two improvements on the traditional plasma thruster, the Princeton team has been able to power their thruster for more than 500 hours with little erosion. Enhancing these improvements is one of the issues facing the team. Performance is another area in which the Princeton team is making its mark. Efficiency is the “most important factor for performance,” says Dr. Choueiri. He and his graduate student assistants continue to work on increasing the Li-LFA thruster’s efficiency in several ways. One of their most novel improvements is a system that stores the lithium as a liquid until it is injected into the thruster. Current models store lithium in its gaseous state until it is needed as plasma in the thruster itself. Unfortunately, in order to keep the lithium as a gas, “you have to put lots of heat into the system,” says Andrea Kodys, one of the grad students in Dr. Choueiri’s lab. Generating and maintaining that heat in expensive. The new liquid feed system would allow the storage tanks to be made of a cheaper, less heat resistant metal. A liquid feed would also allow the flow of lithium to the thruster to be controlled more precisely. Once her liquid system has been perfected and is ready for use, there will be very little in the way of thruster improvements keeping Andrea’s thruster on the ground. Yet, even once the thruster itself is ready, it is not likely to launch for years. The Li-LFA requires massive amounts of power – somewhere on the scale of 100 kilowatts – in order to drive the intensely powerful current and ionize the plasma. Considering that most household light bulbs run on 60-75 watts of power, it is not hard to imagine that producing 100,000 watts of power might be rather difficult. As things now stand, the only possible way of generating enough power is by installing a nuclear power source: “Nuclear is the only way to go,” Andrea claims. The enormous solar arrays that power electrical systems on board today’s spacecraft cannot harvest anywhere near enough power to drive the Li-LFA thruster. So, nuclear it must be. Not surprisingly, most of the people in Washington are pretty leery of a nuclear reactor in space. Images of Chernobyl and nuclear fallout follow closely with thoughts of nuclear reactors, which is not exactly what the Li-LFA wants to project. However, Andrea is confident that getting the nuclear power that the Li-LFA thruster requires won’t be that difficult – once the push to get to Mars is in place. She also says the big thing is “educating people about what we’re doing.” The mission to Mars is something of a holy grail for much of humanity. Most people view it as something wonderful and great, but altogether unattainable. Mars is something we see on our TV screens and in movie theaters, not somewhere we send real-live spacemen. But wait a few years. The plasma drive is on its way.