quote:

John A. Wheeler, a visionary physicist and teacher who helped invent the theory of nuclear fission, gave black holes their name and argued about the nature of reality with Albert Einstein and Niels Bohr, died Sunday morning at his home in Hightstown, N.J.
...
Under his leadership, Princeton became the leading American center of research into Einsteinian gravity, known as the general theory of relativity — a field that had been moribund because of its remoteness from laboratory experiment.

“He rejuvenated general relativity; he made it an experimental subject and took it away from the mathematicians,” said Freeman Dyson, a theorist at the Institute for Advanced Study across town in Princeton.

Among Dr. Wheeler’s students was Richard Feynman of the California Institute of Technology, who parlayed a crazy-sounding suggestion by Dr. Wheeler into work that led to a Nobel Prize. Another was Hugh Everett, whose Ph.D. thesis under Dr. Wheeler on quantum mechanics envisioned parallel alternate universes endlessly branching and splitting apart — a notion that Bryce DeWitt, of the University of Texas in Austin, called “Many Worlds” and which has become a favorite of many cosmologists as well as science fiction writers.

Recalling his student days, Dr. Feynman once said, “Some people think Wheeler’s gotten crazy in his later years, but he’s always been crazy.”
...
Max Tegmark, a cosmologist at the Massachusetts Institute of Technology, said of Dr. Wheeler, “For me, he was the last Titan, the only physics superhero still standing.”

quote:

He was an iconic figure: a veteran of the Manhattan Project, a pioneer of the search for a quantum theory of gravity, and an originator of such evocative terms as "black hole." Most physics students know him as co-author of the standard textbook on Einstein's general theory of relativity—a tome that defies almost every stereotype of a textbook, much as Wheeler's own career defied almost every generalization. He was rigorous yet playful, and he always had a pithy, Zen-like phrase for profound ideas and questions: "it from bit," "mass without mass" and "Why the quantum?". An out-of-the-box thinker who wasn't afraid to speculate, he always carefully identified speculation as such. In so doing, he opened up space for his colleagues to push the boundaries.

quote:

Edward N. Lorenz, a meteorologist who tried to predict the weather with computers but instead gave rise to the modern field of chaos theory, died Wednesday at his home in Cambridge, Mass.
...
As recounted in the book Chaos by James Gleick, Dr. Lorenz’s accidental discovery of chaos came in the winter of 1961. Dr. Lorenz was running simulations of weather using a simple computer model. One day, he wanted to repeat one of the simulations for a longer time, but instead of repeating the whole simulation, he started the second run in the middle, typing in numbers from the first run for the initial conditions.

The computer program was the same, so the weather patterns of the second run should have exactly followed those of the first. Instead, the two weather trajectories quickly diverged on completely separate paths...Dr. Lorenz had entered...rounded-off numbers, and even this small discrepancy, of less than 0.1 percent, completely changed the end result.

Even though his model was vastly simplified, Dr. Lorenz realized that this meant perfect weather prediction was a fantasy. A perfect forecast would require not only a perfect model, but also perfect knowledge of wind, temperature, humidity and other conditions everywhere around the world at one moment of time. Even a small discrepancy could lead to completely different weather.

Dr. Lorenz published his findings in 1963...At a meeting of the American Association for the Advancement of Science in 1972, he gave a talk with a title that captured the essence of his ideas: “Predictability: Does the Flap of a Butterfly’s Wings in Brazil Set Off a Tornado in Texas?”
...
In discovering “deterministic chaos,” Dr. Lorenz established a principle that “profoundly influenced a wide range of basic sciences and brought about one of the most dramatic changes in mankind’s view of nature since Sir Isaac Newton,” said a committee that awarded him the 1991 Kyoto Prize for basic sciences.