Edward Norton Lorenz

His father, Edward Henry Lorenz (1882-1956), majored in mechanical engineering at the Massachusetts Institute of Technology, and his maternal grandfather, Lewis M. Norton, developed the first course in chemical engineering at MIT in 1888.

Meanwhile, his mother, Grace Peloubet Norton (1887-1943), instilled in Lorenz a deep interest in games, particularly chess.

Later in life, Lorenz lived in Cambridge, Massachusetts with his wife, Jane Loban, and their three children, Nancy, Cheryl, and Edward.

He was an avid outdoorsman, who enjoyed hiking, climbing, and cross-country skiing.

He kept up with these pursuits until very late in his life.

Edward Norton Lorenz (May 23, 1917 – April 16, 2008) was an American mathematician and meteorologist who established the theoretical basis of weather and climate predictability, as well as the basis for computer-aided atmospheric physics and meteorology.

He is best known as the founder of modern chaos theory, a branch of mathematics focusing on the behavior of dynamical systems that are highly sensitive to initial conditions.

Lorenz was born in 1917 in West Hartford, Connecticut.

He acquired an early love of science from both sides of his family.

Lorenz received a bachelor's degree in mathematics from Dartmouth College in 1938 and a master's degree in mathematics from Harvard in 1940.

He worked as a weather forecaster for the United States Army Air Forces during World War II, leading him to pursue graduate studies in meteorology at the Massachusetts Institute of Technology.

In the late 1940s and early 1950s, Lorenz worked with Victor Starr on the General Circulation Project at MIT to understand the role the weather system played in determining the energetics of the general circulation of the atmosphere.

He earned both a master's and doctoral degree in meteorology from MIT in 1943 and 1948.

His doctoral dissertation, titled "A Method of Applying the Hydrodynamic and Thermodynamic Equations to Atmospheric Models" and performed under advisor James Murdoch Austin, described an application of fluid dynamical equations to the practical problem of predicting the motion of storms.

Lorenz spent the entirety of his scientific career at the Massachusetts Institute of Technology.

In 1948, he joined the MIT Department of Meteorology as a research scientist.

In the 1950s, Lorenz became interested in and started work on numerical weather prediction, which relied on computers to forecast weather by processing observational data on such things as temperature, pressure, and wind.

This interest was sparked, in part, after a visit to the Institute for Advanced Study in Princeton, New Jersey, where he met Jule Charney, then head of the IAS's Meteorological Research Group and a leading dynamical meteorologist at the time.

By the late 1950s, Lorenz was skeptical of the appropriateness of the linear statistical models in meteorology, as most atmospheric phenomena involved in weather forecasting are non-linear.

It was during this time that his discovery of deterministic chaos came about.

In 1955, he became an assistant professor in the department and was promoted to professor in 1962.

(Charney would later join Lorenz at MIT in 1957 as a professor of meteorology.) In 1953, Lorenz took over leadership of a project at MIT that ran complex simulations of weather models that he used to evaluate statistical forecasting techniques.

In 1961, Lorenz was using a simple digital computer, a Royal McBee LGP-30, to simulate weather patterns by modeling 12 variables, representing things like temperature and wind speed.

He wanted to see a sequence of data again, and to save time he started the simulation in the middle of its course.

He did this by entering a printout of the data that corresponded to conditions in the middle of the original simulation.

To his surprise, the weather that the machine began to predict was completely different from the previous calculation.

The culprit: a rounded decimal number on the computer printout.

The computer worked with 6-digit precision, but the printout rounded variables off to a 3-digit number, so a value like 0.506127 printed as 0.506.

This difference is tiny, and the consensus at the time would have been that it should have no practical effect.

However, Lorenz discovered that small changes in initial conditions produced large changes in long-term results.

Lorenz's discovery, which gave its name to Lorenz attractors, showed that even detailed atmospheric modelling cannot, in general, make precise long-term weather predictions.

His work on the topic, assisted by Ellen Fetter, culminated in the publication of his 1963 paper "Deterministic Nonperiodic Flow" in Journal of the Atmospheric Sciences, and with it, the foundation of chaos theory.

He states in that paper:

"'Two states differing by imperceptible amounts may eventually evolve into two considerably different states ... If, then, there is any error whatever in observing the present state—and in any real system such errors seem inevitable—an acceptable prediction of an instantaneous state in the distant future may well be impossible....In view of the inevitable inaccuracy and incompleteness of weather observations, precise very-long-range forecasting would seem to be nonexistent.'"

From this work, in 1967, Lorenz published a landmark paper, titled "The Nature and Theory of the General Circulation of the Atmosphere," on atmospheric circulation from an energetic perspective, which advanced the concept of available potential energy.

His description of the butterfly effect, the idea that small changes can have large consequences, followed in 1969.

From 1977 to 1981, Lorenz served as head of the Department of Meteorology at MIT.

In 1983, the MIT Department of Meteorology and Physical Oceanography merged with the Department of Geology to become the current MIT Department of Earth, Atmospheric and Planetary Sciences, where Lorenz remained a professor before becoming an emeritus professor in 1987.

His discovery of deterministic chaos "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," according to the committee that awarded him the 1991 Kyoto Prize for basic sciences in the field of earth and planetary sciences.

On April 16, 2008, Lorenz died at his home in Cambridge from cancer at the age of 90.