Professor Edward N. Lorenz, the meteorologist and father of modern chaos theory, has died at this home in Cambridge, Massachusetts at the age of 90.

Professor Lorenz worked as a meteorologist for most of his life and it was while working on computer weather simulations that he discovered the effects of chaos on large mathematical models.

He hit on the principle when inputting data for a weather simulation into a computer manually, and discovered that a tiny variation in input data could produce a completely different weather result, often with dramatic effects.

Professor Lorenz first published reports on the topic in 1963 but it was his presentation entitled Predictability: Does the Flap of a Butterfly's Wings in Brazil Set Off a Tornado in Texas? which drove him into the public gaze.

The thesis postulated that there could never be a perfect weather forecast, since to obtain one would require a precise mapping of all particles on the planet at a particular point in time.

The slightest difference, therefore, could result in profound changes in the system.

The theory has since been applied to everything from financial markets development to population movement in crowds. In 1991 it got him the 1991 Kyoto prize for basic sciences.

At the time of the award it was said that Professor Lorenz "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".

Professor Lorenz died of cancer but was active to the end, going hiking three weeks ago and finishing a new paper last week.