
It was 1960 when Edward Lorenz developed a model for forecasting weather conditions at first sight rather simple. He must have considered it simple too.
The model could be written as a system of nonlinear differential equations, quite simple, which however could not find a solution in the closed form. In other words it was not possible to integrate its differential equations, so as to make evident time dependence of the three variables.
This explanation would have helped to write each of the three variables as a function of time (eg y = f (t)) - which is tantamount to find a closed-form solution for the system of equations, as the mathematicians love to say, and that would have helped get a punctual forecast of the weather, or at least a prediction consistent with the assumptions Lorenz made in the development of its model.
This approach was perfectly compatible with the physical thought that dominated almost the entire last century, that all phenomenologies might be considered within the mathematic determinism, becaus the observable reality is an expression of some stability form of the observed system. And I apologise for the extreme synthesis of these concepts.
Although closed-form solution cannot be found, the system developed by Lorenz can be solved numerically, with the help of computer. The geometric representation - in the space of phases - of the trajectories of state that emerges from these simulations is surprising, and is today the most famous example of a chaotic system. The trajectories never repeat, neither two of them will ever cross or overlap.
The system is unpredictable, because you can not write the integral functions, nonetheless it is stable and shows some regularity. A hidden order, impossible to imagine a priori.
The system is sensitive to initial conditions: the smallest variation of these can give rise to a dynamic evolution completely different from what you would have if the change had not been there.
Then the famous reflection of Edward Lorenz:
The model could be written as a system of nonlinear differential equations, quite simple, which however could not find a solution in the closed form. In other words it was not possible to integrate its differential equations, so as to make evident time dependence of the three variables.
This explanation would have helped to write each of the three variables as a function of time (eg y = f (t)) - which is tantamount to find a closed-form solution for the system of equations, as the mathematicians love to say, and that would have helped get a punctual forecast of the weather, or at least a prediction consistent with the assumptions Lorenz made in the development of its model.
This approach was perfectly compatible with the physical thought that dominated almost the entire last century, that all phenomenologies might be considered within the mathematic determinism, becaus the observable reality is an expression of some stability form of the observed system. And I apologise for the extreme synthesis of these concepts.
Although closed-form solution cannot be found, the system developed by Lorenz can be solved numerically, with the help of computer. The geometric representation - in the space of phases - of the trajectories of state that emerges from these simulations is surprising, and is today the most famous example of a chaotic system. The trajectories never repeat, neither two of them will ever cross or overlap.
The system is unpredictable, because you can not write the integral functions, nonetheless it is stable and shows some regularity. A hidden order, impossible to imagine a priori.
The system is sensitive to initial conditions: the smallest variation of these can give rise to a dynamic evolution completely different from what you would have if the change had not been there.
Then the famous reflection of Edward Lorenz:
can the beat of wings of a butterfly in Brazil generate a hurricane in Texas?