*Science gives us the idea that one day, everything will be under control, since everything obeys regular rules. We just need to find the mathematical formulas which best mimic the observations, in order to make predictions.In fact, it is true in an environment where everything is under control, and if we accepte the limits of what we can observe on our scale of space and time.*

The laws of gravity don’t explain some movements of the stars, for example the fact that galaxies are moving away from each other faster and faster. To explain it, we invoke “dark matter”, unobservable directly, and exerting a gravity force. But in fact, we do not know.

Even in our conceptual and sensorial framework, it is difficult to reproduce an environment accurately, and therefore to make perfect predictions, because our measuring instruments are limited. And we know that **very small differences in initial conditions, which are not always measurable, can produce very different results**.

This was observed by a meteorologist named Lorenz in the sixties. He made weather forecasts based on complex mathematical formulas taking into account climatic conditions such as wind speed, temperature and pressure. By entering more digits after the comma, so by entering more accurate measures, the results become far different. He concludes that subtle variations can produce big changes.

A butterfly flapping its wings in Brazil can produce a tornado in Texas.

Edward Lorenz, 1972

Before Lorenz, Mary Lucy Cartwright and John Edensor Littlewood had observed a phenomenon as surprising, during the Second World War, about radio waves. When the amplitude of the radio waves was particularly small, their transmission became more unstable, in other words, unpredictable.

When one goes to extremely small scales, at the level of the supposed constituents of the atoms, the predictability becomes harder, and the physicists calculate probabilities of events. This is the domain of quantum physics. Some observations go as far as to defy common sense, for example the fact that a photon or an electron can behave sometimes as a wave, sometimes as a particule.

Only in the mathematical world, our conceptual world, can we produce perfect predictions. The knowledge that we have in other disciplines are simple observations from which we have identified recurrences giving us a sufficient predictability on our scale of time and space, and which can sometimes be described with mathematical formula.

Thus, no human being can fully define reality, because we are limited in what we are able to observe and to conceive. **We can observe redundancies and deduce rules, they remain valid for our level of observation only, in an environment under control**.