The theories concerning the origin and the evolution of the solar system complex and are varied, bringing into play many scientific disciplines, like the Astronomie, the Physique while passing by the Géologie and the Planétologie. Through the centuries, much of theories relative to its creation were advanced, but the 18th century had had to be waited so that the modern theories start to take form. At the dawn of the space age, the images and the structures of the other worlds within our solar system refined our comprehension, while the Nuclear physics gave us our first saw fundamental processes inside stars, led finally to our first theories of their creation and their final destruction.

Solar nebula

See also: Nebulous solar

The assumption most usually allowed on the formation of the solar system is the assumption of the primitive nebula, initially suggested in 1755 by Emmanuel Kant and independently formulated by Pierre-Simon Laplace. The theory of nebula supports that the solar system was formed following the collapse of the gravity of a gas cloud called the solar Nébuleuse. It had a diameter of 100 ua and had a mass two or three times that of the sun.

In the course of time, a disturbance (probably a close Supernova) hustled nebula, pushing back the matter towards the interior until the gravitational forces exceed the gas pressure, it then started to crumble. Whereas nebula crumbled, the conservation of the kinetic moment led so that it rotates more quickly and that it becomes hotter.

Dating

By using the radioactive Dating, the scientists evaluate the age of the solar system to 4,6 billion years. The oldest terrestrial rocks have an age of 3,9 billion year. Rocks of this seniority are rare, as the earth's crust is constantly modelled by erosion, the volcanicity and the plate tectonics. To estimate the age of the solar system, the scientists must use meteorites which were formed during the beginning of the condensation of solar nebula. The oldest meteorites (such as the Météorite of Canyon Diablo) prove to have an age of 4,6 billion years, consequently the solar system must be old at least 4,6 billion years.

Subsequent evolution

It was thought first of all that the planets had been formed in the vicinity or in their current orbits. However, this representation underwent a radical change at the end of the 20th century and at the beginning of the 21e century. Today, it is thought that the solar system seemed very different from its initial training, with five objects at least as massive as Mercure in the internal solar system (against four currently), the external solar system being more compact than it is not now, and girdles it of Kuiper further started than it is it now. It is thought today that the impacts of meteorites represent a regular share (nevertheless not very frequent) of the development and evolution of the solar system. The formation of the Moon, just like that of the system Pluto-Charon is the result of a collision of objects of the belt of Kuiper. The other moons close to the asteroids and other objects of the belt of Kuiper would be also the product of the collisions. That of such entrechocs continue to occur can be shown by the recent collision of the Comet Shoemaker-Levy 9 with Jupiter in 1993, or the event of Toungouska.

Chaotic evolution of the orbits

The study of the orbits of planets showed repeated failures a long time, the observations tending to deviate from tables however increasingly precise. Thus the existence of Neptune it was had a presentiment of to correct the mistakes of Uranus. However, once the trajectories of planets correctly modelled for current times, the question remained posed regularity of these movements on the long run. When Kepler introduces the elliptic movements into the heliocentric system , the movements are described like Périodique S, stable and indefinitely regular. The Newtonian Gravitation deteriorates then this diagram by imposing relative disturbances, but the apparent stability of the solar system results in thinking that the divine intervention maintained the cohesion of the solar system. Laplace and Lagrange show finally that the irregularities observed are hardly but light oscillations of the form of orbits (Excentricité).

However, when calculations of trajectories are carried out for moved back times, the solutions utilize increasingly important margins of error, so that the movement of the orbits is not regular any more but chaotic. The current model shows an exponential divergence of the trajectories and orientation of the orbital plans. Actually, the apparent stability of the results of Laplace and Lagrange are due especially to the fact that their solutions were based on partial equations. Beyond a few tens of million years, uncertainty on the orbits is enormous. In the middle of these evolutions the phenomenon of orbital Résonance is, which can generate critical phases in the evolution of the orbits on the long run (see thus the example of Mars and the impact on its climate). However, the chaotic evolution of the orbits is limited: With very long run, the standard Modèle of cosmology predicts that the universe has a stable behavior: concerning the orbits of planets of the solar system, J. Laskar speaks thus about “marginal stability. ”