Kant-Laplace hypothesis or nebular hypothesis is the hypothesis of the origin of the solar system from the primary nebula (nebula). Nebula, according to theory, had spherical shape and consisted of various hot gases. Due to its own gravitational attraction it was gradually thickened. Because of gravity forces in the central part the Sun was created , and on the edge of the nebula the planets are formed.
Today, most astronomers believed that Earth and other planets originally formed from the nebula that surrounded the sun. It is believed that it happened about 5 billion years ago. Study of radioactive material on Earth shows that could not be older than this, because if it is, this material would be ruined and turned into a lead.
This theory is known as a modern nebular hypothesis, the modification of old nebular hypothesis. But, as the nebula consisted primarily of hydrogen and helium, this hypothesis does not offer a satisfactory explanation, that on the Earth formed heavier elements, and also on rocky inner planets (Mercury, Venus and Mars). Outer gas planets (Jupiter, Saturn, Neptune and Uranus) are, in part, very similar to the Sun. The largest part of their mass, as in the case of the Sun consists of hydrogen and helium, so that their formation is in accordance with nebular hypothesis. Just the presence of heavier elements on the rocky planets is what has not yet been explained satisfactorily.
Nebular hypothesis appeared somewhere around second half of the 18th century. The authors of these hypothesis are E.Kant and P.Laplace. The reason why it is so called is because it is considered that the nebula (nebula) is the source of planetary material that is actually a huge cloud of dispersed material that just floats in space. Of course, their theory has many flaws, but they accepted it because it is a real feature that the emergence of Sun as a star associated with the emergence of the planet.