![]() ![]() The most significant criticism of the hypothesis was its apparent inability to explain the Sun's relative lack of angular momentum when compared to the planets. The current standard theory for Solar System formation, the nebular hypothesis, has fallen into and out of favour since its formulation by Emanuel Swedenborg, Immanuel Kant, and Pierre-Simon Laplace in the 18th century. The first recorded use of the term "Solar System" dates from 1704. This concept had developed for millennia ( Aristarchus of Samos had suggested it as early as 250 BC), but was not widely accepted until the end of the 17th century. ![]() The first step toward a theory of Solar System formation and evolution was the general acceptance of heliocentrism, which placed the Sun at the centre of the system and the Earth in orbit around it. Ideas concerning the origin and fate of the world date from the earliest known writings however, for almost all of that time, there was no attempt to link such theories to the existence of a "Solar System", simply because it was not generally thought that the Solar System, in the sense we now understand it, existed. Main article: History of Solar System formation and evolution hypotheses Pierre-Simon Laplace, one of the originators of the nebular hypothesis Ultimately, over the course of tens of billions of years, it is likely that the Sun will be left with none of the original bodies in orbit around it. Some planets will be destroyed, and others ejected into interstellar space. In the far distant future, the gravity of passing stars will gradually reduce the Sun's retinue of planets. In roughly 5 billion years, the Sun will cool and expand outward to many times its current diameter (becoming a red giant), before casting off its outer layers as a planetary nebula and leaving behind a stellar remnant known as a white dwarf. Planetary migration may have been responsible for much of the Solar System's early evolution. The positions of the planets might have shifted due to gravitational interactions. Unlike the planets, these trans-neptunian objects mostly move on eccentric orbits, inclined to the plane of the planets. Several thousand trans-Neptunian objects have been observed. ![]() Beyond Neptune many sub-planet sized objects formed. Collisions between bodies have occurred continually up to the present day and have been central to the evolution of the Solar System. ![]() Still others, such as Earth's Moon, may be the result of giant collisions. Many moons have formed from circling discs of gas and dust around their parent planets, while other moons are thought to have formed independently and later to have been captured by their planets. The Solar System has evolved considerably since its initial formation. Since the dawn of the Space Age in the 1950s and the discovery of exoplanets in the 1990s, the model has been both challenged and refined to account for new observations. Its subsequent development has interwoven a variety of scientific disciplines including astronomy, chemistry, geology, physics, and planetary science. This model, known as the nebular hypothesis, was first developed in the 18th century by Emanuel Swedenborg, Immanuel Kant, and Pierre-Simon Laplace. Most of the collapsing mass collected in the center, forming the Sun, while the rest flattened into a protoplanetary disk out of which the planets, moons, asteroids, and other small Solar System bodies formed. The formation of the Solar System began about 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Modelling its structure and composition Artist's conception of a protoplanetary disk ![]()
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