The hypothesis of the original nebular condition of the system, with the consequent explanation of the great phenomena of planetary formations and movements of the satellites and rings, is unquestionably to be assigned to Kant.
The daily outpour of heat from the sun at the present time suggests a profound argument in support of the nebular theory.
Again by Sir William Huggins, the spectrum of the Orion nebula was photographed on the 7th of March 1882; and the method has gradually become nearly exclusive in the study of nebular emanations.
But even after the omission of all cometary objects we can still count in the solar system upwards of five hundred bodies, almost every one of which pronounces distinctly, though with varying emphasis, in favour of the nebular theory.
Sions be secured of such faint objects as nebulae, tele scopic comets, and the immense majority of stars, or of the dim ranges of stellar and nebular spectra.
Such was the nebular theory as it was originally sketched.
In this remarkable work Kant, proceeding from the Newtonian conception of the solar system, extends his consideration to the entire sidereal system, points out how the whole may be mechanically regarded, and throws out the important speculation which has since received the title of the nebular hypothesis.
Yet the boldness and the splendour of the nebular theory have always given it a dignity not usually attached to a doctrine which from the very nature of the case can have but little direct evidence in its favour.
There is quite a different method of considering the nebular origin of our system, which leads in a very striking manner to conclusions practically identical with those we have just sketched.
Thus in 1864 the spectroscope yielded him evidence that planetary and irregular nebulae consist of luminous gas - a conclusion tending to support the nebular hypothesis of the origin of stars and planets by condensation from glowing masses of fluid material.