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William Herschel found that the Solar System is moving through space within our disk-shaped Milky Way galaxy. Edwin Hubble showed that the Milky Way galaxy is just one of many galaxies in the universe. Examination of the galaxy's position and motion in the universe led to the Big Bang theory and the whole of modern cosmology. Modern tests
Diagram of the Milky Way, with galactic features and the relative position of the Solar System labelled. The Solar System is located in the Milky Way, a barred spiral galaxy with a diameter of about 100,000 light-years containing more than 100 billion stars.
Formation and evolution of the Solar System. Artist's conception of a protoplanetary disk. There is evidence that 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. [1] Most of the collapsing mass collected in the center, forming the Sun, while the rest ...
The theory of gravity allowed scientists to rapidly construct a plausible heliocentric model for the Solar System. In his Principia , Newton explained his theory of how gravity, previously thought to be a mysterious, unexplained occult force, directed the movements of celestial bodies, and kept our Solar System in working order.
The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System (as well as other planetary systems ). It suggests the Solar System is formed from gas and dust orbiting the Sun which clumped up together to form the planets. The theory was developed by Immanuel Kant ...
The theory of galactocentrism was an important step in the development of cosmological models as speculation on the existence of other galaxies, comparable in size and structure to the Milky Way, placed the Earth in its proper perspective with respect to the rest of the universe. Shifts from heliocentrism to galactocentrism and later acentrism ...
The rotation curve of a disc galaxy (also called a velocity curve) is a plot of the orbital speeds of visible stars or gas in that galaxy versus their radial distance from that galaxy's centre. It is typically rendered graphically as a plot, and the data observed from each side of a spiral galaxy are generally asymmetric, so that data from each ...
Rare Earth hypothesis. The Rare Earth hypothesis argues that planets with complex life, like Earth, are exceptionally rare. In planetary astronomy and astrobiology, the Rare Earth hypothesis argues that the origin of life and the evolution of biological complexity, such as sexually reproducing, multicellular organisms on Earth, and subsequently ...