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Earth: 3rd Planet: Earth is the third planet from the Sun and the subject of historical misconception for centuries. [4] [5] Earth was never formally 'discovered' because it was never an unrecognized entity by humans. However, its shared identity with other bodies as a "planet" is a historically recent discovery.
The Andromeda Galaxy, for instance, was once referred to as the Andromeda Nebula (and spiral galaxies in general as "spiral nebulae") before the true nature of galaxies was confirmed in the early 20th century by Vesto Slipher, Edwin Hubble, and others. Edwin Hubble discovered that most nebulae are associated with stars and illuminated by starlight.
The first planetary nebula discovered (though not yet termed as such) was the Dumbbell Nebula in the constellation of Vulpecula.It was observed by Charles Messier on July 12, 1764 and listed as M27 in his catalogue of nebulous objects. [10]
Another example is Earth's axial tilt, which, due to friction raised within Earth's mantle by tidal interactions with the Moon , is incomputable from some point between 1.5 and 4.5 billion years from now. [104] The outer planets' orbits are chaotic over longer timescales, with a Lyapunov time in the range of 2–230 million years. [105]
The first eon in Earth's history, the Hadean, begins with the Earth's formation and is followed by the Archean eon at 3.8 Ga. [2]: 145 The oldest rocks found on Earth date to about 4.0 Ga, and the oldest detrital zircon crystals in rocks to about 4.4 Ga, [34] [35] [36] soon after the formation of the Earth's crust and the Earth itself.
9.257 billion years (4.543–4.5 Gya): Solar System of Eight planets, four terrestrial (Mercury, Venus, Earth, Mars) evolve around the Sun. Because of accretion many smaller planets form orbits around the proto-Sun some with conflicting orbits – early heavy bombardment begins. A large planetoid strikes Mercury, stripping it of outer envelope ...
The geological history of the Earth follows the major geological events in Earth's past based on the geological time scale, a system of chronological measurement based on the study of the planet's rock layers (stratigraphy). Earth formed about 4.54 billion years ago by accretion from the solar nebula, a disk-shaped mass of dust and gas left ...
Its orbit revealed that it was a new planet, Uranus, the first ever discovered telescopically. [20] Giuseppe Piazzi discovered Ceres in 1801, a small world between Mars and Jupiter. It was considered another planet, but after subsequent discoveries of other small worlds in the same region, it and the others were eventually reclassified as ...