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All planets in the Solar System, plus their major moons along some asteroids and comets, have now been visited to varying degrees by spacecraft launched from Earth. Through these uncrewed missions, humans have been able to get close-up photographs of all the planets and, in the case of landers , perform tests of the soils and atmospheres of some.
[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 Earth's position in the Solar System was correctly described in the heliocentric model proposed by Aristarchus of Samos. [6] Moon: Earth I
c. 16th century BCE – Mesopotamian cosmology has a flat, circular Earth enclosed in a cosmic ocean. [1]c. 15th–11th century BCE – The Rigveda of Hinduism has some cosmological hymns, particularly in the late book 10, notably the Nasadiya Sukta which describes the origin of the universe, originating from the monistic Hiranyagarbha or "Golden Egg".
For almost five millennia, the geocentric model of the Earth as the center of the universe had been accepted by all but a few astronomers. In Aristotle's cosmology, Earth's central location was perhaps less significant than its identification as a realm of imperfection, inconstancy, irregularity, and change, as opposed to the "heavens" (Moon ...
Although the distance traveled by light from the edge of the observable universe is close to the age of the universe times the speed of light, 13.8 billion light-years (4.2 × 10 ^ 9 pc), the proper distance is larger because the edge of the observable universe and the Earth have since moved further apart. [52]
1964 - First black hole, Cygnus X-1, discovered; 1964 – CP violation discovered by James Cronin and Val Fitch. 1965 – Arno Penzias and Robert Wilson: Cosmic Microwave Background (CMB) discovered; 1967 – Unification of weak interaction and electromagnetism (electroweak theory) 1967 – Solar neutrino problem found
5th century BC: The earliest documented mention of a spherical Earth comes from the Greeks in the 5th century BC. [31] It is known that the Indians modeled the Earth as spherical by 300 BC [32] 460 BC: Empedocles describes thermal expansion. [33] Late 5th century BC: Antiphon discovers the method of exhaustion, foreshadowing the concept of a limit.
c. 475 BCE – Parmenides is credited to be the first Greek who declared that the Earth is spherical and is situated in the centre of the universe, believed to have been the first to detect the identity of Hesperus, the evening-star, and Phosphorus, the morning-star (Venus), [13] and by some, the first to claim that moonlight is a reflection of ...