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The age of Earth is estimated to be 4.54 ± 0.05 billion years (4.54 × 109 years ± 1%).[1][2][3][4] This age may represent the age of Earth 's accretion, or core formation, or of the material from which Earth formed. [2] This dating is based on evidence from radiometric age-dating of meteorite [5] material and is consistent with the ...
Earth is the third planet from the Sun and the only astronomical object known to harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all of Earth's water is contained in its global ocean, covering 70.8% of Earth's crust.
[56] [60] [61] During this primary depletion period, the effects of the giant planets and planetary embryos left the asteroid belt with a total mass equivalent to less than 1% that of the Earth, composed mainly of small planetesimals. [59] This is still 10–20 times more than the current mass in the main belt, which is now about 0.0005 M E. [62]
The four outer planets, called giant planets or Jovian planets, collectively make up 99% of the mass known to orbit the Sun. [h] All four giant planets have multiple moons and a ring system, although only Saturn's rings are easily observed from Earth. [91] Jupiter and Saturn are composed mainly of gases with extremely low melting points, such ...
In physical cosmology, the age of the universe is the time elapsed since the Big Bang.Astronomers have derived two different measurements of the age of the universe: [1] a measurement based on direct observations of an early state of the universe, which indicate an age of 13.787 ± 0.020 billion years as interpreted with the Lambda-CDM concordance model as of 2021; [2] and a measurement based ...
Mercury, Venus, Mars, Jupiter and Saturn were identified by ancient Babylonian astronomers in the 2nd millennium BC. [7] They were correctly identified as orbiting the Sun by Aristarchus of Samos, and later in Nicolaus Copernicus ' heliocentric system [8] (De revolutionibus orbium coelestium, 1543) Venus. 2nd Planet.
Astronomical naming conventions. In ancient times, only the Sun and Moon, a few stars, and the most easily visible planets had names. Over the last few hundred years, the number of identified astronomical objects has risen from hundreds to over a billion, and more are discovered every year. Astronomers need to be able to assign systematic ...
Historical models of the Solar System. Approximate sizes of the planets relative to each other. Outward from the Sun, the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Jupiter's diameter is about 11 times that of the Earth's and the Sun's diameter is about 10 times Jupiter's.