Earth

The image above, known as The Blue Marble, was taken by the Apollo 17 Mission(1972)

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Properties:

Mass: 5.972 * 10²⁴ kg

Equatorial Radius: 6,371 km

Semi-major Axis: 149,598,023 km(1 AU)

Orbital Period: 365.256 days(1 yr)

Rotational Period: 23 hours, 56 minutes, 4.100 seconds(0.997 days)

Surface Gravity: 9.81 m/(s²)

Etymology: Middle English <-- Old English(eorðe) <--- eorðe means the ground, soil, human world, etc.

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Earth is the third planet from the Sun and possibly the most notable astronomical body in the universe for mankind. After all, it is the homeworld of humanity and as of now, the only planet that is known to sustain significant forms of "intelligent" life. Here on Earth, 29.2% of the surface consists of land features, like continents. The remaining 70.8% is water, be it oceans, lakes, rivers, and more.

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The Sun is believed to have been formed mainly through hydrogen and helium from the collapse of a massive molecular cloud. Once the Sun formed, a solar nebula formed which eventually flattened and spun out into a circumstellar disk. This disk then gave rise to many of the early planets, including Earth through extremely long periods of accretion. This is the leading theory as to how the Earth was formed.

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The key element of the Earth which distinguishes it from other planets, of course, is its ability to harbor life and develop it over time. Thanks to experiments like the Miller-Urey Experiment, an experiment that simulated the conditions of the early Earth that could've given rise to advanced organisms, it is now inferred that many of the fundamental chemicals necessary for life could have been created through inorganic reactions in the atmosphere due to the abundance of methane(CH4) and ammonia(NH3) in the early Earth. Another theory is known as the panspermia hypothesis believes that much of Earth's life could have been brought from outer space, through meteoroids and other foreign objects. This is also justified because it is well-known that there are significant amounts of organic molecules out in interstellar space. However, the panspermia hypothesis fails to explain how those organic molecules themselves could've come about.

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