Glossary term: Earth
Description: Earth is the third planet of the Solar System and one of its inner planets, together with Mercury, Venus, and Mars. It is the fifth largest planet in the Solar System in terms of diameter and mass, and has the highest density. Earth is home to millions of species of living creatures, including humans; it is the only place to date known to have life in the Universe. It is believed to have formed about 4.54 billion years ago. Earth has an atmosphere that works to block harmful radiation and hence allowed the multiplication of organisms that live only in the presence of oxygen and the formation of the ozone layer. Earth also has extensive surface water (the only planet in the solar system known to do so), giving it a blue color.Related Terms:
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Term and definition status: This term and its definition is still awaiting approval
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Earth as observed from Apollo 17Caption: Full disk view of the Earth taken on 7 December 1972, by the crew of the Apollo 17 spacecraft en route to the Moon at a distance of about 29,000 kilometres (18,000 mi). It shows Africa, Antarctica, and the Arabian Peninsula.
Credit: NASA/Apollo 17 crew/Project Apollo Archive
License: PD Public Domain icons