♁Earth
The pale blue dot we call home. The only planet in the known universe where life exists.
- Distance from Sun
- 1.00 AU (about 149.6 million km)
- Diameter
- 12,742 km
- Orbital period
- 365.25 days
- Rotation period
- 24 hours
- Moons
- 1 (the Moon)
Science
The scienceEarth is the third planet from the Sun and the only known home of life, with 71% of its surface covered by liquid water in the form of oceans. Its exquisite distance from the Sun (the habitable zone) keeps water from freezing or boiling away, while a thick atmosphere and magnetic field shield it from harmful cosmic radiation. Its single moon is a precious companion that stabilizes Earth's axial tilt and keeps the seasons regular. In 1990, Voyager 1 photographed Earth from about 6 billion km away, and it appeared as a single "pale blue dot," a mote of dust in space.
Name & Myth
The story behind the nameUnlike the other planets, which are named after gods, Earth's name comes not from myth but from ancient Germanic and English words meaning "ground" or "soil." To the ancients who gazed up at the stars and planets, Earth was not an object to observe but the very world beneath their feet. In the East it was called "Ji-gu," meaning the round earth, using not the element Earth (土) but the character for "land" (地) that signifies all things.