Earth
Earth, the third planet from the Sun, is our home planet. It's the only place we know of in the Universe that has life.
"Blue Marble" taken by Apollo 17 crew, December 7, 1972
Credit: NASA
Facts About Earth:
- Earth is the largest of the terrestrial (rocky) planets, although it's only slightly larger than Venus.
- Earth is believed to have formed about 4.5 billion years ago. Life first appeared about 1 billion years later.
- 71% of the surface is water.
- Earth rotates once per day but its rotation is slowing down by 1.4 milliseconds per century. When the dinosaurs were around, a day lasted 23 hours.
- Earth orbits the Sun at a relative speed of 30 km/second.
- Earth's Moon is unusually large compared to the planet it orbits.
- About 100 tons of meteorite dust lands on Earth every day. On average a meteor the size of a car enters the Earth's atmosphere about once per year. Most burn up before hitting the ground.
- There are more than half a million pieces of space junk orbiting the Earth.
- Earth is the only planet we know of that has liquid water on the surface.
- Earth will remain habitable for somewhere between 500 million years and 2.3 billion years.
- More energy from the Sun hits Earth every hour than the planet uses in a year.
- People have known that the Earth is a sphere since at least 500 B.C.
- Although most astronomers expect to find signs of alien life one day, at this stage Earth is the only place in the Universe we know of that has life.
Classification: Planet, terrestrial
(orbiting Sun)
Names: Sol 3, Terra, Papa-tū-ā-nuku
Satellites: 1Diameter: 12756.2 km
Circumference: 40030 km
Mass: 5.972e+24 kg
Surface Temperature: 287 K
Rotation period: 0.997 days
Rotation Velocity: 1674.4 km/h
Axial Tilt: 23.5000 °
Surface Pressure: 1013.25 hPa
Albedo: 0.3000
Volume: 1080000000000 km3
Density: 5.5100 g/cm3
Surface Area: 510100000 km2
Surface Gravity: 1.0000 g
Escape Velocity: 11.1860 km/s
Adjective: Terrestrial
