Earth: The Blue Planet

Overview

Earth is the third planet from the Sun and is our home planet. It's also the only planet that we know of so far that's inhabited by living beings. While Earth is the 5th largest planet, it is the only planet in the solar system with liquid water on its surface, thus earning the nickname, The Blue Planet. It's slightly larger than Venus and is the biggest among the four terrestrial* planets.

Description

Earth is formed around 4.5 billion years ago with a radius of 3,959 miles (6,371 kilometers). From an average distance of 93 million miles (150 million kilometers), Earth is exactly one astronomical unit away from the Sun.** It takes about 8 minutes for light from the Sun to reach Earth.

Potential for Life:
Earth has a very hospitable temperature and mix of chemicals that have made life abundant here. The temperature here allows liquid water to exist for extended period of time and its vast oceans provided a convenient place for life to begin about 3.8 billion years ago.

Orbit and Rotation: Earth completes one rotation every 23.9 hours, and one lap around the sun 365.25 days. That extra quater of a day will be added every four years as a leap day. The Earth's axis of rotation is tilted 23.4 degrees. This tilt causes our yearly cycle of seasons.

Structure:
Earth is composed of four main layers, that is the inner core, the outer core, mantel and crust. The inner core is a solid sphere of iron and nickel metals about 759 miles (1,221 kilometers) in radius. The temperature there is as high as 5,400 degrees Celsius (9,800 degrees Fahrenheit).

Surface:
Like Mercury and Venus, Earth is dotted with volcanoes, mountains and valleys. Earth's lithosphere (the crust and upper mantle) is divided to multiple plates that are constantly moving, thus contributing to the formation of volcanoes and mountains. These moving plates are called tectonic plates.

Temperatures:
The average temperature on Earth is about 13.9 degrees Celsius (57 degrees Fahrenheit) with it being warmer at a rate of 0.15 to 0.2 degrees Celsius (32.27 to 32.36 degrees Fahrenheit) per decade.

Atmosphere:
Earth has an atmosphere that consists of 78% nitrogen, 21% oxygen and 1% of other gases. The atmosphere protects us from harmful radiation from the Sun and also meteoroids, most of which burns up in the atmosphere.

Magetosphere:
Earth has a magnetic field that is shaped like a teardrop. It is created by the planet's rapid rotation and molten nickel-iron core. The magnetic field is also the cause for aurorae. The geologic record tells us that a magnetic reversal takes place about every 400,000 years, where the north and south gets swaped.

Moon:
Earth has a single moon, and it's the brightest in our night sky. The moon is responsible to the rise and ebb of tides. The moon is 1,080 miles (1,738 kilometers) in radius and 238,855 miles (384,400 kilometers) away from Earth.

Fun Facts!

• The Earth isn't shaped perfectly round, but rather an oval.
• Days on Earth are getting longer and longer.
• The Earth has 2 Co-Orbital Satellites*** - 3753 Cruithne and 2002 AA29.
• Earth is the only planet in the solar system that is not named after Greek and Roman god or godesses.

Footnotes:

*The 4 terrestrial planets are the four innermost planets, (Mercury, Venus, Earth and Mars).

**One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. This unit provides an easy way to quickly compare planets' distances from the Sun.

***Co-Orbital Satellites (or Co-Orbital Configuration) is a configuration of two or more astronomical objects orbiting the same or very similar path around a central object.