EARTH

Overview

Earth is the third planet from the Sun, orbiting at an average distance of about 150 million km (one astronomical unit). It is the largest of the rocky "terrestrial" planets and the only world known to hold liquid water on its surface and to harbor life.

About 78% of its atmosphere is nitrogen and 21% is oxygen — and that oxygen-rich air is itself a product of living things. Roughly 70% of the surface is covered by oceans, which is why Earth shines blue when viewed from space, earning it the nickname "the Blue Planet."

Features

Earth rotates once roughly every 24 hours and completes one orbit of the Sun in about 365.25 days. Because its axis is tilted about 23.4 degrees relative to its orbital plane, the planet experiences seasons.

Its interior is layered: an iron-rich core at the center, a surrounding mantle, and a thin outermost crust. Earth also generates a magnetic field, which acts as a shield protecting the atmosphere and life from the high-energy particles of the solar wind.

Its only natural satellite, the Moon, is comparatively large — about a quarter of Earth's diameter. The Moon's gravity drives the ocean tides and is thought to help keep the tilt of Earth's axis stable.

Trivia

Surface temperature — The average is around 15°C. Recorded extremes range from about -89°C at the coldest to roughly 57°C at the hottest. This mild range, where liquid water can exist, is one of the key conditions that makes life possible.

The "habitable zone" — The band of distances from a star where water can stay liquid — neither too hot nor too cold — is called the habitable zone. Earth orbits comfortably within the Sun's.

Earth from space — "The Blue Marble," photographed by the crew of Apollo 17 in 1972, remains one of the most famous images ever taken of the entire planet.

In Gravity Weaver

Earth is the third stage of the solar system run (3rd of 9). Guide the Solar Shard with your gravity fields and bring it home to Earth to clear the stage.

From this stage onward, meteors begin to appear at a slow, gentle pace. Since it is still early, there is plenty of room — a calm place to practice the core skill of drawing Gravity Wells to shape the Solar Shard's path. Getting into the habit of reading a meteor's motion before drawing a field will pay off in the constellation stages ahead.