Mohammad Hanief
Earth, our home, is the third planet from the sun. While scientists continue to hunt for clues of life beyond Earth, our home planet remains the only place in the universe where we’ve ever identified living organisms.
Earth is the fifth-largest planet in the solar system. It’s smaller than the four gas giants – Jupiter, Saturn, Uranus and Neptune – but larger than the three other rocky planets, Mercury, Mars and Venus.
Earth has a diameter of roughly 8,000 miles (13,000 kilometers) and is mostly round because gravity generally pulls matter into a ball. But the spin of our home planet causes it to be squashed at its poles and swollen at the equator, making the true shape of the Earth an “oblate spheroid.”
Our planet is unique for many reasons, but its available water and oxygen are two defining features. Water covers roughly 71% of Earth’s surface, with most of that water located in our planet’s oceans. About a fifth of Earth’s atmosphere consists of oxygen, produced by plants.
Earth has a very hospitable temperature and mix of chemicals that have made life abundant here. Most notably, Earth is unique in that most of our planet is covered in liquid water, since the temperature allows liquid water to exist for extended periods of time. Earth’s vast oceans provided a convenient place for life to begin about 3.8 billion years ago.
While Earth orbits the sun, the planet is simultaneously spinning around an imaginary line called an axis that runs through the core, from the North Pole to the South Pole. It takes Earth 23.934 hours to complete a rotation on its axis and 365.26 days to complete an orbit around the sun – our days and years on Earth are defined by these gyrations.
Earth’s axis of rotation is tilted in relation to the ecliptic plane, an imaginary surface through the planet’s orbit around the sun. This means the Northern and Southern Hemispheres will sometimes point toward or away from the sun depending on the time of year, and this changes the amount of light the hemispheres receive, resulting in the changing seasons.
Earth happens to orbit the sun within the so-called “Goldilocks zone,” where temperatures are just right to maintain liquid water on our planet’s surface. Earth’s orbit is not a perfect circle, but rather a slightly oval-shaped ellipse, similar to the orbits of all the other planets in our solar system. Our planet is a bit closer to the sun in early January and farther away in July, although this proximity has a much smaller effect on the temperatures we experience on the planet’s surface than does the tilt of Earth’s axis.
As Earth orbits the Sun, it completes one rotation every 23.9 hours. It takes 365.25 days to complete one trip around the Sun. That extra quarter of a day presents a challenge to our calendar system, which counts one year as 365 days. To keep our yearly calendars consistent with our orbit around the Sun, every four years we add one day. That day is called a leap day, and the year it’s added to is called a leap year.
Earth sometimes temporarily hosts orbiting asteroids or large rocks. They are typically trapped by Earth’s gravity for a few months or years before returning to an orbit around the Sun. Some asteroids will be in a long “dance” with Earth as both orbit the Sun.
Like Mars and Venus, Earth has volcanoes, mountains, and valleys. Earth’s lithosphere, which includes the crust (both continental and oceanic) and the upper mantle, is divided into huge plates that are constantly moving. For example, the North American plate moves west over the Pacific Ocean basin, roughly at a rate equal to the growth of our fingernails. Earthquakes result when plates grind past one another, ride up over one another, collide to make mountains, or split and separate.
Scientists think Earth was formed at roughly the same time as the sun and other planets some 4.6 billion years ago when the solar system coalesced from a giant, rotating cloud of gas and dust known as the solar nebula. As the nebula collapsed under the force of its own gravity, it spun faster and flattened into a disk. Most of the material in that disk was then pulled toward the center to form the sun.
Other particles within the disk collided and stuck together to form ever-larger bodies, including Earth. Scientists think Earth started off as a waterless mass of rock.However, analyses of minerals trapped within ancient microscopic crystals suggest that there was liquid water already present on Earth during its first 500 million years.
Radioactive materials in the rock and increasing pressure deep within the Earth generated enough heat to melt the planet’s interior, causing some chemicals to rise to the surface and form water, while others became the gases of the atmosphere. Recent evidence suggests that Earth’s crust and oceans may have formed within about 200 million years after the planet took shape.
Earth Day is an annual celebration that honors the achievements of the environmental movement and raises awareness of the need to protect Earth’s natural resources for future generations. Earth Day is celebrated on April 22 throughout of the world.
The first Earth Day was celebrated in 1970, when a United States senator from Wisconsin organized a national demonstration to raise awareness about environmental issues. Rallies took place across the country and, by the end of the year, the U.S. government had created the Environmental Protection Agency. By 1990, Earth Day was an event celebrated by more than 140 countries around the globe. Our planet is an amazing place, but it needs our help to thrive! That’s why each year on April 22, more than a billion people celebrate Earth Day to protect the planet from things like pollution and deforestation. By taking part in activities like picking up litter and planting trees, we’re making our world a happier, healthier place to live.
