Earth

Earth is our home in space.

It is the third planet from the Sun. Most of our world is covered in water.

This water is in big oceans. The rest of the world is dry land. Huge ice sheets also hold much water. The ground is made of moving plates. These plates can make mountains and volcanoes.

Earth is a very special place for life.

Earth is our home in space.

It is the third planet from the Sun. Earth is the only place we know that has life. This is because it has liquid water on its surface. Most of the planet is covered by oceans. These oceans cover about 70.8% of the crust. The crust is the hard outer layer of Earth.

The rest of the world is dry land. Most land is covered by green plants.

Earth has a special layer of air called an atmosphere. It is mostly made of nitrogen and oxygen. This air protects us from space rocks and light from the Sun. Gases like carbon dioxide help trap heat. This keeps the planet at a steady temperature. This temperature is about 14.76 °C.

Earth also has a magnetic field. This field comes from the liquid outer core. It acts like a shield against solar winds. Earth also has one moon. The Moon's gravity helps keep our planet steady. It also causes the tides in our oceans.

Earth is the third planet from the Sun. It is the only place in space known to have life. This is possible because Earth is an ocean world. It is the only planet in our Solar System with liquid water on its surface. Most of the planet is covered by a global ocean. This water covers 70.8% of the Earth's crust.

The other 29.2% is dry land. Most land is covered by green plants and is quite humid. Large ice sheets at the poles hold more water than all our rivers and lakes combined.

Our planet has many moving parts that work together. The crust is made of tectonic plates that move very slowly. These plates bump into each other to make mountains and volcanoes. Deep inside, a liquid outer core creates a magnetosphere. This acts like a shield to deflect solar winds and radiation. Earth also has an atmosphere made of nitrogen and oxygen.

This layer of air protects us from meteoroids and harsh light. Greenhouse gases like carbon dioxide help trap heat from the Sun. This keeps the average temperature at a steady 14.76 °C.

Earth has been around for a very long time. It formed about 4.5 billion years ago from gas and dust.

Scientists believe the Moon formed when a Mars-sized object named Theia hit Earth. This collision sent material into space that eventually gathered into the Moon. Over time, the oceans formed from volcanic activity and water from comets. Life began to spread across the globe during the first billion years. About two billion years ago, a big event called the Great Oxidation Event changed the atmosphere.

There are many interesting numbers that describe our home. Earth is the largest and most massive of the four rocky planets. Its circumference is about 40,000 kilometers long.

It takes about 365.25 days to orbit the Sun once. Earth also spins on its axis in about 23 hours and 56 minutes. This spin is slightly tilted, which is why we have seasons.

The Moon orbits us at a distance of 384,400 kilometers. The Moon is about one-quarter as wide as the Earth itself.

Everything on Earth is connected in a giant system. The Moon's gravity pulls on our oceans to cause tides.

Humans appeared about 300,000 years ago in Africa. We have since spread to every continent on the planet. We rely on the biosphere and natural resources to survive. However, human activities are changing the climate and the environment. These changes can make life hard for many different living things.

Earth is the third planet from the Sun and the only known astronomical object that harbors life. This unique status is largely due to Earth being an ocean world. It is the only planet in our Solar System that sustains liquid surface water. The global ocean covers 70.8% of Earth's crust, leaving only 29.2% as land. Most of this land exists as continental landmasses within the land hemisphere.

Much of this land is humid and covered by vegetation. However, massive ice sheets in polar deserts actually hold more water than all groundwater, lakes, rivers, and atmospheric water combined.

Our planet functions through complex, interconnected physical mechanisms. The Earth's crust is divided into slowly moving tectonic plates. These plates interact with one another to produce mountain ranges, volcanoes, and earthquakes. Deep beneath the surface, a liquid outer core generates a magnetosphere. This magnetic field acts as a shield, deflecting destructive solar winds and cosmic radiation.

Additionally, the atmosphere protects the surface from most meteoroids and ultraviolet light. This atmosphere is composed primarily of nitrogen and oxygen gases.

A vital process called the greenhouse effect helps maintain habitable temperatures. Water vapor and carbon dioxide (CO2) act as greenhouse gases in the atmosphere. These gases capture energy from the Sun's light to keep the planet warm. This process maintains a current average surface temperature of 14.76 °C (58.57 °F). At this temperature, water can remain in a liquid state under normal atmospheric pressure. Differences in solar energy absorption between the equator and the poles drive atmospheric and ocean currents. These currents create a global climate system that allows elements like carbon and nitrogen to cycle.

Earth's physical structure is an ellipsoid with a circumference of about 40,000 kilometers. It is the densest planet in the Solar System and the largest of the four rocky planets. Earth orbits the Sun at a distance of about one astronomical unit (1 AU). It takes approximately 365.25 days to complete one full revolution around the Sun. The planet also rotates on its own axis every 23 hours and 56 minutes. Because the axis of rotation is tilted, Earth experiences different seasons throughout the year.

Earth is also orbited by the Moon, a natural satellite roughly one-quarter the width of Earth.

The Moon orbits at 384,400 km and helps stabilize Earth's axis while causing tides.

The history of Earth began about 4.5 billion years ago. Like other bodies in the Solar System, Earth formed from gas and dust in a solar nebula. The Moon likely formed when a Mars-sized object named Theia collided with the early Earth. This glancing blow released material that eventually accreted into the Moon. Between 4.0 and 3.8 billion years ago, the Late Heavy Bombardment brought many asteroid impacts to Earth.

During the first billion years, oceans formed through volcanic outgassing and impacts from comets. By 3.5 billion years ago, the magnetic field was established to protect the atmosphere.

Over long periods, the movement of tectonic plates has reshaped the surface. These forces have caused continental crust to group into supercontinents and then break apart. For example, the supercontinent Rodinia began to break apart about 750 million years ago. Later, the supercontinent Pangaea formed and eventually began to break up around 180 million years ago.

Earth has also experienced cycles of glaciation. The Last Glacial Period, or the last ice age, ended roughly 11,700 years ago. These geological and climatic shifts show how dynamic our planet truly is.

Humanity has a significant relationship with the Earth's biosphere. Humans emerged approximately 300,000 years ago in Africa and have since spread to every continent. We depend entirely on Earth's natural resources and biological systems for our survival. However, human activities are currently impacting the climate and the biosphere in unsustainable ways. These changes are causing widespread extinctions and threatening the livelihoods of many life forms.

Looking much further ahead, the Sun will eventually evolve into a red giant. This will change Earth's environment forever, demonstrating the deep connection between our planet and its star.