Earth

Earth is a special planet because it is an 'ocean world.' About 70% of its surface is covered in water, which helps life grow.

We have a thick atmosphere made of nitrogen and oxygen that protects us from space. One cool fact is that Earth has one Moon that orbits us. The Moon's gravity causes the tides in our oceans!

Earth is also the densest planet in our solar system.

It formed about 4.5 billion years ago from gas and dust.

Earth is the third planet from the Sun and the only one known to have life. It is a rocky planet with a very active surface. The outer layer, called the crust, is broken into pieces called tectonic plates.

These plates move slowly, creating mountains and volcanoes.

Inside, Earth has a solid inner core and a liquid outer core that creates a magnetic field. This field protects us from solar winds.

Our atmosphere is mostly nitrogen and oxygen. It uses the 'greenhouse effect' to keep the planet warm enough for liquid water. Without this, Earth would be a frozen -18 degrees Celsius!

Most of our water is in the oceans, but some is frozen in huge ice sheets at the poles. Humans have lived on Earth for about 300,000 years, but our activities are now changing the climate. We must take care of our natural resources to protect the many species that live here.

Earth is the third planet from the Sun and the largest of the four rocky, or terrestrial, planets in our Solar System. It is unique because it is the only place we know of that supports life. This is largely because Earth is an 'ocean world,' with liquid water covering about 70.8% of its surface.

The planet is shaped like an ellipsoid, which means it is mostly round but bulges at the center (the equator) due to its rotation. It takes about 365.25 days to orbit the Sun, a period we call a year.

Because Earth’s axis is tilted at an angle of about 23.4 degrees, different parts of the planet receive more sunlight at different times of the year, which creates our seasons.

Earth is also orbited by one large natural satellite, the Moon, which helps stabilize our planet's tilt and creates the tides in our oceans.

Inside, Earth is made of several layers. The outer layer is the crust, where we live. Below that is the mantle, followed by a liquid outer core and a solid inner core.

The movement of the liquid outer core creates a magnetic field called the magnetosphere. This field acts like a shield, protecting Earth from harmful solar winds and radiation.

The crust itself is broken into tectonic plates that move very slowly. When these plates push together or pull apart, they create mountains, volcanoes, and earthquakes.

Earth’s atmosphere is composed mostly of nitrogen (78%) and oxygen (21%). It also contains greenhouse gases like carbon dioxide and water vapor. These gases trap heat from the Sun, keeping the average surface temperature at a comfortable 14.76 degrees Celsius (58.57 degrees Fahrenheit). Without this greenhouse effect, Earth would be too cold for most life to exist. Life began on Earth about 4 billion years ago. Today, humans live on every continent, but our use of resources like fossil fuels is changing the climate.

Protecting Earth's biosphere is now a major challenge for the future.

Earth is the third planet from the Sun and the only astronomical object known to harbor life. It is the largest and densest of the Solar System's four terrestrial planets. What distinguishes Earth from its neighbors is its status as an 'ocean world'; it is the only planet in our system where liquid water remains stable on the surface. Approximately 70.8% of the planet is covered by a global ocean, while the remaining 29.2% consists of continental landmasses and islands.

The formation of Earth occurred approximately 4.54 billion years ago from the solar nebula. Shortly after its formation, a Mars-sized body named Theia is thought to have collided with Earth, leading to the creation of the Moon.

This large natural satellite plays a critical role in Earth's habitability by stabilizing the planet's axial tilt, which prevents chaotic climate shifts. The Moon also generates tides, which have gradually slowed Earth's rotation over billions of years. Due to tidal interaction, the Moon is actually receding from Earth at a rate of 38 mm per year.

Geologically, Earth is divided into layers based on chemical and physical properties. The outermost layer, the lithosphere, includes the crust and the uppermost rigid mantle. This layer is fragmented into tectonic plates that migrate across the more fluid asthenosphere.

These movements are driven by the escape of internal heat, generated by primordial heat from the planet's formation and the radioactive decay of isotopes like potassium-40 and uranium-238. Plate interactions at boundaries result in volcanic activity, mountain building, and the recycling of the oceanic crust.

Deep within the planet lies a liquid outer core composed mainly of iron and nickel. The motion of this fluid generates Earth's magnetic field, or magnetosphere, which shields the atmosphere from destructive solar winds.

Earth’s atmosphere is a dynamic mixture of gases, primarily nitrogen (78.08%) and oxygen (20.95%). It serves several vital functions: it provides the gases necessary for life, protects the surface from ultraviolet radiation via the ozone layer, and moderates temperature through the greenhouse effect. Trace gases like carbon dioxide and methane capture thermal energy, maintaining an average surface temperature of 14.76 °C.

Without this natural insulation, the average temperature would plummet to -18 °C. The unequal distribution of solar energy—with the equator receiving 1361 W/m2 and the poles receiving much less—drives atmospheric and oceanic currents, creating diverse climate regions.

The planet's rotation and orbit are fundamental to its environment. Earth rotates on its axis once every 23 hours and 56 minutes (a sidereal day) and orbits the Sun at an average distance of 150 million kilometers.

Its axial tilt of 23.4 degrees is responsible for the progression of seasons.

The orientation of this axis changes over time, precessing in a complete circle every 25,800 years. The orbit is slightly elliptical, reaching its closest point to the Sun (perihelion) in January and its farthest (aphelion) in July.

Humanity emerged roughly 300,000 years ago and has since spread across the globe, significantly altering the biosphere.

We rely on Earth's natural resources, including minerals and biological products, but our current impact is increasingly unsustainable. Activities such as burning fossil fuels have increased greenhouse gas concentrations, leading to global warming and rising sea levels.

Scientists have identified 'planetary boundaries' to quantify these impacts, noting that several—including climate change and biodiversity loss—have already been exceeded. Looking toward the far future, Earth's fate is tied to the Sun. In about 1.1 billion years, increased solar luminosity will cause the oceans to evaporate, and eventually, the Sun will expand into a red giant, potentially vaporizing the planet.