When and how was our home, the Earth, formed? The Earth is located in a vast universe. The Earth is in a solar system at the edge of a cluster of stars called the Milky Way galaxy. Now, let’s look into the secret of the Earth’s formation. 

The events that started the Earth’s formation go back about 5 billion years ago. Somewhere in the universe, a star exploded. The force of the blast created a large swirling of fine gas and dust particles. Matter gathered together at the center of the swirl and got hotter and hotter. Eventually, the matter got hot enough to trigger a nuclear fusion reaction. What this produced is the sun.

At the same time, gases in the circling swirl cooled and formed tiny particles. These particles grouped together and eventually formed large masses called minor planets. The minor planets were drawn together by gravitational attraction, making bigger and bigger minor planets. These were the original forms of the Earth and other planets. The original Earth is thought to have formed about 4.6 billion years ago.

Did you know the Earth was formed from a swirl of tiny gas and dust particles? Around the same time, gases and dust clumped together to make other planets.

There are eight planets in our solar system. Starting from the closest to the sun, they are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. You can think of the solar system’s planets as brothers and sisters. Even though the planets are in the same solar system, they are different sizes and have different characteristics. The four planets closest to the sun — Mercury, Venus, Earth, and Mars — are smaller and are made of rock. Jupiter, Saturn, and Uranus are mostly made of gas and are very large.

The Earth has lots of air and water and is home to a rich diversity of life forms. You can say the Earth is a very special planet with lots of characteristics not found on any other planet in the solar system.

Can you imagine what the Earth looked like immediately after it was formed? At the very beginning, the Earth didn’t have any oceans or any land. The Earth was a huge sea of hot magma. Magma is rock that has melted at temperatures over 1,200 degrees Celsius. Many minor planets and meteorites were also crashing into the Earth at this time. High in the sky, water vapor started to gather and make clouds.

Eventually, as fewer minor planets and meteorites hit the Earth, the sea of magma began to cool. When the Earth’s surface temperature fell to around 300 degrees Celsius, clouds formed near the surface and rain started to fall. The rain cooled the hot surface very quickly.

And as the surface cooled more, the water vapor in the atmosphere also cooled, causing more rain. The rainwater pooled on the Earth’s surface, making rivers, ponds, and lakes. Huge floods happened over and over again. The floods joined the pools of water together until they eventually turned into oceans. It poured rain constantly for an incredible 3,000 years. By the way, do you know why the oceans are salty?

From space, the Earth looks like a blue shining planet. This is because 70 percent of the Earth’s surface is covered by water. And this is why the Earth is called the Water Planet.

But how was land made if everything was covered by water? Let's take a look at the bottom of the oceans and the inside of the Earth. The ocean floor was covered by the Earth’s crust. The crust is made up of a thin layer of rock. Under the crust was a hot mass of rock called the mantle.

Several hundred million years after the Earth was formed, an even hotter core formed in the center of the Earth. The super-hot core heated the mantle, which made the mantle lighter and caused it to rise up. This mantle was cooled at the ocean floor and became plates, or bedrock. These plates moved with the flow of the mantle and collided with other plates. At the boundaries where plates collided, lots of islands were formed. The islands were made of a light rock called granite. It’s thought these granite islands collided and clumped together, eventually creating continents.

Take a good look at a world map or a globe. If you moved North and South America and placed them beside Africa, can you see how neatly they would line up? About 220 million years ago, all of today’s continents were joined together in one super huge continent. It’s believed cracks formed in the super continent and the pieces slowly drifted apart. Over time, these pieces moved into their current shape.

So why did the continents move? The answer is related to the mantle inside the Earth. The mantle is a hot mass of rock that moves under the Earth’s surface. The mantle’s movement causes the continents to move.

For example, the area where the Himalayas are now was once a shallow sea long ago. What happened was the Indian subcontinent drifted and collided with Asia. The powerful impact raised the sea up into the sky and formed the Himalayas. The Japanese archipelago was sunk at the bottom of the sea until about 300 million years ago. The archipelago rose up from the seafloor about 200 million years ago, rising above the sea and sinking back down again and again. All this time, it was joined to the Asian continent. The continent and Japan were connected by land until about 100,000 years ago. People, animals, and other living things were able to come to Japan because of the land bridge.

What exactly is the center of the Earth like? The inside of the Earth is a bit like a half-boiled egg. The Earth’s surface is covered by a very thin layer called the crust. We dig into the crust to obtain minerals and fuels like coal and oil. But looking at the entire planet, this layer is like a very thin shell of an egg.

If we go down deeper toward the center of the Earth, we will reach a layer called the mantle. The mantle is like the white part of an egg. Going farther down beyond the mantle, we will reach the core, which is like the yolk of an egg. The core is molten and is said to be as hot as 6,000 degrees Celsius. The mantle is made of rock. When rock in the mantle is heated by the core’s extreme heat, the rock becomes lighter and rises. When the rock cools, it becomes heavier and sinks. This process is called convection. It’s why rock in the mantle is always moving. As the mantle moves, land on the surface also moves little by little. It’s like the land is dragged along by the mantle.

The sun’s height in the sky and where it rises and sets changes, depending on the season. On the day of an autumnal equinox or a spring equinox, the sun rises in the true east and sets in the true west. Daytime and nighttime are exactly the same length on these days. On the day of a summer solstice in the northern hemisphere, the sun is at its highest in the sky and daytime is the longest. This is why summers are hot. On the day of a winter solstice, the sun is at its lowest in the sky and daytime is the shortest. This is why winters are cold.

Besides the seasons, temperatures change depending on what latitude you are at. Near the equator, the sun shines directly overhead, making temperatures higher. At higher latitudes, the sun shines at an angle, so the temperature is lower. The Earth can be divided into tropical, temperate, and polar climate zones, depending on the latitude.

Water on the surface of the ocean is heated by the sun and turns into water vapor. The water vapor rises into the sky, where it cools and forms clouds. It then turns into rain or snow and falls back to the Earth’s surface. The water flows over the land, passes through rivers, and returns to the oceans again. This repeating cycle is called the water cycle. Water has been constantly traveling through the sky, land, and oceans for millions of years.

The Earth has a lifespan like everything else. Its lifespan is closely related to the sun. The sun is always shining light on the Earth. But the sun will not shine forever.

The sun’s lifespan is said to be about 10 billion years. The sun has gotten brighter by about 1 percent every 100 million years. About 500 million years from now, because of the sun’s increasing heat, the Earth’s seawater will have evaporated and no life will be able to live on the Earth. And about 5 billion years from now, the sun will have expanded out so far that it will swallow the Earth.

At the very end, the sun will explode. Everything will go back to being gas and dust. It’ll be just like before the sun and the planets in our solar system were formed. But because of the sun’s explosion, the gas and dust will be scattered throughout the universe and become the materials for the birth of a new star.

The Age of Discovery began in the 14th century, when Europeans began sailing the seas all over the world. As they discovered new sea routes and continents, they also figured out the Earth is a round, spherical planet.

Still, they believed the sun and stars revolved around the Earth. The astronomer Copernicus was the first to say that the Earth and other planets circle around the sun. Still at the time, no one believed the Earth revolved around the sun.