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Earth Develops

The Earth that we live on is an amazing planet. It is home to millions of diverse species. In fact, scientists have not yet found life forms on any other planet! So how did the Earth develop?

An image of the earth in space.

Planet Earth viewed from Outer Space.

The Birth of the Solar System

 
To find out how Earth developed, we first need to look at the birth of the universe. Everything started 13.8 billion years ago with the Big Bang.  This created all the matter in our universe. It is from this matter that all galaxies and solar systems formed.

 

An image of the Big Bang

Here is an illustration of what the Big Bang may have looked like.

All explosions release a lot of heat. The Big Bang was no exception. The hot soup of the universe collapsed into giant clumps of matter. From this, a massive spinning disk was formed into our galaxy.  Within the galaxy, our solar system eventually formed.

An image of the galactic disk

The galaxy looks like a giant spinning disk!

Our solar system formed by dust clumping together because of gravity.  The gasses at the center fused together and ignited, becoming the sun.  The sun is the closest star to us, and gives us the light, heat, and energy that we need to survive! Dust on the outer rings of the solar system came together to create planets. Each planet has its own orbit around the sun. This means that planets are different distances away from the sun. 

An image depicting our solar system.

The planets in our solar system orbiting around the sun.

Earth Develops

The Hot Earth

We divide the history of our Earth into eons. The first eon was 4.6 billion years ago when the Earth was first created. This is the Hadean eon, named after the Greek god of the underworld, Hades. In the Hadean eon, the conditions on the Earth were exactly like Hades: very hot and uninhabitable! 

Earth formed first as a molten planet. Lava oceans took up most of Earth’s surface. Volcanoes erupted frequently. Cosmic debris and meteorites fell to Earth all the time. There was also no oxygen anywhere. Helium and hydrogen would have made Earth’s first atmosphere extremely deadly. The planet was too hot for any water to exist in its liquid form.

An image of lava activity.

At one point, lava oceans covered the entirety of the Earth.

 The Cooling Earth

As the Earth began to cool down the surface solidified into a crust.  This left a molten core in the center of the planet. Liquid water also appeared on Earth.  Scientists think that water might have come from multiple volcanic eruptions. Or it could have come to Earth as ice by meteorites and comets.  Earth’s oceans appeared sometime after this.
 
The Hadean eon ended 3.8 billion years ago. The Archean age took its place, signifying the beginning of life on Earth. Even though there was very little oxygen in the air, life forms began to develop. These bacteria could handle the hostile conditions on Earth. From these simple bacteria cells, more complex living organisms developed. 

An image of Earth from Outer Space.

The Earth is now very different than it first was.

Why Earth?

There are a lot of reasons why life could have begun on Earth, but not on other planets. One of these is water. Water is very important for cells to develop.

 

Earth is the 3rd closest planet to the Sun. It exists in what is called the Goldilocks zone. Earth is not as hot as Mercury and Venus, but not as cold as Mars. This means that water doesn’t freeze or evaporate, and can exist as a liquid. 

An image of water in a glass.

Life-giving water!

Other Great Resources

Birth of the Earth and The Beginning of Life: https://www.youtube.com/watch?v=MKn0xWM7qh0

Khan Academy on the History of Life on Earth: https://www.khanacademy.org/science/biology/history-of-life-on-earth/history-life-on-earth/v/earth-formation

News Article on Earth’s Formation: https://www.universetoday.com/76509/how-was-the-earth-formed/

Timeline Overview of Earth’s Formation: https://www.bobthealien.co.uk/earth/formation.htm

Detailed Article about the Beginning of Life on Earth: http://www.ecology.com/2011/09/10/earths-beginnings-origins-life/

How did the Earth Form?: https://www.theguardian.com/science/2008/apr/28/starsgalaxiesandplanets.geology

 

Written by: Minh Nguyen