What is Earth? - Facts, Layers & Population

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: The Changing Earth: Volcanoes, Weathering & Deposition

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
Your next lesson will play in 10 seconds
  • 0:01 Planet Earth
  • 1:18 Earth's Interior
  • 2:18 Earth's Surface
  • 3:00 Earth's Human Population
  • 4:04 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Speed Speed
Lesson Transcript
Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

This lesson is about our one of kind home planet, Earth! We'll talk about what makes Earth so special, the layers inside the Earth, the unique features that are on or surround the Earth, and our own human population living on its surface.

Planet Earth

We're all familiar with this large rock we live on called Earth; but what is the Earth, really? What's inside of it? Why does it support life? All these questions and more will be answered - at least to the best of current scientific knowledge - in this lesson. If you're curious about this unique planet we call home, stay tuned.

The Earth is the third planet from the sun in our solar system, which is part of the galaxy known as the Milky Way. Earth's distance from the sun is important and allows for moderate temperatures and the sunlight that supports life. The temperatures on Earth, its atmospheric composition, and the presence of liquid water make it the perfect home for life. In fact, Earth is the only planet known to contain liquid water and, hence, life as we know it.

The Earth has a diameter of about 7,900 miles (or about 12,700 kilometers) and an approximate mass of 6 x 10^24 kilograms. It orbits (or circles) the sun every 365 days or so, which is one year on Earth. The Earth also rotates on its axis every 24 hours, creating the night and day we are all familiar with. Earth has one moon (or satellite) orbiting it.

Earth's Interior

Let's talk about what really makes up the Earth. There are the inside layers that we can't see, the crust (which is what we live on), and the atmosphere.

The innermost layer of the Earth is called the inner core, which is made of the densest materials - iron and nickel. In this layer, these metals are solid. Next comes the outer core, which is a liquid layer of iron and nickel. The core layers are very hot, as you can imagine it would be in order to have liquid metals. In fact, scientists estimate that it is as much as 10,800 degrees Fahrenheit, or 6,000 degrees Celsius.

After the outer core comes the mantle, which is made of hot magma (liquid rock). This layer moves around based on density and temperature and causes mountain formation, earthquakes, and other geological activities. Finally, above the mantle is the crust, which is where we live. In fact, humans reside on virtually all of the land masses of the crust, and our population is over 7 billion and continues to grow.

Earth's Surface

Now let's talk about the surface, or crust. The crust and upper portion of the mantle are referred to as the lithosphere because they interact to create the movement of large pieces of the crust called tectonic plates which can cause earthquakes and volcanoes to erupt. The crust is solid and formed of rocks. Trees, other plants, water, and animal life cover the crust of the Earth.

To unlock this lesson you must be a Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use

Become a member and start learning now.
Become a Member  Back
What teachers are saying about
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account