The Diameter of Earth — Reading Comprehension

Earth is a nearly round planet shaped like a ball, which scientists call a sphere. One way to describe the size of Earth is by talking about its diameter. The diameter is the distance across the planet through its center, from one side to the other. Earth’s diameter is about 12,742 kilometers (about 7,918 miles). That means if you could dig a straight tunnel from one side of Earth through the center to the other side, you would travel almost 8,000 miles!

Knowing Earth’s diameter helps scientists understand how big our planet really is. It also helps them make models of the solar system, measure distances, and learn about Earth’s layers. For example, Earth has a core, mantle, and 

, and measuring the diameter tells scientists how thick these layers are.

Earth’s diameter is much bigger than the Moon’s, which is only about 3,474 kilometers (2,159 miles). That is one reason Earth has stronger gravity than the Moon. The bigger a planet is, the more gravity it has to pull things toward it.

Learning about Earth’s size helps us compare it to other planets and understand why life is possible here. Knowing Earth’s diameter helps explain why our planet can keep its air, water, and living things safe.

Earth is just the right size to support life. Its diameter is one of the reasons it is such a perfect place for us to live.

Fun Fact: Did you know that if you could drive a car around the Earth's middle, it would take you about 16 days if you drove day and night without stopping? That's how big Earth is!

What shape is our Earth?

What is the name for the length going straight through the middle of Earth?

Can we use a small ruler to measure Earth's diameter?

About how many kilometers is Earth's diameter?

Why is Earth's diameter a "really, really big number"?

What does knowing Earth's diameter help us understand?

What is the main idea of this passage?

If you wanted to find the diameter of a round pizza, what would you measure?