The Earth

Question 1

What are the distinguishing features of Earth?

Answer 1

• Liquid water
• Atmosphere of N2 and O2
• Life

Question 2

How did Erastothenes make the first accurate calculation of the circumference of the Earth?

Answer 2

He used shadows formed behind towers in different places at the same time to work out the angle between the two places (on Earth using the elevation of the sun). He then calculated the distance between these places and knew that a circle is 360 degrees so can work out circumference.

Question 3

What is the shape of the Earth?

Answer 3

Flattened sphere.

Question 4

What is the diameter of the Earth?

Answer 4

13,000 km

Question 5

What are the main benefits of Earth’s atmosphere?

Answer 5

• Respiration
• Blocks UV, x-ray and gamma
• Moderates temperature
• Protects us from small meteorites

Question 6

Why is the sky blue? Why is a sunset red?

Answer 6

The atmosphere refracts white light from the sun, and blue is refracted the most (almost along the plane of the sky) making the sky appear blue.
Sunset is red for the same reason - red light is only refracted a little bit and blue light is refracted a lot, meaning we see red when the sun is on the horizon.

Question 7

What is the evidence that the Earth is approximately spherical?

Answer 7

In a Lunar eclipse, Earth casts circular shadow on the Moon.