Too big to look round

About this video

Look out over a field or the sea and the Earth looks flat. Hills, rivers, seas, forests and towns, and every person, animal and plant you have ever seen, all sit on it. This video shows why it looks flat, and what it really is.

The Earth is a giant ball. It is so big that the small piece you can see around you looks flat, like an ant walking on a huge football. The video moves slowly away from a flat horizon: the farther away we go, the more the line bends, until it closes into a ball.

Long ago, people argued about this. Some thought the Earth was flat, like a plate, and some even said it had an edge: travel too far and you would fall off. Others said it was a ball. More than 2,000 years ago, thinkers in ancient Greece had already found clues that it is round.

Today we don't have to guess. Astronauts fly so high above the Earth that they can see the whole of it at once: a round blue ball of sea and land, with white clouds around it.

The Earth makes no light of its own. The Sun gives it light and heat, and the Sun can only light one side of a ball at a time. So half of the Earth is always in sunlight and half is in shadow, an idea that explains day and night.

The Sun is also far bigger than the Earth. It only looks small because it is so far away: you would need 109 Earths side by side to stretch across it.

The big idea: the Earth is the huge ball we all live on. It looks flat to us, but from space you can see it is round.

Transcript

1. 0:00Look out over a field or the sea. The Earth looks flat.
2. 0:06Hills, rivers, forests, towns. Everything you have ever seen is on it.
3. 0:13But is it really flat?
4. 0:20Let's move away from it.
5. 0:23The farther we go, the more the flat line bends. It is a ball.
6. 0:32It looks flat because it is huge.
7. 0:35Like an ant on a huge football, we see only a small piece.
8. 0:44Long ago, people argued. Some thought it was flat, like a plate.
9. 0:50Some even said it had an edge. Travel too far, and you fall off.
10. 0:57Others said it was a ball.
11. 1:00More than two thousand years ago, thinkers in Greece found clues that it is round.
12. 1:08Today we don't have to guess.
13. 1:11Astronauts fly so high that they see the whole Earth at once.
14. 1:17A round blue ball of sea and land, with white clouds.
15. 1:30The Earth makes no light of its own. The Sun lights it.
16. 1:36And a ball can only be lit on one side at a time.
17. 1:42So half of the Earth is always in sunlight, and half in shadow.
18. 1:54And the Sun is far bigger than the Earth.
19. 1:58Put Earths side by side across it, and you need one hundred and nine.
20. 2:06The Sun only looks small because it is so far away.
21. 2:16The Earth is a huge ball we all live on. It only looks flat.