Rainbows

We are all happy to see a rainbow in the sky. Beautiful rainbows look like seven-color bridges in the sky. Rainbows sometimes appear （出现） in pairs（成对） . Have you ever thought about where rainbows come from？ When can we see them？ Why do rainbows usually appear after it rains？     

我爱科学

The planet we live on is called earth. It is special （ 特别的） in the universe（宇宙） because it has life on it. It moves around the sun so we call it a planet（行星）.Our home planet is a rocky one （石质行星）.Our rocky planet has water.Water covers about 70% of its surface（表面）.That＇s why the Earth looks blue from space.