How far away is the Sun?

第 1 章Light takes timeYou know your street and your city. But how far is it to the next big house in the neighborhood — the Sun? Nobody has ever been there, and nobody has sent a tape measure. And yet we know its average distance to within a few meters.1 关中已完成 0 关

第 2 章Measuring the skyNobody has walked to the Sun or a star. So how do we know how far they are? With a thumb, a planet crossing the Sun and a lot of patience.3 关中已完成 0 关

1. 第 1 关Light takes its time
2. 准备好了第 2 关Measuring with your thumb
3. 准备好了第 3 关A light-year is a distance
4. 准备好了第 4 关Closer means faster