I chose to talk on the cosmic distance ladder – the hierarchy of rather clever (yet surprisingly elementary) mathematical methods that astronomers use to indirectly measure very large distances, such as the distance to planets, nearby stars, or distant stars. This ladder was really started by the ancient Greeks, who used it to measure the size and relative locations of the Earth, Sun and Moon to reasonable accuracy, and then continued by Copernicus, Brahe and Kepler who then measured distances to the planets, and in the modern era to stars, galaxies, and (very recently) to the scale of the universe itself. It’s a great testament to the power of indirect measurement, and to the use of mathematics to cleverly augment observation.

https://terrytao.wordpress.com/2007/05/31/the-cosmic-distance-ladder/

PPT: cosmic-distance-ladder2.pptx

视频 http://v.youku.com/v_show/id_XMjE4NTE0NjQw.html

中文版：http://www.mysanco.cn/wenda/index.php?class=discuss&action=question_item&questionid=6665