Cosmic distance ladder | 宇宙距离

The class has no homework today.  We watched the video lecture by Terence Tao (see link below).   The name of the video is “Cosmic Distance Ladder”.  Quite a mystifying name.

The stories, which Terence Tao told in the lecture, were about philosophers and astronomers from ancient times, such as Aristotle and others, and those who were closer to us in history.  What all of them have in common is that they were able to use good observations and ingenious reasonings to indirectly measure the distance between the Earth and the Moon, and the Sun, and the distance of the galaxies, without any technology (the earliest did not even know the number Pi), with amazing accuracy (as verified by what we know today).

You should definitely watch the video a few times.  Think about this: compare with human observation and reasonings, what computers can do is still just technology and tools.  The computers can’t do indirect reasonings that connect the dots from disparate information. It makes zero sense to believe computers (including phones) are smarter than you are.

So, use your great mind. Let your mind observe and reason, and make computers help you along the way.