Thursday, October 07, 2010

A Terence Tao Talk -- check

Last night I got a chance to listen to Terence Tao speak. And thankfully it was non-technical so the mathematically-challenged like me could understand. It was on the "Cosmic Distance Ladder" which at first glance seems like a highly technical term/object in physics/cosmology. But it turns out to be a fascinating story of how human beings over the last 3000 years or so have measured astronomical distances using clever indirect measures where direct measurement was technologically impossible. Here's a thought experiment: Lets say you knew that a lunar eclipse spanned 3 hours. And you knew that the Moon takes a month to go around the earth. Can you approximately compute the distance from the Earth to the Moon in terms of Earth radii using no other piece of information?

The most clever trick he talked about was how Kepler estimated the orbits of the Earth and Mars (assuming them to be non-circular) using the multi-year data on Mars' declination collected by Tycho Brahe. This led Kepler to formulate his laws of planetary motion which led Newton to formulate his theory of gravitation. A great story of giants standing on the shoulders of giants...

Here's the slides in case someone's interested.

It was surprising to see how comfortable Tao was discussing a subject thats not his main area of expertise. He even fielded a few questions from the audience in the end.

All in all, a great treat!

1 comment:

Anonymous said...

Hi pranav,

enjoyed reading your blogs...

we go a long way back in Indore..your neighbours..sanjay kale from Mumbai..when we used to visit Indore, I used to talk to you from Terrace.....very great and informative blog for me... do keep posting...