What We Cannot Know: Explorations at the Edge of Knowledge

by Marcus du Sautoy

I need only know 39 digits of π to be able to calculate the circumference of a circle the size of the observable universe to a precision comparable to the size of a hydrogen atom.

It is amazing to me how time and again the physical world seems to turn into a piece of mathematics. We have to ask to what extent this is just a good story that helps tie the physical universe together, or is the physical universe actually a piece of physicalized mathematics?

the fact that light takes time to cross space means that I am in fact looking back in time. A snapshot of the sky depicts the Sun as it was 8 minutes and 20 seconds ago, the nearest star as it was four years ago, and the most distant galaxies as they looked billions of years ago.

how do you answer the question: what’s south of the South Pole? The question doesn’t really make sense. It is striking that often when a question arises to which it seems we cannot know the answer, it turns out that I need to acknowledge that the question is not well posed.

we can never truly know for sure what it is we cannot know.