Here's a thread from last year which have a few insightful discussions on the topic: https://news.ycombinator.com/item?id=13762614 https://news.ycombinator.com/

Here's a thread from last year which have a few insightful discussions on the topic: https://news.ycombinator.com/item?id=13762614 https://news.ycombinator.com/item?id=13762614 I imagine he used some of the "tools in his toolbox" he acquired from various fields of Physics. Given that it was a PDE his answer also probably was an approximation