Koine Greek
One idea I've toyed with for a while is the idea of learning Koine Greek so I can read the New Testament in the original. This is slightly (very slightly!) less daunting for someone with a maths/physics background, because so many of the letters are used to stand in for various parameters - lambda (λ) for wavelength, pi for 3.14, etc. Alpha, beta and gamma particles come in to nuclear physics (needed in astronomy), delta is a variable in calculus and so on.
However, I'd put that aside because it is more necessary to learn the seventeenth century language of Science: Latin.
This weekend I'd gone back to Greek, for tomorrow I will be teaching a session on ancient Greek mathematics for Year 5 (9 - 10 year olds). I couldn't find all the notes I'd made last year, so I was checking up Greek maths words still in use today. I stil get a small kick out of the fact that the modern words for parable and for parabola are the same in Greek (which came first? I wish I knew).
The topic I will teach is the Elements, the famous Greek geometry book used for 2000 years as the basis of geometry. And in my surfing, I came across this website, about learning Greek to be able to read the Elements. The text of the Elements that we have is written in the literary koinh/ typical of the 1st century AD it said.
So now comparing the Elements (second most published book) and the Bible has another strand: it uses the same language.