Help with the different twilight definitions
It is either somewhere in the cobwebs of the mind or in one of the reference books groaning the office shelves, but could someone please remind me of not only the definition/difference among Astronomical twilight, Nautical twilight, and Civil twilight...but also, and equally important, why we have those distinctions?
I was brought up short when a non-pilot friend asked me about these and I had to admit that I could not remember. Yes, I know tucking into Wikipedia would be a good first cut at it but I also know that tech forum members will undoubtedly bring some keen insight (ha ha) to the answer.