The two primary ones are that by the time anyone bothered to codify rules of war, lighthouses went on the list of do not attack pretty much immediately, and so it would be a rather pointless war crime to commit; the second reason is related to why they went on the list of do not attack targets very quickly, and that is that lighthouses are completely nondiscriminatory as to who they alert to what's going on in terms of danger and coastlines and hidden rocks and such[…]

A cup of warm tea eventually cools to the ambient temperature.

You noticed I stopped drinking caffè mocha?

As is well-known in algebraic number theory, there is a far-reaching analogy between number fields and algebraic function fields in one variable with finite constant field.