"The telescope lets you look further" - a nie "farther". Którego słowa użyć?

Przeczytaj wszystko: http://random-idea-english.blogspot.com/2011/10/q-further-or-farther-british.html , a gdyby Ci się bardzo nie chciało, to zwróć uwagę chociaż na: "In the USA especially, many commentators followed the advice of that OED editor, and it is now stated on many grammar websites (mainly American) that farther should be used for distance and further for 'more' etc.
In Britain, however, while generally agreeing about the use of further when talking about quantity, amount or degree, most British commentators see further as just as correct as farther when talking about distance. Swan, the standard usage guide for learners (BrE) says:
We use both farther and further to talk about distance. There is no difference in meaning. ... We can use further (but not farther) to mean 'additional', 'extra', 'more advanced' "