Why is it important for us to know the distance between these two cities? so much so that the Gemara stops mid sentence of explaining the Machlokes of the Mishna to give us a feeling of this distance? what clarity in the Mishna is gained by this knowledge? besides what is the practical application of this (meaning in modern times)?
Thank you.
chein, montreal
Your question is indeed asked by the Tiferes Yaakov. He answers that this must mean something other than distance. Rather, it means that just as Bei Kubi was a city that was partially within the Techum of Pumbedisa, and one could enter the Techum of Pumbedisa by entering into part of Bei Kubi, so too Kefar Ludim was partially within the Techum of Eretz Yisrael, and one could enter into the Techum of Eretz Yisrael from within Kefar Ludim. This helps us understand the Mishnah, as it is explaining how Kefar Ludim is "Muvla" into Lud and Eretz Yisrael. (It must be noted, however, that most commentaries do seem to understand it is referring to distance.)
All the best,
Yaakov Montrose