Eruvin 43: When We're Too Busy to Welcome the Messiah

Does the concept of techum apply to a space that's over 10 tefachim? Again the overlap with eruv chatzerot, and so on. Seven teachings were taught twice, first in Sura, and then in Pompedita. How could that happen - at that distance? Eliyahu HaNavi! He could fly and bring the information. Alternatively, a demon. Pertaining to the vow of a Nazir. And the eruv and 10 tefachim. But can the messiah come, if he has to travel out of techum? Eliyahu has to travel and also the messiah to come the following day... And each day that Eliyahu doesn't come, the one who takes an oath that he'll be a Nazir as soon as the messiah arrives can drink that day. And then everyone will celebrate Shabbat and the non-Jews will help the Jews keep Shabbat. How hard would it be for everyone if the messiah came when everyone is preparing for Shabbat or yom tov. Also: again, on the ship - can they disembark on Shabbat? Rabban Gamliel says they had entered the techum before Shabbat, so they can depart the ship. He had a device that enabled him to scope out the shore from 2,000 amot away, using geometry to calculate the distance (astrolabe). Likewise, geometry was used to determine the height of a date palm, by measuring and comparing the lengths of shadows.