Eiruvin 43a, b

The rabbis want to know more about movement with regard to Shabbat boundaries.  In 42a and b (which I did not comment on over Shabbat), they discuss  throwing as a form of carrying.  In 43a, they inquire about limits (four cubits? more? or perhaps four cubits in the outdoors is the same as in a permanent residence, which is actually the full residence?) of walking while on a boat.  Those limits could be different depending on whether the boat is moving or stationary.  Then the rabbis discuss the limitations of movement on Shabbat if a person is in the air; above 10 handbreadths.  (As an aside, they make mention of Rav Chisda in Sura and the seven teachings, which concern the halachot of animals who will die within one year).  And we learn about Yosef the demon, who may have been a demon or may have communicated with demons.

I love these 'asides'!  I wish that we could focus more on those fabulous facts.  Demons?  What demons? What are they talking about?  Why did this come up?  But now I digress, too.

In 43b, the rabbis discuss other factors that might help us understand Shabbat boundaries above 10 handbreadths.  What would breach an aerial boundary?  The moshiach, of course!  The rabbis get extremely creative and discuss one who vows to become a nasir  upon the arrival of moshiach.  When would s/he actually have to give up drinking if we know that Elijah will come the day before the moshiach arrives?  We have been told that moshiach will not arrive on Shabbat or a Festival because of the disruption that would ensue.  How does the day of the week change the nasir-to-be's vow?

In the name of understanding better the measurement of an eiruv, we are told of Rabban Gamliel's special tube that can measure 2000 cubits without having to travel that distance.  The rabbis then mention a similar tube that can help to measure the depth of a valley.  Further, they digress and explain how to measure the height of a tall palm without climbing it: by comparing the relative size of the shadows of a palm and a measured reed, the height of the palm can be calculated.

Finally, we learn that Rabbi Nechemya has wandered beyond the Shabbat boundary.  To alleviate his distress, Jews or gentiles can create a "human partition".  Rabbi Nechemya can walk through that permitted partition.

I know there are gaps in my understanding of eiruvin.  I am confused about this human partition and the permanence or transience of any eiruv.  Even the philosophical underpinnings of eiruvin sometimes seem fuzzy to me.  But I do love the opportunities that the rabbis use to explain their thinking - mathematical, logical, nautical (in 43a and b in particular), social, and on and on...

To end today's musings, a question: why would a person vow to become a nasir/a upon arrival of Moshiach? Once moshiach arrives, wouldn't that vow be simple to complete?  And until that time, how would a vow like that affect anything in one's life?  I wonder about the social cache that might come from making such a vow.  Or perhaps it could offer some sort of hope: looking forward to a time when one will be devoted to a spiritual life beyond a physically focused existence.  But if moshiach won't come in that person's lifetime (which, I believe, is pretty much assured), why make a vow like this at all?  Or perhaps I'm missing something here, too...