Eruvin 46 - Water Cycle

The Mishnah from the previous page set out the circumstance of acquiring without intention.

IF A MAN SLEPT BY THE WAY (on Friday) AND WAS UNAWARE THAT NIGHT HAD FALLEN, (while he slept) HE IS ENTITLED TO MOVE WITHIN TWO THOUSAND CUBITS IN ANY DIRECTION;

Now that is a bit surprising since he had no intention of establishing a Shabbat zone. The answer comes through an analogy with rain:

Since a man awake acquires his place so does also a man asleep? — R. Joseph replied: Come and hear: If rain fell on the eve of a festival the water may be carried within a radius of two thousand cubits In any direction, but if it fell on a festival day the water is on a par with the feet of every man.

The water also falls without intension. But that is imperfect, since we can trace it back:

But why? Should not the rain water acquire its place for the Sabbath in the ocean?

 The water still had to get there:

But why should not the water acquire its place for the Sabbath in the clouds? 

Rather than waiting for the rain to fall, why don't we base the Shabbat laws on the rain's formation into clouds? Well, that might be hard to determine.

But is it not possible that those (clouds) moved away and these (clouds) are others? —

It is a case where one can recognize them by some identification mark.

Ok, identifiable clouds.

But should it not then be forbidden all the more because it was produced on the festival? — The fact, however, is that the water in the clouds is in constant motion.

Now that you have arrived at this explanation you can raise no difficulty about the ocean either, since the water in the ocean is also in constant motion, and it was taught: Running rivers and gushing springs are on a par with the feet of all men.

The water cycle puts rain into a different category. it is cycling, flowing and moving. So it can be carried without regard for when it formed.