Rabbinic Precision - Shabbat 7
Thus they consider the case of throwing an object onto a wall – if the wall were over 10 tefakhim (3-4 feet), he would be exempt because it is as if he threw it into the air; if the wall were lower, it would be like throwing onto the ground in a karmelit [intermediate space], and thus a liability-inducing transfer from private to other space would have taken place. Can one really throw an object exactly on top of a wall? They consider the case of throwing something sticky, like a juicy fig cake, or perhaps throwing an object into a cavity in the wall. Some question whether such a case is really possible, but in the end the resolution is that the original saying must refer to “on” a wall rather than “into” a wall.
The last example, something touched on in earlier pages, is the most relevant. Rabbi Hisda claims that if one puts a rod in private ground and throws something upwards that lands on it, it is still private ground because private ground extends upwards to the sky. The Talmud then asks if his case is like that of Rabbi Judah ha-Nasi, who considered this case: if a tree is in private ground but its branches tilt into the street, and one throws an object that gets caught in the branches, is the tree considered private or public ground? Rabbi Judah would consider the branches as legally part of the tree, but the other Rabbis follow contemporary homeowner ethics – the branches over your head are your problem, even if the tree is planted in the other person’s yard. Just don’t gather those branches on Shabbat – a different mitzvah violation!
Rabbi Adam Chalom