Working with or against gravity TB Eruvin 84

Gravity plays a role in today’s daf TB Eruvin 84. We have learned previously whichever courtyard has a more convenient access to middle ground may include that middle ground in its eruv. If both courtyards have equal access to that middle ground, the middle ground is forbidden to both unless the two courtyards make a joint eruv. (TB Eruvin 76b)

Zerika (זְרִיקָה) is gaining access by throwing an object up to the middle ground between the courtyard and the balcony. Shilshul (שִׁלְשׁוּל) is gaining access by lowering an object down to the middle ground. Zerika is working against gravity and is harder than Shilshul because it is working with gravity. Whenever the Gemara is speaking about Zerika, it is talking about a case where the middle ground is higher than 10 tefakhim. Conversely, whenever the Gemara is speaking about Shilshul, it is talking about a case where the middle ground is lower than 10 tefakhim. Who has access to the middle ground when the balcony is higher than 10 tefakhim then the middle ground and at the same time the middle ground is higher than 10 tefakhim above the courtyard. Both accesses are difficult but for different reasons.

“What is the halakha concerning a place that can be used by the residents of this courtyard only by lowering an object down to it and by the residents of that courtyard only by throwing an object on top of it? In other words, if an area is lower than one courtyard but higher than the other, so that neither set of residents has convenient access to it, which of them is entitled to use it?

“Rav said: It is prohibited for both sets of residents to use it. As the use of the area is equally inconvenient to the residents of both courtyards, they retain equal rights to it and render it prohibited for the other group to use. And Shmuel said: The use of the area is granted to those who can reach it by lowering, as it is relatively easy for them to lower objects to it, and therefore its use is more convenient; whereas for the others, who must throw onto it, its use is more demanding. And there is a principle concerning Shabbat: Anything whose use is convenient for one party and more demanding for another party, one provides it to that one whose use of it is convenient.” (TB Eruvin 83b, Sefaria.org translation)

Today’s daf musters different proofs with some supporting Shmuel and some supporting Rav. So far each of the proofs is rejected as being inconclusive. The conversation continues on tomorrow’s daf. Spoiler alert! According to Rambam in the Mishneh Torah, Sefer Zemanim, Laws of Eruvin, chapter 3 halakha 16, the halakha follows Rav’s position because we decide Jewish law according to his position when it comes to bans and permission (איסור והתר).