Rosh Hashanah, Chapter 2, Mishnah 8. In Mishnah 6 the Mishnah described how the witnesses who came to testify about the new moon were interrogated and examined. Our Mishnah opens with a method that was used to simplify that examination, and then continues with two incidents that occurred in the days of Rabban Gamliel concerning testimony about the new month.
Rabban Gamliel's Diagrams of the Moon:
"Demus tzuros levanos hayu lo l'Rabban Gamliel" - Rabban Gamliel, the Nasi of the Sanhedrin, had images of the various shapes of the moon. "B'tavla u'vakosel ba'aliyaso" - on a tablet attached to the wall of his upper chamber. "Shebahen mar'eh es hahedyotos" - with these he would show the shapes to the simple people who came to testify about the moon, "v'omer: hakazeh ra'isa o kazeh?" - Did you see it like this, or like this?
This method was far more effective for the many people who were not expert in fine distinctions and could not fully grasp a purely verbal explanation. The visual illustration helped them give precise testimony.
The First Incident - Seen in the Morning and in the Evening:
"Ma'aseh sheba'u shnayim v'amru: ra'inu shacharis b'mizrach" - two witnesses came and testified that they had seen the old moon in the morning in the east, where it is expected to be seen, on the twenty ninth day of the month, "v'arvis b'ma'arav" - and that same evening, which begins the thirtieth day, they saw the new moon in the west.
Rabban Yochanan ben Nuri said: "Eidei sheker heim" - they are false witnesses, since it is physically impossible for the old moon and the new moon to be seen so close to one another. The Gemara explains that at least twenty four hours must pass during which the moon is not visible at all, between the setting of the old moon and the appearance of the new moon.
However, "k'sheba'u l'Yavneh kiblan Rabban Gamliel" - when the witnesses arrived in Yavneh, the seat of the Sanhedrin, Rabban Gamliel accepted their testimony. The reason: Rabban Gamliel knew that seeing the new moon on that night was entirely possible, and as for the old moon, the witnesses must have erred and seen something that they thought was the moon but was not.
The Second Incident - Seen at Its Proper Time and Not Seen on the Following Night:
"V'od ba'u shnayim v'amru: ra'inu bizmano" - the Mishnah uses the term "at its proper time" when the moon is seen on the thirtieth day, meaning that the witnesses testified that they saw it on the night of the thirtieth, the night that leads from the twenty ninth into the thirtieth day. "U'v'leil ibburo lo nir'ah" - but on the following night, the night that leads into the added day, the thirty first day, the moon was not seen at all.
Apparently it was a clear night, and the expectation was that if the new moon had been seen on the previous night, it would certainly be seen the following night as well. Nevertheless, "v'kiblan Rabban Gamliel", for he knew that seeing the new moon on the night of the thirtieth was possible; and as for its not being seen the next night, something may have occurred, a light cloud cover or the like, that prevented it from being seen.
Rabbi Dosa ben Harkinas said: "Eidei sheker heim". He based his claim on a parable: how can one testify about a woman who gave birth, and the next day her belly is still as full as it was before, meaning that she looks exactly as pregnant as she was previously, with no change at all? Something must be amiss, for the witnesses testify that they saw the new moon, and the next day it is not seen at all.
Rabbi Yehoshua answered him: "Ro'eh ani es devarecha" - I agree with you. Rabbi Yehoshua, who was the Av Beis Din and second in rank in the Sanhedrin, thereby disagreed with Rabban Gamliel the Nasi.
In summary: we learned about the tablet of moon diagrams that Rabban Gamliel had in his upper chamber, with which he made it easier for simple people to give precise testimony; and about two incidents in which Rabban Gamliel accepted witnesses who appeared to be disqualified - in the first incident Rabban Yochanan ben Nuri disagreed with him, and in the second Rabbi Dosa ben Harkinas and Rabbi Yehoshua disagreed with him.
This dispute between Rabbi Yehoshua and Rabban Gamliel will lead us into the continuation of the story, which we will learn in the next Mishnah.