Rosh Hashanah 20b (כ:) — the Talmud in English

And we answer:

this—

when the new moon is seen on the thirtieth day, and the witnesses do not testify concerning the matter, it is

apparent falsehood.

The falsehood is evident to the public, because many others saw the moon, and it appears that the court intercalated the month through a falsehood.

But

this—

when the new moon was not seen at its proper time, even if the witnesses falsely testify that they saw it, nevertheless

it is not apparent falsehood.

This falsehood is not evident to the public, for although the other people did not see that the moon had renewed itself, it is possible that the witnesses did see it.

The Gemara continues to discuss the matter of sanctifying the new moon:

Shmuel said: I can establish the calendar for the entire Diaspora—

I can establish the order of the years and months for all the members of the Diaspora without seeing the moon, because I am expert in the course of the moon and in the order of the constellations. And if I were required to establish a calendar, I would be able to do so.

Abba, the father of Rabbi Simlai, said to Shmuel:

Does

the Master know this matter taught in the secret of intercalation—

does the Master know the explanation of the words of the beraita called “the secret of intercalation,” in which matters were stated by way of allusion?

“It was born before midday or it was born after midday.”

There is a distinction between whether the birth of the moon occurred before midday or after midday. This statement is an allusion.

He said to him,

Shmuel:

No,

I do not know its meaning.

Abba,

the father of Rabbi Simlai,

said to him: Since the Master does not know this, there is another matter that the Master does not know.

Since you do not know this concept, it appears that there are other things you do not know.

When Rabbi Zeira ascended—

when Rabbi Zeira went up to Eretz Yisrael—

he sent them—

two matters that he had learned in Eretz Yisrael to his colleagues in Babylonia: First, according to those who say that the witnesses who did not see the renewal of the moon on the thirtieth day are intimidated into giving false testimony in order to sanctify the new moon before its proper time, this does not apply in every case. Rather—

there must be a night and a day of the new month.

It is necessary that on the night preceding the thirtieth day, the moon belonging to the previous month should no longer be visible.

But if, on that night preceding the thirtieth day, the moon of the previous month is still visible, the entire day follows the preceding night,

and since the night belonged to the previous month, the day likewise belongs to the previous month.

And the new moon is not sanctified before its proper time, because since the moon of the previous month was still visible at night, everyone knows that this day is not the first of the month. If they were to sanctify the month on that day before its proper time, it would be apparent to everyone as a falsehood.

2.

And this is what Abba, the father of Rabbi Simlai, said

before Shmuel—and since he did not know how to explain the distinction between “born before midday” and “born after midday,” this is its meaning:

The molad is the time at which the moon is renewed and begins the cycle of the new month.

The moon circles the earth [according to the average calculation known from earlier generations through the tradition of the Sages] once every twenty-nine days, twelve hours, and 793 halakim [each “helek” is approximately three seconds].

Only half of the moon is illuminated by the rays of the sun, while its other half is perpetually dark.

During its orbit around the earth, the illuminated portion of the moon that faces the earth changes gradually. At the beginning of the orbit, primarily the dark portion of the moon is turned toward us, and only a small part of its illuminated portion faces us. The gradual waxing of the moon, from the beginning of the month until its midpoint, and likewise the waning of the moon after the midpoint of the month, result from the constant change in the moon’s position as it circles the earth.

The sun radiates its light onto the moon, and the moon reflects it toward the earth. When the moon completes half of its orbit around the earth, the entire side of the moon that faces the rays of the sun is exposed toward the earth, and therefore the moon appears full in the middle of the month. At the time of the molad itself, the moon completes its monthly orbit around the earth, and then it is not visible at all. For at that time it is located between the earth and the sun, and the entire illuminated side faces the sun.

Toward the end of the orbit, and likewise at the beginning of the orbit, the moon “disappears” from the sight of every observer because of the small amount of light reflected from it, since the human eye is then unable to detect such faint rays of light.

We calculate its offspring—

the time of the molad of the month of Tishrei, which is Rosh HaShana, by calculation, and on this basis we know when it will be visible:

If

it was born before midday

that day—

it is known that it will be seen

by the eye after six hours,

close to sunset,

and that day is Rosh HaShana.

But if

it was not born before midday—

it is known that it will not be seen

by the eye

close to sunset,

but only afterward, and it is impossible to make that day Rosh HaShana.

Because the moon is seen after the molad at the southwestern edge of the sky,

and it is close to the inhabitants of Eretz Yisrael, who live in the west, as will be explained below. Therefore, they see it six hours after the molad.

And we raise an objection:

What practical difference does it make

when the moon will be visible? For the month is sanctified on the basis of witnesses, and in any event they cannot testify until the moon is visible!

Rav Ashi

answered:

Rav Ashi:

The practical difference is

to disprove

the witnesses!

If we know that the molad occurred after midday, and the witnesses testify that they saw the moon before sunset, it is known that they are false witnesses.

Rabbi Zeira said in the name of Rav Naḥman: For twenty-four hours the moon is concealed.

The moon is hidden from sight for twenty-four hours:

If it happened that the molad occurred at midday, then:

For us—

for the residents of Babylonia—the moon is concealed

six hours from the old cycle and eighteen hours from the new cycle.

Six hours before the molad, the moon is concealed from us in the cycle belonging to the previous month, and eighteen hours after the molad, the moon is concealed in the cycle belonging to the following month.

For the residents of Babylonia, who live east of Eretz Yisrael, the sun sets on the last day of the month before it sets in Eretz Yisrael, and they cannot see the appearance of the moon close to sunset as it appears then in Eretz Yisrael, six hours after the molad that occurred at midday.

Therefore, the moon is concealed from them during the six hours before the molad, and it does not appear to them until the following morning, eighteen hours after the molad. [However, because of the sunlight at sunrise, it cannot normally be discerned then, but only close to sunset.]

Whereas

for them—

for the residents of Eretz Yisrael, which lies west of Babylonia—the moon is concealed

for six hours from the new cycle,

six hours in the cycle belonging to the new month,

and eighteen hours from the old cycle,

eighteen hours in the cycle belonging to the old month.

This is because the new moon [after the molad] is located in the southwestern corner, which becomes visible later to the inhabitants of Eretz Yisrael. Therefore, it is concealed from them for only six hours and appears close to sunset. But before the molad, the last time it can be visible, when it rises in the east, it is then far from Eretz Yisrael, and therefore they do not see it for eighteen hours before the molad.

It follows that in every place the moon is concealed for a total of twenty-four hours.

What practical difference does it make

in this matter?

Rav Ashi said: To disprove the witnesses.

If the witnesses said that they saw the old moon and the new moon within twenty-four hours, it is known that they are false witnesses.

The Master said,

Rabbi Zeira, above:

There must be a night and a day of the new month.

The old moon must not be visible even on the night preceding the thirtieth day, on which the new moon is sanctified.

But if it was visible at the beginning of the night, the court cannot sanctify the new moon for the purpose of establishing the thirtieth day.

And we raise an objection:

From where do we know

this law?

And we answer:

Rabbi Yoḥanan said:

Because it is stated [Leviticus 23] concerning Yom Kippur:

“From evening to evening

shall you observe your Shabbat.” From here it follows that on the Festivals the day follows the night [the Festival begins at night and ends at the conclusion of the day].

And likewise with regard to the first of the month: it begins at night. Therefore, even the night of the first of the month must not belong to the previous month.

Reish Lakish said:

Because it is stated [Exodus 12] concerning the eating of matza during the Festival of Passover: “On the first, on the fourteenth day of the month, in the evening, you shall eat matzot,

until the twenty-first day of the month, in the evening.”

From here it follows that the Festival ends at the beginning of the evening. That is, the Festivals begin at night and end at the conclusion of the following day.

And we raise an objection:

What is the difference between them—

what is the halakhic difference between them?

Abaye said: The difference between them is only the derivation of the verses.

There is no practical halakhic difference between them; rather, they disagree about from where this matter is to be derived.

Rava said:

If the moon was seen in the cycle belonging to the previous month before

midnight,

in this

there is a difference between them.

There is a practical halakhic difference between Rabbi Yoḥanan and Reish Lakish:

According to Rabbi Yoḥanan, who learned that the day follows the night from the verse concerning Yom Kippur, the moon belonging to the old cycle must not be visible from the beginning of the night. For Yom Kippur begins at the beginning of the night, as it is stated: “From evening to evening.”

But according to Reish Lakish, who learned that the day follows the night from the verse concerning the eating of matza, the beginning of the night does not belong to the first of the month until midnight.

For the verse says: “On the first [of Nisan], on the fourteenth day of the month, in the evening, you shall eat matzot, until the twenty-first day of the month, in the evening.”

And this verse speaks of optional eating during the seven days of Passover, for there is an obligation to eat matza only on the first night.

And on the first night of Passover, when eating matza is obligatory, it is eaten together with the Paschal offering, concerning which it is stated: “They shall eat the flesh on this night; with matzot and bitter herbs they shall eat it.” The Paschal offering may be eaten until midnight.

And since the Paschal offering was slaughtered on the fourteenth of Nisan, its eating, and the eating of the matza with it, belong to the fourteenth day, on which the Paschal offering was slaughtered.

It follows that only from midnight onward is the eating of matza considered to belong to the fifteenth of Nisan, which is the first Festival day of Passover.

Therefore, according to Reish Lakish, if the old moon was not visible until after midnight, if the court wished to intimidate the witnesses on the following day into testifying that they had seen the renewal of the moon, in order to sanctify it before its proper time and thereby distance Yom Kippur from Shabbat, they are permitted to do so.

Rabbi Zeira said in the name of Rav Naḥman:

In the Diaspora, where people do not know when the court will sanctify the month, two Festival days are observed due to uncertainty.

And

every uncertainty—

we cast it forward!

Every second Festival day observed because of uncertainty is observed on the day following the date written in the Torah, according to the calendar used in the Diaspora on the basis of calculation.

For example, the first Festival day of Passover, which is on the fifteenth of Nisan, is observed on the fifteenth and sixteenth according to their calculation.

Similarly, the first Festival day of Sukkot, which is on the fifteenth of Tishrei, is observed on the fifteenth and sixteenth. [

In the Diaspora, they calculated the calendar on the assumption that Elul and Adar were deficient, while the other months were generally made alternately full and deficient, as we calculate them today by means of calculation.]

And Rav Naḥman comes

to say,

that

we observe the fifteenth and sixteenth

but

we do not observe the fourteenth.

They observe only the fifteenth and sixteenth as Festival days, but not the fourteenth before them.

And we challenge this:

Let us observe the fourteenth as well,

let them make the fourteenth a Festival day,

lest

perhaps

they made Av deficient and Elul deficient.

For we, the inhabitants of the Diaspora, consider Av to be an intercalated month [and Elul deficient], with the result that on the thirtieth day of Elul, on which Rosh HaShana falls according to our calculation, it was already the second of Tishrei in Eretz Yisrael [and their Rosh HaShana fell one day earlier].

Therefore, it is necessary to observe the fourteenth of Tishrei as a Festival day as well, because it is the fifteenth in Eretz Yisrael.

And similarly with regard to Nisan, there is concern that perhaps in Eretz Yisrael they made Shevat deficient, whereas the inhabitants of the Diaspora consider Shevat to be an intercalated month.