📋 Shiur Overview
Summary of the Lecture – Laws of Sanctifying the New Month, Chapters 9-10
—
General Introduction: The Difficulty of the Solar Year
The Rambam’s Words
Shnat hachamah (the solar year) is the time it takes for the sun to travel through all twelve constellations (mazalot) and return to the same point.
Explanation
Shnat hachamah is the solar year – the cycle of the seasons. The Rambam deals in Chapter 9 with the calculation of tekufot (equinoxes/solstices) – when each season begins.
Novel Insights and Explanations
(a) The solar year is more complicated than one thinks: The simple assumption is that the solar year is a well-known, simple thing – “even the gentiles know about it” – and only the lunar year is complicated (because one must calculate the molad). But the solar year is approximately as complicated as the lunar year, and perhaps even more so.
(b) The course of the moon is actually easier to observe: Every person can look up at the sky and see the phases of the moon (full, half, new, quarter), and the cycle is clearly visible. Calculating the exact molad is difficult, but the cycle itself is obvious. With the solar year, however, it is much harder to notice when exactly the cycle ends:
– The days don’t change at a uniform rate – not every day becomes equally longer or shorter.
– Without a clock (that has equal hours) it is very difficult to measure exactly how long the day is. The clock itself is based on the sun (sundial), so one must measure shadows, which is very complicated.
– We only notice it easily because we have a clock – but in ancient times there was no clock.
A midrash is brought that calculating the length of the year was “the first thing that Adam HaRishon tried to figure out,” and it troubled him.
(c) A small error accumulates: A small error of a few minutes per year accumulates over hundreds of years into large deviations. For example, our calendar that follows tekufat Shmuel is today already off approximately twelve days from the true sun.
(d) The ancient sages of the nations (Babylonia) had an institution — a kind of “kollel” supported by the king — that engaged in astronomy for hundreds of years, recorded observations, and made averages. They had lists of solar eclipses for a hundred years precisely. The Babylonian sages are already mentioned in the Book of Jeremiah — a very ancient tradition.
—
The Constellations – The Main Tool for Measuring the Solar Year
The Rambam’s Words
The Rambam in Hilchot Yesodei HaTorah writes that the heavens are divided into twelve equal parts (mazalot) – they are called by the names of the pictures (constellations) that are in those regions, but the mazalot are not actually the pictures, but rather twelve equal sections.
Explanation
The most precise and easiest way that the ancient astronomers (chachmei hatekufot) used to measure the solar year is through mazalot – the twelve groups of stars in the sky.
Novel Insights and Explanations
(a) How it works:
– The stars have a rising and setting just like the sun – they come up from the east and go down in the west. If someone watches all night, he sees different stars coming up and others going down.
– The sun travels together with the stars (both go from east to west), but the sun moves approximately one degree each day relative to the stars (360 degrees ÷ 365 days ≈ 1°/day). Therefore the sun stands in a different constellation each month.
– How one observes it: One cannot see which stars are behind the sun during the day (because it’s bright). But one can at sunset see which stars come out first, or at sunrise see which stars come up right before the sun – and from this one calculates that the sun is in the opposite constellation.
(b) Why this is easier than all other methods:
– One doesn’t need any instruments (no sundial, no shadow measurement).
– One only needs to go out at night and see which constellation is visible at sunset/sunrise.
– It is more precise than trying to measure how long the day is.
(c) Main insight – the solar year = the year of the constellations: “Simply put, the solar year is the year of the constellations – the same thing.” The solar year means that the sun travels through all twelve constellations, and when it returns to the same point where it began – that is a year.
(d) Why is it still difficult to calculate precisely? If one can see in which constellation the sun stands, why can’t one simply make 365 markers in the sky (stars as markers) and know precisely to the day? Answer: It is difficult for a person to recognize a specific star – one can only recognize a group of stars (a constellation). One can see whether the sun is before the group, in the middle, or after the group – but not more precisely than that. Additionally, one needs many years of observation to arrive at a precise calculation – one year’s measurement can have small errors that accumulate.
(e) [Digression: how the stars rotate vs. the sun] According to the ancient model (spheres), there is a sphere of the constellations that rotates every 24 hours from east to west, and a separate sphere for the sun that also rotates, but slightly differently – therefore the sun moves relative to the stars. The precise calculation of how the two spheres work together (whether they are on the same sphere or separate ones, and how the tilt affects it) was not clearly worked out. Important: The constellations have no “influence” on the sun – it is a purely astronomical observation, not an astrological one. The two spheres (sun and stars) go separately, and the difference between them produces the effect that the sun “wanders” through the constellations.
—
Historical Development of the Calculation of a Solar Year
Novel Insights and Explanations
(a) Stages of precision:
– In ancient times people thought a year was 360 days — apparently from this comes the fact that a circle has 360 degrees (not 365).
– Later they discovered 365 days, then 365 and a quarter — this is approximately tekufat Shmuel.
– The Greek sage Hipparchus discovered a better calculation — only 6.5 minutes off from reality. This is approximately 4 minutes less than 365.25 days. This is approximately the calculation known as tekufat Rav Ada (not exactly the same, because Rav Ada goes with chalakim).
– In the Rambam’s time there was already al-Battani with an even better calculation — only 2 minutes off. The Rambam himself had a calculation that was only 4 seconds off.
– The Maya had the most accurate calculation of all ancient civilizations — only 17 seconds off.
– Today we know that the earth’s rotation changes slightly (a second every year or so).
—
Chapter 9 – Tekufat Shmuel
The Rambam’s Words
The solar year according to Shmuel’s calculation: 365 and a quarter days. The tekufot fall on specific days of the week in a cycle of 28 years.
Explanation
The calculation of tekufat Shmuel is based on a solar year of 365 and a quarter days. All of Chapter 9 deals with how to calculate when each tekufah falls – which day of the week, which hour.
Novel Insights and Explanations
(a) Why is it interesting to know which day of the week the tekufot fall? It is still not clear why this is so important to know. All the calculations of Chapter 9 are more or less only on this topic.
(b) Tekufat Shmuel vs. tekufat Rav Ada – opinions among Rishonim and Acharonim:
There is a fundamental dispute whether Shmuel actually meant that his calculation is precise, or whether he knew it was only approximate:
– The opinion of several Rishonim (Rabbi Chiya and others): Tekufat Shmuel is only approximate (befarhesya — for the public), and tekufat Rav Ada is the more precise calculation (betzin’a — a secret). The language is: “Tekufat Shmuel befarhesya, tekufat Rav Ada betzin’a.” The problem with this opinion: they thought that Rav Ada is precise, but we know today that Rav Ada is also not precise.
– The Rambam’s opinion: The Rambam, who already knew that tekufat Rav Ada is also not precise, did not say that Shmuel actually also knew Rav Ada’s calculation. He said that it is actually a dispute – they didn’t know, and later they knew better. The Rambam even said: “The sages of Israel disagreed and also the sages of the nations of the world disagreed” – it’s not a specifically Jewish question, but a general astronomical question. The sage who holds one opinion saw the proofs of the other, and he didn’t like them. This is not a deficiency.
– Proof that it’s a historical development: The book Me’or Einayim (cited by the author “Avidan”) brings a nice proof: Shmuel’s calculation was correct for his time — because the error accumulates, and in Shmuel’s time it hadn’t yet accumulated enough to notice. In Rav Ada’s time his calculation was correct. Later they saw that even Rav Ada’s calculation is not precise enough.
(c) The Chazon Ish’s opinion – halachah leMoshe miSinai: The Chazon Ish was very concerned about saying that the Sages didn’t know something, even in scientific matters that we clearly know today, even against the Gemara in Pesachim (where it says that the sages of Israel admitted to the sages of the nations). He suggested that all calculations are halachah leMoshe miSinai. Against this is cited Rabbeinu Asher who says: “Know that tekufat Shmuel is included in the Torah… that we should conduct ourselves with what we heard” — that is, tekufat Shmuel was given at Sinai only in the sense that we should conduct ourselves according to it, not that it is actually precise. But to question witnesses (when questioning witnesses for kiddush hachodesh) we don’t go according to tekufat Shmuel.
(d) “Ki chochmatechem” – the value of astronomical calculations: The value of knowing tekufot and mazalot is a “hanhagah muskalat” – that a person can reckon with time. Today one might perhaps say that whoever has a good clock understands well.
—
Birkat HaChamah (Kiddush HaChamah) – The Only Halachic Practical Difference of Tekufat Shmuel
Explanation
The only halachic practical difference of tekufat Shmuel is kiddush hachamah (birkat hachamah) — every 28 years when according to the calculation Nissan begins on the same day and hour as the Creation of the world (Saturday night, the beginning of the fourth night).
Novel Insights and Explanations
(a) What is the point of birkat hachamah? The sun doesn’t do anything special at that moment — it’s only a human discovery (a mathematical convergence of the solar cycle with the days of the week).
(b) Why did they make tekufot at all? To know kiddush hachamah? “Seriously? It makes no sense.” Tekufot were made to know when the year goes, not for birkat hachamah.
(c) Birkat hachamah is essentially a blessing on the fact that ma’aseh bereishit goes with an order, with a calculation — that one can calculate. But the sun doesn’t actually do anything at that moment.
—
[Side Note: The Author “Avidan”]
The lecture mentions an author who writes under the name “Avidan” — this is probably a pen name (“Amitai is not usually a real name”), and he “considers himself terribly clever.” This is not the Ya’avetz (who says “more Chassidic Torah”).
—
Chapter 10 – Another Calculation for the Solar Year (Tekufat Rav Ada)
Laws 1-2: The Solar Year According to the Second Method
The Rambam’s Words
“The solar year according to those who say it is less than a quarter from the sages of Israel” – there are sages of Israel who say that the solar year is less than 365 and a quarter days. The precise length: 365 days, 5 hours, 997 chalakim, and 48 rega’im. A rega is introduced here: “A rega is one of seventy-seven parts of a chelek” – one rega is 1/77 of a chelek.
Explanation
Chapter 10 brings an alternative calculation for the length of a solar year, which is more precise than tekufat Shmuel. This is what is called “tekufat Rav Ada” (although the Rambam doesn’t call it that explicitly – the Ra’avad also doesn’t call it “tekufat Ra’avad,” it is a baraita cited in the Rishonim).
Novel Insights and Explanations
(a) The addition of the solar year over the lunar year according to this calculation: According to tekufat Shmuel, the difference between a solar year and a lunar year was 10 days, 21 hours, and 204 chalakim. According to the new calculation it is 10 days, 21 hours, 121 chalakim, and 48 rega’im. The difference between both calculations is approximately 80 chalakim (plus rega’im) – the new calculation makes the year slightly shorter.
(b) The great advantage of this calculation – no remainder in 19 years: According to tekufat Shmuel, after every 19-year cycle a remainder is left over (an hour with something), which accumulates over time. According to the new calculation the 19-year cycle works out precisely – 7 leap years in 19 years results in nothing left over. This is one of the main reasons why this is a better calculation.
(c) The calculation from tekufah to tekufah: According to tekufat Shmuel, between one tekufah and the next is 91 days with something. According to the new calculation it is 91 days, 7 hours, 519 chalakim, and 31 rega’im. This is more complicated because one also needs rega’im, but therefore more precise.
(d) Why the calculation is more complicated: The addition of “rega’im” as a new unit of measurement is the price for the greater precision. With tekufat Shmuel one didn’t need rega’im.
(e) The first tekufah is calculated differently: According to tekufat Shmuel, the first tekufah was approximately 7 days before the first molad. According to the new calculation, tekufat Nissan of the first year (before the Creation of the world) was at a different time – he mentions “six hours and six hundred” (the precise numbers). The main reason it’s different is because according to the previous calculation one would have too much left over.
(f) Structure of Hilchot Kiddush HaChodesh: Chapter 10 (and one more chapter) is “simple,” and from Chapter 11 onward begins “the real astronomy” – the more technical and precise part of the Rambam’s astronomical calculations.
📝 Full Transcript
The Solar Year and the Constellations: How One Measures the Year Through the Stars
Introduction: The Difficulty of the Solar Year
Speaker 1:
Let’s say, we’re learning here, which chapter did we learn last night? Chapter 7? 8? 9? Where are we holding? Chapter 9, right? About the topic of… we finished 9, actually, the topic of the tekufot (seasons).
Ah, so I feel like I never really grasped, what’s the story here? It’s something like, there was some difficulty in knowing how long the year is? It seems like yes.
We think that you look at a light, and you know everything. Because we don’t grasp it. And also, there are the years, it’s a simple thing. People always say, ah, the lunar year is a bit complicated, you have to look at the moon when it comes, the molad. And the solar year, when is the molad of the sun? In my head something was lying that the gentiles…
Speaker 2:
Very good.
Speaker 1:
So how do you also know that there is such a thing as a solar year? What does that mean?
Speaker 2:
Okay, so I guess the word is, when it’s gone through a year and you see again the same length of the day, that the day and the night are the same length, otherwise because… so today we have a clock, it’s quite easy to see.
Speaker 1:
Very good, but just be clear. And actually in Chazal (our Sages) it says that this was the first thing that Adam tried to figure out. And it was a short day. A beautiful midrash. But except for one who lives in nature, can indeed see that the sun shines strong and light. It’s actually not.
Let me tell you the actual history, or what Chaitchevitz told me, I don’t know. So, we’re trying to talk about this now.
So, it’s actually, first of all, obviously, you can see that the days get longer. First of all, it depends on where you live. So, well, you live. But let’s say…
So, in short, we think, I always learned in my head that the solar year is just a thing, even the gentiles know about it. It’s not complicated. Turns out, it’s about as complicated as the lunar year. And perhaps even more.
Why the Lunar Year is Actually Easier
Speaker 1:
The moon is quite easy. You can struggle with when exactly the molad was, but that the moon has a cycle, it’s very obvious. You can see, everyone can look up and see. The moon is white today, it’s the middle of the month, first it’s about the four quarters of the month.
It’s much harder to see. Ah, very good. You can, all these things you can see, but first of all it’s much more compact. Say between exactly. Again, roughly that it’s in the summer, that I grasp. But to know exactly, even within a few weeks, it’s not so easy.
The Difficulty of Measuring the Length of the Day
Speaker 1:
Will I say now how long the day is. You have a clock, with having a clock you can easily calculate how the day is. But you didn’t have a clock, the clock itself is based on the sun, so you actually have to check the shadows, it’s very complicated.
And why do we notice because we have a clock? Because we don’t live with the sun, we live with the clock. The clock has equal hours, it’s easy to calculate relatively. But once there wasn’t a clock, right?
So he shows me a few things that you can see, right? So it seems, for some reason, I didn’t understand that properly. So, I’ll tell you maybe like this, maybe you can think that it’s hard to know, to make a calculation how long it takes. I don’t know.
For some reason, I asked the chacham (scholar) today, why is it so? But for some reason, what the astronomers see, that is, there is, certainly, a normal person saw, it gets longer, it even gets colder, such sorts of things.
First of all, it can be that it’s harder to imagine with this. You can see that today it got longer, but how… it doesn’t always go the same size, right? Not every day does it get so much shorter, so much longer.
So, for some reason, it wasn’t so easy to know when winter will come. By the way, this is something you need to know, a farmer needs to know when to prepare your fence.
The Constellations: The Most Precise Way to Measure the Solar Year
Speaker 1:
So, the most precise way, for some reason, truly, at the root the cause is always the same cause, but the thing that they found is the thing called mazalot (constellations). Very interesting, I don’t know about this, the scholars also talk about it.
Speaker 2:
You should live which stars the sun comes out with.
Speaker 1:
Very good, you have it. The stars don’t move, when will the stars stay in the same place.
Speaker 2:
Very good, very good.
How the Constellations Work
Speaker 1:
So the two you figured out. I wondered about this today. The answer is roughly like this: the stars, not just the stars, so there are very many stars and very many stars that you can even find such pictures, as if you connect two stars together. There are about eighty counted today. Eighty are counted today. That you can see in 88 if it’s a number. This has nothing, these are just imaginations.
Speaker 2:
No, just what always you the pictures…
Speaker 1:
Not always. You only see half of it every night, right? It depends on which season of the year which you see at night, or where you live. Normally, any night you can only see half of the sky, but what you can indeed see any night, that’s not entirely true.
At once you can only see half, but it rotates. That is, beginning of night you see different stars than end of night. The stars have a setting. With a rising just like the sun and the moon. The moon also has a rising, it goes up and down, you know?
Speaker 2:
If someone looks at the stars for a whole night, he’ll see changes.
Speaker 1:
Exactly. It’s simple, you can even make pictures. There are people making pictures, it rotates. It’s a bit different than the sun, but it rotates. It goes up and it comes down. Also from east to west. Everything comes up from the east and it goes to the west. Okay? So?
Speaker 2:
Or the stars also go from east to west, so?
The Sun and the Constellations: How They Rotate Together
Speaker 1:
Exactly. Roughly so in a day, roughly in the same length as the sun goes, from east to west. Therefore, the gedolim (great scholars) today say the world rotates, one would have said, there is a galgal hamazalot (sphere of constellations), it rotates around every day from east to west, every twenty-four hours, roughly it rotates the whole thing.
Now, besides this there is the sun. The sun also goes every day from east to west, you can see that by day. But it doesn’t go exactly… it’s not on the same cycle exactly as the constellations. So it travels together with the constellation. But notice that every month, the constellations eighth, what are called twelve constellations, are eighth that they divided the sky into twelve precise parts.
Just as the Rambam said in Hilchot Yesodei HaTorah, precisely in that area were the pictures, they call it by the name of the pictures, but mazalot don’t actually make the pictures. Clock time.
So the sun, every month stands in a different twelfth of the sky. It comes up with a different twelfth. As if it travels a bit faster than the… yes, a drop faster than the… do you understand what I’m saying? As if now to say it travels a bit faster than the constellations, so it moves with one degree every day roughly, 365 degrees, there are roughly 360 degrees, it moves roughly with one degree every day around that.
But the constellations are also in the direction of north to south, but they only move to the constellations, further must to the constellations. The reason why… it moves to from every day comes out a bit different, but the on the constellations on the thing.
Discussion: Why Does the Sun Move Relative to the Constellations?
Speaker 1:
Something, I didn’t understand that clearly. Something, the reason why, this is not just today, the reason why I say they should be. Simple way that it’s fast. The true reason is actually about this. It changes, it doesn’t go so fast, it goes just as fast. But anyway, the world rotates, but actually about this it tilts a bit, about that it looks different. I didn’t understand properly what the calculation is.
So, I don’t know the difference, if they’re both on the same sphere, if they’re certainly different spheres. About that it’s different, because they have a different… they go a bit differently. I didn’t understand that clearly, I need to review that.
How One Notices in Which Constellation the Sun Stands
Speaker 1:
But what I understood is simple, I want to still… I simply understood, what does a person see? Simply, I go outside. The answer is like this: I see, you can’t see which stars. In the day it’s not dark, it’s light.
So what do I do? I go at sunset and I see from the other side which it is, I make a calculation. Or I can see which star comes up right before the sun. You know that the sun is right after. These are roughly such calculations.
But you can see that every day the sun is in a certain constellation. That is, there are twelve constellations, there are twelve, yes, twelve months roughly of the solar year. So the meaning is simple that the sun travels with, the month it travels with that group of stars, with that area in the sky, in other words. That’s the whole thing of the constellations.
Solar Year = Year of the Constellations
Speaker 1:
Therefore, this is a precise thing, this is awesome, much more precise, easier to see perhaps, or more precise than it’s easier to calculate it than the other things that were discussed, that the day gets longer, all these things. For some reason it’s easier. Therefore, the sages of the tekufot mazalot always calculated, the tekufot mazalot calculated, how the sun is according to the calculation, because you can know tekufat taleh (season of Aries), Nisan, etc.
Discussion: Do the Constellations Have an Influence on the Sun?
Speaker 2:
Did they only take it as a sign, or did they already take it more significantly, they held something that the stars bring the sun?
Speaker 1:
No, not necessarily. Again, how it works, as you always said, as you, there are two spheres, one carries the sun, one carries the stars, and it has something different, therefore it comes out. But the… not that the constellation has some pull on the sun. No, no, that’s not necessary for me.
The idea of the constellation is, it’s an astronomical idea. It’s simple to calculate, this is the simplest way, a person can look in the sky, or perhaps the most precise way, I don’t know precisely.
It can be that, I’ll tell you, it can be that to calculate, as I say, to calculate how long the day is, you need special instruments, you need to be able to measure precisely, today you’ll have a clock, once there was a sun clock, you need to calculate. Roughly you can, you can make a mark, true, but you need to make the mark.
For the constellations you don’t need any mark. You simply need to see, go at night, see which constellation comes out before the sun, or which at sunset, the opposite, which is the first that comes up, you’ll know that the sun is in the other from that. It’s very simple. You don’t need any instruments at all, it’s supposedly the easiest way to know.
Innovation: The Solar Year is the Same Thing as the Year of the Constellations
Speaker 1:
So I didn’t grasp this until today, that simply the solar year is the year of the constellations. The same thing. What does the solar year mean? It means that the sun travels through the twelve constellations throughout the year. And when it comes again to where it started, you know that a year has passed. And to calculate this precisely was hard to calculate. Precisely. Obviously roughly, what’s ten days roughly, everyone always knew. But to be precise was a great…
Discussion: Why Not Make More Than Twelve Constellations?
Speaker 1:
I found this… let’s say, why did they make twelve?
Speaker 2:
Let’s say, if they made twenty-four it would have been easier, because every two weeks it would have been a different byte. I don’t know why is it hard to calculate? I don’t know why is it hard to calculate that he can always make three hundred and sixty-five lines on the sky with stars. Then one could have known to the precise day, or is it simply relevant?
Speaker 1:
Yes yes, technically you can, it’s hard. You need to say not just clear stars that will be able to… it was indeed, it’s good. The stars stand in one place, but you need to have a calculator. I don’t know why it’s hard actually to calculate. I didn’t understand why is it actually so hard to…
No, I mean the word is because you don’t calculate against living a specific star, because it’s very hard for a person to recognize which star is a specific star. But a group of stars you can indeed see, and can see whether the sun is before the group of stars, in the middle of the group of stars, or after.
You need to stand there and… you simply need to stand there and calculate. You need to have a calculation, you need to know a few years, to know precisely, right? Not at once will you know precisely, because you make a small mistake it’s ruined in your calculation, right?
So, the sages of the ancient nations, he has a chart of this. Not the person, but the person. He made a nice chart. How is it? The sages of the ancient nations, this was one of the things that they struggled with how long precisely is a year.
Generally, until this very day it’s a question, to know precisely, and you need to calculate two on one year, ah, very good.
The Historical Development of Astronomical Calculations and the Dispute Between Tekufat Shmuel and Tekufat Rav Ada
The Difficulty of Precise Astronomical Calculations
I don’t know why it’s hard actually to calculate. I didn’t understand why is it actually so hard to… No, I mean the word is because you don’t calculate against living a specific star, because it’s very hard for a person to recognize which star is a specific star. But a group of stars you can indeed see, and can see whether the sun is before the group of stars, in the middle of the group of stars, or after.
Okay, you need to stand there and… you simply need to stand there and calculate. You need to have a calculation, you need to know a few years, to know precisely, right? Not at once will you know precisely, because you make a small mistake it’s ruined in your calculation, right?
The Sages of the Ancient Nations and Their Institutions
So, the sages of the ancient nations, he has a charge of this. Not the person, but the person. He made a nice charge. How is it? The sages of the ancient nations, this was one of the things that they struggled with how long precisely is a year.
Generally, until this very day it’s a question, to know precisely, and you need to calculate, so on one year, ah, very good, to know one year is no great wisdom, it’s approximately. But you want to be able to calculate for a thousand years around, and if you make a mistake of one minute, you’re off by a few days.
Here begins the difficulty, our friends of the calendar, yes? We make the cycles of the years of Creation. If you’re a few minutes on… but you’ll understand the few minutes, because it can’t be, one year can’t be bigger than the small. All years are the same. If you’ll add every year a few minutes, let’s say… after a few years, today for example, as he says, today that we go with tekufat Shmuel, our calendar goes with tekufat Shmuel, we’re already off, roughly twelve days from the sun. It accumulates, right? It adds up. All the time.
So, this is the wisdom, to know precisely. And for this you need… what do you need? You simply need someone to stand every day and calculate with you. I don’t know if there’s something a greater wisdom than this, but it’s simply a… it’s not easy. It’s not simple that someone who doesn’t know such a near roughly you can know, but to know precisely is complicated.
The Sages of Babylon and Their Astronomical Tradition
So, he has a long list the person found from the ancient nations how long each one said the year is. There was generally, once people thought that the year is three hundred and sixty days. Supposedly about that they have three hundred and sixty degrees and not three hundred sixty-five, I don’t know, because they made the degrees.
Afterwards, finally found out that it’s already three hundred sixty-five. Afterwards, this is the… three hundred sixty-five and a quarter, this is more or less tekufat Shmuel, right? And so on.
Chapter 10 – Another Calculation for the Solar Year
He says that the most accurate from ancient times was the Maya, that they had a truly punctual calendar, which was off by only seventeen seconds. Very interesting.
This is the interesting story, that once, let’s leave aside the Maya, that’s not relevant to us. What is relevant to us is that the ancient astronomy that existed in the time of the Sages (b’zman chachamim), was more or less the Babylonian, and afterwards the Greek which they took over from the Babylonians.
And Babylon was a very… he also brings Persians, I don’t know who the Persians are, I haven’t grasped it yet, but I know that the Babylonians, I said that the Sages of Babylon are already mentioned in the Book of Jeremiah, it’s a very ancient thing. For hundreds of years they had lists of exactly when there is a solar eclipse, also something that had lists for hundreds of years of exactly how it works.
And each one was some sage. No, not one sage, rather it’s an institution, that the king supported a kollel, there was some kollel that was engaged in this. And not, they wrote down, it was an institution, they wrote down over hundreds of years, so, they make averages, you know, each time one can have the calculation. So they had good calculations, and their calculation was three hundred and sixty-five and a quarter. This is approximately tekufat Shmuel.
The Historical Development of the Calculations
Hipparchus and Tekufat Rav Ada
Later came the Greek sage Hipparchus, he discovered that it’s a bit better. It’s only six and a half minutes off from reality. It’s a bit less than three hundred sixty-five and a quarter, right? Four minutes less.
Later, this is approximately the calculation that is called tekufat Rav Ada. It’s not exact, but approximately, because Rav Ada goes with chalakim, perhaps that’s the reason? I don’t know. Approximately, this is the calculation.
Al-Battani and the Rambam
Now, later there is, he says that in the Rambam’s time there was already Al-Battani, and he made an even better calculation, even more accurate. That means, it was known that tekufat Rav Ada is also not accurate, but according to what he says it’s only two minutes off.
And the Rambam says, he has an even better calculation, it’s only four seconds off from reality. We know exactly, that means they calculated by hand, the sages of our time. Okay? Also, the sage should say that it actually changes, the earth rotates a bit, okay, a second every year or something. I don’t know, I don’t know, what’s the story with that? So that’s…
The Dispute Between Tekufat Shmuel and Tekufat Rav Ada
The Author “Avidan” and His Approach
I don’t know, what is it? There is a question from the Rishonim, that’s what the person is talking about. I’m just saying more or less the person’s Torah, a rav, whatever his name is, he considers himself terribly clever. Not Ya’avetz, no, Ya’avetz says more Chasidic Torah. This person, he’s called, it’s a fake name just. Avidan, that’s not his name. Amitai is not usually a real name. There are people called Navitai, but I don’t believe that’s his name.
The Question of Shtutim V’havalim (Foolishness and Nonsense)
There is the question from Chazal, what is the shtutim v’havalim? But the point is that the reasoning is seemingly correct. There are, we have in our sefarim of ibbur, books of astronomy from the Rishonim, there are the two calculations, called tekufat Shmuel and tekufat Rav Ada.
If one wants to present it, tekufat Shmuel is more or less the calculation of the Babylonian sages, which was accepted. Tekufat Rav Ada is approximately Hipparchus’s calculation, right? The Greek calculation is a bit later.
The Historical Understanding: Shmuel and Rav Ada in Their Times
And therefore, a normal person would say that Shmuel was indeed from the first Amoraim, he didn’t yet know, perhaps he did know, but he didn’t know about the calculation of the Greeks. In his region, he lived in Babylon indeed, there were the sages, not in Babylon, the Parthian Empire, whatever. Sorry, the Sassanians. In short, he held an astronomy, he didn’t have everything. He knew his calculation in his time (b’zmano).
Later was Rav Ada who is much later, according to what they say, he knew that later he had the more correct calculation.
The Proof from Maor Einayim: The Calculations Were Correct for Their Times
This is what he says, and he has a nice proof, not him, he says further from Maor Einayim, whatever, that it’s so, because the calculation of Shmuel is correct for his time. That means, since the error accumulates, if one calculates the time of Shmuel, and in the time of Shmuel one makes the calculation of the tekufah according to this calculation… one must be smarter than everyone.
No, no, no, it’s correct. Since the error, if this is a small error, we’re talking about a few minutes of error. In total four minutes is the difference between Shmuel and Rav Ada, approximately, right? Shmuel is three hundred sixty-five and a quarter, and Rav Ada is four minutes less. Four minutes less, right? It’s only four minutes difference. It’s a bit less, a bit less, a whole day’s difference.
Take a few hundred years, I don’t know how long, whatever. So, in the time of Shmuel according to his calculation it came out correct. And in the time of Rav Ada his calculation came out correct. Later on they caught that it’s also not correct. Because more time passed, we saw that more errors accumulated.
So therefore, very nicely one can see that there is indeed a difference in the tekufot, seemingly the two things. This is what today’s, the enlightened Acharonim have said, and so it is seemingly correct in reality.
Approaches in the Rishonim
The Approach of Rabbi Chiya: Tekufat Shmuel Publicly, Tekufat Rav Ada Secretly
In the Rishonim we find two approaches. There is the approach that we already said that Rabbi Chiya, I don’t know who wrote it, and others all said that essentially tekufat Shmuel is only approximate, tekufat Rav Ada is the accurate one, and it was that the language was tekufat Shmuel b’farhesya, tekufat Rav Ada b’tzin’a (Shmuel’s tekufah publicly, Rav Ada’s tekufah secretly).
Now, the problem is that they meant that Rav Ada is indeed accurate, they didn’t know that Rav Ada is also not accurate. Therefore they said this, they said that an approximate calculation was made for the public, but in truth there was a secret.
The Rambam’s Approach: It’s a Dispute
The Rambam, who knew that tekufat Rav Ada is also not accurate, didn’t say that it’s so, didn’t say that Shmuel essentially also knew Rav Ada, rather he said that it’s actually a dispute, and the Rambam even said that the gentiles also have this dispute, don’t get lost, it’s a dispute. They didn’t know, today we know better.
The Chazon Ish’s Approach: Halacha L’Moshe MiSinai
The Chazon Ish and such other pious ones are terribly upset, and they are very interested in saying that all are halachot l’Moshe miSinai, all calculations, everything everything. So? Yes, very funny. It’s not about “ki yachach mitachtecha mimunatecha,” because the Rambam says so… No, about the entire halacha.
He is very worried that our calendar goes according to a falsehood, according to something that is an error, and he is terribly concerned. The Chazon Ish was terribly concerned to say that the Sages didn’t know something, even a science that we know clearly, even the things that we know, even though there is the Gemara in Pesachim. He was very against this, therefore he invented all kinds of halachot l’Moshe ben Sinai with things.
But he brings it like this. Rabbi Asher, Kashya Shlomo, “v’yada d’tekufat Shmuel b’chlal haTorah. You see the piece about nitnah ben Sinai, d’tanhag bahem b’mah shemu’am, l’nakesh l’edim one doesn’t go with that”. So regarding what does one conduct oneself with tekufat Shmuel?
In short, it’s not… it’s very not… not clear, because the entire nafka mina of tekufat Shmuel is regarding Kiddush HaChama.
The Problem of Kiddush HaChama (Birkat HaChama)
What Is the Point of Birkat HaChama?
If one wants to find a halachic difference, because the opposite, tekufat Shmuel is only… why did they make tekufot? To know Kiddush HaChama? Seriously? It doesn’t make sense. Tekufot should be known when the year will be.
No, no, no, besides the yearly cycle, does the sun have another cycle? Not from north to south… No, another cycle is just a calculation. The twenty-eight is only… if I understand correctly, it doesn’t do anything. The sun doesn’t change anything. The only thing that changes is that we… again, all these calculations which is how one is human, other… other cycles one to the second, right?
What is the tekufat hachama? Right, not chama relative to levana. What did we learn? Birkat HaChama is simply the sun with the days of the week. That’s all it is. I don’t know what’s the point of it.
Every ninety-eight years Nissan begins on the same, not only the same day, on the same day and at the same hour, as it began on Shabbat Bereishit according to the calculation that we also thought. What’s the point? I have no idea. It’s fake. I don’t know.
Birkat HaChama Is a Human Invention
It’s very interesting, because what is there to see? Okay, perhaps the blessing is made on the fact that one should be able to make calculations. It’s simple. It’s simply a human invention that was found. Yes, it’s a… all kinds of fears are added to make a mitzvah.
Ah, you would have wanted to make that blessing? Okay, ma’aseh bereishit goes with an order, with a calculation. But one can… the sun doesn’t actually do anything in that blessing.
Tekufat Rav Ada – Another Calculation for the Solar Year
End of Chapter 9 – Tekufat Shmuel
Speaker 1: In total that the days of the week match with the same… because one says according to the calculation, there is indeed four times seven. That’s the whole calculation. I don’t know why that’s so interesting.
It doesn’t make sense to say that because of this Shmuel made the calculation, he made the calculation for the calculation for astronomy, and it was a bit wrong. What’s bad that it’s a bit wrong?
The other person is also about the other thing that I didn’t actually talk about the calculation of the circle and square, and the calculation of pi, which stands in the Gemara that it’s one to three and it’s a bit more. And he says that it’s actually what they thought then. What do you want from us? Seemingly he’s right, and it’s not a problem.
No, one doesn’t need to be foolish. I’m not accustomed to being more foolish than the standard. One must be approximately the same. You must be every sage of the inheritance of Israel, you are an expert in halacha, in Kabbalah, you must also be an astrolabe, it’s not possible, it’s above the natural way.
One must want inheritance, it’s not a problem. On the contrary, as the Rambam says, “nachlu chachmei Yisrael v’gam nachlu chachmei umot ha’olam” (the Sages of Israel disputed and also the sages of the nations of the world disputed). Presumably, the sage who held this way, saw the proofs of the one who says that way, and well, it appealed to him, the second is exactly the opposite. It’s not that it’s extreme, you understand to say, it’s nothing interesting here. Okay, enough.
This is up to here what I understood until now, the topic of the tekufot. And enough. What we call tekufot, simply the quarters of the, when the sun is the longest, the shortest, and so on, as you said. Enough.
Why is it so interesting to know which day of the week these things can be? I haven’t understood that yet at all. But these are all the calculations of Chapter 9. They are more or less only about this.
Afterwards there is Chapter 10, and another chapter which is simple. Afterwards, Chapter 11 begins the real astronomy. If you want, we can learn it. Yes. Okay.
Chapter 10 – The Solar Year According to Another Calculation
Law 1: The Solar Year According to One Who Says It Is Less Than a Quarter
Speaker 1: Chapter 10, let’s learn. Okay? The solar year, what is there?
Speaker 2: Do you have a thought? What are the words here? Another calculation for the solar year.
Speaker 1: Ah, the real one, the correct one. Earlier we spoke about tekufat Shmuel, now we’re speaking about a more correct tekufah. The Raavad doesn’t call it tekufat Raavad. The Raavad is just an invented thing. It’s not a clear… The Rambam already says there, I don’t know.
Speaker 2: Yes, it’s a Baraita brought in the Rishonim, I know.
Speaker 1: Okay, this asks our master… No, sorry, I’m in the wrong place. The solar year, I went to the wrong place. Well, where is my… Not there? No, not good.
What is the great virtue of knowing these things, to calculate tekufot and mazalot? Simply to know when how we stand in the year. Perhaps one can say today that a… “ki chochmatechem” (for this is your wisdom), whoever has a good watch understands well. It’s such a bit of wise conduct of a person, that he can reckon with time, something like that, I don’t know.
Okay, Chapter 8, 10. The solar year according to one who says it is less than a quarter from the Sages of Israel. What? It’s interesting, there is already there, “l’mi mei’chachmei Yisrael she’yomar” (according to one of the Sages of Israel who says), yes? What does he mean? That it’s less than a quarter of a day?
Speaker 2: Quarter means 365 and a quarter.
Speaker 1: But the earlier Sages, that there are Sages of Israel who say it’s a quarter, there is a measure less than a quarter. Okay, so the one who says it’s less than a quarter, what does he say? Like a quarter of today’s Sages of Israel. That is to say, he will also say that the length of a year is three hundred and five… what is the less than a quarter? That’s what he just wants to say, what is the less than a quarter?
It’s 365, five hours, 997, and 870 chalakim? What is a rega? A new thing, have you never heard of it? A rega.
Speaker 2: No, a rega is one of seventy-six in a chelek. I know.
Speaker 1: 5? I need to make numbers. 997? And 48, rega? What this is a 67th on… 900 chalakim, one doesn’t remember anymore how much it is. How many chalakim are there in an hour?
Speaker 2: 800.
Speaker 1: 800. Ah, it’s about half an hour. Whatever.
Discussion: The Difference Between the Two Calculations
Speaker 1: According to this calculation the calculation comes out differently. He won’t calculate the calculations of the cycle of the moon and the sun according to this calculation. It comes out according to this calculation, the addition of the solar year to the lunar year is not eleven days, but… ten days and the end of ten and most of fourteen chalakim, and seventy-eight he brings others. The sign is 35 14 21 101 48.
How did it say earlier the addition of the solar year to the lunar year? I don’t remember.
Speaker 2: He held a different number.
Speaker 1: Yes, that is seemingly in chapter. Chapter 6, very how did we learn the calculation of nineteen years? Perhaps he says, 6 a different one? Yes. Chapter 6? Chapter 6 end or what? No, why? It remains… No, that doesn’t speak about this. How did it say the… He doesn’t say how it was. Already sir, it’s already not a moon. Whom do we ask about it?
In the solar year, three hundred and sixty-five and six hours. It comes out that it’s hours and days and one and an hour, and four chalakim, right? That’s the number according to the calculation that was spoken about earlier of a quarter day. And according to what we learn, right? 11 days, 21 hours, and 204. 1080, there are one thousand and eighty. There are one thousand and eighty chalakim in an hour. I’m making a mistake. One thousand and eighty.
And here, according to this calculation how much is it? How much is that? 10 days and 21 hours. 10 days, 21 hours, and 121 out of 1080. 48 out of 67, correct? It’s less, right? It’s a bit shorter than that one. That one was 204 chalakim in the end, and this is 121 chalakim. These are the main chalakim. Here it says 47, here it says 48, it could be in the end. Yes, 48.
Speaker 2: What’s the difference?
Speaker 1: Yes, yes. No, not the earlier one. The earlier one he added here the rega’im. The rega’im weren’t there before. Earlier there was only the topic of how long is the solar year, which this was 21 and 204, right? The difference between the solar year and lunar year. Correct? Yes. Is there a difference here? Here it says how many chalakim is it? Both are 21 hours, right? Correct?
It’s only a difference of about one hundred chalakim. Here it has two hundred. Four chalakim, here is one hundred with… four such chalakim, no? One hundred with one hundred and twenty-one chalakim, okay? Correct? About a difference of eighty chalakim, with more rega’im with things.
And according to this it’s a bit shorter, that’s the difference. They caught that according to the second tekufah, the approach of Rav Ada as it’s called, the approach of Rav Ada, the year is a bit shorter.
The Great Advantage of This Calculation – No Addition in 19 Years
Speaker 1: It comes out, according to this calculation there is no addition in the nineteen years. The nineteen years match exactly. And one makes seven leap years in nineteen years, it comes out exactly the other one comes an addition, of about one hundred chalakim.
What was said that something remains left over after each year, an hour with something, and after each nineteen years something remains? According to this calculation nothing remains left over, it’s on this one reason why it’s a better calculation, right?
And according to this calculation also, there are different numbers between the tekufos (seasons), because the numbers are smaller. Consequently, between one tekufah it’s not 91 days and whatever it was there, but 91 days and seven hours exactly, right? Correct? Just 91 days with… with… yes? And the calculation from between one tekufah and the next tekufah is also a different number. 91 days… and 7 hours, and 519 chalakim, and also rega’im, 31 rega’im.
You see then why the calculation is more complicated, you need rega’im also, true? Right? Why it’s more complicated.
Halacha 2: The Same Calculation According to the New System
Speaker 1: Okay, for us according to this calculation it’s the same thing. According to this calculation you’ll know when one tekufah, you’ll calculate from this, you’ll know the same thing, just as was done in the previous calculation. From here you calculate the number of days, you arrive at the next tekufah. Correct.
And another thing, according to this calculation, there’s something different. For some reason, the first molad is also calculated differently. The first tekufah is also calculated differently. Earlier, remember, we said that the first tekufah was approximately seven days before the first molad.
According to this calculation they say differently, that tekufas Nissan, according to this calculation, was in the first year, before the world Nissan, the six hours and six hundred years and six hundred, and two why less? Because the reason why the calculation was made that way, at that time you would have had too much left over… that’s somewhat the reason. Rabbeinu le’olam, lekol sha’ah in the shoresh it comes.