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I have heard claims that experts in the world of Torah were significantly ahead of their counterparts in the world of natural science (or mathematics, or psychology, or…) in that they knew X (some fact) centuries before the scientists/whatever did. I've never seen evidence of any of these claims. Is there any such true claim?

To be precise: Is there any scientific/similar fact (or fiction) which is now accepted by the establishment but which was claimed by rabbis generally or by some famous rabbi before it was accepted by the (non-Jewish) establishment?

(Answers with good evidence only, of course.)

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One problem you may have in getting an answer is that once the Rabbis demonstrated such knowledge it became part of the accepted knowledge, and we think of the secular world as knowing that. History is not precise enough to tell us that the Rabbis were the ones who originated this knowledge. –  Ariel Dec 18 '12 at 10:03
I heard a really good one about the number of known stars in the universe being mentioned by the Gemara. And I heard it from a NASA scientist who was telling me how impressed he was! I have to ask him again to tell me the details... –  Seth J Dec 18 '12 at 15:42
I emailed this question to R' Natan Slifkin, and he responded that he's looked into this extensively and never found an example that holds water. –  Isaac Moses Dec 20 '12 at 4:45
@LazerA, that should be a fine book for those interested in the subject. I would argue it's sufficient to show that Chazal consistently held views that corresponded with the best science available at their time. That itself would indicate they were ahead of their time. You'll find that some of the best scientists of any era, had/have a tendency to engage in pseudoscience and superstition outside their own field. Today, there are countless doctors, supposedly educated in science, who believe in and promote crackpot medicine. –  Ephraim Feb 9 '14 at 9:43

24 Answers 24

Ralbag (Gersonidies) has the earliest known use of a proof by mathematical induction in his mathematical work Maase Hoshev (1321 CE).

Source: Rabinovich, N. L. (1970). Rabbi Levi Ben Gershon and the Origins of Mathematical Induction. Archive for History of Exact Sciences, 6(3), 237-248. Available in JSTOR here.

(For comparison, the prevalent thought before the above article was written was that mathematical induction was first used explicitly by Pascal ~1665 CE.)

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This brings up the question: Does this count as other than "the world of natural science"? In other words, when he wrote about math, was the Ralbag building/drawing on a tradition from Torah sources, or one from secular sources? –  Isaac Moses Dec 18 '12 at 17:13
However true this may be, induction is not a fact, as asked in the original question. It is a mathematical method. –  rbp Sep 28 '14 at 14:26
@rbp The fact that it's not fallacious? –  Double AA Sep 28 '14 at 14:34

I would say the biggest explanation ahead of its time was not by the rabbis, but by the Torah, steadfastly defended by even the most rational rabbis in the face of prevailing secular thought. Up until 1929 (and perhaps even as late as 1949), the leading view in astronomy was that we lived in a steady-state universe with no beginning and no end. People often talk about the clash between Big Bang theory and ma'asei bereshit, but in fact they are much more in line with each other than the prevailing secular theories up until that point.

For those numerologists out there, Tehillim 147:4 "He counts the number of the stars; He calls them all by name. ד. מוֹנֶה מִסְפָּר לַכּוֹכָבִים לְכֻלָּם שֵׁמוֹת יִקְרָא:" With 22 letters in the Hebrew alphabet, there are 22! = 1.1x10^21 possible permutations, pretty close to the number of stars in the observable universe (if shin and sin are counted separately, as they should be, you get 23! = 2.6x10^22, even closer to the "correct" number) [as an interesting aside, this is remarkably close to the number of grains of sand on the beach: 5x10^21 according to some estimates]

And for my favorite, which doesn't really count as preceding modern science, but is cool anyways, Tehillim 148:3 "Praise Him, sun and moon; praise Him, all stars of light. ג. הַלְלוּהוּ שֶׁמֶשׁ וְיָרֵחַ הַלְלוּהוּ כָּל כּוֹכְבֵי אוֹר:" Isn't "stars of light" redundant?? NO! there must also be stars of darkness, i.e., black holes!

I'm not really a big kabbalist, but from what I understand of the sefirot, it is conceptually very similar to our modern particle physics theories of symmetry breaking.

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I don't see why there are 22! permutations of letters. Can't letters be repeated or unused in a name? In any event, the part of this that answers the question is the first paragraph AFAICT. –  msh210 Dec 18 '12 at 19:14
@msh210 and it does seem the biggest explanation ahead of time. Except that everybody knew it when Adam was created... Doesn't that also count as a scientific fact (back then)? :) –  yair Dec 19 '12 at 1:01
@msh210: like I said, it's a bit of numerology. I guess you have to think of some unique naming system, so permutations of the alphabet seems as good as any. –  Jeremy Dec 19 '12 at 13:57
Why would black holes be exempt from praising HaShem? –  Seth J Mar 14 '13 at 17:39
@SethJ: they'd be included in the more generic כל צבאיו of the previous verse. –  Alex Jun 25 '13 at 16:05

Rabbi Y.L. Rapaport suggested that R' Yehoshua Ben Chananiah's statement

(כוכב אחד לשבעים שנה עולה ומתעה את (הספינות

(בבלי מסכת הוריות דף י עמוד א)

refers to the periodicity of Halley's comet, about 1500 years before Halley discovered this.

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Suggested by whom? –  msh210 Jun 23 '13 at 16:58
@msh210 Rabbi Yehoshua Ben Chananiah –  Argon Jun 23 '13 at 17:20
He suggested that his statement refers to Halley's comet? Can you cite where he did so? –  msh210 Jun 23 '13 at 19:27
@msh210 He did not say he was referring to "Halley's comet" explicitly (what would he even call it?). However, this "star" that occurs every "seventy years" is generally assumed to be referring to Halley's comet, as it recurs every 75-76 years. See e.g. books.google.com/… –  Argon Jun 23 '13 at 20:18
This is another ridiculous claim. The Talmudic term for comet is כוכבא דשביט - see ברכות נח. It's improbable that a comet, which is distinct from navigational stars would confuse sailors. We NOW know that Halley's comet returns every 76 years and could not possibly been seen at time of the cited story. (It should be noted that when it was conjectured that this gemara refers to Halley's comet, the exact period of the comet was not known. Some scientist believed that the period was degrading and slowing down. Hence, it was believed that centuries earlier, the comet returned every 70 years.) –  Ephraim Feb 9 '14 at 9:01

Dr. Jeremy Brown, in a post on his Talmudology blog on science in the Daf Yomi, points out that Rava, quoted in Yevamot 97a, provides the first published claim that boys' puberty can be delayed by their being either overweight or underweight.

כי אתו לקמיה דרבא אי כחוש אמר להו זילו אבריוהו ואי בריא אמר להו זילו אכחשוהו דהני סימנין זמנין דנתרי מחמת כחישותא וזמנין דנתרי מחמת בריותא

Whenever people came [with such a case]* before Raba, he used to tell them, if [the youth was] emaciated, ‘Let him first be fattened’; and if he was stout, he used to tell them, ‘Let him first be made to lose weight’; for these symptoms disappear sometimes as a result of emaciation and sometimes they disappear as a result of stoutness.

* Of one who reached the age of twenty without having produced two hairs.

(Translation and footnote from Soncino [PDF])

Dr. Brown points out that these associations have only been confirmed in the scientific literature in the past fifteen years, citing two papers as the first published confirmations of excessive weight and insufficient weight, respectively, being associated with delayed puberty in boys:

(Hat-tip to Rationalist Judaism.)

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The Ramban, in his commentary on Bereishit, writes that there were only two actual "creations" and the rest were more of "formations". He says that the two things that were actually "created" were light (and the resulting difference between that and darkness) and a "small point that had no substance" (נקודה קטנה שאין בה ממש). This seems to be a reference to the Big Bang, in which there was a large amount of positive energy that was in a very small "point".

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+1, but more information would be appreciated. –  Shmuel Apr 17 '14 at 22:11
if i remember correctly on that Ramban he says that his point became something that "has substance". Energy into matter, perhaps... –  bondonk May 13 '14 at 4:20

Torah Shleimah (BeReishis 1:1 note 30) quotes the Rama in Toras HaOlah who says that Chazal (Yerushalmi Avodah Zarah 3:1, BaMidbar Rabbah 13, Zohar VaYikra 10, Zohar Chadash 15) knew the earth was round before the non-Jews (he gives the date that they knew as 5252, i.e. 1492, whereas Wikipedia claims that it was already known by that time that the world was round).

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en.wikipedia.org/wiki/Round_world It seems the Greeks had figured it out long before, even if many Medieval Europeans were unaware. –  Double AA Dec 18 '12 at 6:12
The Zohar (not sure where in the Zohar) says the world was round. –  Hacham Gabriel Dec 18 '12 at 14:41
@HachamGabriel This answer says it's in Zohar VaYikra 10 and Zohar Chadash 15, but even the Zohar was written after the Greeks had figured it out. –  Double AA Dec 18 '12 at 14:55
@HachamGabriel Sure but anything could be. Just speculating that is a pretty weak answer. (If you had a source on the other hand...) –  Double AA Dec 18 '12 at 15:04
I don't understand this Toras Sheleima. The Yerushalmi says that Alexander saw that the earth is round and that idols were made holding balls (since the earth is round). Moreover, there is a famous Shvus Yaakov where he says that the Gemara implies that the world is flat. –  Shmuel Brin Dec 18 '12 at 22:34

One example I have heard is the amount of stars in the universe (from here):

In case you're concerned that the rabbis of the Talmud really hadn't a handle on what's going on in the skies, here's something to make you think again: The current estimate of the number of stars in the universe is about a thousand billion trillion (10^24). The Talmud (Brachos 32b) states as follows:

Each of the Zodiac constellations has 30 armies. Each army has 30 legions. Each legion has 30 divisions. Each division has 30 cohorts. Each cohort has 30 camps, and each camp has 365,000 myriads of stars.

Doing the math: 12 x 30 x 30 x 30 x 30 x30 x 365,000 x 10,000 = 1.06434 x 1018

But then we have to include the other non-Zodiac constellations, bringing us closer to the 24th power. Apparently, these rabbis had a higher source of knowledge.

Rabbi Zamir Cohen published a book called "The Coming Revolution", bringing many examples of how "Science discovers the Truths of the Bible". This audio shiur, "Nothing New Under the Sun - Science in Torah" attempts to collect several more such examples.

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I would be very cautious (or rather selective) when citing Zamir Cohen. A lot of the material in his books is absolute nonsense, superstitious pseudoscience and has nothing to do with Torah. (And thus, raises the issue of דרכי האמורי). –  Ephraim Feb 9 '14 at 8:53
@Ephraim (+1 for comment), i couldn't agree more. Sensationalist Judaism. –  bondonk May 13 '14 at 4:18
This only accounts for the stars along the ecliptic. That's only maybe 20% of the total stars? (Not that I think reading such an obviously allegorical midrash literally is talmud torah at all.) –  Double AA Oct 1 '14 at 6:33

Apparently Rambam said:

בבוקר אכול כמלך, בצהריים כבן מלך ובערב כאביון

eat breakfast like a king, lunch like the son of a king and dinner like a pauper.

among his other advice for health which seems to have stood the test of time.

I read about this study last year which seems to confirm the wisdom of the above advice:

High caloric intake at breakfast vs. dinner differentially influences weight loss of overweight and obese women.



Few studies examined the association between time-of-day of nutrient intake and the metabolic syndrome. Our goal was to compare a weight loss diet with high caloric intake during breakfast to an isocaloric diet with high caloric intake at dinner.


Overweight and obese women (BMI 32.4 ± 1.8 kg/m(2) ) with metabolic syndrome were randomized into two isocaloric (~1400 kcal) weight loss groups, a breakfast (BF) (700 kcal breakfast, 500 kcal lunch, 200 kcal dinner) or a dinner (D) group (200 kcal breakfast, 500 kcal lunch, 700 kcal dinner) for 12 weeks.


The BF group showed greater weight loss and waist circumference reduction. Although fasting glucose, insulin, and ghrelin were reduced in both groups, fasting glucose, insulin, and HOMA-IR decreased significantly to a greater extent in the BF group. Mean triglyceride levels decreased by 33.6% in the BF group, but increased by 14.6% in the D group. Oral glucose tolerance test led to a greater decrease of glucose and insulin in the BF group. In response to meal challenges, the overall daily glucose, insulin, ghrelin, and mean hunger scores were significantly lower, whereas mean satiety scores were significantly higher in the BF group.


High-calorie breakfast with reduced intake at dinner is beneficial and might be a useful alternative for the management of obesity and metabolic syndrome.

Here's a write up on the study in the Wall Street Journal, apparently it was done in Israel:

Bigger Meals Earlier Can Help Weight Loss

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Finding the source in the Talmud would greatly improve this answer. You also need to show that the scientific establishment did not accept this as fact back in the days of the Talmud. –  Double AA Oct 7 '14 at 7:46
It's not even generally accepted today... but I'll add some links to show that. –  Robert S. Barnes Oct 7 '14 at 10:10

If we're counting mathematical comments by rishonim (Medieval Scholars), then in addition to @DoubleAA's reference to Ralbag (Gersonidies) who has the earliest known use of mathematical induction, other Jews have made some strides here as well.

R. Avraham bar Chiyya has an interesting proof that the area of a circle is equal to half its radius times circumference. This is also shown in Tosfos to Sukka 8a, who I presume got it from Avraham bar Chiyya.

In addition, while this is no scholarly source, there's a magazine article discussing how Maimonides/Rambam was the first to state that pi is an irrational number. However, seeing as the Rambam doesn't prove this, it seems like he was just saying that his own instruments weren't able to measure pi precisely.

Of course, cases like these merely show that these Jews were involved in science and mathematics, and may have made discoveries in those fields.

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Was R Avraham bar Chiyya the first to prove that? –  Double AA May 12 '14 at 21:15
@DoubleAA Yes, and though his mechanical proof isn't considered to be a 'proof' by today's standards, it has been proven mathematically by Israeli mathematicians. I'll find try to find the article later –  Matt May 12 '14 at 21:25
Those who came up with pi would be the first to realize that the formula is a never ending one, hence an irrational number. –  HaLeiVi May 28 at 15:40

The Baal HaTanya writes:

והיינו הגוף שלהם גדול כ"כ שהוא בבחי' מקום ומאחר שהם בבחי' מקום הרי הם ג"כ בבחי' זמן שהמקום והזמן שניהם הם נבראים בבחי' א

So in other words, time cannot exist without space, and space cannot exist without time, they are one type of creation.

Although I'm not sure the exact date of this Maamar, given the style it would seem to be somewhere between 1798 and 1813.

At that time Newtonian physics was what was popular, and in it (according to Wikipedia) space and time are not interconnected at all. This view was abandoned with special relativity around 1905.

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Space and time still had been grouped together before special relativity, eg. as forms of basic intuition in The Critique of Pure Reason. –  Double AA May 12 '14 at 20:42
@DoubleAA, I don't know what you mean by "grouped together". You mean that he suggests that one cannot exist without the other, and that lacking one would mean the other isn't there was well? Is that the earliest date you have for that concept? –  Yishai May 12 '14 at 20:45
It means that they have certain properties in common and certain different (as in all analogies). Frankly I don't know what בחינה א' means either. Does it mean that they are both part of a 4D manifold? Is that what בחינה means? –  Double AA May 12 '14 at 20:47
@DoubleAA, of course it can mean different things depending on context. But the context here is that one cannot exist without the other, and that if one doesn't exist, by definition the other doesn't as well, so the creation of one is the creation of the other. –  Yishai May 12 '14 at 20:51
Does science agree to that, though? Could the world have been created with 6 time dimensions and 2 space dimensions? Or 4 space dimensions and 0 time dimensions? I don't know that science has an opinion on that. Special relativity AFAIK doesn't. –  Double AA May 12 '14 at 20:54

It seems that Rambam anticipated certain aspects of Einstien's General Relativity.

The traditional view was that time is absolute and constant:

"Absolute, true, and mathematical time, of itself, and from its own nature, flows equably without relation to anything external."

Issac Newton

However, in the Guide to the Perplexed, Rambam sees time as something not having an existence of it's own, but deriving from the movement of bodies, and that time is not constant but variable. This is in contradiction to Midrash Rabbah Genesis which sees time as existing prior to the creation of our world.

...of these it is very difficult to form a correct notion, especially when the accident which forms the substratum for the other accident is not constant but variable. Both difficulties are present in the notion of time: it is an accident of motion, which is itself an accident of a moving object; besides, it is not a fixed property; on the contrary, it's true and essential condition is, not to remain in the same state for two consecutive moments. This is the source of ignorance about the nature of time.

Guide: M. Friedlander 1881

I have to credit my wife with pointing this out to me.

Mendel Sachs says the following in his paper Changes in concepts of time from Aristotle to Einstein in the Journal Astrophysics and Space Science:

From my reading of the twelfth century scholar, Moses Maimonides, he proposed a variation of Augustine's 'time' wherein the time that was created with the matter of the universe and it's laws was to be a manifestation of matter, rather than a 'thing-in-itself'. Indeed, the latter view is closer to Einstein's interpretation of time in his twentieth century theory of General Relativity, as we will discuss later.

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similar judaism.stackexchange.com/a/38139/759 –  Double AA Oct 19 '14 at 0:07
I don't think Maimonides/Rambam can be credited with coming up with an idea that already existed in Plato's Timaeus. The truth is that well before Newton, many other ancient and medieval philosophers/naturalists had differing ideas about the nature of time and its relation to space or movement –  Matt Dec 16 '14 at 7:09
@Matt It seems clearly from Dr. Sachs article in a pear reviewed journal that this idea did not exist in ancient sources, as the whole point of the article is to trace changes in the concept of time from Aristotle to modern times. –  Robert S. Barnes Dec 16 '14 at 17:45

I saw a presentation which gave 2 specifics (though I'm no scientist and had to take the presenter's word for it):

that the gemara posits a 10 dimensional universe (or some number like that) and science is now coming around to a similar view [I found this which seems to be related]

that the gemara puts an embryo turning into a fetus (first heartbeat) at 40 days and science eventually comes up with 42 days or some such.

but again, I'm a liberal arts guy so take with as many grains of salt as you wish.

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is there any proof that either of those were "ahead of their time" or just reflecting things around them? –  Charles Koppelman Dec 18 '12 at 22:11
are you asking if, in the time of the gemara, there was medical knowledge that the first heartbeat is at 40 or so days? or is contemporaneous with the kabbalah there was a scientific opinion that we live in a 10 dimensional universe? –  Danno Dec 18 '12 at 22:43
I was asking about the heartbeat, but it applies to both. –  Charles Koppelman Dec 18 '12 at 23:26
medieval theologians believed (in other religions as well, though I have seen people trace the christian notion to the talmudic source material) that the soul was infused at 40 days. I don't know of medieval medicine which tied that to a first heartbeat which has been, with the advent of ultrasound, measured at between 36-40 days. –  Danno Dec 18 '12 at 23:44
Why medieval? The gemara was written long before medieval Europe (whose science, incidentally, was much less sophisticated than the time when the gemara was written). In order to answer if the gemara's science was ahead of its time, we'd have to compare it with contemporary sources - Babylonian and Roman science from around the 5th century. –  Charles Koppelman Dec 19 '12 at 20:37

An excerpt from Alei Shur (Shaar Rishon Ch. 12 p. 56):

והנה בערך בזמנו של רבנו הקדוש היה חי באלכסנדריא האסארונום הגדול פטולימייוס מחבר ספר האלמגסט שמתוכו למדו אסטרונומיא עד הזמן החדש. כאשר נודע לפטולימייוס זה על מחזור הי"ט שנה והידיעות הברורות בחשבון סיבוב הלבנה וכו' עליהן הוא מתבסס - השתומם מאד, כיצד היתה בידי חכמי ישראל ידיעה שחכמי האומות טרם עמדו עליה, וכתב שזה מוכיח שהיתה ביניהם נבואה. דבר זה מספר ר' יצחק אברבנאל בפרושו על התורה פ' בא עה"פ החדש הזה לכם ד"ה והלימוד הג

In approximately the time of Rabbeinu HaKadosh there lived in Alexandria the great astronomer Ptolemy, author of the book The Almagest, from which astronomy was learned until recently. When Ptolemy became aware of the 19 year cycle and the clear knowledge of the calculations of the rotations etc. on which it is based - he was flabbergasted, how could there be in the hands of the Sages of Israel knowledge which the scholars of the nations had only just discovered, and he wrote that this proves that there was prophecy among them. R' Yitzchok Abrabanel tells of this in his commentary to the Torah, Parshas Bo, on the verse "This month is for you" s.v. the third topic.

Apparently the world's most preeminent astronomer acknowledged that the Rabbis knew some astronomy before the rest of the world did.

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Ptolemy's astronomy though is not "now accepted by the establishment" (quite the opposite, in fact: it is the paradigm of early pseudoscientific folly) so I don't see how this answers the question. –  Double AA Oct 1 '14 at 5:38
@DoubleAA Are the parts that are rejected relevant to how we calculate the 19 year cycle? –  yEz Oct 1 '14 at 17:25
There is no 19 year cycle... so: yes. (Using the approximation of 19 years in our fixed calendar loses about 4.5 hours off every cycle.) –  Double AA Oct 1 '14 at 17:35
@DoubleAA I don't know what you mean by that. There is no halachic 19 year cycle of leap years? –  yEz Oct 1 '14 at 18:11
Our calendar currently uses one. But there's no physical 19 year cycle of anything. –  Double AA Oct 1 '14 at 18:14

Here's another "grain of salt" answer. If you accept the Vilna Gaon's drasha on Melachim Aleph 7:23, then Shlomo HaMelech knew pi to be 333/106=3.14151, a value not surpassed in accuracy by the scientific community for more than 1000 years, with Ptolemy's publication of 3.1416 in c150 CE.

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Not Sh'lomo but whoever wrote M'lachim. (Yirmiya IIRC but I'm not looking it up now.) –  msh210 Dec 1 '14 at 18:26
Also, not the Vilna Gaon, but a twentieth century author –  wfb Jun 4 at 15:48

Nidah 51b states: “All fish that have scales also have fins and are kosher, but there are fish that have fins but do not have scales and are unkosher".

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You're missing half of your answer: does the "scientific establishment" agree to this statement? –  Double AA Dec 19 '12 at 14:18
Also, do you know that Chazal were the first to claim this? –  Double AA Dec 19 '12 at 14:26
I highly doubt that Chazal were the first people to realize what kinds of fish exist. –  Shmuel Apr 17 '14 at 22:09
@Shmuel You kidding? We plumb the depths of the ocean these days, and it's still true. Neither Chazal nor anyone else did that then. –  SAH Feb 16 at 9:49

Chazal understand HaShem's name Shakai to mean "She-amer dai" - that the universe expanded until HaShem said enough. (http://www.jewfaq.org/name.htm)

According to prevailing scientific theory, there was an inflationary epoch, wherein the universe expanded much faster than the speed of light until "between 10−33 and 10−32 seconds after the Big Bang", when it slowed dramatically.

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So the world was big enough 10<sup>-32</sup> seconds after it was created? (BTW, I didn't downvote, just trying to understand your answer). –  Yishai May 12 '14 at 20:49
@Yishai Perhaps larger than 10^{10^{10^{122}}} megaparsecs. A megaparsec in 3 billion billion kilometers. –  Ypnypn May 12 '14 at 20:52
Isn't the prevailing theory that the universe is still eexpanding at the speed of light? –  user6591 Oct 7 '14 at 11:02
@user6591 not at the speed of light - it's slightly slower. The inflationary epoch was about the acceleration and subsequent decceleration of the universe, which still technically fits within Chazal's understanding of Shakai. –  Isaac Kotlicky May 29 at 17:49
@Isaac I can't accept that the word והעמידו means decceleration. Especially if it is such a minute degree. –  user6591 May 29 at 17:56

The Ben Ish Chai writes that the Arizal said that air has weight, and that this was laughed at with questions of why we don't get crushed. Then it was found to be true and the question was easily answered.

There is also the famous Gemara which differentiates between honey and milk.

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This answer would be more valuable if you would edit in citations/quotations of the Ben Ish Chai, the Arizal, and the Gemara, details of what the Gemara said, and documentation of the Gemara's contemporary scientists saying otherwise. –  Isaac Moses May 28 at 15:56
He pointed to the pasuk in Iyov (28:25) When He maketh a weight for the wind, and meteth out the waters by measure. –  josh waxman May 28 at 16:04
The counterpoint however is that even as galileo argued that air had weight, he pointed to Aristotle, a contemporary of chazal , who said the same: ""But can you doubt that air has weight when you have the clear testimony of Aristotle affirming that all the elements have weight including air, and excepting only fire?" (Galileo Galilei, Dialogues Concerning Two New Sciences)" –  josh waxman May 28 at 16:06
-1 per Josh's second comment which shows that science claimed this first. –  Double AA May 28 at 16:36
@DoubleAA The OP did ask, in his precise final description of the question, for that which was not accepted, not that which was not known. –  yEz May 28 at 20:04

Here's an interesting one from the end of Kesuvos (111b) - some rabbannim are trying to encourage one of their number to make aliyah. Then they give him some advice if he choses to remain in Bavel:

Do not sit too much, because it is bad for the stomach.

Do not stand too much, because it is bad for the heart.

Don't walk to much because it's hard on the eyes (not clear what this means).

Rather, divide you day between 1/3 sitting, 1/3 standing, and 1/3 walking.

You might have noticed some articles recently discussing that sitting at a desk all day has been linked with health problems, most notably more "belly fat" and shorter life expectancy. They have also found that standing raises blood pressure and is, similarly, unhealthy. The medical establishment didn't "know" this until recently.

Modern medicine recommends alternating between sitting and standing, interspersed with brief periods where you walk around.

So yeah, Chazal were 1500 years ahead of their time on that one...

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I'm would appreciate it if the downvoter could explain what about my answer they find unsatisfactory... –  Isaac Kotlicky May 29 at 18:28
Do a search for Aristotle. Sedentary lifestyle and see what he says, and how it plays with arête , such that one should avoid excess. –  josh waxman May 29 at 18:59
@joshwaxman That's entirely distinct from what's being said here - that a purely ACTIVE LIFESTYLE is ALSO unhealthy (otherwise, they'd encourage excluding sitting entirely). The real chiddush is that even Standing or Walking excessively is actually unhealthy (and not just a question of arete), and THAT is not in Aristotle. –  Isaac Kotlicky May 29 at 19:06
That is the second part, arete. Aristotle says exactly that. books.google.com/… –  josh waxman May 29 at 19:45
Btw I am not the downvote on this one –  josh waxman May 29 at 19:49

The theory of the diurnal rotation of the Earth. According to this article in Isis, the journal of the History of Science Society,

After the Twelfth Century, references to the theory [of the diurnal rotation of the Earth] multiply, there being in the subsequent era at least six writers who discuss the hypothesis. Five among these, AL-SHIRAZI, ABU-L-FARAJ, AL-KATIBI, GIOVANNI CAMPANO DA NOVARA, and Saint THOMAS AQUINAS reject it... Its lone advocate is RAB HAMNUNA THE ELDER, who is described in the Zohar as stating in his "Book" that the inhabited world "turns round in a circle like a ball."

It should be noted that Gershom Scholem rejected this reading of the Zohar, and argued that the correct reading was not מתגלגלא, but סגלגל, which means round, and therefore does not indicate rotation of the Earth (see note 163 here). However, in his recent critical edition of the Zohar, Daniel Matt preserves the printed version's מתגלגלא. (However, I have not seen his translation, and Scholem also argues that even if the word reads מתגלגלא, it should be understood as "round" and not "revolves.")

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ISIS has journals? –  Shmuel Brin Jun 4 at 18:07
@ShmuelBrin press.uchicago.edu/ucp/journals/journal/isis.html –  wfb Jun 4 at 18:09

Many people, specifically Breslov chasidim put a huge emphasis on being happy. Nowadays scientists are beginning to say that being happy mentally actually effects the body physically in a positive way.

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Did those people (such as the Breslov chasidim) claim that being happy was a good physical thing to do, or spiritual thing to do? –  Double AA Feb 21 '13 at 5:36
Both. Though probably more so spiritually. The point still stands that they recognized it was the "right" way to live, and now science is justifying that. –  andrewmh20 Feb 21 '13 at 5:39
@DoubleAA Reb Noson zy'a says (I think in Likutey Halachos but maybe elsewhere) that a person who is happy will not experience suffering physically from any ailments they might have. Now that I think of it it's probably Yimei Moharnat, in the context of his intestinal illness. –  yoel Feb 21 '13 at 5:45
מצוות לאו ליהנות ניתנו –  b a Feb 21 '13 at 6:26
What do you mean? –  andrewmh20 Feb 21 '13 at 12:27


An accepted scientific theory is that the universe was created ex nihilio.

a)This article illustrates a Jewish precursor to the Greek ideology with whom this theory is mostly attributed to. http://www.hashkafacircle.com/journal/R2_RS_exni.pdf


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-1 Article (b) has many issues, and is certainly not an "accepted scientific theory." The Big Bang, btw, is not "ex nihilo." –  Shmuel Apr 17 '14 at 22:14
@Shmuel According to Wikipedia it is indeed a "widely supported" theory. And I really don't think he was confusing "ex nihilo" with "ex Big Bang." –  SAH Feb 16 at 9:53

Chazal knew that metal utensils can absorb the taste of food, despite being seemingly perfect. Modern engineers also discovered that micro-fissures are created in metal by expanding and contracting, letting the taste of food enter it.

See Dave's answer to "Blias" in today's pots and pans.

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Can you demonstrate that 1) the scientific establishment did not think metal pots absorb taste, and that 2) the scientific establishment now does think metal pots absorb taste? Citing a hearsay story of one unknown engineer is hardly proof of a consensus in the establishment. –  Double AA Oct 1 '14 at 6:06
Also how do you know chazal were not talking about their own pots and pans, which were the metzius? –  josh waxman Oct 1 '14 at 11:27
@DoubleAA Why would #1 be necessary –  SAH Feb 16 at 9:50
@sah to show that we predate them. –  Double AA Feb 16 at 15:30

Rabbi Abraham Zacuto (1452-1514) was a contemporary of Leonardo da Vinci, a leading astronomer who stood at the cradle of great geographical discoveries of 16th century, advised Columbus and guided Vasco da Gama, was a luminary at the Court of Kings of Spain and Portugal, merged science and Kabbala, taught at Salamanca University and lived in the Templar-built mysterious Castle of Tomar, travelled through the Orient from Tunis to Constantinople, to find his eternal rest in Jerusalem. Rabbi Zucuto perfected the astrolabe, which only then became an instrument of precision, and he was the author of the highly accurate Almanach Perpetuum that were used by ship captains to determine the position of their Portuguese caravels in high seas, through calculations on data acquired with an astrolabe. His contributions were undoubtedly valuable in saving the lives of Portuguese seamen, and allowing them to reach Brazil and India. While in Spain he wrote an exceptional treatise on astronomy/astrology in Hebrew, with the title Ha-jibbur Ha-gadol. He published in the printing press of Leiria in 1496, property of Abraão de Ortas the book Biur Luhoth, or in Latin Almanach Perpetuum, which was soon translated into Latin and Spanish. In this book were the astronomical tables (ephemerides) for the years 1497 to 1500, which were instrumental, together with the new astrolabe made of metal and not wood as before, to Vasco da Gama and Pedro Álvares Cabral in their voyages around the open Atlantic ocean (including the Southwest Atlantic) and in the Indian Ocean, to India, and to Brazil and India respectively.

See http://www.zacuto.org/

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Downvote isn't mine, but what specifically did he know that others didn't? How to perfect an astrolabe? How did you find, as the OP said, " they knew X (some fact) centuries before the scientists/whatever did"? –  yEz Dec 1 '14 at 18:50
Rabbi Zacuto was on the cutting edge of navigational science at the time, which included creating some important measurement equipment and mathematical formulae that did not yet exist. That is what Rabbi Zacuto added to the world's knowledge of the time. There was a nice article in the Naval Institutes Proceedings Magazine back in 1992 which discusses the various navigational experts of Columbus' era on whom he must have relied, R. Zucuto being one (plus another rabbi as I recall). I think that there is more evidence that Columbus and Rabbi Zucuto actually knew each other and conferred. –  Bruce James Dec 1 '14 at 18:56
Down-voter, please explain. –  Bruce James Dec 1 '14 at 18:56

Rabbi Yonason Eibshitz(born 1690) in his sefer Tiferes Yonason on the Torah he writes in parshas Noach that during the for haflaga there were people who were trying to flee and land on the moon and live there.He describes a flying ship with masts some like to say he was referring to a spaceship.From the way he details the ship it is not like our spaceships per se but definitely an advanced craft to think of and mechanics it works with.

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Read it inside here hebrewbooks.org/pdfpager.aspx?req=19492&st=&pgnum=17 –  sam Jul 11 '13 at 1:00
Rav Eybeschutz was not the first person to speculate on traveling to the moon. See McDermot's "Trip to The Moon", 1728. There are other examples dating back to the mid-17th century. RYE's vision was not unique. –  Ephraim Feb 9 '14 at 10:11
Do they describe how to get there? –  sam Feb 9 '14 at 18:38
@joshwaxman ^^^ (just saw this now and thought you'd like to comment) –  Matt Dec 16 '14 at 7:01
He describes the rocket ad being catapulted with gunpowder. This is (luckily) not how we do it. Tintin also wrote about space travel before is was done, and the high rate of acceleration is also not real. –  HaLeiVi May 28 at 15:50

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