Friday, November 7, 2025
Witnesses to Sedom's Destruction
Thursday, October 16, 2025
Jews are from Jewpiter
Emunah in Time and Space
The Two Luminaries
Please see Pi's comment below with some nice alternative understandings of this פסוק.
Monday, December 5, 2011
Ominous Eclipse Predictability
THE BOOK (BEING PUBLISHED BY ISRAEL BOOK SHOP), THE SECRETS OF THE STARS, WILL BE IN STORES NEXT WEEK!!! KEEP YOUR EYES OPEN!
Wednesday, June 2, 2010
Yam Suf 7 or 8 Days from the Exodus?
One of the issues that has been addressed regarding this Rashi is that it seems contradictory to another Rashi. When commenting on the events of Krias Yam Suf, Rashi mentions that it happened on the seventh day of the Exodus. Rashi even states that this is the basis for the custom to read the Torah portion of Krias Yam Suf on the seventh day of Pesach. (Rashi Shemos 14:5)
I would like to offer two suggestions that our founded on how to calculate when one's day begins. The first answer is suggested by Rabbeinu Bachye. He maintains that even though Jewish law usually recognizes night as preceding day, when it comes to sacrificial offerings the day comes first (regarding sacrifices, the portion placed on the Mizbeach is able to be burnt the night following the day in which the blood was sprinkled).
Our Exodus began on the 14 of Nisan when the Korbon Pesach, a sacrificial offering, was brought in the early afternoon. Thus, the morning of what we would refer to as the seventh day of Pesach is actually the eighth day from the Exodus if one is utilizing the sacrificial offering system. In this regard both the Rashi that maintained that it was day seven and the one that states that it was day eight are correct, they are just describing the event based on separate systems. (Rabbeinu Bachye Bamidbar 15:41)
Seeming to support this assumption is the fact that the Rashi that maintained that it was day eight focused on the time when Klal Yisrael sang and not when the Egyptians perished in the sea. They perished just before morning, (Shemos 14:27) but we did not sing until after daybreak. (Rashi Shemos 14:5) Unfortunately, Rabbeinu Bachye leaves hidden the reason why Tzitzis reflect the sacrificial offering system and the Torah portion read on Pesach reflects the regular system.
Before presenting another approach I would like to say, as an aside, that it is pretty fascinating that the evening during which the sea split had a very rare occurrence happen in the sky. That night the moon partially blocked Mars making it appear as if the two were touching (I know that I posted a similar thing with Saturn regarding the first Tisha B'Av earlier this week, but these events truly are rare which makes it even more fantastic that they seem to happen on these monumental dates in Jewish history). Astrologically, this event portends malevolent tidings. (Ibn Ezra Reishis Chachma 7) Interestingly, it occurred in the constellation Aquarius which is considered the be the mazal of Klal Yisrael. (Ibn Ezra Shemos 31:18) Aquarius, depicted as a man pouring a bucket of water, would have been seen as being afflicted by this sign. It seems interesting that Hashem bestowed His mercy that evening and saved this young nation. Just as he split the water of the Yam Suf, he "split open" the evil tidings found in the constellation of water that symbolized this nation and protected them miraculously. In fact, quite unbelievably, Rabbeinu Bachye mentions that the Jewish nation should have perished at the Yam Suf because the Egyptians had tapped into the inlfuence of Mars which is associated with death. It was only because of God's tremendous mercy that he saved us. (Rabbeinu Bachye Shemos 14:25)

I am certainly not qualified to argue with Rabbeinu Bachye, but I would like to suggest an alternate way one could have read Rashi based on the Meiri. The Meiri states that their are four accepted ways that civilizations have decided to begin their days. One is the Jewish way and that is the start from evening. A second way is to start from daybreak. Another is to start at midnight (like is the practice here in the U.S.) and the last way is to start from midday when the sun is at its peak. This last way, says the Meiri, is based on deep astrological meaning and this is how the ancient Egyptians began their day. (Meiri Pesachim 5a)
Rashi mentions that Paroh sent a messenger with us when we left Egypt to make sure that we would return after three days. When we did not, Paroh came out with his armies and advanced towards our camp on days five and six. The night of the seventh day of our Exodus his battalions were drowned in the sea. (Rashi Shemos 14:5) In fact, this is the same Rashi that mentions the reason for reading this portion on the seventh of Pesach.
The Sifri mentions that we left Egypt at midday. (Sifri Devarim 337) Rashi quotes from this Sifri elsewhere implying that he is of the same opinion. (See Rashi Bereishis 7:13) If Rashi agreed with the Meiri then Paroh sent his messenger with us right at the "beginning" of the first day which coincides with 15 Nisan in the Jewish calendar at midday (this is the day after the Korbon Pesach and the first day of our holiday of Pesach). That means that seven Egyptian days after would have the Egyptian destruction occurring on the night of the eighth day of the Jewish count. Since we do not follow the Egyptian calendar we commemorate this event with the seventh day based on our count and we read the Torah portion of this event on the seventh of Pesach. The Rashi at the end of our Parsha, though, would also be accurate. The Egyptians perished on what we would call the eighth day, but the seventh Egyptian day from our Exodus.
Tuesday, June 1, 2010
Solar Powered Giants or Orion's Belt Loosened?
This week's Parsha tells us that the spies sent into Canaan were witness to giants dwelling in the land. Rav Yehonasan Eibshitz zt"l wonders why there are no longer giants roaming the Earth. He then cites from various statements of Chazal that maintain that these giants are called "Anakim" in the Torah because the were "maanik" (block out) the sun when they would stand up. (Tiferes Yehonasan Bamidbar 13:28)
Rav Eibshitz then contends that their supersize and strength came from magical powers that they would draw from the sun. Since such magical powers have ceased to exert power in today's society, these beings can no longer exist. (Ibid.) In biblical times, however, such powers were around and in order to effectively combat them, Moshe, and later Yehoshua, caused the sun to stand still when battling these formidable foes. The sun would be positioned and stalled in order to cut the power source of these warriors. (Ibid. 13:30)
Another celestial suggestion as to who these giants may have been can be found be focusing on a later verse that states that they were the offspring of the Nephilim. (Bamidbar 13:33) Rashi comments that these Nephilim were Shemchazai and Azael that fell from heaven in the times of Enosh (Adam's grandson). (Rashi Bamidbar 13:33) Rashi appears to be paraphrasing the Yalkut Shimoni that tells over a fascinating story.
The Yalkut Shimoni mentions that in the times of Enosh there were some angels (Shemchazai and Azael) that wished to prove that they could withstand the pressure to sin if they were only given the chance to descend to the earthly realm. Hashem granted their wish and they "fell" to Earth. They are called Nephilim because the root of the word is "nephal" which means to fall. Once on Earth they began to sin and they started to try and intermarry with human women. There was one woman that withstood their advances, Istahar, and for her piety she was placed in the heavens as a star in the star cluster called Kimah, the Pleiades. (Yalkut Shimoni Bereishis 366)
Interestingly enough, the word Nephla, of the same root as Nephilim, is the Aramaic word for the constellation Orion, Kesil. (Targum Iyov 9:9) It is even more fascinating to note that the young girl, Istahar, was placed in the Pleiades which, according to Chazal, are supposed to project the opposite influence to Orion. (Berachos 58b) If these angels fell from the heavens from the region of Orion (perhaps meaning that they were considered to be angels that exert the influences associated with this constellation) then it would almost be as if Hashem was saying that this girl was able to counteract the influence of these beings so she would forever be memorialized in the area of the sky that demonstrates the ability to withstand Orion.
Sunday, May 23, 2010
The Rambam Knew Math!!!
The issue that one can have with this is that, currently, this is no longer true. Over hundreds of years the stars shift, relative to us, and currently things are one constellation off. The stars that currently reside behind the sun during the month of Sivan are actually those that form the constellation Shor, Taurus.
The reason for this shift is usually described by comparing the earth to a spinning top (dreidel). As a top spins it also wobbles. The earth's wobble is relatively slow; it completes one "wobble" every twenty-five thousand plus years. During the in between time, the constellations slowly "shift" and that results in the system that Chazal put forth not being recognizable to us.
The Rambam notes this phenomenon in his Mishnah Torah (Yesodei HaTorah 3:7) and provides a relatively accurate rate of wobble (1 degree per approximately seventy years; interestingly enough this number is also given by the Ibn Ezra in his Sefer HaTa'amim. The Greeks felt it was more like 1/100; the Arabs refined it more in line with the number chosen by the Ibn Ezra and Rambam. It was only after Newton provided his theory of gravity that the currently accepted number of 1/72 was chosen). The Rambam mentions that the mazalos have shifted and states that the mazal of a month is not connected to the physical arrangement of stars, rather, it is connected to the time of year and, therefore, the mazal of the month of Sivan (from our example) is still Teomim. The Rambam then informs us that the time the names of the constellations were chosen was during the time of the Mabul, Great Flood.
Since Chazal and the Greeks seem to agree on the names, positions and forms of the constellations, it stands to reason that they would agree upon where the exact borders between constellations can be found. The problem I had with the Rambam was the if one does the math of when the Mabul was and "moves" the stars back to their relative positions, he will find that the vernal equinox was located in the constellation of Shor (both using the 1/72 ratio agreed upon by contemporary science, and the 1/70 provided by the Rambam himself). The vernal equinox is the place where the sun is on the first day of spring. Since Nisan is the month that this should be happening in, the vernal equinox should be in T'leh, the mazal of Nisan. The Rambam was certainly capable of doing the simple math of calculating how many degrees one needs to move the constellations based on how many years had passed since the Mabul. How could the Rambam state that the constellations shift at a rate of 1/70 and in the same halacha mention that the origination of the names of the mazalos was in the time of the Mabul!?!
The answer seems to be that the assumption that Chazal necessarily agreed with the Greeks as to the place of the borders is incorrect. There is a discrepancy in Rashi as to where the stars of Kimah are located, either in T'leh (Rashi R"H 11b) or in Shor (Rashi in a note at the end of R"H). The Rashash on Midrash Rabbah in last week's parsha (that's why I decided to post this now) writes that these "Rashis" are in disagreement and that this reflects a disagreement between Shas and the Midrash Rabbah. (Rashash Bamidbar Rabbah 10:8:29; also see 30 in which the Rashash refers to an alligator as an Akrav) I believe many would assume (and perhaps the Rashash himself believes) that the disagreement is that we do not know what Kimah is and there are different star patterns that are being suggested (perhaps the Hyades would be the other opinion). I, however, believe that it is possible that all agree that Kimah is the Pleiades (the conventional translation), and the disagreement is where the borders of Shor and T'leh are (and, perhaps, other borders could be disputed).
If correct, Kimah was in T'leh at the time of the Mabul. It would, therefore, be logical to assume that the Rambam would be of this second opinion and then his statement makes sense perfectly (based on his calculations).
I have included a recreation of these constellations and borders as they were in the time of the Mabul. The recreation reflects the currently accepted numbers and, therefore, if one were to draw a vertical line just to the right of Kimah, the equinox would still be in Shor. One must keep in mind that the Rambam had a ratio of 1/70 and not 1/72. According to his calculations, the equinox would be a few degrees more to the left and Kimah would barely be in T'leh. The Rashi that is of this opinion calls Kimah "the tail of T'leh" making this position seem accurate.
Monday, May 17, 2010
Midrash Similar to Mythology

Wednesday, May 12, 2010
A Lifetime of Space Travel
Wednesday, May 5, 2010
Determining the Identity of the Unicorn
In the times of the Greeks there were forty-eight constellations, and the Ibn Ezra contends that Chazal agree with both this number and the actual division. These were considered to be Divinely created and to exert influence on life on this planet. As time continued, people decided that they needed to subdivide the sky into more regions (without any Divine intervention) otherwise it would be too difficult to converse with one another. The new divisions, which became standardized, provide a framework for both scientists and laymen to discuss the sky with relative ease. These constellations were generally created by astronomers interested in contemporary science and not astrologers who were interested in the influences of these regions. As such, the names of these often reflect more scientific objects such as Microscopium, etc. Currently, there are eighty-eight recognized constellations.
Now, let's talk about unicorns. There is a constellation called Monoceros. Monoceros is Greek for unicorn (mono = one and ceros = horn; interestingly, often times if you exchange the "c" in a Greek word for a "k" you get the Hebrew word, for example, Okaynus, and Oceanis for the word for Oceans. In this instance you get keresh) and that is what this constellation depicts. There is a discrepancy as to when this constellation was "created", but it seems that it was in the sixteenth or seventeenth century. It appears that Plancius is the first confirmed source for it and Bartsch(ius) definitely included it in his later work. A notable point is that there is discussion as to whether the, slightly earlier and very reputable historian, Joseph Scaliger allegedly claimed to have seen this constellation in a much earlier ancient Persian source. If so, that would, perhaps, place it as far back as the time of Chazal. If the Persians' unicorn was similar to that of the ones mentioned by Chazal, then this information could be used to ascertain this beast's identity.
About a year ago I made, what I feel, is a big discovery. I was learning the Ibn Ezra's Reishis Chachma for my upcoming sefer (sorry, I had to put in another shameless plug). When the Ibn Ezra delineates the constellations he only mentions the standard forty-eight of Chazal. However, he constantly refers to other segments and star patterns in the sky. This would be comparable to looking at the map of the U.S. and, in addition to the states (our constellations), we could also see some counties and regions. These are currently referred to as asterisms (i.e. the Big Dipper which is a segment of the constellation Ursa Major). When discussing Gemini, the constellation associated with the upcoming month of Sivan, the Ibn Ezra discusses some nearby asterisms. One of them is, you guessed it, Monoceros!!! At first I was completely amazed. It seemed that I had historical proof that this "constellation" did, in fact, predate (since the Ibn Ezra lived hundreds of years before) and that Scaliger's claim may have validity. Not only that, but the Ibn Ezra also refers to all the objects mentioned in his work as having influence on the planet, a suggestion implying that these are Divinely created asterisms. Since the only Reishis Chachma that I was able to get was a translation I set out to find a copy of the original Hebrew (something I had wanted to do anyway).
I finally located a copy published in 1939 that contained the original Hebrew as well as a French and English translation. The Hebrew reads "חיה בעלת קרן" which does sound like unicorn, but, I must concede, is not definitive anymore since one could argue that it just means a horned animal. I do find it very unlikely to be something other than the unicorn, though, because what is the likelihood of that happening in the exact location of the modern Monoceros which Scaliger claims predates its "modern creation".
Based on Scaliger's testimony and the above proof, it seems that Plancius and Bartsch were aware of the older asterism and decided to include it into the sky as a constellation (by the way, there is no reason to suspect that they intended to present this as their own creation, rather, it is very possible that they just intended to upgrade an asterism of ancient to the status of constellation in order to divide the sky into smaller parts). Scaliger's alleged sighting in the Persian source would have included a picture of the animal (it was common to draw the stars with fancy artistic representations of their associated items behind them) and it stands to reason that Plancius was aware of this information. Therefore, they would have known the Persian unicorn's true identity, which would probably be identical to the Ibn Ezra's.
There has been speculation as to the possibility of the unicorn being a giraffe. The giraffe has two horns on the top of its head, but another bump in the middle of its head. If it is the unicorn, then, what Chazal meant when they said an animal with one horn between its eyes was that in addition to two regular horns it had a third in between its eyes. The translation as unicorn would, then, be in error. If the giraffe is the only species of unicorn mentioned then, perhaps, the above stellar discoveries put a little doubt on this assertion (in addition to the asterism/constellation being called Monoceros as opposed to Triceros). There is another constellation created by Plancius and charted by Bartsch, Camelopardalis. In case you haven't figured it out, camelopardalis means giraffe in Latin (originating from the Greek) and Plancius was dedicating this region of the sky to this animal (once again, camel = gamal, o = u and pardalis = bardalis, a spotted cat like an ocelot; this would show the Hebrew equivalent of a mix between a camel and bardalis, a giraffe does look something like a mix of the two). The fact that there was another constellation created by the same people indicates that the two cannot be one and the same. The depiction that is in use, stemming from Plancius and Bartsch, is a horselike creature with a horn on its head.
Monday, March 29, 2010
Goodnight Moon
Tuesday, March 16, 2010
A Thirteenth Tribe of Yisrael?
Tuesday, March 9, 2010
Too Much Chiddush for Rosh Chodesh!
Tuesday, February 23, 2010
Esther's Astronomical Identity Crisis
Thursday, January 14, 2010
Yeshaya HaNavi's New World Order?
The pasuk states (Yeshaya 66:3),
"שוחט השור מכה איש זובח השה ערף כלב מעלה מנחה דם חזיר מזכיר לבנה מברך און וגו'"
One who slaughters an ox [is as if he] has struck a man, the offering of a sheep [is like] the killing [by means through the back of the neck] of a dog, the giving of a flour offering [likened to] pig’s blood, the burning (see Metzudos) of frankincense is a forced blessing, etc."
The prophet is discussing the order of the world as man develops. At first the prophet focuses on the destructive path of man (as seen above) but the end of the chapter details the end of times when order will be restored and the wicked punished. It is interesting to see that the aforementioned verse seems to contain a very astronomical idea.
As we all know, there are four season and they start on the dates of the two equinoxes and two solstices. These dates are not just points in time, but the placement of the sun in the sky on these dates is integral. The location against the backdrop of stars is also referred to by the names of equinox and solstice. These areas were given significant weight by all ancient civilizations (see Ibn Ezra’s Sefer HaTa’amim).
At the time of Creation these four points were located in Shor/Taurus, Aryeh/Leo, Akrav/Scorpius, D’li/Aquarius. Over long periods of time, the stars appear to drift from their original place and, by the time of Chazal, these points shifted to being in the location of T’leh/Aries, Sartan/Cancer, Moznayim/Libra and G’di/Capricorn. Currently they have shifted even more and are in: Dagim/Pisces, Teomim/Gemini, Besulah/Virgo and Keshes/Sagittarius. The next shift will be similar to the first one mentioned, but with the order having D’li first and Akrav last. The shifts will continue in that fashion causing one to state that there are three basic makeups of these four points over the course of this world’s lifespan.
When analyzing the pasuk above, one sees that every grouping of three has two objects that seem to refer to two points of four from each set. All show the destruction of that item and could be showing that that item’s importance was being destroyed as the sun will no longer be placed in it during these important times.
The slaughter of an ox is compared to the striking of a man. The ox is the first point mentioned, Shor, and D’li, the last point, is considered to be a human pouring water and described, astrologically as human (see Ibn Ezra’s Reishis Chachma and Sefer HaTa’amim). The next grouping has a sheep and a dog. The sheep is T’leh, the first of the second set, and the dog, perhaps, is referencing Sartan. The dog is described as being killed from the back of its neck. If one looks to the constellations representing dogs in the sky, Canis Major and Canis Minor, he will see Cancer/Sartan, riding on the back of their necks. The next reference is the offering of flour and the blood of a pig. This seems to be showing the in between stage of the second and third set. (The first switching of sets had primarily happened in the time of Yeshaya , so perhaps, from the first to second set the prophet saw no need to discuss the in between motion.) In the hand of the Besulah is the star Spica and it is considered to be represented as stalks of wheat (see Ibn Ezra’s Reishis Chachma) and it is on the edge of Besulah. On the edge of Cancer is a star pattern that the Ibn Ezra tells us is represented as an iron pig (Reishis Chachma). Finally, the frankincense and the forced blessing can be shown as Dagim and Besulah. Dagim is considered to rule over many species plant life, including frankincense, and the way to describe the destruction of a Besulah would be to discuss the idea of her being forcibly taken (this is how Chazal reference the act of forcibly taking a woman as Ones, force). Therefore, perhaps, the "forced" blessing is showing the destruction of the Besulah.
Throughout the exile these changes of stellar position have all happened. Perhaps, the future will bring us something new. This can be seen in the phrase used by Yeshaya later in the Haftarah (Yeshaya 66:22),
"כי כאשר השמים החדשים והארץ החדשה אשר אני עשה וגו'"
"Because like the new heavens and the new world that I make, etc."
May we all merit to seeing this realization soon.
Tuesday, January 5, 2010
Moshe Rabbeinu's Birth and Demise Seen in the Stars?
When looking back to the year of Moshe Rabbeinu's birth (1392 B.C.E.) and the day on which he was born 7 Adar, one can, perhaps, see a little bit of what these astrologers saw. Saturn was entering into the constellation Pisces. Saturn is considered to be the planetary influence of the Jewish people (Ibn Ezra's Reishis Chachma). Pisces is considered to be the constellation that influences the Jewish people's houses of worship (Ibn Ezra's Reishis Chachma), and is associated with water as it is depicted as fish. While entering, Saturn could be viewed as the sign of the Jews finally finding its place of success, in the shul.
Interestingly, on the eighth day after his birth (his bris) Venus came extremely close to Saturn. Venus is associated with fertility (Ibn Ezra's Reishis Chachma) and at the bris is when the male child is considered completed. This celestial spectacle would been seen as the growth and development of this new savior. It also would have been easily predicted in advance by the Egyptian astrologers.
Even though, as mentioned by Rashi, the Egyptians did not know whether this savior was Jewish or not, since the eight day has significance to the Jewish people as being this day of completion, its occurrence would not have been discounted. So, perhaps, the Egyptian astrologers saw the entering into Pisces and deduced that the birth of the savior was possible, but they still could have thought that this was not indicative of the birth certainly occurring. Saturn is the slowesr moving naked eye planet, but it still makes a complete circle around the night sky over a thirty to forty year period. Maybe thirty to forty years later would signify the birth when Saturn would return to this position. However, once they saw that Venus would be touching it eight days later, they knew that this had to be the time of the actual birth.
How did they deduce that Moshe Rabbeinu would experience failure with water? Perhaps, they had seen a couple months earlier, when Moshe Rabbeinu was developing as a fetus, that Mars touched Saturn while in the constellation Aquarius. Mars does not come this close to Saturn on a regular basis. It can be centuries in between events like this from any given location. Mars, associated with death and blood (Ibn Ezra's Reishis Chachma) would be seen as affecting Saturn and, interestingly, it was occurring in the constellation Aquarius, the Water Carrier. Aquarius is seen as a man pouring out water from a bucket. The obvious connection would be to assume that the savior of the Jews, expressed by Saturn, would meet his demise, as seen with Mars, in the context of water, Aquarius.
(It is also of note that in the Midrash Rabbah, Rashi's source, the Midrash states that the astrologers made this prediction when Yocheved was pregnant with Moshe Rabbeinu. That seems consistent with this supposition because they would have begun making their predictions from that point and would use the future calculated events to continue their theories. Therefore, the Midrash and Rashi, if my theory is correct, are both accurate).
Perhaps, the most fascinating aspect of this entire theory is how it came to fruition. We know that Moshe Rabbeinu passed away 120 years later and it was punishment for hitting the rock (which brought forth water and showed the accuracy of the Egyptian prediction) that denied his entry into Eretz Yisrael. That year, and that day of his death, Saturn was in the same place as it was on the day of his birth; a place of water. Interestingly (although I don't know exactly what to make of the following), on day thirty of his passing, the last day that Klal Yisrael mourned Moshe Rabbeinu, Mars, Venus and Mercury all came extremely close (within a few degrees) of Saturn. This is an unusually rare event!!! Since I am not an astrologer, nor do I pretend to understand or study astrology (I have learned through some sifrei rishonim about it in order to understand some other ideas, such as astronomy, that they espoused), I don't know exactly what the significance of this event is, but I can tell you that any self respecting astrologer in those days would have seen it as a truly astronomical event.
Wednesday, December 23, 2009
No Kidding
The truth is that, although not symbolic of a new year, this time period is, in fact, associated with a time of new beginning by Chazal. The Midrash (Tanchuma Haazinu 1) compares the life cycle of a human to the yearly cycle. While doing this, it states that after the individual has received his judgment from Tishrei (apparently enacted in Cheshvan) he begins anew in Teves. The Midrash mentions that this is why the mazal of Teves is a G'di, a kid. Just like a kid will develop into a mature goat, so too, this person is starting with a fresh start and able to mature.
Perhaps, the association follows the fact (certainly the secular new year does) that this time of year does mark a time of new growth. The sun's position begins to decline in the sky starting from late June. It continues to get lower and lower in the sky until right around the beginning of Teves. At that point the sun stops and reverses itself and begins to ascend higher and higher every day until late June. The days get longer and the nights shorter.
While no actual agricultural growth can be seen at this time, the sun's position allows one to see that things will turn around and the winter will end (hopefully sooner than later). This may not be a significant renewal to warrant a new year or beginning of the months, but it allows one to see that even though this time marks the beginning of the harshest season, it also marks the fact that that is already beginning its end. Eventually, when the sun is high enough the earth will have heated up enough and the spring will come around again!!!
Monday, November 23, 2009
Can the Torah's South be North?
"צרור עון אפרים צפונה חטאתו."
"Ephraim’s iniquity is bound, his sin is hidden."
Earlier, the navi had made it known, clearly, that the sin of Ephraim was idolatry. Idolatry being "hidden" is something that actually refers to an astronomical fact. More specifically, that which is hidden shows that idolatry is ridiculous.
Rabbeinu Bachye (Bamidbar 2:2) informs us that the cardinal directions, east (מזרח), west (מערב), north (צפון) and south (דרום) are named such because of the sun’s perceived motion (also see Ramban Shemos 26:17). מזרח is the word for east because it comes from zarach meaning to shine. It is from this direction that the sun begins its journey every day. מערב is from erev which means nightfall because the sun’s journey ends here at nightfall. דרום is actually a contraction of two words, dar and rom, meaning dwells high.
The sun, to those at northern latitudes, rises from the east and travels on the southern portion of the sky and sets in the west. צפון also means hidden and that is why north is referred to as such. While the sun can definitely set and rise from a slightly northern direction, it NEVER travels on this side of the sky. The sun, the most commonly chosen idol, should have been rejected as a god for this reason. The fact that it has no power in this area, and that it sets, shows its impotence!!! The Rema (Toras HaOlah) tells us that this is why the pending destruction of the first Beis HaMikdash was described by the navi, Yirmiyahu, as coming from the north. This was to show the idol worshippers that they were horribly wrong. Perhaps, this is why Ephraim’s sin is depicted as being hidden, as well.
When describing these types of ideas, people sometimes ask why the Torah seems to totally disregard those in the southern hemisphere. For them, it is the northern side that the sun travels on and the southern side is "hidden". I am not 100% sure, but I feel that the answer is either that since the Torah was given in the northern hemisphere it is told from that perspective, OR that the Torah would have called north darom and south tzafon to these people!!! The idea is not the actual direction, but the solar movement. If so, then it is reasonable that this would be the case.
