Friday, January 30, 2009

All the Water and Air on Earth

Conceptual computer artwork of the total volume of water on Earth (left) and of air in the Earth's atmosphere (right) shown as spheres (blue and pink), shown on the same scale as the Earth.

Left: All the water in the world including sea water, ice, lakes, rivers, ground water, clouds, etc. This sphere measures 1390 kilometres across and has a volume of 1.4 billion cubic kilometres. This includes all the water in the oceans, seas, ice caps, lakes and rivers as well as ground water, and that in the atmosphere.

Right: All the air in the atmosphere gathered into a ball at sea-level density. This sphere measures 1999 kilometres across and weighs 5140 trillion tonnes. As the atmosphere extends from Earth it becomes less dense. Half of the air lies within the first 5 kilometres of the atmosphere.

The spheres show how finite water and air supplies are.

(from here)

Friday, January 23, 2009

Lecture Tour

I will be visiting the NY region on an extensive lecture tour during February. I still have some openings in my itinerary from Feb. 12-17th, so if you are interested in arranging a lecture for your shul or a presentation for a high-school, please write to me at

Frogs and Crocs

The second plague to befall Egypt was that of tzefardea. It is widely believed that the term tzefardea refers to frogs, but Ibn Ezra notes that there are actually two views on this matter:

"The commentators differed in their understanding of the word tzefarde'im. Many said it referred to a sort of fish found in Egypt, called al-timsah in Arabic, which comes out of the river and seizes human beings. Others say they are the creatures found in most of the rivers and that they make a sound. This explanation, which is well known, seems correct in my view." (Ibn Ezra to Exodus 7:27)

The former explanation is describing a crocodile. It is referred to as a fish, even though it is a reptile, because the Torah concept of fish also includes other aquatic creatures. Support for this identification is advanced from the description of how the frog plague ceased. The Midrash comments on the statement that the tzefarde’im shall remain in the river:

“ 'The tzefarde’im shall retreat from you and your courtiers and your people; they shall remain only in the Nile' (Exodus 8:7) – Rabbi Yitzchak said, There are still deadly beasts in it that come out and kill people every year ... Moshe did not pray that the tzefarde’im be wiped out, only that they not harm Pharaoh, as it says, 'And Moshe cried out to the Lord in the matter of the tzefarde’im which He had inflicted upon Pharaoh'(Exodus 8:8)." (Midrash haGadol[1])

Rabbeinu Bachya elaborates at greater length:

"Moshe’s words in his prayer stayed true for that time and for all generations. In accordance with his words, 'they shall remain only in the Nile,' to this very day the creeping water creature known as the al-timsah remains there. There it lives, and it is said that sometimes it comes out of the Nile where it lives, rising onto the river’s edge and swallowing whatever it finds, even two or three humans at a time. Neither spear nor arrow can overcome its body, unless aimed for its belly. Physicians say it is venomous and that touching its body, even after its death, is harmful to man. It is of the tzefardea type, and from the power of Moshe’s words, this creature remains there... This is also how Rabbeinu Chananel explained it, and regarding this it states, 'Speak of all His wonders' (Psalms 105:2)." (Rabbeinu Bachya, Exodus 10:19)

According to the second identification, preferred by Ibn Ezra, the tzefardea is the commonly found animal that makes a sound – the frog. This is also the explanation preferred by others:

"Some say it looks like a fish, that it is the timsah, which moves its upper jaw, unlike all other lowly creatures, and that it seizes humans and animals passing by the river’s edge. But the correct explanation is that they are the known creatures of rivers and pools." (Sefer haMivchar[2])

We find the following evaluation in Sefer HaToda'ah:

"This type of destructive tzefardea did not exist in the Nile previously. After it was then created, it remains in the Egyptian river forever. It grows in the Nile to a great size, and damages and swallows creatures big and small. It is the tamsah, which is found in the Nile until today, as a memorial to that plague. And there are some of the commentaries who say that the tzefardea referred to here is the small croaking creature, and so it appears from the words of our rabbis in the midrashos." (Sefer HaToda’ah 23)

The midrashim to which he refers describe the frog as a small and weak creature, prey to snakes and aquatic creatures, that is extremely vocal. This description can only match the frog and does not match the crocodile at all.

What of the etymology of the name tzefardea – does that give an indication either way? Some claim it to be a word from an unknown foreign source.[3] It may be a combination of the root tzafar, meaning to chirp (as frogs do), along with the root rada, “muddy marsh,” which is the frog’s favored habitat. But there are those who state that the name tzefardea is a combination of two words, tzipor de’ah, “the bird of knowledge.” Some explain this to refer to the frog, which chirps like a bird and knows when to stop:

"Tzefardea – a creeping creatures that emits cries all night, until morning, and it is tzipor da, 'the knowing bird,' that it knows the time of morning, to cease from its cries." (Chatzi Menasheh[4])

There is another explanation of “the knowing bird” that is more difficult to ascribe to either animal:

Ba-tzefarde’im” – what is this word, tzefarde’a? There was a bird (tzipor) in the Nile that had intelligence (de'a), and when this bird called to them they came, and so they were named after this bird with intelligence: tzefar-de'a. (Midrash Lekach Tov to Exodus 7:28; cf. Yalkut Shimoni 7:182)

Neither frogs nor crocodiles are known to respond to the calls of birds. But there is a suggestion based on this midrash that there are similar reasons for positing that tzefardea refers to the crocodile.[5] There is an account by Herodotus, who visited Egypt in 459 B.C.E., of a small bird picking food from the teeth of a gaping crocodile. It has been suggested that this refers to the Egyptian plover, Pluvianus aegyptius, which has since also earned the name of “crocodile plover.” It is said that while the crocodile rests with its mouth open, these intelligent birds peck at the crocodile’s teeth in search of parasites. The crocodile makes no attempt to eat the bird and is apparently aware of its benefits. The bird is extremely cautious and gives a call when fleeing from danger, thus also warning the crocodile. Perhaps the tzefardea is the crocodile, named after its symbiotic partner, the intelligent bird that cleans it and warns it of danger.

A problem with this charming explanation is that the described phenomenon may not actually be true. The picture above is a digital reconstruction! Whether such a mutual relationship exists is hard to determine; in the zoological literature, few apart from Herodotus are actually recorded as having seen it.[6] One ornithologist claims that “…no reliable observer since then has seen [it] acting as a crocodile toothpick... The myth has been perpetuated in the literature and needs finally to be laid to rest, unless contrary proof can be found.”[7] On the other hand, Israel’s legendary crocodile hunter Ofer Kobi, who spent decades hunting and farming crocodiles in Africa, informed me that he has observed it.[8] If it does exist, it is rare, and seems more likely to be opportunistic rather than symbiotic.

In conclusion, while there are those who have explained the tzefardea of Egypt to refer to the crocodile, its usage in Midrashic sources and its etymology indicate that the frog is the more likely contender, as several of the commentaries conclude. Some suggest that the name tzefardea refers to amphibious herptiles in general, and could thereby include both frogs and crocodiles. This is the explanation given by the Netziv, who states that whereas most of Egypt was plagued only by frogs, Pharaoh and his entourage were attacked by crocodiles.[9]

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[1] Margaliyot edition, pp. 121-122; originally from Mishnat R. Eliezer, p. 354.
[2] Cited in Torah Sheleimah, Shemos 8:16.
[3] Rabbi Yaakov Kamenetsky, Emes LeYaakov, Shemos 7:27.
[4] A collection of manuscripts cited in Torah Sheleimah 7:108. This explanation is also given by Maharil, cited in B’Shmi U’lekavodi Berasiv, tzefardea.
[5] Prof. Daniel Sperber, “The Frog was a Crocodile,” Bar-Ilan University’s Parashat Hashavua Study Center, Parashat VaEra 5759/1999.
[6] “Despite being corroborated by two eminent German ornithologists in the 19th and 20th centuries, this alleged behavior has never been properly authenticated.” Richford, Andrew S., and Christopher J. Mead, “Pratincoles and Coursers,” in Christopher Perrins (Ed.). Firefly Encyclopedia of Birds (Firefly Books 2003) pp. 252–253.
[7] Maclean, G. L., “Family Glareolidae (Coursers and Pratincoles)” in del Hoyo, J., Elliott, A., & Sargatal, J., eds. Handbook of the Birds of the World (Barcelona: Lynx Edicions 1996) vol. 3 pp. 364-383.
[8] Personal conversation at the Crocoloco ranch, September 2008. For further information on Kobi, whose amazing ranches I visited in Kenya and Israel, see
[9] See HaEmek Davar, Shemos 7:28-29 for his ingenious method of deriving this from the verses.

Monday, January 19, 2009

Letter from a Reader

Rabbi Slifkin,

I read your book "Mysterious Creatures" with great intrigue. However, I was greatly disappointed by your conclusion regarding the category you use to introduce the theme of the book. Were you to have taken the time or effort to visit Eretz Yisroel before drawing your conclusions you might have seen for yourself what animals are actually native to the land before spewing your apikorsus. I am attaching a photo of creatures that I have encountered in many parks and open areas around the country, which are arguably certain to be the adnei ha-sadeh described by Chazal (albeit that they may have become domesticated to some degree over the millennia, as I have witnessed adults and children playing with and around these creatures without ever being attacked and apparently with no fear of such an incident).


M. J.
Jerusalem, Israel

Monday, January 12, 2009

Playing Possum

This passage from the Zohar Chadash describes a monkey that plays possum. But there aren't any possums in the Old World. If anyone has any ideas as to which species it is referring to, I would appreciate it!

זהר חדש פרשת תרומה מאמר נפילת אפים
מ"ט. בגין דנפילה דא, דאתמסר בר נש למותא, אצטריך לכוונא רעותיה, ולמעבד נחת רוח לההוא סטרא דשרייא ביה מותא, כמה דעביד קוף בחרבות ובהרים, אחזי גרמיה דמית, ואתחזי דמית קמי חיותא חדא דדחיל מינה. כיון דההיא חיוותא קריב לגביה, וחשיב לקטלא ליה, ולנשכא ליה, חמא ליה נפיל לארעא כמת, וחשיב דאיהו מת, כדין תב לאחורא, ולא מקטרג ליה. ועל דא אסתלקו אלין ב' אתוון, דלא ידע בהו בר קב"ה דלחודוי:

(Thanks to Rav Moshe Tzuriel, shlita, for the reference)

Wednesday, January 7, 2009

Still nothing to do with animals

Today, everyone is talking about the IDF bombing the UN school. The global media is reporting how "Israel claims" that the school was being used for mortar attacks against Israel. This spin makes it sound like this claim is dubious; but in fact, there is incontrovertible video evidence here:

Here is an excellent IDF video that gives an overview of the entire situation:

It's good to see that Israel is finally learning how to fight a PR war, even if the odds are overwhelmingly against us in that department.