Nedarim 15a ~ How Long Can You Go Without Sleep?

נדרים טו א

והא"ר יוחנן שבועה שלא אישן שלשה ימים מלקין אותו וישן לאלתר

...Rabbi Yochanan said "An oath that I will not sleep for three days" - we lash him [since he took an oath in vain] and he may sleep immediately...(Nedarim 15a)

How long can you go without sleep? If you are like me, staying awake for just one night can be very challenging.  I worked my share of night shifts in the emergency department for over fifteen years (amounting to hundreds of overnight shifts) but it never got any easier with time. We all push ourselves when we need to, but is there a physiological limit to the amount of time that you can stay awake?

The World Record for Staying Awake

The world record for staying awake is an amazing eleven days. Eleven days – that’s 264 hours (and 24 minutes to be precise) without sleep. It was set in 1965 by Randy Gardner, who was then seventeen years old. Gardner seems to have suffered little if any harm by his marathon period of sleep deprivation. But don’t try and beat the record. The Guinness Book of Records no longer has an entry for staying awake – because it is considered too dangerous an ordeal to undertake. (You can hear a review of sleep deprivation stunts in general and a wonderful interview with Gardner himself here.)

The Health Risks of Sleep Deprivation

A 1970 study of four volunteers who stayed awake for 205 hours (that’s eight and a half days!) noted some differences in how the subjects slept once they were allowed to do so, but follow-up testing of the group conducted 6-9 months after the sleep deprivation showed that their sleep patterns were similar to the pre-deprivation recordings.

Although Randy Gardner and these four volunteers seem to have suffered no long-term health consequences of staying awake for over a week, scientists have long noted that sleep deprivation is rather bad for the body. Or to be more precise, the bodies of unfortunate laboratory rats who are not allowed to sleep. In these animals, prolonged sleep deprivation causes the immune system to malfunction. This results in infection and eventual lethal septicemia. The physiologist who kept these rats awake noted that there are “far-reaching physical implications resulting from alterations in immune status [which] may explain why sleep deprivation effects are risk factors for disease and yet are not well defined or specifically localized.” In other words, sleep deprivation makes rats really sick, but we don’t know how, or why…

One possible explanation was suggested in a 2013 by a group from the University of Rochester Medical Center. They demonstrated that during sleep, the space between the cells of the brain (the interstitial space) increased by up to 60%, allowing toxic metabolites to be cleared. This raises the question of whether the brain sleeps in order to expel these toxic chemicals, or rather it is the chemicals themselves that drive the brain to switch into a sleep state.

The extracellular (interstitial) space in the cortex of the mouse brain, through which cerebral spinal fluid moves, increases from 14% in the awake animal to 23% in the sleeping animal, an increase that allows the faster clearance of metabolic waste products and toxins. From Suzana Herculano-Houzel. Sleep it out. Science 2013: 342; 316

Not having any sleep is bad for your health - but so too is going without enough sleep. Chronic restriction of sleep to six hours or less per night can produce cognitive performance deficits equivalent to up to two nights of total sleep deprivation. So be sure to get a full night's rest.

How long did the Vilna Gaon stay awake?

In his recent book on the Vilna Gaon, Eli Stern reviewed an episode in which the Gaon (d. 1797) was jailed on charges of kidnapping. (It’s a long story, but the Vilna Gaon was involved in the kidnapping of a young Jewish man who had converted to Christianity.) This episode occurred in January 1788, after which the Gaon was arrested and held for over a month.  The case was later tried, and on September 15, 1789 (sic) the Gaon of Vilna (together with others involved in the kidnapping) was sentenced to twelve weeks in jail.  Although it is unclear how long he was imprisoned, he was there over Sukkot, and the Lithuanian authorities were hardly in the practice of providing imprisoned Jews with a sukkah.  But since one is not permitted to sleep outside of the sukkah, what was the Gaon to do?  Simple.  He’d stay awake, and by doing so he would not transgress the prohibition of sleeping outside the sukkah.  Here’s how the episode is described in the work Tosefet Ma’aseh Rav published in 1892. 

Our Leader, teacher and Rabbi may he rest in peace, when he was imprisoned on Sukkot, tried with all his strength, and walked from one place to another, and held his eyelids open, and made an extraordinary effort not to sleep outside the sukkah – not even a brief nap – until the authorities released him to a sukkah.

We don’t know for how long the sixty-nine year-old Elijah stayed awake, but any suggestion that he was awake for the entire holiday of Sukkot seems to be far fetched (though as we have seen, not entirely impossible).

Hard, But Not Impossible

In today’s daf, Rabbi Yochanan ruled that since it impossible to stay awake for more than three days, any vow to do so is considered to have been a vow made in vain – and punishment follows swiftly.  Here is how the ArtScroll Talmud explains this ruling, (based on the explanation of the Ran).

Since it is impossible for a person to go without sleep for three days, the man has uttered a vain oath. Hence, he receives lashes for violating the prohibition (Exodus 20:7): לא תשא את שם ה׳ אלוקיך לשוה, You shall not take the Name of Hashem, your God, in vain. And since the oath -being impossible to fulfill -has no validity, he is not bound by it at all and may sleep immediately.

We have seen however, that while it’s not a good idea to do so on any kind of regular basis, it is certainly possible to stay up for longer than three days. (Back in the 1970s, some volunteers would even do so for as little as $100). Maimonides codified this law and also assume that it is impossible to stay awake for three consecutive days. 

רמב"ם הלכות שבועות פרק ה הלכה כ

נשבע שלא יישן שלשת ימים, או שלא יאכל כלום שבעת ימים וכיוצא בזה שהיא שבועת שוא, אין אומרין יעור זה עד שיצטער ויצום עד שיצטער ולא יהיה בו כח לסבול ואח"כ יאכל או יישן אלא מלקין אותו מיד משום שבועת שוא ויישן ויאכל בכל עת שירצה

Based on what we've reviewed, Rabbi Yochanan was incorrect when he stated that it was impossible to stay awake for three days. It's certainly not impossible, but that hardly means it's a good idea to try. 

“Sleep deprivation reduces learning, impairs performance in cognitive tests, prolongs reaction time, and is a common cause of seizures. In the most extreme case, continuous sleep deprivation kills rodents and flies within a period of days to weeks. In humans, fatal familial or sporadic insomnia is a progressively worsening state of sleeplessness that leads to dementia and death within months or years. ”

— Lulu Xie et al. Sleep Drives Metabolite Clearance from the Adult Brain. Science 2013. 342.317

This may explain the teaching of Rabbi Chaninah ben Chachina'i in Masechet Avot  (3:4) who taught that one who stays awake at night "will forfeit with his life."  Now that's a warning to heed.

רבי חנינא בן חכינאי אומר הנעור בלילה ... הרי זה מתחייב בנפשו 

Talmudology Redux ~ Could the Vilna Gaon Have Stayed Awake Over Sukkot?

The Vilna Gaon, (lit. The Genius of Vilna) lived from 1720-1797, and next week, the 19th of Tishrei, is the Hebrew anniversary of his death. He was one of the leading talmudic and halakhic authorities of his time. His works are widely studied to this day, and his legal opinions are often cited. Today’s question is: did the Vilna Gaon stay awake for several consecutive days one Sukkot? Here is the background:

The Vilna Gaon.

In January 1788 the Vilna Gaon was involved in the kidnapping of a young Jewish man who had converted to Christianity. For his role in the kidnapping Rabbi Eliyahu (the given name of the Gaon) was arrested and held for over a month.  The case was later tried, and on September 15, 1789 (sic) the Gaon of Vilna, together with others involved in the kidnapping, was sentenced to twelve weeks in jail.  Although it is unclear how long he was imprisoned, he was there over Sukkot, and the Lithuanian authorities were hardly in the practice of providing imprisoned Jews with a sukkah.  But since one is not permitted to sleep outside of the sukkah, what was the Gaon to do?  Simple.  He’d stay awake, and by doing so he would not transgress the prohibition of sleeping outside the sukkah.  Here’s how the episode is described in the work Tosefet Ma’aseh Rav published in 1892. 

Our Leader, teacher and Rabbi may he rest in peace, when he was imprisoned on Sukkot, tried with all his strength, and walked from one place to another, and held his eyelids open, and made an extraordinary effort not to sleep outside the sukkah – not even a brief nap – until the authorities released him to a sukkah.

We don’t know for how many nights the sixty-nine year-old Rabbi Eliyahu stayed awake, but is such a claim even plausible? As it turns out, it is.

The World Record for Staying Awake

The world record for staying awake is an amazing eleven days. Eleven days – that’s 264 hours (and 24 minutes to be precise) without sleep. It was set in 1965 by Randy Gardner, who was then seventeen years old. Gardner seems to have suffered little if any harm by his marathon period of sleep deprivation. But don’t try and beat the record. The Guinness Book of Records no longer has an entry for staying awake – because it is considered too dangerous an ordeal to undertake. (You can hear a review of sleep deprivation stunts in general and a wonderful interview with Gardner himself here.)

The Health Risks of Sleep Deprivation

What are the health risks of prolonged sleep deprivation? A 1970 study of four volunteers who stayed awake for 205 hours (that’s eight and a half days!) noted some differences in how the subjects slept once they were allowed to do so, but follow-up testing of the group conducted 6-9 months after the sleep deprivation showed that their sleep patterns were similar to the pre-deprivation recordings.

“Sleep deprivation reduces learning, impairs performance in cognitive tests, prolongs reaction time, and is a common cause of seizures. In the most extreme case, continuous sleep deprivation kills rodents and flies within a period of days to weeks. In humans, fatal familial or sporadic insomnia is a progressively worsening state of sleeplessness that leads to dementia and death within months or years. ”

— Lulu Xie et al. Sleep Drives Metabolite Clearance from the Adult Brain. Science 2013. 342.317

Although Randy Gardner and these four volunteers seem to have suffered no long-term health consequences of staying awake for over a week, scientists have long noted that sleep deprivation is rather bad for the body. Or to be more precise, the bodies of unfortunate laboratory rats who are not allowed to sleep. In these animals, prolonged sleep deprivation causes the immune system to malfunction. This results in infection and eventual lethal septicemia. The physiologist who kept these rats awake noted that there are “far-reaching physical implications resulting from alterations in immune status [which] may explain why sleep deprivation effects are risk factors for disease and yet are not well defined or specifically localized.” In other words, sleep deprivation makes rats really sick, but we don’t know how, or why…

One possible explanation was suggested in 2013 by a group from the University of Rochester Medical Center. They demonstrated that during sleep, the space between the cells of the brain (the interstitial space) increased by up to 60%, allowing toxic metabolites to be cleared. This raises the question of whether the brain sleeps in order to expel these toxic chemicals, or rather it is the chemicals themselves that drive the brain to switch into a sleep state.

The extracellular (interstitial) space in the cortex of the mouse brain, through which cerebral spinal fluid moves, increases from 14% in the awake animal to 23% in the sleeping animal, an increase that allows the faster clearance of metabolic waste products and toxins. From Suzana Herculano-Houzel. Sleep it out. Science 2013: 342; 316

Not having any sleep is bad for your health - but so too is going without enough sleep. Chronic restriction of sleep to six hours or less per night can produce cognitive performance deficits equivalent to up to two nights of total sleep deprivation. So be sure to get a full night's rest.

Hard, But Not Impossible

The world record set by Randy Gardner has implications for a talmudic decision. In the tractate Shavuot (26b) Rabbi Yochanan ruled that since it was impossible to stay awake for more than three days, any vow to do so is considered to have been a vow made in vain – and punishment follows swiftly.  Here is how the ArtScroll Talmud explains this ruling, (based on the explanation of the Ran).

Since it is impossible for a person to go without sleep for three days, the man has uttered a vain oath. Hence, he receives lashes for violating the prohibition (Exodus 20:7): לא תשא את שם ה׳ אלוקיך לשוה, You shall not take the Name of Hashem, your God, in vain. And since the oath -being impossible to fulfill -has no validity, he is not bound by it at all and may sleep immediately.

Maimonides codified this law and also assumed that it is impossible to stay awake for three consecutive days. 

רמב"ם הלכות שבועות פרק ה הלכה כ

נשבע שלא יישן שלשת ימים, או שלא יאכל כלום שבעת ימים וכיוצא בזה שהיא שבועת שוא, אין אומרין יעור זה עד שיצטער ויצום עד שיצטער ולא יהיה בו כח לסבול ואח"כ יאכל או יישן אלא מלקין אותו מיד משום שבועת שוא ויישן ויאכל בכל עת שירצה

If a person swore that he would not sleep for three days, or would not eat anything for seven days, or something similar, this is considered a false oath. We do not tell the person to stay awake until it is impossible to do so, or fast for as long as possible until the discomfort is too great to bear, and then allow him to eat or sleep. Rather he is punished with lashes immediately for making a false oath, and is then allowed to sleep or eat as much as he wants…

Based on Randy Gardner’s feat, Rabbi Yochanan was incorrect when he ruled that it was impossible to stay awake for three days. It's certainly not impossible, but that hardly means it's a good idea to try. 

It also means that the story of the Gaon of Vilna’s sleepless nights in that cold prison might indeed have occurred. Still it is best not to disrupt your usual sleep patterns. Perhaps that is why Rabbi Chaninah ben Chachina'i in Masechet Avot  (3:4) taught that one who stays awake at night "will forfeit with his life."  Now that's a warning to heed.

רבי חנינא בן חכינאי אומר הנעור בלילה ... הרי זה מתחייב בנפשו

HAPPY SUKKOT FROM TALMUDOLOGY

From the Talmudology Archives: The Vilna Gaon’s Sleepless Nights over Sukkot

Tonight is the start of the joyous festival of Sukkot (Tabernacles) in which we remember our time in the wilderness by conducting all of our daily activities outside, in makeshift booths. In honor of Sukkot, here is a Talmudology encore presentation that involves vows, sleep, and the Vilna Gaon’s refusal to sleep in prison over Sukkot.

Let’s start with the Talmud in Nedarim, the tractate that deals with vows.

נדרים טו א

והא"ר יוחנן שבועה שלא אישן שלשה ימים מלקין אותו וישן לאלתר

...Rabbi Yochanan said "An oath that I will not sleep for three days" - we lash him [since he took an oath in vain] and he may sleep immediately...(Nedarim 15a)

How long can you go without sleep? If you are like me, staying awake for just one night can be very challenging.  I worked my share of night shifts in the emergency department for over fifteen years (amounting to hundreds of overnight shifts) but it never got any easier with time. We all push ourselves when we need to, but is there a physiological limit to the amount of time that you can stay awake?

The World Record for Staying Awake

The world record for staying awake is an amazing eleven days. Eleven days – that’s 264 hours (and 24 minutes to be precise) without sleep. It was set in 1965 by Randy Gardner, who was then seventeen years old. Gardner seems to have suffered little if any harm by his marathon period of sleep deprivation. But don’t try and beat the record. The Guinness Book of Records no longer has an entry for staying awake – because it is considered too dangerous an ordeal to undertake. (You can hear a review of sleep deprivation stunts in general and a wonderful interview with Gardner himself here.)

The Health Risks of Sleep Deprivation

A 1970 study of four volunteers who stayed awake for 205 hours (that’s eight and a half days!) noted some differences in how the subjects slept once they were allowed to do so, but follow-up testing of the group conducted 6-9 months after the sleep deprivation showed that their sleep patterns were similar to the pre-deprivation recordings.

Although Randy Gardner and these four volunteers seem to have suffered no long-term health consequences of staying awake for over a week, scientists have long noted that sleep deprivation is rather bad for the body. Or to be more precise, the bodies of unfortunate laboratory rats who are not allowed to sleep. In these animals, prolonged sleep deprivation causes the immune system to malfunction. This results in infection and eventual lethal septicemia. The physiologist who kept these rats awake noted that there are “far-reaching physical implications resulting from alterations in immune status [which] may explain why sleep deprivation effects are risk factors for disease and yet are not well defined or specifically localized.” In other words, sleep deprivation makes rats really sick, but we don’t know how, or why…

One possible explanation was suggested in a 2013 by a group from the University of Rochester Medical Center. They demonstrated that during sleep, the space between the cells of the brain (the interstitial space) increased by up to 60%, allowing toxic metabolites to be cleared. This raises the question of whether the brain sleeps in order to expel these toxic chemicals, or rather it is the chemicals themselves that drive the brain to switch into a sleep state.

The extracellular (interstitial) space in the cortex of the mouse brain, through which cerebral spinal fluid moves, increases from 14% in the awake animal to 23% in the sleeping animal, an increase that allows the faster clearance of metabolic waste products and toxins. From Suzana Herculano-Houzel. Sleep it out. Science 2013: 342; 316

Not having any sleep is bad for your health - but so too is going without enough sleep. Chronic restriction of sleep to six hours or less per night can produce cognitive performance deficits equivalent to up to two nights of total sleep deprivation. So be sure to get a full night's rest.

How long did the Vilna Gaon stay awake?

And now, with this background, we can turn to Sukkot. In his book on the Vilna Gaon, Eli Stern reviewed an episode in which the Gaon (d. 1797) was jailed on charges of kidnapping. (It’s a long story, but the Vilna Gaon was involved in the kidnapping of a young Jewish man who had converted to Christianity.) This episode occurred in January 1788, after which the Gaon was arrested and held for over a month.  The case was later tried, and on September 15, 1789 (sic) the Gaon of Vilna (together with others involved in the kidnapping) was sentenced to twelve weeks in jail.  Although it is unclear how long he was imprisoned, he was there over Sukkot, and the Lithuanian authorities were hardly in the practice of providing imprisoned Jews with a sukkah.  But since one is not permitted to sleep outside of the sukkah, what was the Gaon to do?  Simple.  He’d stay awake, and by doing so he would not transgress the prohibition of sleeping outside the sukkah.  Here’s how the episode is described in the work Tosefet Ma’aseh Rav published in 1892. 

Our Leader, teacher and Rabbi may he rest in peace, when he was imprisoned on Sukkot, tried with all his strength, and walked from one place to another, and held his eyelids open, and made an extraordinary effort not to sleep outside the sukkah – not even a brief nap – until the authorities released him to a sukkah.

We don’t know for how long the sixty-nine year-old Elijah stayed awake, but any suggestion that he was awake for the entire holiday of Sukkot seems to be far fetched (though as we have seen, not entirely impossible).

Hard, But Not Impossible

As we read in the Talmud, Rabbi Yochanan ruled that since it impossible to stay awake for more than three days, any vow to do so is considered to have been a vow made in vain – and punishment follows swiftly.  Here is how the ArtScroll Talmud explains this ruling, (based on the explanation of the Ran).

Since it is impossible for a person to go without sleep for three days, the man has uttered a vain oath. Hence, he receives lashes for violating the prohibition (Exodus 20:7): לא תשא את שם ה׳ אלוקיך לשוא, You shall not take the Name of Hashem, your God, in vain. And since the oath -being impossible to fulfill -has no validity, he is not bound by it at all and may sleep immediately.

We have seen however, that while it’s not a good idea to do so on any kind of regular basis, it is certainly possible to stay up for longer than three days. (Back in the 1970s, some volunteers would even do so for as little as $100). Maimonides codified this law and also assume that it is impossible to stay awake for three consecutive days. 

רמב"ם הלכות שבועות פרק ה הלכה כ

נשבע שלא יישן שלשת ימים, או שלא יאכל כלום שבעת ימים וכיוצא בזה שהיא שבועת שוא, אין אומרין יעור זה עד שיצטער ויצום עד שיצטער ולא יהיה בו כח לסבול ואח"כ יאכל או יישן אלא מלקין אותו מיד משום שבועת שוא ויישן ויאכל בכל עת שירצה

Based on what we've reviewed, Rabbi Yochanan was incorrect when he stated that it was impossible to stay awake for three days. It's certainly not impossible, but that hardly means it's a good idea to try. 

“Sleep deprivation reduces learning, impairs performance in cognitive tests, prolongs reaction time, and is a common cause of seizures. In the most extreme case, continuous sleep deprivation kills rodents and flies within a period of days to weeks. In humans, fatal familial or sporadic insomnia is a progressively worsening state of sleeplessness that leads to dementia and death within months or years. ”

— Lulu Xie et al. Sleep Drives Metabolite Clearance from the Adult Brain. Science 2013. 342.317

This may explain the teaching of Rabbi Chaninah ben Chachina'i in Masechet Avot  (3:4) who taught that one who stays awake at night "will forfeit with his life."  Now that's a warning to heed.

רבי חנינא בן חכינאי אומר הנעור בלילה ... הרי זה מתחייב בנפשו

Happy Sukkot from Talmudology 

Sukkah 26b ~ How do Horses Sleep?

In a discussion about various aspects of sleep, the Talmud today discusses equine sleeping patterns:

סוכה כו, ב

אָמַר רַב: אָסוּר לָאָדָם לִישַׁן בַּיּוֹם יוֹתֵר מִשֵּׁינַת הַסּוּס. וְכַמָּה שֵׁינַת הַסּוּס — שִׁיתִּין נִשְׁמֵי

Rav said: It is prohibited for a person to sleep during the day longer than the duration of the sleep of a horse. [One who sleeps for longer is derelict in the study of Torah.] And how long is the duration of the sleep of a horse? It is sixty breaths long.

Elsewhere, Rabbi Zeira extols the virtues of sleeping like a horse at night. It is what King David did.

ברכות ג, ב

רַבִּי זֵירָא אָמַר: עַד חֲצוֹת לַיְלָה הָיָה מִתְנַמְנֵם כְּסוּס, מִכָּאן וְאֵילָךְ הָיָה מִתְגַּבֵּר כַּאֲרִי. רַב אָשֵׁי אָמַר: עַד חֲצוֹת לַיְלָה הָיָה עוֹסֵק בְּדִבְרֵי תוֹרָה, מִכָּאן וְאֵילָךְ בְּשִׁירוֹת וְתִשְׁבָּחוֹת

Rabbi Zeira said: Until midnight, David would doze like a horse, [as a horse dozes, but never sleeps deeply]. From midnight on, he would gain the strength of a lion. Rav Ashi said: Until midnight, he would study Torah, as it is written: “I rose with the neshef and cried, I hoped for Your word,” and from midnight on, he would engage in songs and praise, as it is written: “At midnight I rise to give thanks.”

To which the medieval French commentator Rashi add this observation

רשי שם

מתנמנם כסוס – עוסק בתורה כשהוא מתנמנם. כסוס הזה שאינו נרדם לעולם אלא מתנמנם ונעור תמיד

The horse never sleeps. Instead it naps and then always wakes

Most of us don’t keep horses, and so cannot judge what exactly is going on. So today, for all you non-horse owning folk, Talmudology asks: How do horses sleep?

An Introduction to Equine Sleep

The thing is, for a long time the way horses sleep has been a bit of a mystery. Then we developed all kinds of clever recording devices like EEGs that allowed us a harmless peek inside the brain of the sleeping horse. In his review of sleep patterns in the horse published in the September 1990 edition of Equine Practice, the veterinarian Theodore Belling wrote that “usually a horse falls asleep while standing and is in a drowsing state. The lids are partially open and the head hangs down at a medium level.” As the horse slips into a deep sleep known by its electric patterns as Slow Wave Sleep its head gradually gets lower and lower until the horse decides all is good, and while remaining asleep, actually lies down. Like this:

Once in this position, known technically as lateral recumbency, “the horse sleeps in short cycles or episodes, rather than one continuous interval, as it does in humans.” There is a short period of slow wave or deep sleep, usually lasting about five minutes, followed by a five minute paradoxical sleep, a stage also known as the rapid eye movement (REM) period. (When we enter the REM period, that’s when we dream.) The horse then enters another five minute slow wave cycle, and then wakes up. It slept for a total of about 15 minutes and will stay awake for another 45 minutes or so, before doing the whole thing again. The total sleep time of the horse is somewhere between 2.5-5 hours per night. Oh, and if you drive past a field with a horse sleeping in the day, there is nothing wrong. Some horses like to do that.

“Horses are neither diurnal nor nocturnal but have intermittent periods of rest and sleep during the day with most of their sleep happening at night, particularly when confined in a stall. Certain relaxing situations, such as grooming may even lead to episodes of sleep in normal horses. This is, perhaps, the equine equivalent of sleeping in class.”

— Aleman M. et al. Sleep and Sleep Disorders in Horses. AAEP Proceedings 2008. 54: 180-185.

EEG recordings from a pony. From From Andre Dellaire. Rest Behavior. Veterinary Clinics of North America Equine Practice 1986:2 595.

This basic outline has been confirmed in a number of other studies. A 2008 paper in Proceedings of the American Association of Equine Practitioners noted that “horses require far less sleep than most humans, averaging a total of only 3–5 h/day” though foals, being baby horses, sleep more per day than do the adults.

And so it turns out that the horse sleeps a lot less than might be expected. Here for example are the times spend awake or asleep in a few different species. The horse is the most wakeful of them all.

Time Spent (Hours) in Wakefulness and Sleep States per Day in Domesticated Species
Animal	Awake	Drowsy	Deep Sleep	Dreaming	Total Sleep Time
Cat	10	2	8.5	3.5	12
Dog	11	4	6.5	2.5	9
Swine	11	4	6.5	2.5	8
Sheep	16	4	3	<1	4
Horse	18	2	3	<1	4
From Andre Dellaire. Rest Behavior. Veterinary Clinics of North America Equine Practice 1986:2 592.

The Rav and Rabbi Zeira clearly knew about horses. The horse does indeed only take short naps, and these rabbis extol us to do the same. These are examples of a careful observation the natural world, from where many talmudic statements are derived. This might seem obvious, but it is not. As we have noted in the past, the rabbis didn’t always demonstrate an accurate understanding of the animal kingdom. Abayye thought that wild geese have a scrotum. But they don’t. And Rabbi Shimon ben Chalfta thought that ant colonies have kings. But they don’t. At the same time the rabbis knew much about the world that we had to rediscover. Like sound traveling further at night, or the periodicity of ‘Halley’s’ Comet.

So the next time you see horses lying in a field, or even dozing while standing, don’t disturb them. They are doing what comes naturally. Instead, do what the rabbis did. Observe, and ask: what can I learn from this moment?

NEXT TIME ON TALMUDOLOGY:

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