Michael el Chayil

With out a doubt, the best part of giving a shiur is how much I learn in preparation. (The worst part, but the way, is agonizing and panic in the weeks leading up to giving the shiur making sure I have something to say that is worth the attendees time to hear.) Moreover, I find that while actually giving the shiur, ideas and thoughts that were still a bit murky come into sharp focus. Then there are questions that come up after the shiur. This TftD is in response to one of those questions. So regarding the reason that חנוכה is the name of the holiday that commemorates our victory over the Greeks and the miracle of the one-day-supply-of-oil-that-lasted-eight-whole-days: it's because our enemies stopped bugging us on the 25th of Kislev -- חנו כ''ה/they rested ("parked" according to Google translate) on the 25th. (See Mishna Brura 670, sk 1.) I know that's not what I learned in Sunday school... shocking. But hang on... besides that fact that the commemoration ...

 The " Law of the Excluded Middle " is one of the basic laws of logic. It means that for any proposition A, either "A" or "not A" is true. For example, let's take as our proposition that bumble bees cannot fly. The law of the excluded middle says that either it is true that bumble bees cannot fly (A), or it is true that bumble bees can, indeed, fly (not A); there is no third possibility. That principle is the foundation of many logical proofs, because it is often easier to prove (or disprove) "not A" than "A"; after which one simply invokes the law of excluded middle to claim a victory. Understandably, the strict laws of classical logic do not apply to apply to all situations (as any man who has been married for more than an hour or two can surely testify). It doesn't mean there is anything illogical about the situation, it simply means that the over strict laws of classical logic have been applied incorrectly to the situati...

The title is not entirely accurate, but: (1) if I said "twice removed", I fear many would think כלי שני/second vessel; (2) c'mon... how cool is it to be able to use the word thrice? Besides the opportunity to use the word thrice (thrice, in you include the title and not this one, or just not including this one) in one TftD, I have a more serious reason to write about this. Namely, my rush to incorrectly tell someone that, "Of course the Mishna Brura says you can make tea in a כלי שלישי! It's in that long paragraph where he describes how to make tea on Shabbos." I, in my arrogance did not bother to double check. My friend (still even after this), though, did. Thank goodness. So... the Mishna Brura has a long paragraph (Siman 318, end of s.k. 39) starting by declaring as obvious to the poskim that making tea is a cooking process, for which one would transgress a capital offence if done on purpose and with intention. The Mishna Brura then decries the lax at...

This is yet another reason why you need a rav. A close chaver directed my attention to the third Mishna Brura to siman 672. The Shulchan Aruch there says that if you are really busy/preoccupied and need to light Chanuka candles early, then you can light from פלג המנחה. The Mishna Brura notes that the hour and a quarter is measured in שעות זמניות/hours adjusted for the day length. I looked back to my friend wondering what he wanted so show me. He directed me to look again (Baruch HaShem, my friends are patient with me). Sure... The Mishna Brura notes that פלג המנחה is one and a quarter hours before צאת הכוכבים/night fall and the hours are determined by the length or shortness of the day; that is, שעות זמניות. Wait... backup... before צאת הכוכבים/night fall?! We nearly always means before שקיע/sundown; not צאת הכוכבים/night fall! Right, replied my friend; what do you make of that? The Mishna Brura is not at all shy about mentioning the different ways of calculating...

In parashas תולדות, we are told of one of the most difficult tests for our illustrious patriarch, Yaakov Avinu. Yaakov is the ultimate איש אמת/man of Truth, and he is given the task of subverting his father's plan to give the brachos to the evil Esav. Why Yitzchak Avinu wanted to give the brachos -- which would have been a horrific disaster, and why HaShem wanted him to be put in a position where he needed to be tricked by Yaakov Avinu to do the right thing -- and for which Yitzchak Avinu was very thankful, and how Rivka Imeinu knew that and what to do are all very, very interesting topics. All very, very far outside the scope of this TftD. I want to focus on a single point. When Esav learns of the subterfuge he was devastated; וַיִּצְעַ֣ק צְעָקָ֔ה גְּדֹלָ֥ה וּמָרָ֖ה עַד־מְאֹ֑ד/he howled a very, very great and bitter cry (B'reishis 27:32). (Why it meant so much to him is also outside the scope of this TftD.) The medrash says that Klal Yisrael were punished for causing E...

I have, Baruch Hashem, bli ayin hara, puh-puh-puh, several very bright and adorable grandsons. I have one in particular who has an incredible eye for details. He recently told me that he had a question on Chumash, parshas Lech L'cha; the battle of the four kings vs the five kings. I told him to get a chumash and show me. As he was headed to the Mikra'os HaG'dolos, I redirected him to a regular chumash. (I mean, he's only seven. How complicated could this be?) He showed that in 14:2 and 14:8 the verses tell me that one of the kings was from Bela, which is now called Tzo'ar. Verse 14:3 says that they engaged in the battle in the valley of Siddim, which is the Dead Sea. Verse 14:8 also  mentions that the battle was in the valley of Siddim... but does not mention that the valley of Siddim is the Dead Sea in that second verse. In all innocence, he asked why the new name was repeated for one place but not for the other.  I sent him back for the Mikra'os HaG'dolos....

When I was younger and would express "but if" questions, my father would usually answer, "If a frog had six shooters and a ten gallon hat, then he would be a Texas ranger." As I got older, my "but if" questions got more sophisticated, and my father's response got more colorful. I am going to stick with the frog/Texas ranger response; thank you very much. The truth is, though, that hypothetical situations can be used to reveal insights about real situations. Physicists use thought experiments (the real physicists use "gedanken" experiments; "frummer than thou" permeates all walks of life) to explore the consequences of physical theory. Recently, to my extreme delight, I learned of a situation where the hypothetical is used to drive practical halacha. The pre-setup: We do not daven a regular weekday שמונה עשרה on Shabbos and Yom Tov. This is not  because we have no need of such things as health, livelihood, in-gathering of the exi...

Nearly 30 years ago, when I first encountered Orthodox Judaism as a serious life style choice that threatened to seriously undermine my complacency with my Jewish identity, I approached the anticipated debacle with the many extremely cogent arguments for my point of view based on the Torah itself . I confidently met with the rabbi and was ready to do battle. Then I discovered the תורה שבעל פה/The Oral Torah. That was the first blow to my world view, but I was not out of the fight yet. Then I learned of the Rabbinic injunctions and the מסורה/the careful and meticulous transmission of the entire Torah -- Written with Oral, packaged in Rabbinic wisdom. Sigh... that was the knock out punch and here I am today. In he Maharal's essay on Chanuka, נר מצוה, he explains the necessity and function of Rabbinic injunctions. More than that, the Maharal addresses one of (for me) the most difficult facets of Rabbinic injunctions; חמורים דברי סופרים יותר מדברי תורה/Chazal were often mor...

There is what people think of when the hear the word "work" and there is what the word "work" means in the context of physics. For example, suppose you picked up a bowling ball in the morning, carried it with you all day, then put it down that evening precisely in the place from which you picked it up. You might feel like you've been through the wringer, but -- according to the definition of work in the context of physics -- you have done zero work. While that may sound surprising, it is not difficult to explain why the word "work" is appropriate in both of these contexts. It is , however, outside the context of this TftD. I bring this up, because I'd like to discuss the Torah prohibition of  צער בעלי חיים. Now, if you paste that into Google Translate, you'll get:  Cruelty to animals. Not a bad translation of those words from Modern Hebrew into American English, but not a great rendition of what the Torah prohibition of  צער בעלי חיים really ...

Mathematics is the language that we use to express physical law. As a graduate student in the physics department, therefore, it was important to know a fair amount of mathematics. We (the physics department) and they (the math department) each had a series of classes called "Mathematics for Physicists". I, of course, feeling that taking such a class was beneath my dignity, took the same topics in math classes designed for mathematicians. After all, I reasoned, I'd rather get the fundamentals straight than some watered down elixir. I worked harder in those classes than any of my physics classes. Not that the material was intrinsically more difficult, but that mathematicians just think  differently that physicists. I publicly admit that my filing of a prozbul every seven years before Rosh HaShannah is largely pro forma;  my heart isn't really in it. I mean, after all, I do not own a bank; nor am I someone that anyone would come to for a loan. I think for the same reas...

First, a lesson in modern physics. There are many measurables that we use to characterize a physical object and its motion through space-time. Among these are mass, position, velocity, energy, charge, etc... etc... etc. Among these are groupings known as canonically conjugate variables: location/momentum (mass times velocity), time interval/energy transition, and more. The cool thing that was discovered with the age of modern physics in early 1900s was that the more precisely you measure one member of the pair, the more uncertainty you create in measuring the other member. Suppose, for example, you measure very precisely the position of a proton at one moment. You won't be able to predict where it is the next moment because you created an inherent uncertainty in its momentum (and therefore velocity). The universe just puts hard limits on what it will allow us to know about it. "They" (you know who they are... the same ones who call it dope) say something like that about...