The modern science of thermodynamics (the study of heat and heat transfer) really kicked off in the 19th Century with the desire to make steam engines more powerful and efficient. The groundwork for the study of thermodynamics, however, were lain by Robert Boyle and Robert Hooke in the 17th Century. At the end of the 18th Century, Joseph Black at the University of Glasgow (we really need a blog about the intellectual ferment at the University of Glasgow in the later 18th Century!) developed the concepts of heat capacity and latent heat and our understanding of heat transfer really started to develop scientifically.

The Rabbis of the Talmud did not have these tools to understand the flow of energy that is heat transfer. They used more intuitive concepts – in particular, that as a hot substance is moved from vessel to vessel, it loses heat. However, they focused on the vessel as the agent of change, not the energy inherent in the substance. Therefore, a vessel removed from a fire is more likely to cook than a second vessel into which the contents of the first vessel are poured. In today’s Daf we get much debate about what substances we can pour into what receptacles based on the likelihood that the receiving receptacle will cook or heat past warm the substance being received. We learn about placing water into a kettle, a cup, a bathtub and learn that there are different rules if the water being poured is hot or cold and if the water receiving is hot or cold. In the modern physical world, we understand that the same process of heat transfer is taking place regardless of the direction or the vessel. In the religious, ancient world of the Rabbis, however, the distinctions were crucial.

At the end of today’s Daf, we introduce a new Mishnah and we switch gears. For most of Chapter Three we have discussed the rules of cooking on Shabbat and the closely connected issue of bathing (that is with hot water). For the remainder of Chapter Three, we will discuss Muktzeh. Muktzeh are items that are not typically used on Shabbat, for instance a hammer. If we use a hammer in the normal way, its uses are prohibited on Shabbat. What if we don’t use it in the normal way? Can we use this item in a permissible way even though its normal use would not be permitted?

Our first Mishnah related to Mutkzeh concerns whether on Shabbat we can put a bowl under a lamp to catch dripping oil. We can do this action before Shabbat, but what about on Shabbat? The bowl is not Mutkzeh, but the oil drippings are. They have no use on Shabbat. I want to introduce this Mishnah and the concept of Mutzkeh today. Since this is a new direction for us, I will leave the detailed commentary to the following days.