In physics, a frame of reference is a mathematical point of view (a coordinate system) based on an origin. In the case of motion, an object is defined to be moving if its observed location changes relative to a frame of reference. If I carry an object, relative to me it is not moving, but relative to an observer (say, on the earth) it is moving. There is an interesting gemara in Meseches Shabbos 5b concerning how the Sages dealt with physics concept in the practical applications of the laws of movement with a given domain on Shabbos:
(translation from Sefaria.com The William Davidson digital edition of Koren Noe Talmud Bavli)
The law concerns lifting an object on Shabbos with the possible intent of carrying it from a private to a public domain (which is halachically forbidden). Let us look at Rava’s dilemma from the standpoint of physics. Why is a nut floating on the surface of water not considered its placement? Perhaps Rava is considering the fact that the “natural placement” for the nut would be in a tree(fixed) or on the ground (again fixed). This seems to be an Aristotelian viewpoint. Rava next considers a nut in a vessel. The vessel moves along the water (as it floats with the nut inside) and the question concerns lifting the nut out of the vessel. From the frame of reference of the vessel, the nut is at rest. From the frame of reference of the observer on the river bank, both the vessel and the nut are moving. If Rava were to walk along with the vessel as it moved, it would again appear to be at rest relative to his frame of reference. In the end the dilemma is left unsolved.
Let us consider this “sugya” (portion of a gemara covering a specific topic) from a deeper level. What do we mean by placement, vessel, movement, and lifting from a spiritual standpoint. Consider each one of us. Some of you (like me) may have often wondered about why we are placed on earth? Why was I born at the time and place that I was?
While difficult to answer, we can understand that from a Jewish perspective we were placed on earth to help make it a better place (tikun olam) using the Torah and mitzvot as our guide. Our spiritual “movement”, like the angels in constant motion on the sulam of Yaakov (Jacob’s ladder), our connection to Hashem changes day by day. Sometimes we feel close to Hashem’s presence, and sometime we do not. The motion seems relative to our external environment (the external frame of reference) based on our human interactions (the nut and vessel observed from the outside). But deep within us, we know we are grounded to the Land of Israel and to the Jewish People. Like the nut within the vessel, we can look inward to find our spiritual center while at the same time recognizing that we live within the physical world and must interact within it.
Thus, Rava’s dilemma is also a spiritual one: Do we regard ourselves as isolated individuals existing just within ourselves and for ourselves, or do we live to interact within the greater world and strive to make it a better place for all. We must become the vessel (keili)that carries the spiritual Godliness. The nut, a product that falls from a tree, is a useful metaphor the practical aspects of Torah (which is likened to a tree; recall the saying “It is a tree of life, for those who hold fast to it”; “etz chayim hi, l’machazikim bo” sung at the end of the Torah service on Shabbos. Both fruits and nuts can come from trees. Fruits, represent deeper Torah wisdom (the flavor stays with you). Nuts contain proteins for strength while fruits contain both water and sugar (to nourish life and energy). Both are vital for physical and spiritual life (study and action). Let us be the vessel to carry the Torah. Which way will you choose? The question stands unsolved and left up to you!