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Shabbat Parashat Lech Lecha 5772

Ask the Rabbi: Use of Kinetic Watches on Shabbat

Rav Daniel Mann

Question:  Is it permitted to wear a kinetic watch on Shabbat, which is powered by the periodic natural movement of the hand rather than by a battery or winding by hand?


Answer:  Let us start our discussion with old clocks, which were operated in a manner that is halachically equivalent to winding watches. The Shulchan Aruch (Orach Chayim 338:3) says that one can set such a clock before Shabbat even though it chimes loudly on the hour. Acharonim explain that people will assume he set the matter into motion before Shabbat (and thus the special marit ayin of noises does not apply – Mishna Berura 338:14). There is a major discussion among poskim whether pulling the chains to begin the operation of such clocks is considered creating or fixing a utensil (Chayei Adam 44:19) or whether this is just considered the way of using an existing utensil (Panim Meirot II, 123). According to the former, it is forbidden, very possibly on the Torah level, to set the clock into operation on Shabbat, and this is the consensus.

The next question is whether one can wind a watch that is already working to keep it operational longer than it otherwise would be. The Ktav Sofer (OC 55) compares this to cutting off part of a candle in a way that will make it go out earlier. A simple watch, though, seems to be significantly more lenient in that nothing problematic is happening later, and the question is whether making a change to keep an already operating instrument working longer is equivalent to creating a working instrument. Indeed, the Da’at Torah (on the Shulchan Aruch, ibid.) champions the idea that just extending efficacy is not forbidden. The Ktav Sofer also raises the possible distinction between clocks that chime for more hours than they otherwise would have and cases where the gears and handles just move longer. In any case, the minhag developed to not allow winding to continue the existing operation even if there is no chime, unless there are mitigating or extenuating circumstances (see Mishna Berura 338:15; Sha’ar Hatziyun 338:17; Shemirat Shabbat K’hilchata 28:19-21).

More recent poskim have dealt with the advent of self-winding watches, which wind by one’s movements. In this case, the consensus has been that it is permitted while the watch is still working (see Shemirat Shabbat K’hilchata 28:28). Here the aforementioned case for leniency regarding watches that wind is bolstered by the fact that the person is not doing a discernable or intentional act of winding but that it is happening as a certain side result of his activities (p’sik reishei). Additionally, regarding this relatively new case, a minhag to be stringent has not developed.

The recent invention of kinetic watches is slightly different from self-winding watches. The mechanism of kinetic watches is based on a quartz system, which is normally operated by battery. In this case, instead of a battery, movement generates the small amount of electricity that the watch needs, and the watch stores the energy for anywhere from days to months. The relatively new question of a mini, mechanical electricity recharger is not a simple one, and we have found rabbis coming out in either direction. However, our feeling, is that such a transfer of energy of movement to electricity to be transferred again to “harmless” mechanical movement, without creating new circuits, is not included in the prohibitions of electricity that the halachic world has assumed since the advent of the use of electricity. (We may reverse our decision if a consensus forms to forbid it.)

The matter is more complicated regarding kinetic watches with digital displays, which use electrically generated forms. However, there are significant reasons for leniency here too. The most important one is that the energy provided on Shabbat is rarely needed for operation on Shabbat, as the charge lasts at least a few days.



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