[Avodah] Fitbit on Shabbos

[Micha Berger via Avodah]

On Fri, Apr 01, 2016 at 06:54:06PM -0400, Akiva Miller via Avodah wrote:
: R' Micha Berger responded:
: > I think those two are different in kind.
: 
: > In the floor mat, a hypothetically visible (really, we should use
: > the more generic sensible, and not just talk about one sense)
: > change occurs. It just happens that situationally, we can't see it.
: 
: Exactly which mAcroscopic change are you referring to, that is visible
: hypothetically, albeit not situationally?

We are comparing two ways of making the door open. If making the door open
is not a halachic problem, then there is no contrast.

I am saying that nothing physical happens to an electric eye or UV sensor
to cause the motor to go on. However, with the mat, one is moving two
metal plates together (or a conductive tape against a plate). Cut away
the rubber, and you would see the circuit close. There is a visible cause
and a visible effect.

Even if part of the causality is only explainable by appeal to the quantum
scale.

(BTW, atoms are mostly vacuum. It's only quantum scale repulsion of
electrons that fully explains why hitting a ball with a bat changes the
course of the ball; why things don't just go through eachother.)

...
: If you are referring to the opening of the door, that's not a melacha. For
: it to be a melacha, we would have to be talking about the motion of the
: electrons, and that's what am taking to be the microscopic thing here. Am I
: missing something here?

It wouldn't be the motion of the electronc, even if they were macroscopic.
You might as well prohibit flushing toilets and rolling marbles down a
ramp, if one inherently prohibites the giving elecrons a chance to use
their potential energy (voltage).

All of the theories about why electricity is assur depend on the
visible effects of the cercuit, or the visible making of a circuit,
not the moving of current itself. (Except of course RSZA, who seems
to be saying electricity is assur because we all decided it was assur,
and thereby created an issur derbbanan even without a Sanhedrin.)

: Perhaps the problem is not that the door opens, but that the motor which
: opens it will get hot if the current stays on for too long a time?

Pesiq reishei delo nicha lei. Also on that list: sparking, unless the
motor's spin rate is based on the frequency of the AC current coming in.
But PRDNL wouldn't help with a deOraisa. (RYE Spektor and ROY permit
it for a derabbanan, the MB only for a double-derabbanan.)

Water meters were mentioned. I posted about PRDNL anhd water meters
in 2012 <http://www.aishdas.org/avodah/vol30/v30n105.shtml#11>.
Click on the subject line and see the thread.

: Here's the attitude about electricity that I grew up with: Rav Moshe
: Feinstein, in Igros Moshe O"C 484, gives 4 reasons not to use a microphone
: on Shabbos. The second of them is that one's voice obviously causes the
: electrical current to fluctuate, and he labels this "chashash issur
: d'Oraisa even without hav'ara, v'yesh l'ayen bazeh tuva l'maaseh." ...

That's OC 4:84.

Who doesn't talk about the invisible, but about electric power. "Vreo'in
zeh bechush", although he means you can hear it from the loudspeaker. I do
not see RMF saying that power that goes into results that in principle
you cannot sense would be assur.

: I would point out that in the very next teshuva (4:85, paragraph 5) he does
: try to explain his safek, and rules that because it is only a safek it can
: be allowed for a choleh or tzorech gadol. Perhaps the tiny size has
: something to do with it, but I am bothered by the fact that in both
: teshuvos he goes out of his way to say "even though there is no hav'arah".
: It sounds to me like if there WAS hav'arah -- i.e., if one did not merely
: speak into the system, but powered it up on Shabbos -- then he would not be
: meikil. But if the heter is based on tiny size, then powering it up should
: also be okay, if there is no visible spark when the on-switch is used.

But another part of the permissibility of speaking in the presence of
someone with a hearing aid is that at times even with the hearing aid,
the user doesn't hear anything, thus ruling out pesiq reishei, reducing
it to davar she'ein miskavein.

The problem I have with your "it sounds to me" is that it begs the
question: Can there be havarah that can't be sensed? (Including: Can
there be havarah if something burns below yad soledes bo?)

Tir'u baTov!
-Micha

-- 
Micha Berger             You are where your thoughts are.
micha at aishdas.org                - Ramban, Igeres haQodesh, Ch. 5
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