The strings aren't all in the same direction on a grand piano. The longest strings are at an angle to the rest of the strings. You can see a picture of this here. https://thomaspianoservice.files.wordpress.com/2016/02/used-steinway-baby-grand-piano-for-sale-montgomery-al-strings.jpg
Interestingly, the frame that holds the strings is really massive for a number of reasons. With tension of the approximately 230 strings pulling in adds up to about 2x10^5 N of force. Though measures are used to try to keep the tension even by changing the length of the strings and winding the bass strings with copper, the forces aren't all pulling in quite the same direction. I'm pretty sure that the frame outweighs the strings by a margin otherwise things would get exciting.
Still cast iron and steel has been known to get a residual magnetic field via the earth's magnetic field and vibrations, and I wouldn't be surprised that a piano kept in the same position for a long time might develop a field aligned to the earth's.
I had a steel filing cabinet in a classroom where I once taught that had been stuck into a corner for 50 years by the time I arrived. When we moved it, we could detect a small but measurable field with a Hall Effect probe that deviated from the earth's field.
-Zeke
On Saturday, May 8, 2021, 8:40:32 PM PDT, Bill Norwood via Phys-l <phys-l@mail.phys-l.org> wrote:
Hi Phys-L ‘ers,
No one responded last week when I suggested, in the context of the discussion about sharks’ sense of direction, that the variability in people’s sense of direction might be due to differing amounts of iron in their bodies.
Ok, here is another of my quarter-baked theories:
1. I have no sense of direction - once I make one 90 degree turn I am lost.
2. My son just informed me that his mother, a concert pianist, who did little other than practice on grand pianos since the age of four, had an extraordinary sense of direction.
3. Let’s think about it:
a. Her being stationary and in the same position relative to the grand piano for tens of thousands of hours.
b. The local earth’s magnetic field lines being guided, all in the same direction, by the piano’s 200 or so steel strings and tending to pass thru the pianist all in the same direction.
c. The piano(s) were positioned in the same orientation for decades. (Not 100% sure of this)(Sometimes she did two-piano work, where the strings in one piano were parallel to the strings in the other piano.
d. So, if she had any iron in her body, and we all do, that iron would experience torque from the earth’s magnetic field lines.
e. The vibrating of the strings as she played would have caused a shaking in the magnetic field lines which would have shaken the iron particles in her body so that they would more readily “fall into place.”
f. Did I get most of that right?
Thanks,
Bill Norwood
Retired Sep 2018
Physics Dept
U of MD at College Park