I learned the trick of balancing twelve 16 penny nails on the head of one nail.It seems that the nails twist as a group in a clockwise direction.Is it possible that the earth’s magnetic field is the cause?Or is it simply a slighty out of balance pattern
It is the latter explanation (for those wondering about the trick, here is a video demonstrating it with 10 nails); the Earth’s magnetic field isn’t going to be strong enough to have such an effect on something as big as nails which aren’t freely suspended (and they need to be magnetized, as in a compass). In the video you can see that the two nails (top and bottom) that hold the others together are misaligned, crossing over in an “x” and making the others stick out the way they do (they very well could appear to spiral in the opposite direction).
The nails themselves might be slightly magnetized, but the earth’s magnetic field wouldn’t have much effect. Look at how very light compass needles have to be to respond to the field. Something as heavy as a regular carpenter’s nail would be much slower to respond, and the response would be much weaker.
Geometry is the secret: you’re just stacking things so that the center of mass is directly above the base of support. It’s like building houses of cards: dexterity does it!
Thank you for the concise answer to my question. And thank you for taking the time.
Actually, the centre of mass for the configuration of nails in the video linked above is below the head of the nail on which they are balanced - which is what makes the configuration stable.
The heads are heavy enough so the nails don’t push the top nail away - plus, the heads of the hanging nails “grip” the top nail, effectively clamping the collection together. You can see in the video, he releases the top nail slowly to ensure it is clamped by the nailheads.
then, the whole assembly is balanced. It is fairly stable because as mentioned above, the overall center of gravity is below the balance point of the bottom cross-nail.
I suppose twisted or smooth nails would work the same, provided the heads were wide enough to “clamp” the top.