Moving magnet and conductor problem Updated 2025-07-16
This is a well known though experiment, which Richard Feynman used to emphasize
In the above experiment:
  • from the wire frame, the charge feels electromagnetic force, because it is moving and there is a magnetic field
  • from the single charge frame, there is still magnetic field (positive charges are moving), but the body itself is not moving, so there is no force!
The solution to this problem is length contraction: the positive charges are length contracted and the moving electrons aren't, and therefore they are denser and therefore there is an effective charge from that frame.
Video 1.
How Special Relativity Fixed Electromagnetism by The Science Asylum (2019)
Source.
Multicellularity is polyphyletic Updated 2025-07-16
From Wikipedia:
Multicellularity has evolved independently at least 25 times in eukaryotes
and:
Complex multicellular organisms evolved only in six eukaryotic groups: animals, symbiomycotan fungi, brown algae, red algae, green algae, and land plants.
Pregnancy Updated 2025-07-16
Vice News Updated 2025-07-16
Given:
the norm ends up being:
E.g. in :
Monorepo Updated 2025-07-16

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