Rotation - The jewel of physics !

Many of the non-intuitive phenomena in physics are associated with rotation.

• First, while linear motion is a relative motion which means that two observers with a relative velocity will measure the velocity of the same object differently, rotation seems to be an absolute motion since the two observers will measure the angular velocity of a rotating object to be the same.

• In the frame of a rotating object a new fictitious force appear such as the Coriolis force.

• If you mounted a wheel from a robe fixed in its axle, the wheel will fall down due to the force of gravity. While if you rotate this wheel, its angular momentum will interact with the torque due to the force of gravity and will make it acquire a new component of rotation. This is very non-intuitive and amazing as Professor Walter Lewin from MIT described it in his lecture about the conservation of angular momentum

• Need more ? There is much more...

The magnetic field associated with the elementary charge, its magnetic dipole moment, is associated with its intrinsic angular momentum, which is after all some strange kind of rotation !! ( The strangeness here stems from the counter-intuitive aspects of quantum mechanics. For example, the spin is no longer of a definite magnitude and direction, but can be in a superposition of a multitude of values and directions !)


An interesting question is: If the elementary charge had zero spin, would there ever exist any magnetic field in the world ??