## Thursday, November 17, 2011

### Underfables: The Physics Genie

The Physics Genie

Once upon a time the Physics Genie granted King Solomon not just three, but four wishes. King Solomon said, “My first three wishes are: to be a man more upright than all others; during an age more golden than all others; in a land more holy than all others.”

The Physics Genie said, “But if, to physics, you are a man more upright than all others, then not all directions are physically equal; therefore spin is not conserved.” When the Genie spoke those words, the Earth stopped turning. The Genie continued, “And if, to physics, your age is more golden than all others, then not all times are physically equal; therefore energy is not conserved.” And with those words, the Sun went out. The Genie concluded, “And if, to physics, your land is more holy than all others, then not all positions are physically equal; therefore momentum is not conserved.” And with those words, the Moon fell from orbit, straight down towards where King Solomon stood.

King Solomon hastened to say, “Then my fourth wish is, I take back my first three wishes! Instead conserve spin, energy and momentum!”

The Physics Genie said, “So be it.” The Earth returned to turning, the Sun lit up, and the Moon resumed its orbit. The Genie then said, “But therefore, to physics, all men are equally upright, all ages are equally golden, and all lands are equally holy.”

Moral:  Symmetry conserves.

Commentary on the Underfable:
The king is an exceptionalist; the genie is a universalist. The king wants the one and only; but the genie has only the all.
This Underfable illustrates Emmy Noether's theorem; the conservation laws of physics derive from its symmetries.