Mirror Symmetry in the Universe?

Does our universe have mirror symmetry? That is the question Prof. Michael Longo of the University of Michigan's Physics Department asked. The answer could perhaps be found by studying the rotation directions of spiral galaxies.

Physicists and astronomers have always assumed that the Universe has this symmetry. To test this, Longo and his team of five undergraduates used data from the Sloan Digital Sky Survey to study the rotation directions of spiral galaxies. The mirror image of a counter-clockwise rotating galaxy, like the example, would have clockwise rotation. An excess of one type over the other would be evidence for a breakdown of mirror symmetry, or, in physics speak, a "parity violation" on cosmic scales.…