Editing Body relative direction (section)

==Geometry of the natural environment==
[[File:Sorts on composing stick.jpg|thumb|Type compositing]] A [[right-hand rule]] is one common way to relate three principal directions. For many years a [[parity (physics)|fundamental question]] in physics was whether a left-hand rule would be equivalent. Many [[nature|natural structures]], including human bodies, follow a certain "[[handedness]]", but it was widely assumed that nature did not distinguish the two possibilities. This changed with the discovery of [[Parity (physics)#Parity violation|parity violations]] in [[particle physics]]. If a sample of [[cobalt-60]] [[atoms]] is [[magnetism|magnetize]]d so that they spin [[counterclockwise]] around some [[rotation|axis]], the [[beta radiation]] resulting from their [[nuclear decay]] will be preferentially directed opposite that axis. Since counter-clockwise may be defined in terms of up, forward, and right, this experiment unambiguously differentiates left from right using only natural elements: if they were reversed, or the atoms spun [[clockwise]], the radiation would follow the spin axis instead of being opposite to it.