Topics: Modern Physics, Particle Physics, Quantum Mechanics
Our right and left hands are reflections of one another, but they are not equal. To hide one hand perfectly behind the other, we must face our palms in opposite directions.
In physics, the concept of handedness (or chirality) works similarly: It is a property of objects that are not dynamically equivalent to their mirror images. An object that can coincide with its mirror-image twin in every coordinate, such as a dumbbell or a spoon, is not chiral.
Because our hands are chiral, they do not interact with other objects and space in the exact same way. In nature, you will find this property in things like proteins, spiral galaxies and most elementary particles.
These different-handed object pairs reveal some puzzling asymmetries in the way our universe works. For example, the weak force—the force responsible for nuclear decay— has an effect only on particles that are left-handed. Also, life itself—every plant and creature we know—is built almost exclusively with right-handed sugars and left-handed amino acids.
Nature through the looking glass, Oscar Miyamoto Gomez, Symmetry Magazine
Physics and Nano 