August 13th marked International Left-handers’ Day, a celebration of the uniqueness of left-handed individuals in a world primarily dominated by right-handedness. Beyond human preferences, the concept of handedness extends to various aspects of nature, including our planet and the universe.
Surprisingly, Earth itself exhibits a form of handedness by rotating from west to east. This direction is shared by the solar system as a whole. Notably, research from 2011 revealed that there are more left-handed spiral galaxies in the universe than their right-handed counterparts.
Handedness goes beyond our surroundings to even the basic building blocks of life. Amino acids, crucial to life’s structure, are inherently left-handed.
In the realm of physics, handedness takes on a unique perspective. Left and right orientations are relative in space and can be mirrored. However, nature exhibits a preference for certain configurations. For instance, neutrinos, subatomic particles and the universe’s second most abundant particle after photons, possess left-handed spin, meaning their spin aligns parallel but opposite to their momentum.
Another intriguing facet is the existence of fundamental forces in nature. While the strong and electromagnetic forces are left-right symmetric, following the law of parity conservation, the weak nuclear force, responsible for radioactive decay, defies this symmetry.
In 1956, Chinese-American physicist Chien-Shiung Wu conducted an experiment confirming the weak force’s violation of parity symmetry. Colleagues Chen-Ning Yang and Tsung-Dao Lee were awarded the Nobel Prize for physics in 1957 for their work on this theory. Despite her contributions, Wu’s own Nobel Prize nomination attempts were unsuccessful.
This violation of parity symmetry was a pivotal moment in physics history, leading to theories explaining the asymmetry between matter and antimatter in the universe. While both should have been created in equal amounts after the Big Bang, more matter remains today.
The preference for handedness in nature raises intriguing questions for physicists. Researchers are delving into the origins of this preference at both molecular and astronomical scales, aiming to uncover the fundamental mechanisms that govern nature’s asymmetry.
