Back in 1964 my favorite elementary school teacher, Mrs. Wilson, started class one morning with a question so interesting that it has stayed with me all these years later. Here's the question: "You have two hands . . . are they the same?"
Seems so simple and easy. Yet you should've seen all the kids in class struggle to answer correctly. We were just little kids so, of course, we put our two hands together, palms facing, like when you pray.
Do that and the answer seems to be "Yes".
But that's not the correct answer. When you place your hands palms facing you are inverting or flipping one hand to match it's mate - mirror image style!
The correct answer is "No", right hands are not left hands - you can not superimpose the left and right. Your hands are mirrors of each other. Mrs. Wilson was having a lot of fun watching me and my friends struggle to come to grips with a concept I learned years later in chemistry lab.
The term is chirality and it emphasizes the 3D nature of molecules. Our understanding of the fundamental structure of the universe has expanded greatly as researchers explore "left hand" and "right hand" versions of molecules.
Remember Alice's adventure in "Through the Looking Glass"? She wondered about the nature of the mirror world. "Would it be safe to drink mirror milk?" That's an interesting question. What if the food we eat and drink are "left handed" but science creates "right handed" versions - would you eat any?
Would a true mirror world be safe if we enter it? Is a chiral universe only imaginary?