The other week I was trudging through laps around the court I live on, and a neighbor yelled across the court, first “HI” and I yelled “HI” right back and then he yelled, “THIS IS THE BEST DAY OF THE YEAR!”

So I asked why it was the best day of the year, and trudged a little closer to hear him better even though he was still yelling, “BECAUSE IT’S THE DAY THE CHEMISTRY NOBEL IS ANNOUNCED.” I’ve known this neighbor since he first moved here, buying his first house, he and his wife having their first baby, starting his first real job, which — relevant to our discussion — was as a young professor of chemistry. Chemistry has always seemed to combine the idiosyncratic rats’-nest of biology and the rigorous theology of physics, and I stay away from it. But I’m a science writer and professionally obliged to be curious, so I trudged a bit closer and asked who won the chemistry Nobel. My neighbor was still yelling. “KAGAN AND SOAI,” pronounced so-aye, “FOR HOMOCHIRALITY,” he yelled, which, I haven’t a clue. And because he’s a scientist to his bones, every atom of him is scientist, he was pleased to tell me, unasked, what homochirality is and how it happens and I went over to where he was standing by his car and listened hard.

He started by telling me all the molecules of life — all the molecules of life? so, everything that life is and does? I didn’t ask — had a handedness, which chemists call chirality. Pretty word, ancient Greek, means “hand,” I sort of knew what chirality meant: the way the molecule twists itself, spirals toward the left or right, I pictured a snail shell, a DNA molecule, a helix. He was getting ahead of me already. Turns out that all the molecules of life — whatever they are — have the same chirality, homochirality, “homo,” also ancient Greek, means “same.” Every amino acid in every protein in every cell twists toward the left, they are all left-handed. But chemical reactions — which are what? I didn’t ask — in the lab, create both left- and right-handed molecules. I wasn’t following his argument 100%, more like 50%, and I know from these links I’m inserting that it’s not this simple. But I did get the bottom line: if both chiralities are created equal, how come we’re all molecularly left-handed?

The Nobel Prize winners figured that out and did the experiment(s). In experiments, it turns out — and this is thoroughly above my pay grade — they could do some magic that life must also have done: they could prejudice the outcome just the least little tiny bit toward the left-handed. And then they could take that outcome with the tiny prejudice and repeat — something or other that’s repeated — and by the time it all comes out in the wash, those tiny prejudices toward the left have added up and accumulated and pretty soon life is only left-handed. The word I’m thinking of is “propagated,” used the way physicists use it: one thing leads to another. A tiny difference in a reaction that gets repeated and repeated just gets bigger and bigger. The prejudice propagates and accumulates.

At least, I think that’s what my neighbor was saying. I didn’t ask because 1) I wouldn’t have understood him without a lot more brain work and I hadn’t had breakfast; and 2) I was interrupted by a blinding epiphany. Which was this ⬇️: