I was at the supermarket recently when I took note of something my eyes had passed thousands of times before. The cans of my favorite sodas were 12 ounces, while the bottles were 2 liters. It caught ...

The kilogram — anywhere in the world, for any purpose — is based on the exact weight of a golf-ball-sized chunk of platinum and iridium stored under three glass bell jars in a vault in an ornate ...