What Is the Most Efficient Way to Pack Your Suitcase?

Imagine you're putting balls into a box, like marbles or oranges. Sphere packing is the question of how to fit as many of these balls as possible into the box without them overlapping too much. Sometimes, if you stack the balls in neat rows and columns, you can get more in than if you just toss them all in randomly. This helps explain why people pack suitcases differently, some use a tight grid-like pattern, while others just throw clothes in until there’s no space left.