Step in a Puddle and Splash Your Friends Day

What the day is

Step in a Puddle and Splash Your Friends Day is observed on January 11, in the part of winter that reliably supplies the puddles.

Origin and background

The origin of the observance is not documented.

What it describes is a recognizable kind of play. Researchers who study rough and tumble play in children note that its value lies in being a rehearsal for exactly the thing it looks like: it involves genuine transgression, held inside limits that both parties are constantly negotiating without discussing. Learning where the line sits, noticing the moment somebody stops enjoying it, and repairing the situation afterward are difficult social skills, and this is how they get practiced.

The splash is a neat miniature of that. It only works with reciprocity and consent. Done to a friend who is in the game it is funny; done to a stranger, or to someone who has told you to stop, it is simply an unpleasant thing to do to a person with wet feet for the rest of the day. The activity contains its own lesson, which is presumably why it has survived as a children's game.

The physics is worth a look too, and was photographed long before high-speed cameras existed. In the 1890s a British physicist used electrical sparks to freeze the instant of a droplet striking a liquid surface, revealing that an impact throws up a symmetrical crown of fine points around the rim, which then break into secondary droplets. It is a strikingly regular structure for something that lasts a few thousandths of a second.

One caution: in Britain and elsewhere, deliberately soaking a pedestrian by driving through a puddle can be prosecuted as careless driving, and people have been.

How to take part

• Splash people who are in on it, and nobody else.
• Stop the first time somebody means it.
• Wear boots, and bring a change of socks for the person you got.
• Watch a high-speed video of a droplet hitting water, which is genuinely beautiful.
• Never splash anyone from a vehicle. It is not the same game at all.