Nobody can explain how they learned to swing
Getting a SWING going without a push is a real piece of physics, and every child solves it by about six without a word of instruction. The trick is timing: you have to add your effort at the same point in every cycle, and doing it half a beat early or late cancels out everything you have built up.
What actually works is standing up as you pass through the bottom and crouching at each end, which shortens and lengthens the swing twice per cycle. Engineers call this parametric pumping and use the same maths on suspension bridges. Ask a seven-year-old to describe it and you will get a shrug.
Children spin on purpose for a reason
Deep inside each ear are three tiny loops of fluid set at right angles to one another, and they are how the body knows which way up it is. Spinning on a ROUNDABOUT swirls that fluid, and when the spinning stops the fluid keeps going — so the world lurches even though you are standing still.
Young children seek that sensation out relentlessly, and occupational therapists use swinging and spinning deliberately with children whose balance is slow to develop. The dizziness is not a side effect of the fun. It is a nervous system calibrating itself, and the giggling is included at no extra cost.
Safer playgrounds have a cost
Rubber surfacing, lower platforms and enclosed equipment have cut serious playground injuries substantially, and nobody sensible wants to go back to concrete and iron. But a Norwegian researcher, Ellen Sandseter, has argued that children actively seek out a handful of risky experiences — great height, high speed, rough and tumble, going out of sight of adults — and that these look like a developmental need rather than a nuisance.
The suggestion is that a child who has never assessed a risk has no practice at it. Several countries have responded by building climbing frames higher again, adding loose planks and ropes, and accepting scraped knees as tuition fees. The argument is not settled, but it is being had by serious people.
Hopscotch turns up almost everywhere
Scratch a grid of numbered squares on the ground, throw a stone, hop the course without touching a line. HOPSCOTCH is played in near-identical form across Europe, in India as Stapoo or Kith-Kith, in Latin America as Rayuela and in Malaysia as Ketingting.
It is often claimed the Romans invented it for military training, which appears to be entirely made up and repeated because it sounds good. The likelier story is duller and more interesting: the game is simple enough, and the equipment cheap enough, that children in many places arrived at roughly the same idea on their own.
Everything in the grid
The big equipment first — the SLIDE, SWING, SEESAW, ROUNDABOUT, MONKEYBARS and SANDPIT — then the PARK itself with its GATE and its BENCH for whoever is supervising.
The rest of the list is not equipment at all. RUN, JUMP, SKIP, CLIMB, a BALL, a GAME, HOPSCOTCH, FRIENDS, FUN, LAUGH and PLAY need nothing installed and no budget approved. The SEESAW deserves a mention for being the one thing out there that flatly refuses to work unless somebody else turns up.