The Age When Everything Is Worth Testing

It started because Finn wanted to know if his toy boat would sink.

He'd been dropping things into the bath for weeks - a rubber duck, a bar of soap, a small plastic dinosaur - watching some float and some sink with the focused expression of someone running an important study. He had theories. He'd told me that heavy things sink and light things float, which is mostly right, and that big things float and small things sink, which is mostly wrong, and he was prepared to argue both positions simultaneously.

He was five. This is the ideal age for science.

At this age, children are natural experimenters already. They repeat things to see if the result is the same. They push boundaries to find out where the boundary actually is. They ask why with genuine interest rather than as a stalling tactic.

The risk at this age isn't that they won't engage. It's that we over-engineer the engagement - structured activities, learning objectives, "what did we learn today?" - and accidentally make the thing feel like school rather than discovery.

The experiments that work best at five and six are the ones that start with something the child is already curious about and then just... let them test it.

Three that work reliably

Bubbly water and oil: fill a glass halfway with water, pour a thin layer of oil on top, add a drop of food colouring, then drop in a small piece of Alka-Seltzer. Coloured bubbles rise through the oil and fall back down. It looks like a lava lamp. The gas from the tablet carries the water upward; when the bubble pops, the water sinks back. At this age, watching it is enough. The vocabulary - carbon dioxide, density - can come years later.

Building with sticks and clay: give them popsicle sticks and small balls of clay and ask them to build something that holds weight. Coins work as weights. Let them discover that triangles hold up better than squares without telling them why first. If they ask, you can explain that triangles share the weight across all three sides. If they don't ask, it doesn't matter - they've found it themselves, which is the more durable lesson.

Seeds in a jar: soil, a few seeds (cress sprouts fastest), a sunny windowsill. Check it every morning. Move it away from the window for a few days and watch what happens, then move it back. The plant is slow, which is the point - it teaches patience and close observation in a way that faster experiments can't. Finn checked his jar every morning for nine days before anything happened. On day ten, he ran into the kitchen to tell me it was "doing something."

What to do when they want to change the experiment

Let them.

When Finn decided his lava lamp would be better with three colours, and then with the whole bottle of food colouring, and then with a bigger glass - I let him. The results were progressively less photogenic and much more interesting. He discovered that too much food colouring turns everything brown, which led to a conversation about mixing colours that was more engaged than anything I could have planned.

Following their variation is almost always more valuable than completing the original experiment correctly. The original experiment is just the starting point. The question they ask halfway through is the actual lesson.

The only thing that matters

Not whether the experiment works perfectly. Not whether they can explain the concept at the end. Not whether they remember it next week.

Whether they want to do another one.

If they do, everything else will follow. The vocabulary, the concepts, the understanding - these accumulate gradually over years of messing around in kitchens and gardens and getting things slightly wrong and trying again.

Finn's boat, for what it's worth, sank. It was too small and too heavy and he'd predicted correctly. He was briefly satisfied, then immediately wanted to find something bigger to test.

That's the whole thing, really.