The Unreasonable Magic of Rolling A Tennis Ball Down a Sandcastle

Unlocking The Generative Urgency of Childhood

Here’s a change of pace for your weekend enjoyment. I was lucky enough to be accepted as a fellow in the Roots of Progress Institute’s 2024 Blog-Build Intensive. This essay originated in an exercise for that program: write 500 words on an embarrassingly non-technical topic. It’s slated to be reprinted on the Free-Range Kids and Let Grow websites.

Whenever I take kids to the beach, we always bring three things: a full-size shovel, a telescoping trowel, and some tennis balls.

The shovel is for making a Big Pile Of Sand. Kids can have a pretty good time with a pile of sand.

But tennis balls are the key. Suddenly the project has moving parts.

Children cannot get enough of this. Whenever we get a project going, any other kids in the vicinity drift over, and are soon part of the team:

They’ll work for hours: extending the track, adding branches, making adjustments. But the prized role is that of tester. There’s an instinctive urge to put the ball at the top of the track and see what happens, again and again.

They become invested in some private vision. They’ll scoop out a path, lovingly smooth it with whatever tool they have decided is essential, and call urgently for a test ball.

Sometimes arguments break out: over the choice of route, or whether more sand is needed here, or why did you roll that ball down I wasn’t ready yet! Everything is charged with that urgency of childhood. But mostly there’s a remarkable degree of cooperation and emergent organization.

I mentioned a telescoping trowel. That’s for making tunnels.

I don’t know why Kmart once decided to stock a trowel with a five-foot telescoping handle, but when I saw it in the garden section I instantly realized I had struck gold. To a kid, a tunnel is a teleportation device: the ball vanishes here and reappears over there.

If you have access to a beach and a child, you can easily try this yourself. Bring more than one ball, they’re easy to lose. Start out by making a big pile of sand, as big as you and your underage team have patience for – a full-sized garden shovel is extremely helpful (but don’t let little kids use it – someone might get hurt). As you go, pour lots of water to keep the pile wet and compact.

Once your pile is done, pack it down hard (kids love to help with this part). And then start carving your track. You can use a toy shovel but hands are often best. You start at the top, of course. Wander downhill as fancy strikes; don’t bother with a plan. Send lots of balls down – your little helpers will be glad to take on this task – to test the slope. You want it just steep enough to move the ball at a moderate pace. Your instinct will be to carve a deep, rounded channel, but flat is better. Just bank it for the turns. And, of course, back off as soon as your apprentices show signs of taking over.

And take over they will. I don’t know why it’s so irresistible. Something about the unlimited freedom of digging in the sand, combined with the magic of making a thing that does something.

Thanks to Heike Larson of the Roots of Progress Institute and Lenore Skenazy of Free-Range Kids for feedback, suggestions, and encouragement. And to every kid who has ever wandered over and asked “can I help”?

Tips and Tricks

You and your kids are probably used to building sandcastles by adding sand as you go. This results in weak sand that can crumble and slump. Better to do what I describe here – make a big pile of wet sand, and pack it down hard. That will yield a firm pile to carve into. Also, to build a decent ball run you need some height, and it takes a big wide pile to support a high starting point.

If you get the sand for your pile by digging a hole, then the ball can run all the way from the top of the pile to the bottom of the hole. That sand mountain pictured at the top of the post is not as big as it looks; your eye is measuring to the bottom of the moat, which is where the sand for the mountain came from.

If you do need to add more sand later, don’t be surgical about it. Plop on a big shovelful of wet sand, pack it down, and then re-carve the area. If you try to just pat on a little handful, it won’t make a good bond to the existing structure (though a handful of almost-mud works better than a handful of dry sand).

Don’t try to reshape the sand by smooshing it around – if the sand isn’t wet, you’ll break all the internal bonds. Your moves are to carve away sand, or add wet sand.

All of this is most important if you’re planning to dig tunnels, which are an advanced move. Otherwise you can relax a bit about the sand. But it still makes everything go better if, before anything else, you spend 20 straight minutes just piling up sand with a shovel and wetting / packing it down as you go.

Advanced Moves

Aim for a track that is just steep enough to keep the ball moving. A steeper track wastes precious altitude, and gets the ball moving faster which makes it harder to control.

The track should be flat, like a road; not steep-sided, like a river. Your instinct will be to carve a deep channel, but then the ball will keep rubbing against the sides and lose speed. If your track isn’t too steep, and you’ve banked your turns, then just a shallow slope to either side should be enough to keep the ball on track – see the picture above.

When you’re ready to try digging a tunnel: don’t put the entrance too high up. The “roof” should be at least 4 inches thick at the entrance, probably more when you’re first starting out. Scoop out the entrance and just keep going, being careful to continue in a fairly straight line with a reasonable downhill slope. Don’t jam your hand or shovel in in a way that’s going to shove all the sand around, you want to carve out the tunnel without disturbing the sand around it. A garden trowel works very well for this because it’s sharp enough that you can stick it into the hole and carve with (I usually use a twisting motion). You don’t need the fancy telescoping handle, your arm will do (but if you do find a telescoping trowel, you can dig really long tunnels).

Be careful not to roll a ball into the tunnel until you’ve carved it all the way through and it’s wider than the ball. If a ball gets badly stuck, it can be hard to fish it out without disturbing the rest of the structure.

Extra credit: before heading to the beach, find a newspaper somewhere. Roll each page up into a tight tube, and to keep it from unrolling, wrap a bit of masking tape around each end plus an extra loop around the middle. This makes beautiful straight sticks, suitable for all sorts of construction projects. Laying two of them down next to one another creates a perfect bridge for a tennis ball – again, see the picture above.

Remember To Bring Plenty of Balls!

You can never have too many tennis balls.