The children rush towards Earth, a cherry tomato. ‘Jupiter’s the biggest planet in the solar system,’ I say, ‘which is why it’s a watermelon, but we still don’t have a sun. If earth is this big,’ I hold the tomato between my fingers, ‘then what fruit or vegetable could we use for the sun?’

‘A pumpkin!’ shouts out a dad, getting a bit too into it.

‘Not big enough,’ I say. I can’t quite talk to the adults in the way I can talk to the children, but at least they can hear me now.

‘A dinosaur?’ suggests a girl.

‘Good guess, but that isn’t a fruit or vegetable …Amazingly, if you took all the fruit in the entire world and mashed it together to make one giant, monster fruit, it still wouldn’t be as big as our sun!’

Gasps of genuine amazement break out, and not just from the children. I look at Grandad and he grins. This was just what I had hoped would happen. I tear off one piece of toilet paper. ‘Can anyone guess how many kilometres this represents?’

Answers are shouted back at me: ‘a hundred’, ‘a zillion’, ‘seventy-three!’

‘One piece of toilet paper represents ten million kilometres,’ I say. ‘Now, who wants to see an egg sucked into a bottle?’

TWENTY-FIVE

‘Every single object in the universe is made of atoms,’ I say, ‘including you and me.’ I’m up to the last experiment. By my feet, one of the children yawns and another starts nibbling something off the end of her finger. ‘To show how alive atoms are, we’re going to play with balloons.’ I pick up the bin bags stuffed full of balloons and tip them out. The balloons float across the tent and the children jump to their feet and start hitting them into the air.

‘We’re going to see how many balloons we can stick to a person’s head using static electricity. I need a volunteer, but I should warn you, it’s going to do bad things to their hair!’

‘My brother!’ shouts a voice from the back of the room. ‘Pick my brother!’ Through the balloons and jumping children, I see a boy with messy blond hair stretching his arm high into the air. ‘Please, pick my brother!’ Sitting next to him is another little boy wearing a Minions T-shirt.

Over by the exit, Maggie taps her watch. I need to hurry up.

‘OK. You come up here with your brother. We’re going to have to rub these balloons really hard if we’re going to get them to stick to him.’ I get the other children to sit back down and when I look up, the boy is pulling his brother towards me … only he’s not wearing a Minions T-shirt. His brother is tall and dark, and a gold watch is flashing on his wrist. I’d know that watch anywhere. My stomach drops as I stare at Ed King.

He stops in front of me and folds his arms. ‘Hello, Meg,’ he says.