The next day Dyspepsia had forgotten all about energy and where it came from. But Spookie carries on thinking about things long after everyone else has stopped. So Dyspepsia was surprised to find she wasn’t in front of the television, but out in the garden, wrapping a big lump of Semtex around a can of Dr Pepper.

Dyspepsia hadn’t known they still had some Semtex. Back in the days when they were digging up the Monstosaurus, she always carried a lump of Semtex in her pocket, plus a detonator behind her ear, in case there was a lamp-post that needed to come down. But once the project was over, and she started going back to school, Teacher confiscated all the Semtex and she never got it back.

“What are you doing?” said Dyspepsia.

Spookie was so busy she could only mumble “I’m trying to make thermonuclear energy.”

“What’s that?”

“It’s how the Sun gets all its energy.”

“Why does the Sun need energy? It’s a big ball of hot gas. Hasn’t it got enough energy already?”

Spookie stopped what she was doing and gave a big sigh. “The Earth and the planets have been going for four-and-a-half billion years, right? In all that time the Sun ought to have cooled down, what with all the energy it gives off as sunshine.”

Spookie was good at sums, so Dyspepsia knew better than to argue.

“But it hasn’t cooled down. So there’s something cooking away inside which makes enough energy to make up for all the sunshine. It’s the same thing that makes hydrogen bombs go bang.”

Dyspepsia gave a little shriek. “You’re not making a hydrogen bomb? You’ll get wrong off Daddy!”

“No, I’m not making a hydrogen bomb.” Spookie sounded impatient. “I’m trying to squeeze down the hydrogen in Dr Pepper until it becomes helium. Einstein says that will make a lot of spare energy. If we can make enough, we won’t need to burn oil and coal any more, and go on changing the climate. Electricity will be so cheap they won’t need to charge for it, and old people won’t need to freeze in winter.”

Dyspepsia was still a bit doubtful. “You’ve obviously thought a lot about this. But won’t the Semtex make a loud bang?”

“Yes, I suppose it will. That’s why I’m doing it out in the backyard. Semtex releases a lot of energy when it goes bang, but nothing like the energy we’ll get back in exchange. Dr Pepper makes bubbles, and the pressure inside a bubble depends on the inverse of the radius. A really-really tiny bubble has really-really enormous pressure inside it. If I wrap a band of Semtex round the can, it will give the bubbles an extra squeeze. I’ll make the Semtex go bang a split-second after I pull the can-pull. That’ll squeeze the bubbles back to nothing again as soon as the Dr Pepper starts to fizz.”

Dyspepsia said “You’re not going to stand there and open the can just as the Semtex goes off? You’ll lose your paws!”

“No, silly. Here are two strings. One string is tied to the can-pull. The other string—a tiny bit longer—sets off the Semtex. Now, Remember the Firework Code.

She led Dyspepsia back to what she thought was a safe distance, then she put the strings into her hands. “Be my guest.”

Dyspepsia gave the strings back to Spookie. “You pull them. I want to put my hands over my ears.”

Spookie didn’t need to put her paws over her ears because they fold flat all by themselves. She pulled the strings with a sharp tug.

Dyspepsia was right. They did get wrong off Daddy, because the bang was loud enough to blow everyone’s windows out. But by now the neighbours had got used to the two friends and all the things they got up to, and it didn’t take too much pocket money to mend everyone’s windows.

As Spookie said, “In the cause of Science, sacrifices have to be made”.

…to be continued.