Edward looked around at the other kids. A few heads were nodding uncertainly. One of them — a boy a couple of years older than him, short and chubby with curly ginger hair parted at the side and brutally combed so that his hair kinked in waves to one side, reminding Edward of a Mr Whippy ice cream — raised a hand.

‘Yes, er…?’ said Mr Kelly, raising his eyebrows.

‘Franklyn.’

‘Go ahead, Franklyn.’

‘My dad says zero-point energy is just a bunch of wishful thinking. It’s like getting something for nothing. And that’s impossible in physics, nothing’s free.’

Kelly laughed. ‘Well, Franklyn, that’s a good point, but you see that’s exactly what it is. It is a free lunch. And the idea that there’s such a thing as a free lunch isn’t a new one either. Remember Albert Einstein and his theory of relativity. Well, he argued that even in a complete vacuum there’s a great deal left there. It isn’t just empty space, there’s energy too, endless energy waiting to be tapped. Even the ancient Greeks suspected that we walk through an endless soup of energy. They called it “ether”. But the trick, kids… the trick has always been being able to isolate it, to measure it. Since it exists everywhere, it’s homogenous, isotropic… That’s to say it’s uniformly the same everywhere and in every direction.’

The students stared at him in confused silence.

‘Trying to measure zero-point energy is a bit like trying to weigh a glass of water under the ocean. You know? It’s the same inside the cup as it is outside… and therefore since there’s no measurable difference between what’s in and outside the cup, the logical statement to make would be the “cup has nothing in it”. Which would of course be wrong. So, we have a similar issue with measuring zero-point energy. Only by creating a proper vacuum — and I don’t mean just sucking the air out of a space, I mean a proper space-time vacuum, a tiny one — can we observe what it is that remains.’ He smiled his polished public relations smile. ‘The energy itself.