Holo-field

‘No, no, no,’ the Doctor replied to an earlier question, ‘the walls do not exist! Not that one anyway,’ he modified, gesturing vaguely at the wall behind which the monster, presumably, still lurked. Kevin turned his head to look at it, and, perhaps, to make sure he had the right wall.

‘So why does it hurt when I hit it?’ he asked, reasonably enough.

‘Because it’s solid, of course! What d’you expect to feel when you thump a solid object? Warm all over?’

‘Then if it’s not real, how come I think it’s there?’

‘Because it is!’ sighed the Doctor, exasperated, and beginning to wish he’d never embarked on this crash course in quasi-physical mechanics for beginners. ‘Can’t you trust the evidence of your own eyes? Or are you one of those fellows who has to go around hitting things all the time. Knew a chap like that once,’ he remembered, ‘in Paris...’

‘It doesn’t exist, but it’s real,’ Kevin recapitulated the lesson so far. ‘It’s not there but it’s solid?’

‘At last! I detect a glimmer of understanding!’ Now that he seemed to have got to first base, he thought the wayward brain in front of him might stand the most basic explanation. ‘It’s a simple holo-field... like a hologram, which is just a picture made up of diffracted light, but with enough energy to give it the appearance and physical attributes of solid material – honestly, sometimes it’s just like talking to primitives...’ He poked his head out suddenly, hair awry, a sheepish look on his face. ‘Sorry...’

***

The Nightmare Fair, Chapter 6