Rolf van der Berg had not seen his Uncle Paul for a decade, and it was not likely that they would ever again meet in the flesh. Yet he felt very close to the old scientist – the last of his generation, and the only one who could recall (when he wished, which was seldom) his forefathers' way of life.

Dr Paul Kreuger – 'Oom Paul' to all his family and most of his friends – was always there when he was needed, with information and advice, either in person or at the end of a half-billion-kilometre radio link. Rumour had it that only extreme political pressure had forced the Nobel Committee – with great reluctance – to overlook his contributions to particle physics, now once more in desperate disarray after the general house-cleaning at the end of the twentieth century.

If this was true, Dr Kreuger bore no grudge. Modest and unassuming, he had no personal enemies, even among the cantankerous factions of his fellow exiles. Indeed, he was so universally respected that he had received several invitations to re-visit the United States of Southern Africa, but had always politely declined – not, he hastened to explain, because he felt he would be in any physical danger in the USSA, but because he feared that the sense of nostalgia would be overwhelming.

Even using the security of a language now understood by less than a million people, van der Berg had been very discreet, and had used circumlocutions and references that would be meaningless except to a close relative. But Paul had no difficulty in understanding his nephew's message, though he could not take it seriously. He was afraid young Rolf had made a fool of himself, and would let him down as gently as possible. Just as well he hadn't rushed to publish: at least he had the sense to keep quiet...

And suppose – just suppose – it was true? The scanty hairs rose on the back of Paul's head. A whole spectrum of possibilities – scientific, financial, political – suddenly opened up before his eyes, and the more he considered them, the more awesome they appeared.

Unlike his devout ancestors, Dr Kreuger had no God to address in moments of crisis or perplexity. Now, he almost wished he had; but even if he could pray, that wouldn't really help. As he sat down at his computer and started to access the data banks, he did not know whether to hope that his nephew had made a stupendous discovery – or was talking utter nonsense. Could the Old One really play such an incredible trick on mankind? Paul remembered Einstein's famous comment that though He was subtle, He was never malicious.

Stop daydreaming, Dr Paul Kreuger told himself. Your likes or dislikes, your hopes or fears, have absolutely nothing to do with the matter.

A challenge had been flung to him across half the width of the Solar System; he would not know peace until he had uncovered the truth.

Captain Smith kept his little surprise until day five, just a few hours before turnaround. His announcement was received, as he had expected, with stunned incredulity.

Victor Willis was the first to recover.

'A swimming pool! In a spaceship! You must be joking!'

The Captain leaned back and prepared to enjoy himself. He grinned at Heywood Floyd who had already been let into the secret.

'Well, I suppose Columbus would have been amazed at some of the facilities on the ships that came after him.'

'Is there a diving board?' asked Greenburg wistfully. 'I used to be college champion.'

'As a matter of fact – yes. It's only five metres – but that will give you three seconds of free fall, at our nominal tenth of a gee. And if you want a longer time, I'm sure Mr Curtis will be happy to reduce thrust.'

'Indeed?' said the Chief Engineer dryly. 'And mess up all my orbit calculations? Not to mention the risk of the water crawling out, Surface tension, you know...

'Wasn't there a space station once that had a spherical swimming pool?' somebody asked.

'They tried it at the hub of Pasteur, before they started the spin,' answered Floyd. 'It just wasn't practical. In zero gravity, it had to be completely enclosed. And you could drown rather easily inside a big sphere of water, if you panicked.'

'One way of getting into the record books – first person to drown in space...'

'No-one told us to bring swimsuits,' complained Maggie M'Bala.

'Anyone who has to wear a swimsuit probably should,' Mihailovich whispered to Floyd.

Captain Smith rapped on the table to restore order. 'This is more important, please. As you know, at midnight we reach maximum speed, and have to start braking. So the drive will shut down at 23.00, and the ship will be reversed. We'll have two hours of weightlessness before we commence thrust again at 01.00.

'As you can imagine, the crew will be rather busy – we'll use the opportunity for an engine check and a hull inspection, which can't be done while we're under power. I strongly advise you to be sleeping then, with the restraint straps lightly fastened across your beds. The stewards will check that there aren't any loose articles that could cause trouble when weight comes on again. Questions?'

There was a profound silence, as if the assembled passengers were still somewhat stunned by the revelation and were deciding what to do about it.

'I was hoping you'd ask me about the economics of such a luxury – but as you haven't, I'll tell you anyway. It's not a luxury at all – it doesn't cost a thing, but we hope it will be a very valuable asset on future voyages.

'You see, we have to carry five thousand tons of water as reaction mass, so we might as well make the best use of it. Number One tank is now three-quarters empty; we'll keep it that way until the end of the voyage. So after breakfast tomorrow – see you down at the beach...

Considering the rush to get Universe spaceborne, it was surprising that such a good job had been done on something so spectacularly non-essential.

The 'beach' was a metal platform, about five metres wide, curving around a third of the great tank's circumference. Although the far wall was only another twenty metres away, clever use of projected images made it seem at infinity. Borne on the waves in the middle distance, surfers were heading towards a shore which they would never reach, Beyond them, a beautiful passenger clipper which any travel agent would recognize instantly as Tsung Sea-Space Corporation's Tai-Pan was racing along the horizon under a full spread of sail.

To complete the illusion, there was sand underfoot (slightly magnetized, so it would not stray too far from its appointed place) and the short length of beach ended in a grove of palm trees which were quite convincing, until examined too closely. Overhead, a hot tropical sun completed the idyllic picture; it was hard to realize that just beyond these walls the real Sun was shining, now twice as fiercely as on any terrestrial beach.

The designer had really done a wonderful job, in the limited space available. It seemed a little unfair of Greenburg to complain: 'Pity there's no surf...'