And so many sleepers had complained of strange noises – even of voices – which were obviously illusions, because those awake had heard nothing. Surgeon-Commander Ernst had prescribed a very simple and effective cure; during the sleeping period, the camp was now lulled by gentle, unobtrusive background music.
This night, Commander Norton found the cure inadequate. He kept straining his ears into the darkness, and he knew what he was listening for. But though a very faint breeze did caress his face from time to time, there was no sound that could possibly be taken for that of a distant, rising wind. Nor did either of the exploring parties report anything unusual.
At least, around Ship’s midnight, he went to sleep. There was always a man on watch at the communications console, in case of any urgent messages. No other precautions seemed necessary.
Not even a hurricane could have created the sound that did wake him, and the whole camp, in a single instant. It seemed that the sky was falling, or that Rama had split open and was tearing itself apart. First there was a rending crack, then a long-drawn-out series of crystalline crashes like a million glass-houses being demolished. It lasted for minutes, though it seemed like hours; it was still continuing, apparently moving away into the distance, when Norton got to the message centre.
‘Hub Control! What’s happened?’
‘Just a moment, Skipper. It’s over by the Sea. We’re getting the light on it.’
Eight kilometres overhead, on the axis of Rama, the searchlight began to swing its beam out across the plain. It reached the edge of the Sea, then started to track along it, scanning around the interior of the world. A quarter of the way round the cylindrical surface, it stopped.
Up there in the sky – or what the mind still persisted in calling the sky – something extraordinary was happening. At first, it seemed to Norton that the Sea was boiling. It was no longer static and frozen in the grip of an eternal winter; a huge area, kilometres across, was in turbulent movement. And it was changing colour; a broad band of white was marching across the ice.
Suddenly a slab perhaps a quarter of a kilometre on a side began to tilt upwards like an opening door. Slowly and majestically, it reared into the sky, glittering and sparkling in the beam of the searchlight. Then it slid back and vanished underneath the surface, while a tidal wave of foaming water raced outwards in all directions from its point of submergence.
Not until then did Commander Norton fully realize what was happening. The ice was breaking up. All these days and weeks, the Sea had been thawing, far down in the depths. It was hard to concentrate because of the crashing roar that still filled the world and echoed round the sky, but he tried to think of a reason for so dramatic a convulsion. When a frozen lake or river thawed on Earth, it was nothing like this…
But of course! It was obvious enough, now that it had happened. The Sea was thawing from beneath as the solar heat seeped through the hull of Rama. And when ice turns into water, it occupies less volume …
So the Sea had been sinking below the upper layer of ice, leaving it unsupported. Day by day the strain bad been building up; now the band of ice that encircled the equator of Rama was collapsing, like a bridge that had lost its central pier. It was splintering into hundreds of floating islands, that would