If anything unusual occurred on Earth you could always get advice, and consultations on the most intricate problems could be arranged. Here there was nobody to turn to and spaceship commanders were granted special rights. It would have been easier if such responsibility had been for two or three years instead of the ten to fifteen years that were normal for space expeditions! Erg Noor entered the control tower.

Nisa jumped up to meet him. “I’ve got all the necessary material and the charts,” he said, “we’ll start the machine working!”

The commander stretched himself in his armchair and slowly turned over the thin metal sheets he had brought, calling out the numbers of coordinates, the strength of magnetic, electric and gravitational fields, the power of Cosmic dust streams and the velocity and density of me-teoroid streams. Nisa, all her muscles tensed with excitement, pressed the buttons and turned the knobs of the computing machine. Erg Noor listened to a series of answers, frowned and lapsed into deep thought.

“There’s a strong gravitational field in our way, the area in the Scorpion where there is an accumulation of dark matter near star 6555 CR+11 PKU,” began Noor. “We can save fuel by deviating this way, towards the Serpent. In the old days they flew without motors, using the gravitational fields as accelerators, along their edges.” “Can we do the same?” asked Nisa.

“No, our spaceships are too fast. At a speed of 5/6ths of the absolute unit or 250,000 kilometres a second our weight would be 12,000 times greater in a field of gravitation and that would turn the whole expedition into dust. We can only fly like this in the Cosmos, far from large accumulations of matter. As soon as the spaceship enters a gravitational field we have to reduce speed, the stronger the field the more we must reduce.”