"But the center itself is not actually an attracting force. The fourth dimension is mixed up in this. We have a sort of fourth-dimensional lens that concentrates the lines of any gravitational force. Concentration in the fourth dimension turns the force loose in three dimensions, but we can take care of that by using mirrors of our anti-entropy. We can arrange it so that it turns the force loose in only one dimension."
Greg was thoughtful for a moment. "We can guide a ship by a series of lenses," he declared at last. "But here's the really important thing. That field concentrates the forces of gravity already present. Those forces exist throughout all of space. There are gravitational lines everywhere. We can concentrate them in any direction we want to. In reality, we fall toward the body which originally caused the force of gravitation, not to the concentration."
Russ nodded. "That means we can create a field immediately ahead of the ship. The ship would fall into it constantly, with the concentration moving on ahead. The field would tend to break down in proportion to the strain imposed and a big ship, especially when you are building up speed, would tend to enlarge it, open it up. But the field could be kept tight by supplying energy and we have plenty of that ... far more than we'd ever need. We supply the energy, but that's only a small part of it. The body emitting the gravitational force supplies the fulcrum that moves us along."
"It would operate beyond the planets," said Greg. "It would operate equally well anywhere in space, for all of space is filled with gravitational stress. We could use gravitational bodies many light years away as the driver of our ships."
A half-wild light glowed momentarily in his eyes.
"Russ," he said, "we're going to put space fields to work at last."
He walked to the chair, picked it up and sat down in it.
"We'll start building a ship," he stated, "just as soon as we know the mechanics of this gravity concentration and control. Russ, we'll build the greatest ship, the fastest ship, the most powerful ship the Solar System has ever known!"