That meant the light had the same temperature as ambient space—25 degrees above absolute zero.

That cinched it. A luminous, self-propelled light in space? Never! But just because it was there, dead ahead of him, he gave chase.

The light was growing visibly—and rapidly—fainter. A minute later he verified that it had gained a full 100 kilometers on him. He increased his velocity.

Then the most uncanny thing of all happened.

First the light deliberately let him gain ground—letting him get within 80, 70, then 30 kilometers—before jumping out in front again. Pirx accelerated to 75 kilometers per second; the light, to 76. Pirx applied more thrust, but this time he didn’t pussyfoot around. He opened the jets to half-power, unleashing a powerful forward thrust; the triple gravity shoved him back into the seat’s padded cushion. His AMU had a small rest mass, its rate of acceleration being roughly equivalent to that of a racing car. Before long he was hitting 140.

The little light hit 140.5.

Pirx was beginning to feel hot and clammy. He applied maximum thrust. His AMU-111 hummed; his tachometer, whose readings were based on fixed stars, climbed steadily higher: 155… 168… 190… 200.

At 200 he took a peek through the range finder, which, considering the 4g, was a feat worthy of a decathlon athlete.

He was gaining on the light, which swelled in size as the gap between them closed to 20, then 10, and finally 3 kilometers, at which distance it looked larger than a pea when seen from an arm’s length away. The dark, blurry shapes continued to shunt across its surface, whose brightness was comparable to stars of the second magnitude—except that it resembled more a disk than a starlike dot.

His AMU-111 was giving everything it had, swelling Pirx with pride. During that sudden burst to maximum thrust, not a thing in the cabin had shaken—not a single vibration! The reaction was in the axis of acceleration; the jets were performing to perfection; the reactor was working like a champ.