t.

Beneath his hands the Time Observatory's controls were solid shafts of
metal. But suddenly as he worked he found himself thinking of them as
fluid abstractions, each a milestone in man's long progress from the
jungle to the stars. Time and space--mass and velocity.

How incredible that it had taken centuries of patient technological
research to master in a practical way the tremendous implications of
Einstein's original postulate. Warp space with a rapidly moving object,
move away from the observer with the speed of light--and the whole of
human history assumed the firm contours of a landscape in space. Time
and space merged and became one. And a man in an intricately-equipped
Time Observatory could revisit the past as easily as he could travel
across the great curve of the universe to the farthest planet of the
farthest star.

The controls were suddenly firm in his hands. He knew precisely what
adjustments to make. The iris of the human eye dilates and contracts
with every shift of illumination, and the Time Observatory had an iris
too. That iris could be opened without endangering his companions in the
least--if he took care to widen it just enough to accommodate only one
sturdily built man of medium height.

Sweat came out in great beads on his forehead as he worked. The light
that came through the machine's iris was faint at first, the barest
glimmer of white in deep darkness. But as he adjusted controls the light
grew brighter and brighter, beating in upon him until he was kneeling in
a circle of radiance that dazzled his eyes and set his heart to
pounding.

I've lived too long with fear, he thought. I've lived like a man
imprisoned, shut away from the sunlight. Now, when freedom beckons, I
must act quickly or I shall be powerless to act at all.

He stood erect, took a slow step forward, his eyes squeezed shut.
Another step, another--and suddenly he knew he was at the gateway to
Time's sure knowledge, in actual contact with the past for his ears were
now assailed by the high confusion of ancient sounds and voices!

He left the Time machine in a flying leap, one arm held before his face.
He tried to keep his eyes covered as the ground seemed to rise to meet
him. But he lurched in an agony of unbalance and opened his eyes--to see
the green surface beneath him flashing like a suddenly uncovered jewel.

He remained on his feet just long enough to see his Time Observatory dim
and vanish. Then his knees gave