If you have only lived on Earth, you have never seen the sun. Of course, we could not look at it directly, but only through dense filters that cut its rays down to endurable brilliance. It hung there forever above the low, jagged hills to the west of the Observatory, neither rising nor setting, yet moving around a small circle in the sky during the eighty-eight-day year of our little world. For it is not quite true to say that Mercury keeps the same face always turned toward the sun; it wobbles slightly on its axis, and there is a narrow twilight belt which knows such terrestrial commonplaces as dawn and sunset.

We were on the edge of the twilight zone, so that we could take advantage of the cool shadows yet could keep the sun under continuous surveillance as it hovered there above the hills. It was a full-time job for fifty astronomers and other assorted scientists; when we’ve kept it up for a hundred years or so, we may know something about the small star that brought life to Earth.

There wasn’t a single band of solar radiation that someone at the Observatory had not made a life’s study and was watching like a hawk. From the far X-rays to the longest of radio waves, we had set our traps and snares; as soon as the sun thought of something new, we were ready for it. So we imagined…

The sun’s flaming heart beats in a slow, eleven-year rhythm, and we were near the peak of the cycle. Two of the greatest spots ever recorded—each of them large enough to swallow a hundred Earths—had drifted across the disk like great black funnels piercing deeply into the turbulent outer layers of the sun. They were black, of course, only by contrast with the brilliance all around them; even their dark, cool cores were hotter and brighter than an electric arc. We had just watched the second of them disappear around the edge of the disk, wondering if it would survive to reappear two weeks later, when something blew up on the equator.