Today, a janitor helps us fathom time. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

Jay Gould is a geologic historian. He tells how geologists came to terms with time that ran far older than the Biblical begats. 18th and 19th-century scientists, he says, held opposing views of our ancient past. Some thought that Earth had taken it's shape progressively -- over eons. Others held that Earth is shaped by purely cyclic processes -- that Earth has no history -- no beginning -- no end.

Earth is both things, says Gould. To underscore the point he shows us two strange works of art. First, the frontpiece of Thomas Burnett's 300-year-old book on cosmology. Burnett showed Earth after each catastrophic Biblical event, since the beginning. Then he closed the circle. He showed Earth passing through a matching set of future events that finally return it to perfection. He endowed history with a fearful symmetry.

Burnett was a serious scientist. He labored to fit observed facts into the Biblical accounts. Earth, he said, evolves. Yet it also moves in a great looping cycle. He set the stage for both parts of the debate that followed him.

Gould ends with a work by James Hampton, a barely literate black janitor. In a vision, Hampton was told to build a throne room for the Second Coming. And for 33 years he did. Each night, after work, he shaped it from bits and pieces -- old furniture, light bulbs, beer cans. He captured beauty that we overlook.

The world found Hampton's masterpiece when he died in 1964. It's a glittering array of symbolic furniture. 177 ornate pieces are all wrought in perfect bilateral symmetry. He poured enormous creative energy into his secret room. He transmuted junk into works of strange grace and balance. Gould first saw them in the National Museum of American Art, and he was stunned.

Hampton's throne room was just like Burnett's frontispiece. Both tell of Earth's progressive, symmetrical cycle. Hampton's pieces tell of Alpha and Omega. He arranged them in a circle that begins the ends at the top. Like Burnett's drawing, they retell the past on the right. On the left they prophesy a future that will replay past events in reverse.

With eerie clarity, James Hampton saw what scientists had struggled to see ever since Burnett. He saw that events cycle in time. Things repeat. Day follows night. Nature displays symmetry. But he also saw that time is directional and irreversible. It takes us from one place to another. If science tells of reproducible, or cyclic, events, it also recites our history. It tells the story of our trek through time. Science tells of things that begin and that, someday, must also end.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

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Gould, S.J., Time's Arrow, Time's Cycle. Cambridge, MA: Harvard University Press, 1987.