September 13, 1999
Web posted at: 1:25 p.m. EDT (1725 GMT)

By L.D. Meagher
for CNN Interactive

(CNN) -- If we are to understand the nature of the universe that surrounds us, we might start by trying to determine just how much of it there is. It's an endeavor that has occupied the human mind for at least 2,300 years, including some of the best scientific minds of the 20th Century.

In "Measuring the Universe," science writer Kitty Ferguson traces the evolution of thought that accompanied the ongoing efforts to determine the size of the Earth, the solar system, and ultimately all of space. Each step up what she describes as a "ladder" of measurement has been accompanied by a new way of thinking about how the world works.

Take Eratosthenes, a scholar in Egypt during Hellenistic times. When he learned that a shaft of sunlight penetrated to the bottom of a well in Syrene on the summer solstice, he deduced that he could use the information to measure the circumference of the Earth. That meant, of course, that he understood our planet is spherical. The notion that the Earth is round actually pre-dates the New Testament.

At about the same time, another Egyptian scholar, Aristarchus of Samos, was trying to figure out how far the moon and sun are from the Earth. In the process, he deduced that the moon orbits the Earth, and the Earth orbits the sun. His insight beat Copernicus to the punch by a millennium and a half. Unlike Copernicus, however, nobody believed Aristarchus.

Ferguson uses such examples from the early history of science to illuminate the central point of her book. Taking the measure of a world -- or a universe -- forces us to examine it and try to understand it. She introduces us to a procession of scientists who have helped humanity get a grip on just how much space there is around us. Some are well known figures -- Galileo, Newton, Einstein, Hawking -- while others have toiled in relative obscurity. Astronomer Vesto Melvin Slipher, for example, spent his entire career working at a single observatory. Yet his findings demonstrated that most of the "nebulae" charted in the sky during the early 20th Century were moving rapidly away from us. His work inspired an attorney-turned-astronomer named Edwin Hubble, for whom the Space Telescope is named, to discover that the "nebulae" are in fact distant galaxies and their movement charts the expansion of the universe.

For a book about distances, "Measuring the Universe" contains surprisingly few numbers. Mostly, it focuses on people. Ferguson manages to breathe life into the figures that tower over the history of astronomy. She tells us that Johannes Kepler was intent on becoming a Lutheran minister, and fell into mathematics and astronomy almost by accident. She reveals that while he was working out his landmark laws of planetary motion, Kepler often made ends meet by casting horoscopes.

Today's astronomers and astrophysicists have better tools than a shaft of sunlight in a well. But they demonstrate the same kind of imagination Eratosthenes had as they puzzle out the meaning behind what their instruments detect. "Einstein often spoke of the gift of fantasy being essential to the work he did," Ferguson writes. "Certainly these intellectual descendants of his who speculate about how the universe fits into a larger context have that gift. In one sense, they are all remarkably inventive yarn spinners. And yet their theories and proposals are not science fiction. This is fantasy tethered to the known world by hefty guy wires of mathematical equations."

They are pushing back the boundaries of science itself as they try to determine the distance to the ends of the universe -- and whether it has anything remotely resembling an "end." Ferguson shows us that the expanding scale of the universe is forcing a new way of thinking about how it came to be. "How big" not only determines "how old." It may in some way define what the universe is. On a cosmic scale, it turns out, size really does matter.

L.D. Meagher is a senior writer at CNN Headline News. He has worked in broadcasting for 30 years.