Kitty Ferguson - Measuring the Universe

"In Measuring the Universe, we'll forget we know the measurements or how to make them, and join our ancestors as they tease this information out of a sky full of stars. The laboratory isn't a neat, sterile room where carefully controlled experiments take place. Events in the heavens happen in their own good time and not before, and they are often not repeatable. Astronomers have learned to take what's on offer and make the best of it." (p. 4)

Measuring the Universe, unfortunately, does not have footnotes or direct references. It does contain useful illustrations throughout, a glossary, and a six page "Notes" section. The Notes section is very useful if you are looking for descriptive pointers to future readings on the topics discussed in any given chapter. The references are broken down by chapter and usually include much more than just the recommended book's name.

from the publisher:
More than 2,000 years ago, Eratosthenes, in Alexandria, used a stick, a hole in the ground, sunlight at summer solstice, and elementary geometry to measure the circumference of the Earth with surprising accuracy, long before anyone was able to circumnavigate it. Today, scientists are attempting to measure the entire universe and to determine its origin. Although the methods have changed, the quest to chart the horizons of space and time continues to be one of the great adventures of science.

Measuring the Universe is an eloquent chronicle of the men and women--from Aristarchus to Cassini, Sir Isaac Newton to Henrietta Leavitt and Stephen Hawking--who have gradually unlocked the mysteries of "how far" and in so doing have changed our ideas about the size and nature of the universe and our place in it. Kitty Ferguson reveals their methods to have been as inventive as their results. Advances such as Copernicus's revolutionary insights about the arrangement of the solar system, William Herschel's meticulous creation of the first three-dimensional map of the universe, and Edwin Hubble's astonishing discovery that the universe is expanding have by turns revolutionized our concept of the universe. Connecting centuries of breakthroughs with the political and cultural events surrounding them, Ferguson makes astronomy part of the sweep of history.

To measure the seemingly immeasurable, scientists have always pushed at the boundaries of the imagination--today, for example, facing the paradox of an ever-expanding universe that doesn't appear to expand into anything. In Kitty Ferguson's skillful hands, the unimaginable becomes accessible and the splendid quest something we all can share.

Author
Kitty Ferguson is a science writer and the author of Prisons of Light: Black Holes; The Fire in the Equations: Science, Religion, and the Search for God; and Stephen Hawking: Quest for a Theory of Everything. She is also a professional musician. Ms. Ferguson lives in northern New Jersey.

Excerpt
The following is an excerpt from the book: Measuring the Universe: Our Historic Quest to Chart the Horizons of Space and Time by Kitty Ferguson
Published by Walker & Co; 0802713513; $27 US; Oct. 99
Copyright © 1999 Kitty Ferguson

Chapter 1: A Sphere with a View {400-100 B.C.}

"The great mind, like the small, experiments with different alternatives, works out their consequences for some distance, and thereupon guesses (much like a chess player) that one move will generate richer possibilities than the rest.... It still remains to ask how the great mind comes to guess better than another, and to make leaps that turn out to lead further and deeper than yours or mine. We do not know."  Jacob Bronowski

Eratosthenes's accomplishments were, indeed, numerous and eclectic. He attempted to fix the dates of the major literary and political events since the conquest of Troy; he composed a treatise about theaters and theatrical apparatus and the works of the best-known comic poets of the "old comedy"; he suggested a way of solving a problem that had tantalized mathematicians for two centuries--"duplicating a cube"; and he let his voice be heard on the subject of moral philosophy and felt it essential to criticize those who were "popularizing" philosophy . . . "dressing it up in the gaudy apparel of loose women." But it was none of those achievements that won him his place in the history books. What modern schoolchildren learn about him is that he invented "the sieve of Eratosthenes"--a method for sifting through all the numbers to find which are prime numbers--and that he discovered a way to measure the circumference of the Earth with astounding accuracy.

The idea that scholars before Columbus believed the world was flat is a fable created in modern times. Admittedly, the shape of the Earth probably wasn't of much daily practical interest to most people in the ancient world. However, already long before Eratosthenes, those few who were wondering about it at all were not seriously suggesting that the Earth was any shape but spherical. The Pythagoreans, a school of thinkers revered for their genius in mathematics and music, had decided as early as the sixth and fifth centuries B.C. that the Earth is a sphere. A century before Eratosthenes, Plato pictured a cosmos made up of spheres within spheres, nested one within the other, with a spherical Earth at the center. Only a little later than Plato, Aristotle vigorously subscribed to the idea of a spherical Earth, and his defense proved convincing not only to the ancient world but also to the Middle Ages.

Aristotle rested his case partly on observational evidence: During an eclipse of the Moon, the shadow cast by the Earth on the Moon is always curved. Also, in Aristotle's words:

There is much change, I mean, in the stars which are overhead, and the stars seen are different, as one moves northward or southward. Indeed there are some stars seen in Egypt and in the neighborhood of Cyprus which are not seen in the northerly regions; and stars which in the north are never beyond the range of observation, in those regions rise and set. All of which goes to show not only that the Earth is circular in shape, but also that it is a sphere of no great size: for otherwise the effect of so slight a change of place would not be so quickly apparent.

Aristotle speculated that the oceans of the extreme west and the extreme east of the known world might be "one," and he reported with some sympathy the arguments of those who had noticed that elephants appeared in regions to the extreme east and the extreme west, and who thought therefore that those regions might be "continuous."

Aristotle's philosophy also argued for a spherical Earth. He had concluded that five elements--earth, air, water, fire, and aether--each have a natural place in the universe. The natural place for the element earth is at the center of the universe, and for that reason earth (the element) has a natural tendency to move toward that center, where it must inevitably arrange itself in a symmetrical fashion around the center point, forming a sphere. Aristotle reported that mathematicians had estimated the Earth's circumference as 400,000 stades, that is, about 39,000 miles or 63,000 kilometers (more than half again as large as the modern measurement). No record survives of the method used to arrive at that number.

The Intellectual Spoils of War

When Aristotle died in 322 B.C. at age sixty-two, the military campaigns of his most highly achieving pupil, Alexander the Great, had just ended with Alexander's death. Vastly widened mental horizons were part of Alexander's extraordinary legacy. His campaigns had carried Greek knowledge, language, and culture throughout Asia Minor and Mesopotamia as far east as present-day Afghanistan and Pakistan, all the way to the Indus River, as well as to Palestine and Egypt. The culture of Greece and its colonies and the cultures of the conquered peoples began to mix and enrich one another. This was the dawn of the Hellenistic era, as opposed to the Hellenic. That is, Greekish, as opposed to Greek.

At the time of Alexander's and Aristotle's deaths, within a year of one another, Athens was still the undisputed center of the intellectual world. That preeminence was not to last. Alexander's generals divided his empire, and Ptolemy's portion was Egypt and Palestine. He made Alexandria, near the mouth of the Nile, his capital. This already prospering city began to grow in size and splendor, and Ptolemy and his successors, reputedly ruthless in their exploitation of the lands under their control, amassed a surplus of wealth, some of which they chose to spend on literature, the arts, mathematics, and science. Scholars are divided as to which Ptolemy should get the credit (Ptolemy's successors were also named Ptolemy), but either the first or the second, and perhaps it took both, extended the royal patronage to found a library and a museum. The word museum meant "temple to the muses," both a religious shrine and a center of learning.

Meanwhile the old, justly famous schools across the sea in Athens, schools founded by Plato, Aristotle, Epicurus, and the Stoics, were no longer producing vibrant new ideas to quite the extent they once had, though they were still the places a young man of Eratosthenes's time would have wished to go for his education. Alexandria began to rival and eventually supplanted Athens as the focal point of the thinking world, and the Alexandria Museum and Library became the premier research institution. The library grew large, containing by one ancient estimate nearly 500,000 rolls. The salary of the director, or librarian, came from the royal coffers.

The story (now thought to be apocryphal) is that the contents of the library at Alexandria were burned to heat the public baths for six months in the seventh century A.D. Whether the destruction occurred quickly and calamitously then or, more likely, gradually through neglect and the many political, military, and religious turns of fortune that affected the city of Alexandria, the loss was the symbol and symptom of a greater tragedy: the widespread disappearance of any perception that such intellectual achievement was of value. By the 600s, there was probably little left to burn. It took centuries for humanity in the Western world to reach again an intellectual level on a par with the civilization that had produced that lost collection. But in the third and second centuries B.C., all this was still many centuries in the future. The Alexandria Library was in its heyday.

The scholars connected with this august institution and their forebears in the Hellenic world would have been mystified by the present-day concept of "science" as a distinct category of knowledge and pursuit of knowledge. Some modern words have evolved from terms they used to describe similar areas of interest, but the modern words don't have precisely the same meaning these had in ancient Athens and Alexandria. Some examples: peri physeos historia (inquiry having to do with nature); philosophia (love of wisdom, philosophy); theoria (speculation); and episteme (knowledge). Hellenistic scholars thought of "physics" as one of three branches of philosophy. The other branches were "logic" and "ethics."

Another key difference between the ancient and modern ways of thinking is that Hellenic and Hellenistic scholars tended to be somewhat scornful of the notion that their effort might serve mundane, practical purposes. They preferred to think of it as contributing to wisdom, or improvement of one's character, or leading to greater appreciation of the beauty of the universe and understanding of its creator. The life of a scholar, the life of "contemplation," was considered an exquisitely happy life. Doctors, whose efforts were intended to have more everyday practical value, were apt to differentiate themselves entirely from the "philosophers," whose work was its own reward, an end in itself, not a means to an end. The Ptolemys were of course far from displeased when research could be applied to problems connected with weaponry, but their financial support and their efforts to outbid all competitors when it came to collecting the masterpieces of Greek literature and encouraging distinguished scholars to flock to Alexandria were far more strongly motivated by desire for prestige--to add to the luster and apparent power of the dynasty. It seemed not to occur to these men and women in ancient times that scholarly endeavors might hold the key to material progress.

Theirs was also a perspective in which how to solve a problem was as interesting as actually solving it, often more so, an attitude arising partly out of necessity, for Greek and Hellenistic scholars were fascinated with questions that they lacked the technology to answer definitively. A modern analogy might be the typical "word problem" in grade school. Let's say you're presented with the question: If you ride your bicycle at an average speed of thirty miles per hour, and it takes you ten minutes to get from home to school, how far is school from home? You do not immediately start quibbling that thirty miles per hour is not an accurate measurement of the speed you normally ride, that it actually takes you twelve minutes to get to school, and that this exercise isn't going to end with anyone knowing how far from home your school really is. No. What everyone is interested in is your showing that you understand how to solve the problem. Move back a step and imagine that it is also up to you to invent the method for solving it--that no one, in fact, has ever even thought it possible to calculate the distance from your home to your school and that you can't ride there to measure it directly. You have put yourself in the shoes of Eratosthenes and others whose work this chapter describes, a situation that allows, indeed encourages, the formation of hypotheses, sometimes out of thin air ... statements such as, "We don't know that this is true, but let's assume for a moment that it is, and see where that gets us." Or even such a statement as, "We know that this is not true, but let's pretend for the moment that it is and ask 'what then?'" To criticize the results of an exercise like that by saying the results are "wrong" (i.e., do not accord with twentieth-century findings) is to miss the point.

The scholarly mind-set of his era partly explains why Eratosthenes took on what might seem to have been an impossible problem and tried to find an answer that was of no use to the ancient world: the circumference of the Earth. His success was rooted in the widened horizons and the mixture of cultures that characterized the Hellenistic world. It also had a great deal to do with the sort of man he was.

Copyright © 1999 Kitty Ferguson