Galileo’s Telescope—Only the Beginning!
WHEN Galileo turned his newly invented telescope to the sky, a whole new vision swam into view. He could see ten times as many stars as any man had ever before seen. The Milky Way now appeared, not as a nebulous mass, but as a kaleidoscope of countless stars, great and small. The moon’s surface was transformed before his eyes from a lustrous porcelain into a mosaic of mountains, craters, and waterless seas.
A few months later, he spotted four of the moons of Jupiter. Then he saw the beautiful rings of Saturn. Directing his telescope to Venus, he noticed certain phases of the planet, subtle changes in illumination and apparent shape. These phases could be explained only if the planet moved around the sun. But if one planet moves around the sun, the others—including the earth—must do so also, he concluded. He was right. Thus, in the year 1609, the earth was toppled from its hallowed pedestal as the alleged center of the universe.
But venerated beliefs were not easily abandoned. The Catholic Church ruled that “the view that the earth is not the center of the universe and even has a daily rotation is . . . at least an erroneous belief.” Galileo was hauled before the Inquisition and spent the last years of his life under house arrest. Religious dogmatism, however, could not check the curiosity that the invention of the telescope had raised. The challenge of unlocking the secrets of the universe attracted a growing number of scientists.
Now, after nearly four hundred years of intensive scrutiny, our knowledge of the universe has increased dramatically. Different types of stars, such as red giants, white dwarfs, and pulsars, have been identified. Recently, quasars—enigmatic objects that emit prodigious amounts of energy—have been detected in the outer reaches of space. And mysterious black holes—like unimaginably powerful cosmic whirlpools—are now believed to lurk unseen in many galaxies.
Powerful optical telescopes enable astronomers to peer far into space and thereby in effect journey billions of years back in time, to the very edge of the visible universe. A vast array of stars and galaxies have been discovered, some so distant that their light is calculated to have taken more than 15 billion years to reach us.a
Although stars in general are weak radio sources, other celestial objects, such as pulsars and quasars, have been discovered thanks principally to radio telescopes. As the name implies, these telescopes detect radio wavelengths rather than optical wavelengths. Since 1961, hundreds of quasars have been detected, many of them in the outer reaches of the known universe.
The task of charting the universe was greater than Galileo could possibly have imagined. Only in this century has man begun to comprehend the enormity of the cosmos, the billions of galaxies of which it is composed, and the staggering distances that separate them.
To help us imagine cosmic distances, physicist Robert Jastrow suggests the following analogy. Imagine the sun scaled down to the size of an orange. Then the earth would be a mere grain of sand circling in orbit around the sun at a distance of 30 feet [9 m]. Jupiter would be like a cherry pit revolving around the orange a city block away, and Pluto would be still another sand grain at a distance of ten city blocks from our imaginary orange, the sun. On that same scale, the sun’s nearest neighbor, the star Alpha Centauri, would be 1,300 miles [2,100 km] away, and the entire Milky Way a loose cluster of oranges separated from one another by about 2,000 miles [3,200 km], with an overall diameter of 20 million miles [30 million km]. Even when everything is scaled down, the figures soon get out of hand.
It is not just the distances that are astounding. As scientists have unveiled the secrets of the universe, peculiar phenomena have come to light. There are neutron stars consisting of matter so dense that a mere teaspoonful weighs as much as 200 million elephants. There are tiny stars called pulsars, one of which winks on and off some 600 times a second. And, of course, there are those tantalizing black holes scientists speculate about. The holes themselves cannot be seen, but their insatiable appetite for light and matter may betray their cryptic presence.
Much, of course, still remains a mystery, shrouded by those immense distances and aeons of time. But what have scientists so far discovered about the universe? Does what they know throw new light on how and why the universe exists?
a To make these enormous distances manageable, new units of distance, such as the light-year, had to be created. A light-year is the distance that light travels in one year, some six trillion miles. A car traveling at a fixed speed of 60 miles an hour [100 km/hr] would take more than 11 million years to cover that distance!
[Picture on page 4]
The Jodrell Bank radio telescope, constructed in 1957 in England, was the first fully steerable unit
Courtesy of Jodrell Bank Radio Telescope