The Unfolding Universe

photo of launch vehicle rising from a sea of rocket engine exhaust

"Liftoff! ... We have liftoff!"
A Delta rocket slowly rises from its launch pad to carry yet another payload into space. The development of rocket boosters powerful enough to overcome the gravity of our own planet was a critical step in the scientific exploration of space. This launch in 1975 placed an Orbiting Solar Observatory spacecraft (OSO-8) in orbit above the Earth to make scientific observations of the Sun.

Only 500 years ago, the universe seemed simple, orderly, peaceful, and well-understood. The Earth stood motionless at the center. The Sun, Moon, and planets circled it at no great distance. Slightly further away, the fixed stars were tiny points of light mounted on a sphere of pure crystal. It was a small, comfortable, and reassuring universe, and Man was at the center of everything.

In only a few centuries, the scale of the solar system and of the universe expanded incredibly as a result of investigation and study. The telescope and the Copernican theory replaced the Earth with the Sun at the center of the solar system. The five wandering lights (called planets by the Greeks) became individual worlds. New discoveries in physics and spectroscopy made it possible to analyze and even weigh the distant stars. Still larger telescopes moved the Sun from the center of things to the fringes of the Milky Way galaxy, a huge system of 100 billion or more stars. Then the Milky Way became only one of billions of galaxies in an expanding universe. New telescopes, sensitive to radio waves, probed the universe, discovering strange objects and powerful sources of energy that our eyes could never see.

When we suddenly entered the Space Age with the launch of Sputnik I on October 4, 195 7, we broke through the last two barriers to our exploration of the universe: gravity and air. We now could escape from the pull of Earth's gravity, in which we had spent all of history, and reach other worlds. Astronauts and machines could stand on other planets, study them at close range, and bring back samples to analyze on Earth. Robot spacecraft could fly past other worlds, sending back closeup video pictures that brought distant planets closer to us than our own Moon.

With the Space Age, a second barrier fell away: the blurring and dimming caused by the Earth's atmosphere as we look outward from the ground. Out in space, instruments and human eyes could see the universe directly in all of its incredible violence, immensity, and variety.

An ear for the universe.
An ear for the universe. The dish antenna of a large NASA radio telescope located at Madrid, Spain is outlined against the sunset sky. The antenna is 64 meters (21 Ofeet) in diameter. It is used to track interplanetary spacecraft, to send commands to them, and to receive from them the radio signals that carry scientific information and pictures of other worlds. Other, even larger, radio telescopes analyze radio waves from distant stars and galaxies. Radio telescopes have even detected a whisper of noise from the edge of the universe, an echo of the Big Bang that formed the universe 15 to 20 billion years ago. Radio telescopes like this one could also be used to detect extraterrestrial life - by listening for the communications of other civilizations in space.

phot of a large dish shapped radio telescope

Looking back at the launch of Sputnik 1, we realize how much that we take for granted now - only a generation later - was unknown and in many cases not even suspected then. In the universe of 1957:

The Sun seemed a basically stable, steadily shining star.
Mercury and Venus were just blurs in the telescope; there was no information on their remarkable geologic features.
No one knew that the Earth was surrounded by belts of trapped radiation.
Mars, some astronomers thought, had "canals"; perhaps it sheltered some form of life as well.
The moons of Jupiter were no more than points of light, hardly more visible than they were to Galileo when he discovered them in 1610.
Among the planets, only Saturn was known to have rings.
Pluto had no known moon; the planet size and mass were hardly more than matters of conjecture.
The only known volcanoes were those on the Earth.
No one knew what a moon rock was like; no one had touched or studied one.
Chemists had found traces of the origin of the solar system in meteorites, but no clues to earlier events.
Black holes and neutron stars were creatures of the physicist's imagination.
No one had even speculated that such objects as quasars and pulsars might exist.
The "Big Bang" was just one of several theories for the origin of the universe; it seemed unlikely that evidence to clearly discriminate between them would be found.
No one had gone into space.
It was widely doubted that human beings could survive and work in space, given the dangers of radiation, weightlessness, and meteorites.
Among sciencefiction writers, few predicted that there would be a man on the Moon before, say, the 1990's.

color photo of the 'blue planet' Earth as seen from the lunar horizon

The big blue marble.
Earth, the home planet of humanity, rises above the scorched and cratered surface of the Moon in this photograph taken from the Apollo 11 spacecraft shortly before the astronauts set foot on the Moon. In addition to making it possible for to see new worlds, the Space Age gave us a new view of our own planet. Astronauts, poets, writers, and average people alike were struck by the image of the Earth as a tiny, blue, hospitable, life-bearing world, floating in a vast uncaring blackness, side-by-side with the battered and lifeless Moon.

During a single generation, astronomers and space scientists have compiled a remarkable list of accomplishments and discoveries. Other planets have become individual, familiar worlds that we can see and touch, at least with the aid of remotely-controlled instruments. We have analyzed crystals from the Moon, measured the winds of Mars, and seen the violence of the volcanoes erupting unexpectedly on Jupiter's moon, Io. We have seen our own Sun in a new "light" - X-rays and ultraviolet - and have gained new insights into the character of this star that makes life possible. We have sensed the turmoil in the huge, violent universe beyond: incredible energies and fantastic objects such as quasars, pulsars, and black holes. We have even caught the whisper of creation, the tiny echo of microwave radiation from the moment, billions of years ago, when the new universe was just expanding from the Big Bang.

We have also gained a new viewpoint on ourselves and the Earth. We have found our own origins in the stars: carbon compounds in meteorites, organic molecules in interstellar space, the calcium and iron in our bodies that came from stars that died before the Sun was born. We have a new view of the Earth: a small, blue, habitable island in a vast, forbidding blackness. By studying the life-styles of other worlds, we are learning more about our own: its history, weather, climate, all the circumstances and conditions that are critically important, not only to science, but to our survival.

In a single generation, we have learned more about the cosmos than we did in all the centuries that went before. It seems almost unbelievable that we have been able to discover so much about objects so huge, so ancient, so complex, and so far away. Yet all this knowledge is just the basis for new explorations, discoveries, and understanding. Our current view of the universe probably is no more permanent than were the ideas people had five centuries ago. It will changejust as radically as did the old concepts, as we do more and see further. All that we have done is yet a beginning, and future generations may regard our view of the universe with the same amused tolerance that we reserve today for the ancients' crystal sphere.