My grandmother once told me that she remembered the mail planes buzzing the family farm-house in Nebraska. She lived to see humankind's first and last (so far) steps on the Moon.
My current students were not even born when the Apollo program was canceled over a quarter- century ago. They remember Moon landings only as something in books or movies, and on television.
Let me pose several questions which you have probably heard before: Where were you in 1957, when the world woke up to a small beeping spheroid named Sputnik, circling our world every ninety minutes to tell us that the Russians got there first? Where were you when John Glenn became the first American astronaut to orbit the Earth? Where were you when Neil Armstrong became the first human to plant his footprints in the dust of another world? These are the events with which we usually mark the "space age." By these markers, space exploration is a mere 41 years old. Yet, in a very real sense, the exploration of space is as old as humanity. It began when our ancestors first looked up in awe and wonder at the lights in the sky, and began trying to explain to themselves and their children what it was all about. I am not suggesting that Babylonian mythology is science, yet the underlying human quest to understand the world is at much at the root of one as the other.
We don't have room here to examine the long and exciting history of space exploration, even if we restrict our attention to the current millennium! You see, I contend that Columbus was exploring space when he set out to cross the Atlantic 500 years ago. I contend that Galileo was exploring space when he turned his new telescope on the Moon and stars. But, what of the current century? Perhaps that is a tractable study.
Space, as perceived at the turn of the 20th Century was a very different entity than we now know it. We knew of the Sun and eight planets. We knew approximately how far away they were, and even approximately where they were in relation to one another - though we didn't have a good handle on the orbit of Neptune and we couldn't explain why Mercury didn't follow its calculated orbit, either. Astronomy, aside from calculations of orbits for comets and planets, was largely descriptive, and all that was there to describe were stars and planets and comets. Meteors and meteorites were an unexplained curiosity. We had no clue as to what powers the Sun or any of the other stars. We were getting a grip on the phenomenal distances between the stars, but our picture of the Galaxy in which we live was horribly geocentric and we had the size very wrong. Some thought that certain glowing patches (the "spiral nebulae") were nearby solar systems starting to form. Others thought that they were distant "island universes" like our own Galaxy.
In April of 1920 there was a public debate between Harlow Shapley of the Mount Wilson Observatory, and Heber Curtis of the Lick Observatory. Shapley wanted to defend his measurement of the size of our Galaxy (which would require the spiral nebulae to be relatively nearby, hence part of the Galaxy). Curtis would argue that they were indeed at extreme distances and not part of the Milky Way. The results of the "Great Debate" were inconclusive - yet, as often happens in the story of science, the definitive observations were just around the corner. Edwin Hubble's resolution of the Andromeda Galaxy into individual stars, and his measurement of its distance at millions of light years clinched the argument for Curtis. Yet, even this result was more a beginning than an ending to the story. Indeed, one of Hubble's results was the conclusion that the distant galaxies are all moving away from us - i.e. the Universe is expanding!
In 1905 Albert Einstein changed the way we understand space and time, showing correctly that they cannot be interpreted as independent. One of the consequences of his Special Theory of Relativity, as it was called, is that matter and energy are somehow also equivalent. Virtually everyone, I'm sure, has seen the famous result
which ultimately gave us the clue to what powers the Sun and other stars.
There are many ways to explore - but they essentially reduce to using your senses to observe the world (or universe) around you. The development of the telescope 350 years ago by Galileo can be understood as a way of improving what your eyes can see. In the 19th Century, Bunsen and Kirchhoff brought the tool of spectroscopy into the laboratory - yet another improvement on normal vision. In the 1920s, Karl Jansky stumbled onto radio emissions from the sky - he invented the field of radio astronomy, but that's really just another way to see at wavelengths your eyes can't. World War II gave us radar - and its declassified use extended radio astronomy to shorter and shorter wavelengths. Even so, all of astronomy was restricted to the light of various wavelengths we could capture with our assorted telescopes here on the ground, or flown from high-altitude balloons. The "Great Debate" of the 1950s was over whether the expanding universe had always been as we see it (the so-called Steady State Universe) or had a beginning at some point in the past (the Big Bang).
Then came Sputnik. German rocket engineers, captured by the Soviets at the end of the war against European fascism, helped the Soviet Union launch the first artificial satellites. The United States soon followed. As Lyndon Johnson once said, "Our Germans are better than their Germans."
Remember Telstar? The communication satellite is probably the greatest success of the space age - indeed, it's the only way anybody has come up with to make money. But its importance should not be minimized in how we have come to perceive our world. Nearly instantaneous communication to all parts of the globe would be impossible without that technology. Your next telephone call may travel to a satellite 23000 miles above the equator and back, and you don't have to give it a thought.
But, space and satellites are not just the province of telecommunications. Those early satellites, and their sophisticated cousins of today, lifted humankind's eyes and ears and hands into space, long before Yuri Gagarin's first, tentative single orbit. Freed of the necessity to peer murkily through our atmosphere, satellite technology has extended the range of observation to the entire spectrum. The Universe is now seen in everything from X-rays to radio. Above the soup of our atmosphere, the appropriately-named Hubble Space Telescope extends our clear vision back to the earliest times of star and galaxy formation.
Robot probes, have carried our figurative eyes and ears to all the planets in the solar system, save distant Pluto. We have dug trenches in the soil of Mars, dropped balloons to circumnavigate cloudy Venus. Voyager and Pioneer probes, launched more than 20 years ago and now the most distant human artifacts, are humanity's first ambassadors to the stars. Jupiter and her moons are yielding their secrets - might life once have been possible in the interior oceans of Europa? We know there was once water in abundance on Mars - was there life also?
Compared to our robot eyes and ears, human presence in space is almost trivial. 12 humans have walked the surface of the Moon. The rest of spacefaring activity takes place within a few hundred miles of Earth's surface, only a little farther from home than John Glenn's first orbital flight. Dreams of going to Mars will have to wait yet a while longer - the undertaking will be much more complex than the Moon shots, with no Cold War competition to spur the nation on. Dreams of an international space station are behind schedule and over budget, with the first hardware scheduled for it long-delayed launch in November.
So, why do we do all this? My answer comes at several levels, and you may find them unsatisfactory. First and foremost, we explore space because it is human nature to be curious. We do so because the effort is inspiring - recall the feeling of hearing Neil Armstrong's "One small step for a man, one giant leap for mankind." Recall the jubilation as Pathfinder rolled down the ramp to the martian surface last summer. Feel the awe of Hubble's image of the "pillars of creation" in the Eagle Nebula, or the thousands of galaxies revealed in the Deep Field image of an area on the sky smaller than a grain of sand at arm's length. Recall how our picture of the world changed when Apollo 8 sent us pictures of Earth as seen from lunar orbit, small and lonely and fragile in the vastness of space.
Why send people, when it's so expensive? Space science is probably less exciting to the average person than space flight, though one could argue that NASA has succeeded (except in a few cases, like Apollo 13 or Challenger) in making it appear mundane. The basic science goes along for the ride with Buck Rogers. One of the original Mercury astronauts summed it up by saying, "No Buck Rogers, no bucks."
There's another reason, too, though with this summer's crop of asteroid disaster movies I almost hate to bring it up. Remember those meteors and meteorites I mentioned at the beginning, which were not fully understood at the turn of the century? Well, here's what we now know about them.
The meteors you see as "shooting stars" are mostly fragments of comets - remember Hale-Bopp from last year, or Hyakutake from the year before? The comets are like giant dirty snowballs, and when their orbits bring them in close to the Sun they vent gas and spew lots of dust. When that dust hits the Earth's atmosphere it heats up and vaporizes, which is what you see streaking across the night sky. Our solar system also contains rocky fragments of asteroids - and when these hit the atmosphere, they don't always burn up. Larger fragments can reach the surface, and sufficiently large fragments can do catastrophic damage - at least the movies got that much right!
When Comet Shoemaker-Levy hit Jupiter in 1994, it released more energy than all the nuclear arsenals of the world. Our planet has been struck by large comets or asteroids in the past, and such events are likely to occur again in the future. We believe that such an impact triggered the extinction of the dinosaurs. A small rocky asteroid exploded over Siberia in 1907, flattening a large area of tundra in an explosion which would have been disastrous if it happened over a populated region. Had it happened at the height of the Cold War, it could have started a hot war!
Simply put, it's not especially safe here! And it's not a good idea to leave all of humanity's eggs in a single basket. Humankind has migrated all over this planet, and the time is coming for some portion of humankind to migrate off the surface of the Earth and begin to colonize the solar system. Eventually, we may even colonize the stars. In the words of Konstantin Tsiolkowski, the visionary pioneer of notions of space flight:
Copyright 1998
Dr. George F. Spagna, Jr.
Associate Professor of Physics
Director of the Keeble Observatory
Randolph-Macon College
Ashland, Virginia 23005
