In the early 1600s, a wondrous device was introduced in the Netherlands. It featured a tube with glass lenses at opposite ends and was designed for the purpose of making distant objects appear to be closer. Word of the invention, which would later be called the telescope, spread throughout Europe and came to the attention of Galileo Galilei, an Italian scientist. Although Galileo had not seen the device for himself, he became so intrigued with its potential that he designed and built one of his own.
A devout observer of the skies, Galileo intended to use his telescope to study the stars and planets. His model resembled a small pair of binoculars and used an arrangement of glass lenses for magnification. When he looked through it, objects appeared about thirty times larger than their normal size. In 1609 Galileo became the first person to use a telescope for the purposes of astronomy, and he recorded his findings in a book titled Starry Messenger.
For centuries before Galileo used his telescope, other scientists had been watching the skies and tracking
In the Middle Ages, Ptolemy's philosophy was widely accepted, and was embraced by the Roman Catholic Church, which believed it to be consistent with biblical principles. Any Catholic whose beliefs opposed the geocentric system was considered guilty of a crime called heresy and could be severely punished. Because of the grave risks involved, even scientists who may have disagreed with Ptolemy dared not speak out. For centuries after his death, Europe paid very little scientific attention to studying the planets.
During the Renaissance, a period of heightened interest in the arts and sciences, some people dared to challenge the Earth-centered theory. One of the most famous was a Polish Catholic cleric named Mikolaj Kopernik, who was more widely known by the Latin name he chose for himself, Nicolaus Copernicus. After thirty years of painstakingly charting the motions of the planets, Copernicus wrote about his findings in a book called On the Revolutions of the Heavenly Orbs —and it was clear that his beliefs were radically different from Ptolemy's. According to Copernicus, it was the sun that was at the center of the universe, and all the planets (including Earth) revolved around it. He wrote that no planets or stars orbited Earth, and the only celestial body that did was the moon, which was a satellite rather than a planet. This sun-centered theory became known as the heliocentric system, from the Greek word helios , which means "sun."
Copernicus knew his book would be condemned by the Catholic Church, so he chose not to publish it until shortly before his death in 1543. Yet even though his beliefs were a major step toward correcting the erroneous theories of the past, they were far from perfect. For instance, in discussing what he called the "ballet of the planets," Copernicus proposed that each planet orbited in a perfectly circular motion. (Although this was incorrect, it was a common belief at the time.) Another flaw in Copernicus's theories was its inability to explain why the planets moved the way they did or why Mars sometimes did its peculiar backward march across the sky. Because his book left so many unanswered questions, many scientists did not support Copernicus's ideas.
Several decades after Copernicus's work became public, it attracted the attention of a well-known Danish nobleman and astronomer named Tycho Brahe. Tycho (as he was commonly known) did not agree completely with either Ptolemy or Copernicus, but instead believed there could be a compromise between the geocentric system and the heliocentric system. To observe the skies and chart the movements of the stars and planets, Tycho developed a collection of high-precision instruments. He also founded an observatory on an island located between Denmark and Sweden. The facility, called Uraniborg, came to be known as the finest astronomical observatory in Europe. Among its scientific tools was an instrument called the wall quadrant, which Tycho used to take precise measurements of a celestial object's position in the sky.
Because of Tycho's keen interest in Mars, he focused on it during many of his observations. He noticed that it appeared to move faster than the other planets, so he could chart its movements more frequently. He was particularly interested in knowing
|Scientists Tycho Brahe (left) and Johannes Kepler (center) had differing opinions about the sun-centered theory put forth by Nicolaus Copernicus (right).|
why Mars reversed directions as it moved across the sky. During his twenty years at Uraniborg, Tycho made thousands of measurements of Mars in its various celestial positions.
Toward the end of the sixteenth century, Tycho closed his observatory and moved to Prague, where he was appointed imperial mathematician, the most prestigious mathematics position in Europe. In 1600 he invited German scientist Johannes Kepler to become his assistant. Unlike Tycho, Kepler firmly believed in Copernicus's theory about a heliocentric universe. In spite of their difference of opinion, however, Kepler had a great deal of respect and admiration for Tycho, so he accepted the offer and joined him in Prague. He then began to work on studying the orbit of Mars.
One year after Kepler moved to Prague, Tycho was suddenly stricken with a serious illness. On his deathbed, he pleaded with his assistant to continue with his life's work, saying, "Let me not seem to have lived in vain. . . . Let me not seem to have lived in vain." 3 After Tycho's death, Kepler continued his extensive study of Mars. Over the following years, he proved that Copernicus had been correct: All planets revolve around the sun. One of his findings, though, was particularly astounding—even to him—because it revealed a major flaw in a prevailing scientific belief. Until that point, it was believed that Mars and other planets traveled in circular motions during their orbits. The circle was regarded as the perfect form, and even the most brilliant scientists believed it was impossible for anything less than perfection to guide the movement in the heavens. Kepler himself had shared that belief, but he now knew it was wrong.
During his years of astronomical research, Kepler's calculations had clearly shown that Mars and the other planets did not orbit the sun in a circular pattern at all. Instead, they traveled in the shape of an ellipse, or oval, with the sun off to one side. Kepler found that the shape of a planet's orbit varied based on how close it was to the sun. Those nearest to the sun had a more circular orbit than those farther away. Plus, he noted that a planet's proximity to the sun affected the speed at which it traveled. Because Mars was farther away from the sun than Earth, its orbit time was longer. This discovery was especially profound because it explained why Mars periodically reversed direction in the sky, a phenomenon known as retrograde motion. As Earth traveled along in its orbit, it occasionally passed Mars, which created the illusion that the red planet was moving backward.
In 1609 Kepler announced his findings, which became known as Kepler's laws of motion, and he published a historic book called Astronomia Nova (New Astronomy) . Scientist and author Isaac Asimov explains the importance of these revelations: "Kepler's model of the planetary orbits explained the planetary motions so beautifully and simply that there could be no further doubt that all the planets really moved about the Sun. The system of planets therefore came to be called the 'solar system' from the Latin word for 'sun.'" 4
At the same time that Kepler was making his observations and discoveries, Galileo was using the telescope he had built to get a closer look at the skies. He observed mountains and craters on the moon and spots on the surface of the sun, and he discovered four of Jupiter's moons. Galileo was also able to chart the different phases of the planet Venus, which (like the moon) changed from a full disk to a thin sliver of light. Mars, however, was farther away and not so easily seen. Even though Galileo could see the planet more clearly than was possible with the naked eye, his telescope was quite primitive and not very powerful. Therefore, he could not see any surface features, nor was he able to observe the different phases of Mars as he had with Venus. But he was able to distinguish that Mars's diameter seemed to vary at different times, and he described this in a letter to a friend: "I ought not to claim that I can see the phases of Mars; however, unless I am deceiving myself, I believe I have already seen that it is not perfectly round." 5
Galileo had seen how the appearance of Mars changed based on its proximity to the sun and Earth. He viewed this as undeniable proof that the planets orbited the sun and that Earth was not the center of the universe. Confident in his newfound knowledge, he began to argue publicly in favor of Copernicus's theory, which was still considered a contradiction of biblical teachings. Even though many years had passed since Copernicus's book had shocked and angered the church, any Catholic who supported his theories was in danger of persecution. As a result of his controversial views, Galileo was accused of being a heretic and put on trial. Much to his relief, he was declared innocent and received only a strong warning not to teach Copernican theory.
Yet even threats from the church could not stop Galileo from continuing to observe the skies with his telescope. In 1632 he published Dialogue Concerning the Two Chief World Systems , a book that clearly stated his theory that the universe was not Earth centered. The book infuriated the church, and Galileo was again condemned for beliefs that were considered heresy. At nearly seventy years of age, in order to avoid being tortured and executed, the great scientist denied what he knew was the truth: He publicly stated that he had been wrong to believe that Earth moves around the sun. Galileo's confession saved him from a horrible death, but he lived for the rest of his life under house arrest in his home in Italy.
In the years following Galileo's work with the telescope, scientists developed a heightened interest in studying the skies. One such scientist was Francisco Fontana, an Italian astronomer who produced the first known drawing of Mars in 1636. He continued to study the planet and in 1638 he was able to see its different phases, which he depicted in a second drawing. However, his telescope was only slightly more powerful than Galileo's had been, and he mistook a defect in the lens for variations in the planet's color. As a result, Fontana's drawings did not accurately reflect actual markings on the surface of Mars.
In 1659 a Dutch mathematician and physicist named Christiaan Huygens used his own telescope to observe Mars. Because the model he had built was much more powerful than those used previously, he was able to see a surface feature on the planet that he compared to a large bog. The area, named Syrtis Major, was later confirmed to be one of the darkest
Another Italian astronomer who charted the movement of Mars was Giovanni Cassini, who made drawings of what he observed. He determined that the Martian day was slightly longer than Earth's twenty-four-hour day. He also noticed a white spot at the planet's northern tip, which he assumed was a polar cap.
A few years after Cassini had made his discoveries, Huygens found a second polar cap on the southern tip of Mars. In a book called Cosmotheoros , he explained his views about the possibility of life on Mars. He believed that even though the planet would be colder than Earth because of its distance from the sun, it was possible for life to adapt and survive there. Huygens's health was failing when he wrote Cosmotheoros , and it was not published until 1697, two years after his death. Nevertheless, it was one of the first known publications ever written about extraterrestrial life.
Observations of Mars continued during the eighteenth century. In the late 1700s a British astronomer named Sir William Herschel used his own telescopes to intensively study Mars, and he began to see many similarities with Earth. After measuring the orientation of the Martian poles, he discovered that Mars and Earth were tilted at nearly the same angle, which meant that both planets had four different seasons. He could see that the Martian polar caps grew and shrank as the seasons changed, so he concluded that they were made of snow and ice. In addition, Herschel determined that Mars, like Earth, had some sort of atmosphere, and he (mistakenly) identified dark markings on the Martian surface as oceans.
In a paper titled "The Philosophical Transactions," Herschel described the many similarities between his own planet and Mars:
The analogy between Mars and the earth is, perhaps, by far the greatest in the whole solar system. The [daily] motion is nearly the same; the [slant] of their respective ecliptics, on which the seasons depend, not very different; of all the superior planets the distance of Mars from the sun is by far the nearest alike to that of the earth; nor will the length of the [Martian] year appear very different from that which we enjoy. 6
Because Mars was so much like Earth, Herschel was convinced that the red planet teemed with populations of living creatures. Some scientists shared his viewpoint, while others thought it was nonsense.
As larger and more powerful telescopes were developed, astronomers continued turning their eyes to the heavens. They paid the most attention during oppositions, which was when Mars and Earth were on the same side of the sun. That was when the two planets were closest together and Mars flared more brightly than ever in the sky. The opposition of 1877 was an especially good time for sky watching because Mars and Earth were about 35 million miles apart—as close as they could possibly be. It was during the summer 1877 opposition that American astronomer Asaph Hall discovered the two moons of Mars. He named them Phobos (fear) and Deimos (terror) after characters in Greek mythology.
Another scientist who was intently watching Mars during the 1877 opposition was an Italian astronomer named Giovanni Schiaparelli. In written reports, he noted the location of more than sixty features on the Martian surface, and he drew detailed maps showing them. However, Schiaparelli reported seeing something else during his studies that resulted in decades of myths about Mars: a network of long, dark lines that crisscrossed the brightest areas of the planet. Other astronomers had noticed lines on the Martian surface in the past, but Schiaparelli was the first to report seeing such an extensive collection of them. He called the lines canali , the Italian word for "channels" or "grooves," but the word was mistranslated into English as "canals." This simple error in translation proved to have astounding effects because canals were artificial waterways used for travel, shipping, or irrigation. People throughout the world had become familiar with canals in 1869, when the famous Suez Canal was built to connect the Mediterranean and Red seas. If such waterways existed on Mars, it could mean only one thing—they had been built by some sort of intelligent living beings.
Word of the Martian "canals" traveled fast and soon became front-page news throughout Europe and America. A headline from an August 12, 1877, editorial in the New York Times questioned "Is Mars Inhabited?" and people everywhere wondered what sort of living creatures dwelled on the surface of Earth's neighbor. Noted scientist and writer Sallie Baliunas describes the stir caused by Schiaparelli's announcement:
Speculation about the canal builders spread wildly. The public wished to believe that advanced civilizations existed on Mars. Their ancient oceans gone, their planet dying, Martians had built elaborate canal systems to survive. Brackish areas like Syrtis Major, whose edges changed over the years, were thought of as seasonal plant growth and retreat irrigated by the canals, instead of the shifting sands they are. . . . Plans were devised for signaling the Martians, despite what was sure to be a formidable impediment in translating between Martian and English. 7
One man who was particularly struck by Mars fever was an American self-taught astronomer named Percival Lowell. The news of Schiaparelli's discoveries exhilarated Lowell, and he vowed to devote his time, energy, and substantial financial resources to studying Mars. In 1894 he founded a world-class astronomical research observatory in Flagstaff, Arizona, called the Lowell Observatory. Built at an elevation of more than seven thousand feet, where the air was cool and crystal clear, the facility provided Lowell with the best possible view of the night sky, as well as unparalleled opportunities to examine the red planet.
Lowell spent more than ten years studying Mars, and he identified what he believed to be hundreds of canals—many more than Schiaparelli had discovered. In the process of his observations, Lowell determined that the canals were too wide to be the artificial waterways they were thought to be. Instead, he thought they were agricultural regions with irrigation ditches that were fed when seasonal warming caused the polar ice caps to melt. He became convinced that Mars was a place of intelligent beings who were trying desperately to survive on an aging planet that had grown drier and more barren over time.
During the late 1800s and early 1900s, Lowell gave public lectures and wrote articles for such magazines as Atlantic Monthly and Popular Astronomy. He also published three books: Mars (which included his canal maps), Mars and Its Canals , and Mars as the Abode of Life. Lowell continued to captivate the public with his notions of a living, breathing planet, and newspapers eagerly reported his "discoveries." In 1907 the Wall Street Journal published an article that touted "the proof by astronomical observations . . . that conscious, intelligent human life exists upon the planet Mars." 8 A few years later, the New York Times ran a story titled "Martians Build Two Immense Canals in Two Years," which described Lowell's alleged discovery of Martian canals that were a thousand miles long and twenty miles wide.
This frenzy over Mars sparked the imagination of fiction writers, some of whom were smitten with the red planet. One such writer was Edgar Rice Burroughs, an author who wrote a series of science fiction books featuring a character named John Carter, who has many adventures on Mars. Another famous author who romanticized the red planet was H.G. Wells, whose book War of the Worlds went on to become one of the most famous science fiction books of all time. Wells's book, released in 1898, portrayed Martians as fearsome, brutal, technologically advanced invaders whose mission was to kill thousands of Earth's inhabitants and take control of the planet.
While the general public was being swept away with enticing stories of Martian life, many scientists had begun to question Lowell's findings. Using telescopes that were larger and more powerful than his, they combed the skies, searching for signs of the Martian canals, and could see no trace of them. They suspected that the extensive collection of lines he had professed seeing were actually caused by two things: normal optical illusions and Lowell's overactive imagination. It was eventually determined that the canali seen by Schiaparelli and Lowell were nothing more than natural features and shadows that, when viewed from far away, only seemed to be connected.
In spite of the scientific evidence refuting Lowell's beliefs, he remained convinced that there were intelligent Martians—and canals built by them—until the time of his death in 1916. And even though many of his theories were flawed, to this day he is still considered an important contributor to the heightened awareness of Mars, as noted scientist Robert Zubrin explains:
We now know that Lowell was absolutely wrong in his investigations of Mars, but he did leave an important legacy behind: he fired the imaginations of people to make them see a world on Mars. True, that world turned out to be wildly inaccurate, but its envisionment led to a massive uplifting of at least a segment of the popular mind. . . . Lowell made Mars habitable in the imagination only, but it is from imagination that reality is created. 9