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Chapter 2:
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Chapter Breakdown: |
Earth's Twin Sister
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"She blinded me with science."
--Thomas Dolby |
Although the mountains, continents and canals so carefully sketched by early astronomers turned out to be imaginary, they did make many correct deductions about the physical nature of Venus, and these too conspired to reinforce the impression of another Earth waiting next door.
In 1761, at the University Observatory in Saint Petersburg, Russia, Mikhail Lomonosov observed a transit of Venus, a rare passage directly in front of the Sun. He was hoping to find Venus' diameter by measuring the size of its dark outline, which becomes visible during a transit in stark contrast to the bright Sun behind it. He was able to get a fairly good measurement and found that Venus' diameter was very similar to Earth's. But the precision of his measurement was hampered by a curious phenomenon. The edge of the Venusian disk, instead of appearing sharp, as he had expected, was fuzzy and indistinct, and a gray halo surrounded the planet. Consternation must have quickly turned to wonder as he realized the true source of this annoyance. Lomonosov had discovered the atmosphere of Venus. In his words, he had found evidence of "an atmosphere equal to, if not greater than, that which envelops our earthly sphere."
Observation and inference quickly gave way to speculative extrapolation. 1400 years before Lomonosov's discovery, Venus, as Kukulcan, had bravely battled underworld demons at the side of his brother, the Sun. For the next two centuries it was to act out a new, scientifically supported mythical role: Earth's twin sister.
Considering what we knew about Venus at the time, this is not surprising, especially given the widespread post-Copernican propensity for finding familiar environments on the other planets. Lomonosov's discovery of the atmosphere, and the correct inference by many early observers that the bright, featureless appearance of Venus is due to a planet-wide cloud cover, led to an irresistible line of reasoning. Venus is nearby and the same size as the Earth. It has a thick atmosphere full of clouds--clouds, it was assumed from terrestrial experience, made of water. Since Venus is closer to the sun it must be somewhat hotter there than here. Therefore, Venus must be a hot, wet, thickly vegetated planet--a swamp world. Everything we actually knew about the planet was indeed remarkably like the Earth, so it was easy to extrapolate this likeness to the surface of the planet and imagine a sister Earth beneath the clouds.
In his 1888 book Astronomy with an Opera Glass, Garett Serviss wrote
"It is an interesting reflection that in admiring the brilliancy of this splendid planet the light that produces so striking an effect upon our eyes has but a few minutes before traversed the atmosphere of a distant world, which, like our own air, may furnish the breath of life to millions of intelligent creatures, and vibrate with the music of tongues speaking languages as expressive as those of the earth."
In fact, Venus and Earth really are remarkably similar in many of their basic physical characteristics. In a system of 9 planets where the smallest (Pluto) could fit inside the largest (Jupiter) 240,000 times, they are very nearly the same size and mass, with Earth weighing in as the slightly larger twin. Shrink Earth to the size of an official NBA basketball and, on the same scale, Venus is the size of a soccer ball.1 When it comes to the basic property of size, Venus and Earth are very much in the same ballpark, and no other known planet is even in the same league. One thing that comparative planetology has taught us is that size is everything; It's the most important single quality for determining the course of a planet's evolution. (more on this in chapter four.)
Also, if location has any influence on planetary character, there was all the more reason to expect a very familiar place. For Venus is (as was well known by Early telescopic observers) literally right next door. The closest planet to Earth, at every inferior conjunction she swings to within 100 times the moon's distance.
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Carboniferous ParkSvante Arrhenius, the Swedish chemist who won a Nobel Prize and published numerous popular books, wrote, in 1918 "The humidity is probably about six times the average of that on the Earth. We must conclude that everything on Venus is dripping wet. The vegetative processes are greatly accelerated by the high temperature; therefore, the lifetime of organisms is probably short."
A variation on this theme briefly became popular in the 1950's. Fred Hoyle, a famous British astrophysicist, proposed that the surface of Venus was covered in oil, and that the clouds may be made of oil droplets. Observations going back to the 1930s had detected the infrared signature of carbon dioxide in the atmosphere.2 This was consistent, Hoyle proposed, with a planet-wide coating of petroleum. In 1955 he wrote "Venus is probably endowed beyond the dreams of the richest Texas oil-king." This "Hoyle Oil", as it came to be called by astronomers, was in a sense consonant with the Carboniferous view of Venus, since that is the period when Earth's oil reserves were deposited. But, of course Earth in the Carboniferous was not covered with oil, but with vegetation which only became oil after hundreds of millions of years underground.
As recently as 1955, Russian Astronomer G.A. Tikhoff was publishing scientific papers with detailed inferences on the nature of Venusian vegetation based on current observations. Tikhoff wrote
"Now already we can say a few things about the vegetation of Venus. Owing to the high temperature on this planet, the plants must reflect all the heat rays, of which those visible to the eye are the rays from red to green inclusive. This gives the plants a yellow hue. In addition, the plants must radiate red rays. With the yellow, this gives them an orange color. Our conclusions concerning the color of vegetation on Venus find certain confirmation in the observation ... ... that in those parts of Venus where the sun's rays possibly penetrate the clouds to be reflected by the planet's surface, there is a surplus of yellow and red rays."
This portrait of Venus, as a verdant, rainy, overgrown swamp planet--perhaps complete with tree ferns and jungle animals--became widespread in the popular and scientific literature throughout the 19th and most of the 20th centuries. This vision also fit into a larger view of solar system evolution that remained popular for centuries. According to this scheme, the planets farther out from the Sun were formed first and had longer evolutionary histories. Planets closer to the Sun were more primitive. We can trace this back to the "nebular hypothesis" of solar system origins formulated in 1796 by French astronomer Pierre Simon de Laplace. According to Laplace, the planets were cast off sequentially as rings of gas from a shrinking, spinning cloud surrounding the sun. Each gas ring eventually condensed into a new planet, with the innermost planets forming last. So, the theory suggests, Mars has been here much longer evolution than Earth, and Earth much longer than Venus. Although this hypothesis has been replaced with new ideas about planet formation in greater accord with space age data (See chapter four), its vestiges greatly influenced science and science fiction until quite recently. Mars was often portrayed as "past its prime", like a future vision of a dying Earth, with ancient civilizations nobly struggling against global change. Lowell explained the "canals" as a desperate attempt to survive the desertification of a dying planet by bringing water from the polar caps with a massive engineering project. Venus was consistently portrayed as "Carboniferous Park", a living replica of Earth's past. Venus, so near and yet always hidden by clouds, so Earthlike in every known aspect, helped to perpetuate for centuries a widespread belief in a universe abounding with populated worlds.
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Lost Oceans of the Golden AgeThe birth of modern science fiction probably occurred sometime in the mid 19th century.3 This literature was inspired but not constrained by the scientific revolution. Travel to other worlds and extraterrestrial life became two of its great themes. Science fiction writers have always sought to shape their extrapolations of the future to be consistent with the latest scientific ideas of the day. It is instructive, and fun, to trace the evolving past of the future, and of other worlds, as mirrors of the evolution of scientific ideas and social mores and attitudes. The so-called "golden age" of American science fiction in the late 1930's through the 1950's produced numerous tales of future generations of humans (men, mostly) exploring various manifestations of mysterious, cloud-veiled Venus. Most common among these visions are variations on the theme (exemplified by the passage from Bradbury which begins this chapter) of Venus as Earth's warm water-logged twin, often crawling with more "primitive" versions of Earth-life. Portrayals of this soggy psuedo-Earth range from idyllic Edens to frightening and hostile jungles.
In Isaac Asimov's 1954 novel, "Lucky Starr and the Oceans of Venus", the hero is a member of the powerful and secretive, Council of Science. The Council, which seems to be a combination of scientific society and secret police, defends civilization from the forces of darkness, and spreads science, reason and justice throughout the galaxy. Mysterious trouble has been reported in the Venusian colonies, and Lucky is dispatched to clear things up. In a lecture to his sidekick as they descend towards Venus, Lucky explains,
Until the first explorers landed on Venus, all mankind ever saw of the planet was the outer surface of these clouds. They had weird notions about the planet then. They weren't even sure about the composition of Venus' atmosphere. They knew it had carbon dioxide, but until the late 1900's astronomers thought Venus had no water. When ships began to land, mankind found that wasn't so.
The Venusian colonists live under domed cities built in the shallow parts of the oceans. The characters are all men, except for the ornamental wife of one of the principals who is briefly described as young and pretty, lives to decorate their apartment, and complains that she has to miss all the action. Something has gone horribly wrong on Venus, and Lucky and the other men of Science must navigate its deep, planet-wide oceans, successfully battling Venusian frogs with telepathic power. In one terrifying scene Lucky and his cohorts encounter a giant killer jellyfish. Although the Venusian frogs get the upper hand and even briefly take over Lucky's mind, rest assured that Science eventually triumphs, restoring order and making the solar system once again safe for peace, justice and the American Way.
Another favorite is the camp 1958 film "Queen of Outer Space", which stars Zsa Zsa Gabor as a brilliant Venusian scientist. This time the Venusian scientists are all women, although they are always dressed in evening gowns and pay far more attention to their appearance than most scientists I know. A group of men from Earth crash lands on Venus and, resourcefully, seduce Zsa Zsa and her band of renegade scientists who then save them from their evil (female) dictator when they realize that "Vimmen cannot live wizzout men." It is interesting to see how Venus' role as the only female planet in western mythology is sometimes echoed in the gender roles assigned to Venusians in American pop culture.
Perhaps it is not a coincidence that the "golden age" of science fiction, ended with the advent of the "golden age" of planetary exploration in the 1960's. As we began to explore the solar system, starting with Venus, the solid citadel of clouds which had protected all these fantasy worlds from intrusion began to crack under the persistent attack of science. And early results suggested that all was not comfortably warm and wet in the jungle.
1 Actually, the planetary difference is slightly smaller; Venus would be 2% too large for official soccer play, probably not enough to be disqualified. On this scale, Mercury is a softball and the Moon a tennis ball. Mars is a big ripe red melon.
2 This will be described in Chapter Three.
3 Mary Shelley's Frankenstein (1818) and H.G. Wells' The Time Machine (1895) are often named as the seminal works. Edgar Allan Poe and Jules Verne also get honorable mention as innovators of the form.