The Planets. Dava Sobel

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СКАЧАТЬ vivid aspect in our skies, only about one-sixth of her visible disk remains illuminated. But proximity stretches this little sliver to a great length, allowing the perceived brightness of Venus to increase even as she thins and wanes away.

      Watching Venus through a telescope or binoculars every evening over a period of months shows how she gains in height and brightness as her disk shrinks, and vice versa. Little else becomes apparent, however, since none of Venus’s surface features can ever be discerned by sight through her cloud deck. Thus the very clouds that account for her blatant visibility also act to veil her.

      Those who know just where to look can sometimes pick out the steady white light of Venus against the light blue background of a fully daylit sky. Napoleon spotted Venus that way while giving a noon address from the palace balcony at Luxembourg, and interpreted her daytime venue as the promise (later fulfilled) of victory in Italy.

      On Moonless nights when Venus is nigh, her strong light throws soft, unexpected shadows onto pale walls or patches of ground. The faint silhouette of a Venus shadow, which evades detection by the colour-sensitive inquiry of a direct gaze, often answers to sidelong glances that favour the black-and-white acuity of peripheral vision. But no matter how avidly you hunt the elusive Venus shadow with eyes averted and downcast, your search may still prove vain, while overhead, as though to mock you, the planet’s dazzle mimics the landing beam of an oncoming aeroplane, even triggers police reports of unidentified flying objects.

      I stopped to compliment you on this star

       You get the beauty of from where you are. To see it so, the bright and only one In sunset light, you’d think it was the sun That hadn’t sunk the way it should have sunk, But right in heaven was slowly being shrunk So small as to be virtually gone, Yet there to watch the darkness coming on- Like someone dead permitted to exist Enough to see if he was greatly missed. I didn’t see the sun set. Did it set? Will anybody swear that isn’t it? …

      Robert Frost, ‘The Literate Farmer and the Planet Venus’

      Ancient legends celebrated the beauty of planet Venus by declaring her not only divine but also womanly – perhaps because her visitations generally lasted a significant nine months. Although Venus orbits the Sun in just 224 Earth-days, the Earth’s own orbital motions help govern Venus’s observed behaviour. As seen from the moving Earth, Venus averages 260 days as either morning star or evening star, coinciding with the human gestation period of 255 to 266 days.

      The Chaldeans called the planet Ishtar, the love goddess ascending the heavens, and to the Semitic Sumerians she was Nin-si-anna, ‘the Lady of the Defences of Heaven’. Her Persian name, Anahita, associated her with fruitfulness. The dual (dawn and dusk) nature of Venus cast her by turns as virgin or vamp to her worshippers.

      Ishtar metamorphosed into Aphrodite, the Greek incarnation of love and beauty. She became the Venus of the Romans, revered by the historian Pliny for spreading a vital dew to excite the sexuality of earthly creatures. In China, Venus blended male and female genders in a married couple consisting of the husband evening star, Tai-po, and his wife, the morning star, Nu Chien.

      Only the Mayas and the Aztecs of Central America seem to have seen Venus as consistently male, the twin brother of the Sun. The rhythmic association between Venus and the Sun inspired meticulous astronomical observations and complex calendar reckoning in those cultures, as well as blood rituals to recognize the planet’s descent into the underworld and subsequent resurrection.

      In North America, among the Skidi Pawnee, the veneration of Venus involved human sacrifice to ensure her return. The last teenage girl known to have died in such devotions was kidnapped and ceremonially killed on 22 April 1838.

      As a symbol of loveliness, Venus figures in three paintings by Vincent Van Gogh. His Starry Night of June 1889, the best-known example, depicts Venus as the bright orb low to the east of the village of Saint-Rémy, during the time the artist’s dementia confined him to an asylum there. Art historians and astronomers have also definitively identified Venus in Road with Cypress and Star, which Van Gogh completed in mid-May 1890, the day before he left Saint-Rémy. A few weeks later, in Auverssur-Oise, near Paris, where he created eighty works in the two months before his suicide, Van Gogh depicted Venus for the last time, inside a scintillating halo, hovering above the west chimney of White House at Night.

      Venus voyages … but my voice falters;

      Rude rime-making wrongs her beauty,

       Whose breasts and brow, and her breath’s sweetness Bewitch the worlds.

      C. S. Lewis, ‘The Planets’

      If ever two worlds invited comparison, the twin sisters Earth and Venus lay such a claim, for these planets are almost identical in size, and orbit the Sun at similar distances. Early discoveries about Venus from afar – especially the detection of her atmosphere by Russian astronomer and poet Mikhail Lomonosov in 1761 – fanned widespread fantasies of a lush abode of Earth-like life.

      Recent research, however, has exposed only the most glaring contrasts between the two planets. Although at an earlier epoch Venus probably possessed many of the same attributes as Earth, including once-abundant seas, her water has all boiled away. Now Venus parches and bakes under an obscuring sky that blocks light but traps heat, and bears down upon her surface with heavy pressure.

      The ten Russian Venera and Vega spacecraft that successfully landed on Venus between 1970 and 1984 barely had time to take a few pictures and measurements, or quickly sample the surroundings, before succumbing to the harsh conditions. Within an hour or so of arrival, each vehicle either melted in the heat or crumpled under atmospheric pressure comparable to that found underwater on Earth, nearly three thousand feet below sea level.

      Discoveries of the drastic differences between Earth and Venus evoked surprise sometimes expressed in moral terms, as though one sister had chosen the right course while the other veered down an errant path. Nevertheless Venus, the wayward sister, preaches an important cautionary tale to careless humans, for her hostile environment proves how even small atmospheric effects can conspire over time to convert an earthly paradise into a hellfire cauldron. Indeed, much current study of Venus aims to save humanity from itself by verifying, for example, the destruction that chlorine compounds wreak in high-altitude clouds.

      And art thou, then, a world like ours,

       Flung from the orb that whirled our own A molten pebble from its zone? How must the burning sands absorb The fire-waves of the blazing orb, Thy chain so short, thy path so near Thy flame-defying creatures hear The maelstroms of the photosphere!

      Oliver Wendell Holmes, ‘The Flâneur’*

      Differences between Earth and Venus doubtless began in their youth, with the Sun beating hotter on the closer of the two sisters. The Sun warmed the waters of Venus until they rose in steam, until water vapour and the hot breath of volcanic eruptions enveloped the planet. These gases then did the work of greenhouse glass: they allowed the Sun’s heat to reach the surface of Venus, but refused to let heat escape. Instead of dissipating into space, the heat rebounded back down to ground level and made the surface hundreds of degrees hotter still.

      High over Venus, Sunlight split the water vapour into its components, hydrogen and oxygen, and the lighter hydrogen escaped the planet’s hold. Oxygen remained behind; it recombined with the surface rocks on Venus, and with gases vented by volcanoes, to create an atmosphere consisting almost entirely (97 per cent) of carbon dioxide, the most efficient and pernicious of all greenhouse gases. Today, although only a trickle of solar energy penetrates Venus’s cloud cover and arrives at the surface, the greenhouse effect СКАЧАТЬ