Asimov's New Guide to Science

by Isaac Asimov

  In 1943, the French naval officer Jacques-Yves Cousteau developed a system in which skin divers began carrying cylinders of compressed air, which could be exhaled into canisters of chemicals that absorbed the carbon dioxide and rendered the exhaled air fit to breathe again. These were aqua-lungs, and the sport, which became popular after the war, was called scuba diving, the word scuba being an acronym for “self-contained underwater breathing apparatus.”

  Experienced scuba divers can attain depths of about 200 feet, but that is still very shallow compared with the total depth of the ocean.

  The first practical diving suit was designed in 1830 by Augustus Siebe. A diver in a modern diving suit can go down about 300 feet. A diving suit encloses the human body entirely, but a more elaborate enclosure would amount to an entire vessel suited for undersea travel—a submarine.

  The first submarine that could actually remain beneath water for a reasonable period of time without drowning the person inside was built as long ago as 1620 by a Dutch inventor, Cornelis Drebbel. No submarine could be practical, however, until it could be driven by something other than a handturned propeller. Steam power was not useful because one could not burn fuel in the limited atmosphere of an enclosed submarine. What was needed was a motor run by electrici ty from a storage ba ttery.

  The first such electric submarine was built in 1886. Though the battery had to be periodically recharged, the vessel’s cruising distance between recharges was something like 80 miles. By the time the First World War began, the major European powers all had submarines and used them as war vessels. These early submarines, however, were fragile and could not descend far.

  In 1934, Charles William Beebe managed to get down to about 3,000 feet in his bathysphere, a small, thick-walled craft equipped with oxygen and with chemicals to absorb carbon dioxide.

  The bathysphere was an inert object suspended from a surface vessel by a cable (a snapped cable meant the end). What was needed was a maneuverable ship of the abyss. Such a ship, the bathyscaphe, was invented in 1947 by the Swiss physicist Auguste Piccard. Built to withstand great pressures, it used a heavy ballast of iron pellcts (which are automatically jettisoned in case of emergency) to take it down and a “balloon” containing gasoline (which is lighter than water) to provide buoyancy and stability. In its first test off Dakar,

  West Africa, in 1948, the bathyscaphe (unmanned) descended 4,500 feet. In the same year, Beebe’s co-worker, Otis Barton, plumbed to a depth of 4,500 feet, using a modified bathysphere called a benthoscope.

  Later, Piccard and his son Jacques built an improved version of the bathyscaphe and named the new vessel Trieste, because the then Free City of Trieste had helped finance its construction. In 1953, Piccard plunged 21/2 miles into the depths of the Mediterranean.

  The Trieste was bought by the United States Navy for research. On 14 January 1960, Jacques Piccard and a Navy man, Don Walsh, took it to the bottom of the Marianas Trench, plumbing 7 miles to the deepest part of any abyss. There, at the ultimate ocean depth, where the pressure was 1,100 atmospheres, they found water currents and living creatures. In fact, the first creature seen was a vertebrate, a one-foot-long flounderlike fish, with eyes.

  In 1964, the French-owned bathyscaphe Archimède made ten trips to the bottom of the Puerto Rico Trench, which, with a depth of 51,4 miles, is the deepest abyss in the Atlantic. There, too, every square foot of the ocean Hoor had its life form. Oddly enough, the bottom did not descend smoothly into the abyss; rather, it seemed terraced, like a giant, spread-out staircase.

  The Icecaps

  The extremities of our planet have always fascinated human beings, and one of the most adventurous chapters in the history of science has been the exploration of the polar regions. Those regions are charged with romance, spectacular phenomena, and elements of human destiny—the strange auroras in the sky, the extreme cold, and especially the immense icecaps, or glaciers, which hold the key to our world climate and our way of life.

  THE NORTH POLE

  The actual push to the poles came rather late in human history. It began during the great age of exploration following the discovery of the Americas by Christopher Columbus. The first Arctic explorers went chiefly to find a sea route around the top of North America. Pursuing this will-o’-the-wisp, the English navigator Henry Hudson (in the employ of Holland) found Hudson Bay and his death in 1610. Six years later, another English navigator, William Baffin, discovered what came to be called Baffin Bay, and penetrated to within 800 miles of the North Pole (figure 4.6). Eventually, in the years 1846 to 1848, the British explorer John Franklin worked his way over the northern coast of Canada and discovered the Northwest Passage (and a most impractical passage for ships it then was). He died on the voyage.

  Figure 4.6. Map of the North Pole.

  There followed a half-century of efforts to reach the North Pole, motivated in large part by sheer adventure and the desire to be the first to get there. In 1873, the Austrian explorers Julius Payer and Carl Weyprecht reached within 600 miles of the Pole and named a group of islands they found Franz Josef Land, after the Austrian emperor. In 1896, the Norwegian explorer Fridtjof Nansen drifted on the Arctic ice to within 300 miles of the Pole. At length, on 6 April 1909, the American explorer Robert Edwin Peary arrived at the Pole itself.

  By now, the North Pole has lost much of its mystery. It has been explored on the ice, from the air, and under water. Richard Evelyn Byrd and Floyd Bennett were the first to fly over it, in 1926; and submarines have traversed its waters.

  Meanwhile, the largest northern icecap, which is centered in Greenland, has drawn a number of scientific expeditions. Wegener died in the course of one such expedition in November 1930. The Greenland glacier has been found to cover about 640,000 of that island’s 840,000 square miles, and its ice is known to reach a thickness of a mile in some places.

  As the ice accumulates, it is pushed down to the sea, where the edges break off, or calve, to form icebergs. Some 16,000 icebergs are thus formed in the Northern Hemisphere each year, 90 percent of them breaking off the Greenland icecap. The icebergs work slowly southward, particularly down the west Atlantic. About 400 icebergs per year pass Newfoundland and threaten shipping lanes; between 1870 and 1890, fourteen ships were sunk and forty damaged by collision with icebergs.

  The climax came in 1912, when, on its maiden voyage, the luxury liner Titanic collided with an iceberg and sank. An international watch over the positions of these inanimate monsters has been maintained ever since. During the years since this Ice Patrol has come into existence, not one ship has been sunk by an iceberg.

  THE SOUTH POLE—ANTARCTICA

  Far larger than Greenland is the South Pole’s great continental glacier. The Antarctic icecap covers seven times the area of the Greenland glacier and has an average thickness of 1½ miles, with 3-mile depths in spots. This is due to the great size of the Antarctic continent—some 5 million square miles, though how much is land and how much ice-covered sea is still uncertain (figure 4.7). Some explorers believe that western Antarctica, at least, is a group of large islands bound together by ice; but at the moment, the continent theory seems to have the upper hand.

  Figure 4.7. The major continental glaciers are today largely restricted to Greenland and Antarctica. At the height of the last ice age, the glaciers extended over most of northern and western Europe and south of the Great Lakes on the North American continent.

  The famous English explorer James Cook (better known as Captain Cook) was the first European to cross the Antarctic Circle. In 1773, he circumnavigated the Antarctic regions. (It was perhaps this voyage that inspired Samuel Taylor Coleridge’s The Rime of the Ancient Mariner, published in 1798, which described a voyage from the Atlantic to the Pacific by way of the icy regions of Antarctica.)

  In 1819, the British explorer Williams Smith discovered the South Shetland Islands, just 50 miles off the coast of Antarctica; in 1821, a Russian expedition. under Fabian Gottlieb Bellingshausen, sighted a small island (P
eter I Island) within the Antarctic Circle; and, in the same year, the Englishman George Powell and the American Nathaniel B. Palmer first laid eyes on a peninsula of the Antarctic continent itself—now called Antarctic Peninsula.

  In the following decades, explorers inched toward the South Pole. By 1840, the American naval officer Charles Wilkes announced that the land strikes added up to a continental mass; and, subsequently, he was proved right. The Englishman James Weddell penetrated an ocean inlet east of Palmer Peninsula (now called Weddell Sea) to within 900 miles of the Pole. Another British explorer, James Clark Ross, discovered the other major ocean inlet into Antarctica (now called the Ross Sea) and got within 710 miles of the Pole. Between 1902 and 1904, a third Briton, Robert Falcon Scott, traveled over the Ross ice shelf (a section of ice-covered ocean as large as the state of Texas) to within 500 miles of the Pole. And, in 1909, still another Englishman, Ernest Shackleton, crossed the ice to within about 100 miles of it.

  On 16 December 1911, the goal was finally reached by the Norwegian explorer Roald Amundsen. Scott, making a second dash of his own, got to the South Pole just three weeks later, only to find Amundsen’s flag already planted there. Scott and his men perished on the ice on their way back.

  In the late 1920s, the airplane helped to make good the conquest of Antarctica. The Australian explorer George Hubert Wilkins flew over 1,200 miles of its coastline, and Richard Evelyn Byrd, in 1929, flew over the South Pole. By that time the first base, Little America I, had been established in the Antarctic.

  THE INTERNATIONAL GEOPHYSICAL YEAR

  The North and South polar regions became focal points of the greatest international project in science of modern times. This had its origin in 1882-83, when a number of nations joined in the International Polar Year of exploration and scientific investigation of phenomena such as the aurorae and the earth’s magnetism. The project was so successful that, in 1932-33, it was repeated with a second International Polar Year. In 1950, the United States geophysicist Lloyd Berkner (who had been a member of the first Byrd antarctic expedition) proposed a third such year. The proposal was enthusiastically adopted by the International Council of Scientific Unions. This time scientists were prepared with powerful new research instruments and bristling with new questions—about cosmic rays, the upper atmosphere, the ocean depths, even the possibility of the exploration of space. An ambitious International Ceo physical Year (IGY) was arranged, and the time selected was 1 July 1957 to 31 December 1958 (a period of maximum sunspot activity). The enterprise enlisted heart-warming international cooperation; even the cold-war antagonists, the Soviet Union and the United States, managed to bury the hatchet for the sake of science.

  Although the most spectacular achievement of the IGY, from the stand point of public interest, was the successful launching of man-made satellite:, by the Soviet Union and the United States, science reaped many other fruits THE EARTH 183 that were no less important. Outstanding among these was a vast international exploration of Antarctica. The United States alone set up seven stations, probing the depth of the ice and bringing up from miles down samples of the air trapped in it (which must date back millions of years) and of bacterial remnants. Some bacteria, frozen 100 feet below the ice surface and perhaps a century old, were revived and grew normally. In January 1958, the Soviet group established a base at the Pole of Inaccessibility—the spot in Antarctica farthest inland—and there, 600 miles from the South Pole, recorded new lows in temperature. In August 1960—the Antarctic midwinter—a temperature of −127° F, cold enough to freeze carbon dioxide, was recorded. In the following decade, dozens of year-round stations were operating in Antarctica.

  In the most dramatic Antarctic feat, a British exploring team headed by Vivian Ernest Fuchs and Edmund Percival Hillary crossed the continent by land for the first time in history (with, to be sure, special vehicles and all the resources of modern science at their disposal). (Hillary had, in 1953, also been the first, along with the Sherpa mountaineer Tenzing Norgay, to climb Mount Everest, the highest mountain on earth.)

  The success of the IGY and the warmth generated by this demonstration of cooperation in the midst of the cold war led to an agreement in 1959 among twelve nations to bar all military activities (including nuclear explosions and the dumping of radioactive wastes) from the Antarctic. Thus, Antarctica will be reserved for scientific activities.

  GLACIERS

  The earth’s load of ice, amounting to nearly 9 million cubic miles, covers about 10 percent of its land area. About 86 percent of the ice is piled up in the Antarctic continental glacier and 10 percent in the Greenland glacier. The remaining 4 percent makes up the small glaciers in Iceland, Alaska, the Himalayas, the Alps, and a few other locations.

  The Alpine glaciers have been under study for a long time. In the 1820s, two Swiss geologists, Ignatz Venetz and Johann von Charpentier, noticed that rocks characteristic of the central Alps were scattered over the plains to the north. How had they got there? The geologists speculated that the mountain glaciers had once covered a much larger area and had left boulders and piles of debris behind when they retreated.

  A Swiss zoologist, Jean Louis Rodolphe Agassiz, looked into this notion. He drove lines of stakes into the glaciers and waited to see whether they moved. By 1840, he had proved beyond doubt that glaciers flow like very slow rivers at a rate of about 225 feet per year. Meanwhile, he had traveled over Europe and found marks of glaciers in France and England. He found boulders foreign to their surroundings in other areas and scoured marks on rock that could only have been made by the grinding of glaciers, carrying pebbles encrusted along their bottoms.

  Agassiz went to the United States in 1846 and became a Harvard professor. He found signs of glaciation in New England and the Midwest. By 1850, it seemed obvious that at some time a large part of the Northern Hemisphere must have been under a large continental glacier. The deposits left by the glacier have been studied in detail since Agassiz’s time, and these studies have shown that the glacier advanced and retreated a number of times in the last million years, which make up the Pleistocene epoch.

  The term Pleistocene glaciation is now usually used by geologists for something that is popularly known as the ice ages. There were, after all, ice ages before the Pleistocene. There was one about 250 million years ago, and another about 600 million years ago, and still another, perhaps, in between, about 400 million years ago. Little is known of these earlier ice ages, since the great time lapse has wiped out much of the geological evidence. On the whole, then, ice ages are uncommon and take up only a few tenths of 1 percent of Earth’s total history.

  In regard to the Pleistocene glaciation, it would seem that the Antarctic ice sheet, though now the largest by far, was little involved with the progress of this most recent ice age. The Antarctic ice sheet can expand only into the sea and break up there. The Boating ice may become more copious and be more effective in cooling the ocean generally, but the land areas of the Southern Hemisphere are too far from Antarctica to be affected to the point of growing ice sheets of their own (except for some glaciation in the southernmost Andes Mountains).

  Quite otherwise is the case in the Northern Hemisphere, where great stretches of land crowd close about the pole. It is there that the expansion of the ice sheets is most dramatic; and the Pleistocene glaciation is discussed almost exclusively in connection with the Northern Hemisphere. In addition to the single Arctic ice sheet (Greenland) that now exists, there were three more ice sheets, with an area of 1 million square miles each: Canada, Scandinavia, and Siberia.

  Perhaps because Greenland was the seedland of the northern glaciation, nearby Canada was far more glaciated than more distant Scandinavia or still more distant Siberia. The Canadian ice sheet, growing from the northeast, left much of Alaska and the Pacific slope unglaciated but extended southward until the rim of the ice stretched over much of the northern United States. At its maximum southern extension, the boundary of the ice stretched from Seattle, Washington, to Bismark
, North Dakota, then veered southeastward, following very much along the line of the modern Missouri River, past Omaha and St. Louis, then eastward past Cincinnati, Philadelphia, and New York. The southern boundary seems to have been right along the full length of what is now Long Island.

  All in all, when the ice sheets were at their farthest extent, they covered over 17 million square miles of land in both polar regions or some 30 percent of Earth’s present land surface. This is three times as much land as is covered by ice today.

  Careful examination of the layers of sediment in the soil of areas where the ice sheets existed show that they advanced and retreated four times. Each of the four glacial periods endured from 50,000 to 100,000 years. Between them were three interglacial periods which were mild, even warm, and were also long.

  The fourth, and most recent, glaciation reached its maximum extent about 18,000 years ago, when it stood at what is now the Ohio River. There followed a slow retreat. An idea of the slowness can be obtained when one understands that the retreat progressed at but 250 feet a year over some stretches of time. At others, there was even a partial, and temporary, renewed advance.

  About 10,000 years ago, when civilization was already beginning in the Middle East, the glaciers began their final retreat. By 8,000 years ago, the Great Lakes were clear; and by 5,000 years ago (at about which time, writing had been invented in the Middle East), the ice had retreated to about where it is today.

  The coming and going of glaciers leaves its mark, not only on the climate of the rest of the earth but on the very shape of the continents. For instance, if the now-shrinking glaciers of Greenland and Antarctica were to melt completely, the ocean level would rise nearly 200 feet. It would drown the coastal areas of all the continents, including many of the world’s largest cities, with the water level reaching the twen tieth story of Manhattan’s skyscrapers. On the other hand, Alaska, Canada, Siberia, Greenland, and even Antarctica would become more habitable.