Originally published 30 April 1990
Puttering about in the college library I came across a book published 50 years ago called Unsolved Problems of Science. The author is A.W. Haslett, a science popularizer who was widely read in the late 1930s.
I wondered, how many of the “unsolved problems” can be counted as solved today? Herewith, an assessment of progress during the past half-century, with Haslett’s chapter titles suggesting the problems:
- The Creation of the Universe. The Big Bang theory of creation of everything from nothing about 15 billion years ago looks better and better. The discovery of cosmic microwave background radiation — the afterglow of the Big Bang — in the 1960s convinced most scientists that the Big Bang accounts for the broad outlines of creation. The discovery of quasars and the observed abundances of the light elements also fit the theory for an explosive creation. Verdict: Substantial, exciting progress.
- Are There Other Worlds Than Ours? The space programs has essentially ruled out the presence of life elsewhere in the solar system. Despite a vigorous search for intelligent radio signals from other star systems, none has been found. Verdict: Still an open question.
- The Changing World. Haslett wondered what forces shape the surface of the Earth. No science has undergone a more dramatic revolution in the last half-century than geology. The theory of plate tectonics (sometimes inaccurately called continental drift) convincingly explains virtually every aspect of the changing Earth — mountain ranges, ocean basins, earthquakes, volcanoes. Verdict: Solved.
- Our Weather Cauldron. Stunning breakthroughs have been achieved in reconstructing the Earth’s past climates, with clues coming from ocean-floor sediments and from air bubbles and dust trapped deep in the Greenland and Antarctic ice caps. Super-powerful computers enable researchers to model weather systems mathematically. Greenhouse warming and ozone depletion will focus lots of attention on this still unsolved problem in the next decade. Verdict: Stay tuned.
- Messages from Space. The Earth is continuously bombarded by high-energy particles from space, the so-called cosmic rays. The big question in Haslett’s time was “Where do they come from?” Some evidence suggests that many cosmic rays have their origin in the remnants of exploded stars, or supernovas, but mysteries remain. Verdict: Unsolved.
- The Origin of Man. A half-century of digging up fossils has convinced most paleontologists that humans and apes have a common ancestry, and that early hominids (humanlike creatures) wandered out of Africa about 1 million years ago. Recent comparisons of the DNA of present-day races suggest that all modern humans may have descended from common ancestors who lived in Africa several hundred thousand years ago. DNA analysis will soon add much more to our understanding of origins. Verdict: Solved, but ever so tentatively.
- The Beginnings of Civilization. Many archeologists now believe that climate change at the end of the last Ice Age was the stimulus that led to settled agricultural communities. Urban civilization seems to have evolved independently in three places: the Golden Crescent of the Near East, China, and Central America. Verdict: No big breakthroughs and none expected. Just more patient digging.
- Is Man a Machine? The discovery of the mechanism of heredity — the double-helix structure of DNA — must be counted as one of the greatest discoveries of the past half-century. This is the golden age of molecular biology. The mechanisms — ahem — of thought and memory remain a riddle, despite occasional bursts of optimism by neurologists and artificial intelligence researchers. Verdict: One thumb up, one thumb down.
- The Riddle of Sex. The genetic determination of gender in individuals is pretty well understood. A deeper riddle is why sex evolved in the first place. Biologists vigorously debate what, if any, advantage is conferred on a species by sexual reproduction. Verdict: Sex will always be a mystery.
- Nature’s Building Blocks. What is the world made of? Using ever more powerful accelerating machines, particle physicists have achieved remarkable progress in understanding the origin and unity of matter. Perhaps the most exciting aspect of this work is the way our new knowledge of the subatomic realm helps us understand the universe on the cosmic scale. Haslett does not appear to have foreseen atomic weapons, which appeared on the scene not long after his book was published. Verdict: Spectacular progress, but with an ominous underside.
- Mathematics or Common Sense? Is the universe determined by fixed natural laws, or is there a chancy, probabilistic basis to reality? In Haslett’s time the philosophical implications of the quantum revolution were hotly debated. Verdict: The debate goes on, though not so hotly.
- The Secret of Strength. The theoretical strength of bonds between atoms suggests that steel girders and airplane wings should be stronger than they are. What is the source of the weakness? Fifty years ago the finger of suspicion pointed to invisible imperfections in the crystalline structure of materials, and to something Haslett called “metals getting tired.” Recent aviation disasters suggest that metal fatigue remains a problem. Verdict: Lots of progress in materials research, but airplanes still fall apart.
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