Natural History Magazine | Natural Selections

Bookshelf

May 2008

By Laurence A. Marschall

The Mystery of the Missing Antimatter
By Helen R. Quinn and Yossi Nir (Princeton University Press, 2008; $29.95)

There was a time, around the 1960s and 1970s, when it was easy to tell a particle physicist from a cosmologist: the former studied the smallest things in nature, the latter the largest. But more recently, particle physicists have come to view

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the Big Bang as a particle experiment of cosmic proportions, an accelerator far more powerful than any they could ever create on Earth, and cosmologists have realized that they must study the small bits of the cosmos to understand its large-scale formation.

That is why Helen R. Quinn and Yossi Nir, both eminent particle physicists, have written a book about one of the most mysterious properties of the cosmos at large: the virtual absence of antimatter. The laws of microphysics tell us that, just after the Big Bang, every particle had a mirror twin, opposite in charge but equal in mass. For each electron there was an antielectron, for each quark an antiquark, and for every neutrino an antineutrino.

And presumably it should have stayed that way. Particles and antiparticles are created in pairs and destroyed in pairs; when an electron and an antielectron collide, for example, both vanish in a flash of light. Such fundamental symmetry means that, as the universe expands, the balance sheet for matter and antimatter shouldn’t change. Yet the balance today is skewed toward matter—in fact, there is almost no antimatter in our known universe —so it must have shifted sometime, probably after the first few instants of ultrahot homogeneity, leaving behind a universe of matter particles with no anti-“twins” to annihilate them. How that happened is not yet clearly understood.

The most likely explanation lies somewhere deep in the physics of fundamental particles, a theory that cannot yet adequately describe the earliest moments of creation. We know that the answer must involve some tiny asymmetry in the way the laws of physics operate under extreme conditions, which would produce more particles of regular matter than antimatter. Although a consistent mathematical theory of such conditions has not yet been developed, it’s one of the most active areas of theoretical physics today.

Quinn and Nir have a daunting task explaining the ongoing work in nonmathematical terms, which may make their book hard going for those whose last exposure to physics was in high school. Still, if you liked reading cosmologist Steven Hawking’s A Brief History of Time, or particle physicist Brian Greene’s The Elegant Universe, you will find The Mystery of the Missing Antimatter an absorbing scientific whodunit.

Amazon Expeditions: My Quest for the Ice-Age Equator
By Paul Colinvaux (Yale University Press; 2007; $32.50)

Paul Colinvaux may be in his seventies, but he still has the spirit of a young Turk. Throughout this feisty and often inspiring memoir of his life as a plant ecologist runs a constant stream of argumentation. As he states repeatedly, Colinvaux is convinced that during the last ice age, which ended about 10,000 years ago, the climate of the Amazon forest was not too different from what it is today. That, Colinvaux hastens to state, runs contrary to the orthodox view that during ice ages the Amazon became a much drier place, with only a few “refuges” of rainforest surrounded by semiarid grassland.

Colinvaux begs to differ with conventional wisdom, largely on the basis of evidence he and his colleagues have gathered from lake bottoms and swamps along the equator. The method he employs sounds fairly straightforward, but in practice it’s extremely difficult: First you find a remote lake whose bottom has been collecting sediment for tens of thousands of years. Then you paddle a rubber dinghy out into the lake, hoping for no sudden storms, and sink a coring tube as deep into the lake bottom as you can to extract an undisturbed sedimentary sequence. Safely back in the lab, you examine each layer in the core for evidence of the age and type of vegetation that lived in the vicinity when the layer was laid down. A wide variety of chemical and physical techniques help at this stage, chief among them radiocarbon dating of organic material and a close analysis of the types of pollen found in the layer.

The difficulty of surveying ice-age sediments along the equator is so great that the project took Colinvaux nearly forty years, first to find the proper lakes, then to reach them, and finally to learn to recognize and analyze the pollen they contained. Colinvaux has rappelled into the craters of extinct volcanoes, feasted on roast caiman a hundred kilometers from the nearest human habitation, and battled mites, mosquitoes, and (worst of all) customs agents. He’s backpacked and helicoptered into virtually inaccessible spots encumbered by a full complement of rubber rafts, sounding gear, and drilling pipe.

You don’t need to share his obsession to understand both the difficulty of this enterprise and the care and passion with which he carried it out. And best of all, thanks to this welcome book, you don’t need to break a sweat to accompany him on his journeys.

Hard Work and a Good Deal: The Civilian Conservation Corps in Minnesota
By Barbara W. Sommer (Minnesota Historical Society Press; 2008; $27.95)

The Emergency Conservation Work Program, popularly known as the Civilian Conservation Corps (CCC), was one of the first established and most fondly remembered programs of the New Deal. Proposed to Congress on March 21, 1933, its aim was to put jobless young men to work on the land. By the summer of that year there were already over a thousand CCC camps scattered around the nation, and over a quarter million recruits had moved into barracks where they lived frugally and labored hard.

Doubtless there were those who regarded the CCC as a form of welfare in disguise. But its environmental impact was far more important and lasting than its economic effects. In Minnesota, the focus of oral historian Barbara W. Sommer's study, the CCC came at a time when the conservation ideals of Teddy Roosevelt's era were only beginning to take root. Logging of the 1800s had turned vast northern forests into rocky wastelands. In the southern part of the state, intensive farming had stripped the land of grass and woodland. State forests had been established, and soil conservation agencies existed, but they were still small and poorly funded.

The CCC brought discipline, direction, and most important, manpower, to the conservation tasks at hand. The “boys,” as they called themselves,

Laurence A. Marschall, author of The Supernova Story, is W.K.T. Sahm Professor of Physics at Gettys- burg College in Pennsylvania, and director of Project CLEA, which pro- duces widely used simulation soft- ware for education in astronomy.

set up nurseries to grow seedlings and went out in platoons to plant and prune. The combined camps eventually planted over 120 million trees statewide. Brigades of CCC workers also labored at soil conservation, building stone dams to trap topsoil in outwash gullies, planting windbreaks to prevent wind erosion, and more.

There's nothing like the CCC nowadays. The last camp in the U.S. closed in 1942 as prosperity reduced the number of recruits and the national priorities of wartime came to the fore. But the marks of the CCC remain in park buildings and wilderness roads, windbreaks and trailside shelters, revitalized forests and reclaimed farmland. And, thanks to Sommer, the words and photographs of a generation of CCC workers bring this history of the land of ten thousand lakes to life.