Johan Rockström and colleagues first proposed the concept in 2009 of planetary boundary threats and a safe operating space for humanity. This conceptual framework clarifies environmental problems that are of planetary significance, such as biodiversity loss, climate change, and stratospheric ozone depletion. The most recently articulated planetary boundary threat, or set of threats, relates to chemical pollution of the biosphere. With us to unpack planetary boundary threats as they relate to...

The Wall Street Crash of 1929 and the ensuing worldwide Great Depression left families in economic shock and despair. International trade collapsed to less than half of its previous levels and unemployment skyrocketed. Into this devastating mess stepped Franklin Delano Roosevelt, who began his long presidency in 1933. FDR spearheaded a series of programs known as the New Deal to revive the United States. The most popular of these was the government work relief program called the Civilian...

The ways people think about matters both big and small, from climate change to daily tasks, impact the outcomes. Throughout the history of science and society, key insights arose through a thought process of simplification and subtraction, though the human tendency leans towards complication and addition. Today I discuss the power of subtraction with Leidy Klotz. Leidy is a professor at the University of Virginia, where he studies the science of design. He is the author of Subtract, published...

No matter our claims to the contrary, we are all biased in our perceptions and beliefs. But bias is not random and its directions relate to our evolutionary history and culture, especially to how these interface with human sociality. With us to decipher bias is Jim Zimring. Jim is the author of What Science is and How it Really Works, published by Cambridge University Press in 2019, and Partial Truths: How Fractions Distort Our Thinking, published by Columbia University Press in 2022. Today...

The oceans have been used as the dumping grounds for all manner of toxic waste. Outrage over such dumping led to the Marine Protection, Research, and Sanctuaries Act of 1972 in the United States and the London Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter in 1975. Today I discuss the dumping of DDT and other wastes off the coast of Southern California with Dave Valentine. Dave completed a BS in chemistry and biochemistry at the University of California...

Many landmarks of environmental history share a connection with a single molecule: DDT. During and after the Second World War, it was broadcast into the environment at a scale that far surpassed the applications of any prior chemical. The public met this mass spraying of DDT with enthusiasm, as the war proved it to be highly effective against the vectors of malaria, yellow fever, typhus, and other insect-borne diseases. But these public health successes were short-lived as insects quickly...

At the start of the 20th century, physicists probed the structure of nature. Their discoveries changed our fundamental understanding of matter, of life, and of war. At the center of these discoveries stood the Danish physicist Niels Bohr. Bohr approached problems of atomic structure and quantum theory with a philosophical perspective and an ability to skirt paradoxes with his principle of complementarity. Perhaps as important as Bohr’s discoveries on the atom was his hosting of international...

The advent of agriculture over 10,000 years ago forever altered the trajectory of humanity. Communities grew larger until cities and nations dotted the landscape, labor became specialized, new diseases emerged, civilizations flourished and vanished, warfare increased in scale and lethality, and people colonized every corner of the globe. Agriculture facilitated the exponential growth of the human population, which necessitated ever greater efficiency and productivity and eventually led to the...

The brain is the most mysterious and complex organ of the body, and when things go awry, we may be confronted with personal tragedy and we may gain insights on what it means to be human. With us to discuss neurological disorders and the history of their discovery is Sara Manning Peskin. Sara completed an AB in biochemistry at Harvard University in 2009, an MS in cellular and molecular biology at the University of Pennsylvania in 2013, and an MD also at U Penn in 2015. She completed...

Nothing is so intertwined with human success and folly as economics. The economy, for better or for worse, drives much of our fate from our household budget to our national policies to the outbreak of war. But economic activity also has profound effects on the environment and a close inspection of economics opens the question of whether humans can live sustainably on the only planet we have. The field of economics that focuses on sustainability and the environmental costs of economic activity...

The 60s hosted the space race between the U.S. and the U.S.S.R., which occurred in the midst of the Vietnam War, the Cold War, and civil unrest. How did the culture wars of the 1960s relate to the space race? How did the Civil Rights Movement, the New Left, environmentalism, the women’s movement, and the Hippie counterculture influence NASA, and vice versa? With us to answer these questions is Neil Maher, a professor of history at the New Jersey Institute of Technology and Rutgers University.

Dick Garwin has worked on science and technology problems since the first thermonuclear weapon in 1951. Today we discuss space nuclear detonations, spy satellites, sequential memory, MRI, laser printers, touch-screen monitors, nuclear weapons testing, nuclear reactor accidents, Ebola, oil spills, and gravitational waves. Dick is a member of the National Academies of Sciences, Engineering, and Medicine (all 3). His awards include the 2003 National Medal of Science & the 2016 Presidential...

Today we explore the history of nuclear disarmament with Zia Mian. Zia is a physicist and co-director of Princeton’s Program on Science and Global Security, part of the School of Public and International Affairs, where he has worked since 1997. His research interests include issues of nuclear arms control, nonproliferation and disarmament, and international peace and security. Zia received the 2014 Linus Pauling Legacy Award and the American Physical Society’s 2019 Leo Szilard Award.

How do we distinguish real science from hogwash? How does real science evolve over time into pseudoscience? Michael Gordin is with us to explore the demarcation problem and how it relates to Bigfoot, ESP, UFOs, astrology, alchemy, the ether, Aryan physics, Lysenkoism, phrenology, cryptozoology, Velikovsky, Mesmerism, Uri Geller, cold fusion, and where all of this leaves us as we navigate the waters between science and pseudoscience.

Uncertainty is inherent to science and exploited by those who wish to stymie regulations. Chemical, oil, and tobacco companies kept their products on the marketplace and promoted consumerism by stressing the unsettled nature of research. With us to explore this history, and how it relates to the environment and public health, is Mark Lytle. Mark, the author of important books in environmental history, is among those historians seeking to develop the field of “Environmental Diplomacy.”

George Schaller is a pioneer of wildlife biology, with seven decades of work spanning from the Arctic to the Tropics. His many awards reflect his impacts on wildlife conservation, including the National Geographic Society Lifetime Achievement Award, a Guggenheim Fellowship, the World Wildlife Fund Gold Medal, and the Tyler Prize for Environmental Achievement. He is also known for his many books on wildlife, and he is the recipient of the U.S. National Book Award in Science.

The history of science is punctuated by both the greatest achievements and the greatest tragedies of human endeavors. The development of organic chemistry illustrates this dichotomy. With us to illuminate chemical accidents, brilliant discoveries, searing evils, and the use and misuse of organic chemistry is Joe Schwarcz. Joe is the Director of McGill’s Office for Science and Society, which has the mission of separating sense from nonsense.

The history of mathematics extends back millennia. The needs of trade, taxation, and time-keeping drove the development of arithmetic, algebra, and geometry, which had already acquired some sophistication by 5,000 years ago. Perhaps most fundamental to the development of mathematics has been discoveries on the nature of numbers themselves, or what mathematicians refer to as Number Theory. Our guide to Number Theory is Bryden Cais, professor of mathematics at the University of Arizona.

The most important book in the history of mathematics is Euclid’s Elements, which dates to ~300 BC and is the oldest surviving logical treatment of mathematics as a discipline. Its theorems and constructions are central to the history of scientific discovery and logic. With us to discuss the Elements is David Acheson, who became a Fellow in Mathematics at Jesus College, Oxford in 1977. We discuss his recent book, The Wonder Book of Geometry, published 2020 by Oxford University Press.

Galileo’s discoveries, and the manner in which he presented them in his 1632 book Dialogue Concerning the Two Chief World Systems, hurled his fate into the judgements of the Roman Inquisition. The Dialogue represented much more than a book on Copernican heliocentrism, and the fate of the book in the midst of the Inquisition placed Galileo in a precarious position. With us to decipher the controversy is John Heilbron, author of The Ghost of Galileo in a Forgotten Painting from the English...

The creation of a new discipline based upon a single scientific expedition is rare, but this is what resulted from the 1872-1876 expedition of H.M.S. Challenger. With us to explain the history and significance of the Challenger Expedition is Doug Macdougall. Doug is a fellow of the Meteoritical Society and the American Geophysical Union. We discuss his book Endless Novelties of Extraordinary Interest – The Voyage of H.M.S. Challenger and the Birth of Modern Oceanography, published by Yale...

In the early 1990s, scientists discovered that sperm counts had declined precipitously over the previous half century. With us to discuss human reproductive health, and how it has changed in part due to exposure to pollutants, is Shanna Swan. She is the author of the book Count Down: How Our Modern World Is Threatening Sperm Counts, Altering Male and Female Reproductive Health, and Imperiling the Future of the Human Race.

The boundaries of science are clear, and can be demarcated by the concept of falsifiability. Or so we learn in our science classes. But with some areas of science, falsifiability is not the critical feature, and may be impossible on theoretical or empirical grounds. Worrying about falsifiability might even get in the way of interesting ideas. With us to discuss the history of problems in science and falsifiability is Sean Carroll, a leading physicist and science communicator.

Human health and environmental health are inextricably linked. With us to gain a better understanding of the history of environmental health, especially the impact of pollutants on human health, is Linda Birnbaum. Linda served as Director of the US National Institute of Environmental Health Sciences and the National Toxicology Program from 2009-2019. She has published over 600 scientific articles, and is the recipient of numerous awards related to public health.

David Michaels is a professor of epidemiology at George Washington University, and previously served as the Assistant Secretary for Environment, Safety and Health at the U.S. DoE and as the Assistant Secretary of the U.S. OSHA. David is the author of numerous articles, as well as the books Doubt is their Product: How Industry’s Assault on Science Threatens your Health (2008), and The Triumph of Doubt – Dark Money and the Science of Deception (2020), both published by Oxford University Press.