Is there a point to recycling? Is recycling even good for the environment? In this volume in the MIT Press Essential Knowledge series, Finn Arne Jørgensen answers: it depends. From a technical point of view, recycling is a series of processes - collecting, sorting, processing, manufacturing. Recycling also has a cultural component; at its core, recycling is about transformation and value, turning material waste into something useful - plastic bags into patio furniture, plastic bottles into T-shirts.

Over the past decade and a half, carbon markets have emerged all across the globe. Recently, China, one of the biggest carbon-emitting nations on the planet, created a carbon market that is the biggest in the world. As the focus shifts on combating climate change and cutting carbon emissions, Carbon trade is gaining popularity. 

Over the past 10 years, urban planners, technology companies, and governments have promoted smart cities with a somewhat utopian vision of urban life made knowable and manageable through data collection and analysis. Emerging smart cities have become both crucibles and showrooms for the practical application of the Internet of Things, cloud computing, and the integration of big data into everyday life. Are smart cities optimized, sustainable, digitally networked solutions to urban problems? Or are they neoliberal, corporate-controlled, undemocratic non-places?

Critical thinking is regularly cited as an essential 21st century skill, the key to success in school and work. Given our propensity to believe fake news, draw incorrect conclusions, and make decisions based on emotion rather than reason, it might even be said that critical thinking is vital to the survival of a democratic society. But what, exactly, is critical thinking? Haber describes the term's origins in such disciplines as philosophy, psychology, and science.

Macroeconomics takes a broad perspective on the economy of a country or region; it studies economic changes in the aggregate, collecting data on production, unemployment, inflation, consumption, investment, trade, and other aspects of national and international economic life. Policymakers depend on macroeconomists' knowledge when making decisions about such issues as taxes and the public budget, monetary and exchange rate policies, and trade policies-all of which, in turn, affect decisions made by individuals and businesses. 

In Waves, Fredric Raichlen traces the evolution of waves, from their generation in the deep ocean to their effects on the coast. He explains, in a way that is readily understandable to nonscientists, both the science of waves themselves and the technology that can be used to protect us against their more extreme forms, including hurricanes and tsunamis.

After discussing what an algorithm does and how its effectiveness can be measured, Louridas covers three of the most fundamental applications areas: graphs, which describe networks, from eighteenth-century problems to today's social networks; searching, and how to find the fastest way to search; and sorting, and the importance of choosing the best algorithm for particular tasks. He then presents larger-scale applications: PageRank, Google's founding algorithm; and neural networks and deep learning.

A concise history of GPS, from its military origins to its commercial applications and ubiquity in everyday life.   

Causal Inference provides a brief and nontechnical introduction to randomized experiments, propensity scores, natural experiments, instrumental variables, sensitivity analysis, and quasi-experimental devices. Ideas are illustrated with examples from medicine, epidemiology, economics and business, the social sciences, and public policy.

The grid is an accident of history and of culture, in no way intrinsic to how we produce, deliver and consume electrical power. Yet this is the system the United States ended up with, a jerry-built structure now so rickety and near collapse that a strong wind or a hot day can bring it to a grinding halt. The grid is now under threat from a new source: renewable and variable energy, which puts stress on its logics as much as its components.