This chapter discusses the requirements for a world to be deemed habitable at a given moment in time (instantaneous habitability), with an emphasis on the availability of energy sources and suitable physicochemical conditions. After a brief exposition of some concepts in thermodynamics, the significance of the molecule ATP (the ‘energy currency’ of the cell) and how it is synthesised in the cell by harnessing chemical gradients is described. The two major sources of energy used by life on Earth (chemical and light energy), and the various possible pathways for utilizing such forms of energy are sketched, most notably photosynthesis and methanogenesis. This is followed by delineating the diverse array of extremophiles that inhabit myriad niches on Earth that would be considered harsh for most life. The mechanisms that permit them to survive the likes of high/low temperatures, pressures, salinity, and radiation doses are reviewed.

Global greenhouse gas emissions linked to human activities continue to increase, and as a result global temperatures keep rising and the impact of climate change is increasingly felt by all communities. This chapter reviews the observed evidence of climate change and analyses greenhouse gas emissions in different countries and/or groups of countries to understand how we reached current concentrations and warming levels. The contribution also discusses the key conclusions of the Summary Report for Policy Makers published by Working Group I of the Intergovernmental Panel on Climate Change in August 2021, and applies a quasi-linear relationship between cumulated greenhouse gases and global warming to illustrate how emission reductions could limit global warming

Ever since the first exoplanets were discovered over 30 years ago, their detection has proceeded at a remarkable pace. This chapter describes the techniques for identifying these worlds, as well as characterising their atmospheres and surfaces to seek out possible signs of life. The most common methods for detecting exoplanets are reviewed: radial velocity measurements, transits, gravitational microlensing, astrometry, and direct imaging. This is followed by summarising avenues for characterising exoplanets through performing spectroscopy of three sources of radiation linked to them: (1) transmitted light passing through an exoplanetary atmosphere and reaching us; (2) thermal emission associated with the blackbody radiation of the planet; and (3) starlight reflected from that world. The chapter concludes by commenting on the bright future of exoplanetary science and future telescopes devoted to this area.

In the face of its international reputation for intransigence and foot-dragging on climate warming policy, combined with its deserved reputation for profligate fossil fuel consumption, the USA has actually reduced its greenhouse gas emissions since 1990. Continued compounded muddling, consisting of stricter national administrative regulation of energy efficiency and pollution control, new state and local government initiatives, further non-governmental governance developments and market-driven economic responses are together likely to support extending the current trends of reduced energy intensity and reduced greenhouse gas emissions over the next few decades, perhaps even to accelerate it. But a U.S. commitment to doing the right thing – whether conceived as doing what it would take to achieve the level of zero net emissions by 2050, or to accomplish the even more draconian reductions needed to soon halt global temperature rise – is unlikely in the absence of something that causes coalescence of a new normative political landscape.

The precessions of the Keplerian orbital elements are calculated for several tidal-type accelerations due to the presence of a distant 3rd body: Newtonian, post-Newtonian gravitoelectric, and post-Newtonian gravitomagnetic. The calculation is made, first, in a kinematically and dynamically non-rotating frame. Then, it is repeated in a dynamically non-rotating and kinematically rotating frame accounting for the de Sitter–Fokker and Pugh–Schiff precessions of its axes.

This chapter explains how pressure and density vary with depth and how they together control the different elevations of continental and oceanic regions, and reviews the fundamental concept of isostasy, the principle of flotation, where the lithospheric plates float on hot underlying mantle. It discusses Airy and Pratt models for isostasy and how and when high surface topography is compensated by a crustal root. The fundamental role of temperature is demonstrated in terms of the geotherm, heat production in the lithosphere, mantle and core, and how the Earth loses heat to the atmosphere through plate tectonic processes. The latter point also relates to how the geotherm varies through the upper crust, which again relates to geothermal energy exploitation. Temperature and pressure variations also control melting and magmatism, and this chapter covers the fundamental principles and characteristics of melting and magma crystallization. Also covered is metamorphic rocks and the metamorphic processes that occur in response to plate tectonic processes. Finally different kinds of sedimentary basins and their formation and classification according to plate tectonics are briefly reviewed.

This chapter takes Green Plan implementation as an important test case of climate policy implementation more generally and as an indicator of the potential obstacles to going beyond the mere reconciliation of environmental and human rights issues in pursuit of policies that advance environmental protection and human rights in synergistic ways.