We walk through the different epochs and eras of the universe, going forward in time from the Hot Big Bang. In the earliest universe, radiation (photons) dominated over matter. As the universe cools, electrons are able to recombine with protons, then helium and other light elements were formed in the first few minutes. Cosmic inflation is posited to overcome several problems, but investigations to probe and perhaps confirm inflation are ongoing.

In our everyday experience, there is another way we sometimes infer distance, namely by the change in apparent brightness for objects that emit their own light, with some known power or luminosity. For example, a hundred watt light bulb at close distance appears a lot brighter than the same bulb from far away. Similarly, for a star, what we observe as apparent brightness is really a measure of the flux of light, i.e. energy emitted per unit time per unit area.

Radiation generated in the deep interior of a star undergoes a diffusion between multiple encounters with the stellar material before it can escape freely into space from the stellar surface. We define the optical depth by the number of mean free paths a photon takes from the center to the surface. This picture of photons undergoing a random walk through the stellar interior can be formalized in terms of a di usion model for radiation transport in the interior.

The average adult spends a large portion of their time in paid employment. Depending on their circumstances, these people most likely hold other social roles, too; they may be parents, spouses, children, or grandchildren, for example. Expectations from these additional roles can impact their work schedules, impede paid employment demands, or conflict with the identity of being a “worker” more generally. This is particularly the case in situations where individuals have caregiving obligations, either to young children or elderly family members. The space where work and nonwork roles interact is referred to as the work–family interface. When these roles are experienced as competing or conflictual, stress may result, subsequently impacting one’s mental health. However, these stressful experiences are not created equal. For example, domestic responsibilities tend to fall more often on women, creating an unequal distribution of labor and more vulnerability to the stressors created by competing work and family roles for women compared to men. These experiences can be made even worse by intersecting disadvantages such as low socioeconomic status or racial inequalities. Broader contexts may also impact work–family interface situations, like the COVID-19 pandemic, which dramatically changed the lived realities of work and family for a large portion of the population. Many employed parents were forced to work from home. Childcare services for young children were halted and schools temporarily closed. These transitions placed a greater burden on parents to figure out childcare and at-home schooling while maintaining full-time work schedules. These changes had implications for the stressors and mental health experiences of the work–family interface. Students can discuss the various ways that social circumstances may interact with the work–family interface to either amplify or reduce the mental health consequences associated with stressors like work–family conflict. They may also discuss how workplaces, organizations, and/or employers could implement policies to assist workers in balancing competing work and family responsibilities.

Compared to stars, the region between them, called the interstellar medium or "ISM," is very low density; but it is not a completely empty vacuum. A key theme in this chapter is that stars are themselves formed out of this ISM material through gravitational contraction, making for a star-gas-star cycle. We explore the characteristics of cold and warm regions of the ISM and their roles in star formation.

Although many disciplines study mental illness, not all disciplines think of mental illness in the same way. This chapter considers two things: (1) how different disciplines (e.g., sociology versus psychiatry) and actors (e.g., clinicians versus the public) approach the concept of mental illness, and (2) how decisions regarding what mental illness is affect conclusions regarding its consequences, determinants, and treatability. Although decisions regarding what mental illness is are consequential, they are often made on an ad hoc basis, on narrow psychometric grounds, or on the practical interests of a profession, discipline, or person. This chapter outlines some of these decisions and the interests that inform them, evaluating categorical versus dimensional approaches and lay diagnostic instruments. In addition, it outlines more recent alternatives to conventional measures, including the network approach to symptoms. Long-standing controversies regarding outcomes in mental health research are unlikely to be resolved anytime soon, but the topic of mental illness is no less significant for being unsettled. For discussion: What is the optimal approach to studying mental health problems? What is the best way to think about an “optimal” approach, given many competing conceptions of mental disorders?

Gabe Miller provides an overview of the mental health of sexual and gender minority (SGM) populations. Sexual and gender minority mental health is impacted by multiple levels of influence, including individual, interpersonal, community, and societal-level determinants. In addition to the historical and ongoing medicalization of sexual orientation and gender identity, SGM populations experience unique social stressors that impact their mental health. The high prevalence of mental health disorders observed in SGM populations are the result of higher levels of social stress and social stigma that SGM people experience across the life course, across multiple domains, and across multiple levels. Despite these substantial stressors, SGM people exhibit resilience, resistance, and joy. How might these unique SGM-related social stressors at different levels combine or intersect to impact the mental health of SGM people?

The sociological approach focuses on the factors external to the individual – the environmental or social context – and views mental illness as a breakdown in the face of overwhelming environmental stress. Thoits overviews three dominant theories, or models, and describes their basic assumptions, advantages and limitations, and implications for treating or preventing mental illness. Stress theory is based upon evidence that accumulations of social stressors can precipitate mental health problems. However, the relationship between stress exposure and psychiatric symptoms is not strong because individuals have extensive coping resources to help them handle stress. Researchers focus on the relationship between stress and coping mechanisms, and also on the unequal distribution of chronic strains and a variety of coping resources in the population. One reason that higher rates of mental disorder and psychological distress are found in lower status, disadvantaged groups is that these groups are more likely to be exposed to stressors and less likely to have important coping resources. In order to treat mental illness, one needs to eliminate or reduce stressors, teach the individual different coping resources, and bolster their personal resources. Structural strain theory locates the origins of disorder and distress in the broader organization of society. Mental illness may be an adaptive response to structural strain, or to one’s degree of integration into society. For example, during periods of high unemployment, admissions to treatment for psychosis increase, while periods of economic upturn are associated with lower rates of hospitalization. A structural condition, hard economic times, caused people to experience major stressors and provoked mental illness. Society’s organization places some groups at a social or economic disadvantage. In order to prevent or reduce mental illness, society must be restructured in a fairly major way; for example, creating a guaranteed minimum income to eliminate the strains of unemployment. A third approach to mental illness is labeling, or societal reaction, theory. The logic behind labeling theory is that people who are labeled as mentally ill, and who are treated as mentally ill, become mentally ill. Symptoms of mental illness are viewed as violations of the normative order whereby individuals break taken-for-granted rules about how one should think, feel, and behave. The way to reduce or prevent mental illness is to change those norms that define what is normal versus abnormal behavior. While this may seem idealistic, labeling theory has been very important in alerting us to the consequences of labeling and institutionalization. The reader should think about the various ways the three sociological approaches to mental illness complement each other, as well as how they contribute to the biological and psychological understandings of mental disorder.

Virginia Aldigé Hiday and Bradley Ray examine two prevailing beliefs about mental illness and the criminal justice system: that deinstitutionalization has led to the criminalization of mental illness and that persons with mental illness are dangerous and likely to commit crimes. The chapter reviews the available empirical evidence for these beliefs. Although arrest rates and incarceration rates are indeed higher for persons with mental illness than for the general population, criminalization may be an inaccurate characterization. Furthermore, most people with mental illnesses are not violent, and only a small proportion becomes violent. The chapter goes on to examine how persons with mental illness are handled by the criminal justice system. The authors suggest that there are five subgroups of persons with severe mental illness who come into contact with the criminal justice system: (1) those committing only misdemeanor nuisance offenses; (2) those committing offenses involving survival behaviors; (3) those who abuse alcohol and drugs, which lead to high rates of criminal offenses from the use of illegal substances, from attempts to support their habits, and from violence arising out of their use; (4) those with a character disorder who have high rates of felonious criminal offending, especially for violence against others; and (5) a much smaller subgroup whose members fit the stereotypical image of a severely disordered person driven to criminally violent actions by delusions. All five groups tend to live in impoverished, disorganized communities where it is difficult to survive with a major mental illness. The authors conclude that the criminal justice system is left to pick up the pieces after the failure of other social institutions. What types of social stressors contribute to the criminalization of the mentally ill? What failures of social institutions have led to incarceration of those with mental illnesses?

Hubble’s law gives us the simple and obvious interpretation that we currently live in an expanding universe. The inverse of Hubble’s constant defines the "Hubble time" which effectively marks the time in the past since the expansion began. more realistically, one would expect the universe expansion to be slowed by the persistent inward pull of gravity from its matter. We consider how various theoretical models for the universe connect with the observable redshift that indicates its expansion.

We have seen how a star’s color or peak wavelength indicates its characteristic temperature near the stellar surface. But what about the temperature in the star’s deep interior? Intuitively, we expect this to be much higher than at the surface, but under what conditions does it become hot enough to allow for nuclear fusion to power the star’s luminosity? And how does it scale quantitatively with the overall stellar properties, like mass, radius, and luminosity? To answer these questions, we identify two distinct considerations.

The post-main-sequence evolution of stars with higher initial mass (>8 solar masses) has some distinct differences from those of solar and intermediate-mass stars. We show how multiple-shell burning can lead to core-collapse supernovae, which are important in generating elements heavier than iron. Some supernovae can lead to the curious stellar end points of neutron stars and black holes.

Exoplanets are planets orbiting stars other than our sun. While some have now been detected (or confirmed) by direct imaging, most exoplanet detections have been made via two other more indirect techniques, known as the radial velocity and transit methods. These methods have analogs in the study of stellar binary systems, as outlined in Chapter 10. We explore the population of known exoplanets and how we must compensate for observational biases inherent in each of these techniques.

We start with some of the historical work on measuring distances to galaxies, leading to the Hubble (or Hubble-Lemaitre) law, a linear proportionality between recession velocity and and a galaxy’s distance, with a proportionality constant known as the Hubble constant. For more distant galaxies, it becomes increasingly difficult to detect and resolve even giant stars like Cepheid variables as individual objects, limiting their utility in testing the Hubble law to larger distances and redshifts. For much larger distances, an important alternative method is the Tully–Fisher relation.