Earth's geological history is punctuated by episodes of unusually protracted and large-scale volcanic activity, during which huge volumes of igneous rock are added to Earth's surface and crust. Humans have not witnessed this type of large-scale volcanic activity, known as large igneous province volcanism, but it is often temporally associated with profound environmental and climatic changes, such as mass extinction events. In order to understand what triggers these global changes, we need to consider the fluxes of particles and gas emitted by large igneous province-scale volcanic activity and match our projections with the signals left in the geological record. This is a challenging endeavour and this chapter discusses how evidence from today's active volcanoes can teach us not just about the present-day impact of volcanism, but also about these much larger volcanic eruptions that happened tens to hundreds of millions of years ago. The author argues that by peering into volcanoes, we can shed new light on enigmas surrounding the evolution of Earth's environment and biology over its deep geological history.

This chapter guides the reader through three related enigmas of modern physics. The first is a mystery of quantum mechanics. Important aspects of quantum mechanics are still not truly understood, although competing theories have been proposed, including the Many-Worlds approach. The second enigma is the emergence of spacetime, and especially the way it interacts with gravity. Rather than following the traditional methodology of ‘quantising’ classical theories, the author proposes an alternative approach and instead seeks gravity within quantum mechanics. The chapter concludes with a discussion of the mystery of the arrow of time: what distinguishes the past from the future. Together, these three mysteries of modern physics serve as an important reminder of the endurance of enigmas in the very foundations of scholarly fields. Re-examining founding principles can provide a constructive alternative means of investigating mysteries, not only in modern science but also across other disciplines.

The efforts to decode the mystery of the Antikythera mechanism, a unique machine surviving from around 70–60 BC, extend more than a century since its discovery in an ancient shipwreck off the coast of a Greek island. Although the first experts who looked at the device were baffled by its gear mechanisms, dating, and purpose, this chapter explains how many of these inscrutable aspects slowly came to be clarified and deciphered. The author illustrates the immense efforts it can take to ‘solve’ an enigma: in this case, the combined work of historians, epigraphers, radiographers, X-ray machines, mechanics, filmmakers, and multinational technology companies. The chapter also displays the valuable insights which can come from such endeavours. Decoding the Antikythera mechanism challenged common assumptions about technological skill and astronomical knowledge in antiquity, but it also encouraged innovations in modern technology and revealed something of humanity’s search to understand the cosmos.

We live in an age where emotional literacy and legibility is highly desirable, and where so-called Emotion Detection technologies lead us to believe that, with enough data, we might crack the enigma of other people’s emotions. This chapter begins from a different proposition: what is it to want to remain emotionally inscrutable? Beginning with Darwin’s 1872 observation that studying other peoples’ emotions is ‘difficult’, the chapter then argues that ambivalence and illegibility is part of the nature of emotion itself. It then moves to consider a series of moments when people have deliberately used emotional inscrutability as a form of self-defence and defiance, including in ‘camp’ retorts by early twentieth century cross-dressers, and in Audre Lorde’s refusal to emotionally engage with white women about race because it came at such a high psychological cost to her. In this way, this chapter shines a light on those moments when emotional inscrutability becomes a powerful political tool.

Focusing on human capacity to design, the volume's final chapter draws attention to the fascinating role imagination can play in human life. The relationship between human consciousness and the evolution of the species continues to captivate and puzzle scholars. By revisiting the dialogue between consciousness and evolution, the authors demonstrate how enigmas often necessitate dynamic collaboration between sciences, arts, and humanities. Archaeology provides evidence that the drive for diverse conscious experiences is no new phenomenon, while neuroscience illuminates the ways in which altered states of consciousness can enhance the variety of mental experience. Art, design, and cognitive technologies can build on this picture by providing innovative ways of exploring conscious experience. Inspired by insights from a range of academic disciplines and reflecting on personal experience, this chapter proposes the role of ‘harmony’ as another enigmatic angle of research with potential to shed further light on the functioning both of human society and of the human mind.

Puzzles and codes have multifaceted uses in practices of concealment, especially for militaristic purposes, corporate secrecy, or national security.The term ‘Enigma’ is perhaps most recognisable in modern history and contemporary culture as the name of a cipher device used by the German military to send messages during World War II. This chapter moves to the historical context of the twentieth century and shows how humans sometimes deliberately engineer enigmas to serve their own purposes. The author focuses on the mathematics underpinning the story of the Enigma Machine, setting out the process both of the code’s creation and of its decryption. Following the story of Alan Turing, a mathematician and one of the code breakers at Bletchley Park, the chapter emphasises both the necessity of collaborative labours to solve challenging problems and the importance of individual research and investigation to resolve crucial pieces of a much larger puzzle.

A new therapy that uses the patient's own blood to cure blood cancers (leukaemias) is the focus of this chapter. The history of its detection and diagnosis is related, along with the long and arduous search for effective treatment, arriving at successful employment of bone marrow transplantation in the later twentieth century. More recent developments in chemotherapy are reviewed, leading to a contemporary account of the encouraging progress with T-cell therapies.

In this chapter the author probes beneath the melodramatic surface of the story of Count Dracula, to reveal more subtle narrative threads, relating to Bram Stoker's critical social observations, both looking back in time, where many metaphorical dimensions of ‘blood’ are in play, and forward in time to late-nineteenth-century changes in gender relations, particularly as encapsulated in the figure of the ‘New Woman’. Just as blood-steeped history is conspicuous on the melodramatic surface of the fiction, so a forward-looking, scientific, and liberated future is discernible just beneath that surface.

This chapter explores the historical evidence for cultural attitudes to menstruation. The most commonly promoted medical theories as to why women experienced a monthly bleed are discussed. The many words and circumlocutions early moderns used to describe menstruation and related female reproductive bleeding are considered, along with prevailing cultural expectations about this event.

This chapter starts with a historical review of ideas about blood flow around the body, culminating in an understanding of circulation, the mechanics of which are described. The propagation of the pressure pulse in arteries is discussed, as is the disturbance to smooth flow caused by the complex geometry of arteries. The deformation of blood cells during their passage along the smallest capillaries is considered, as are the interesting effects of gravity on the venous return to the heart in upright animals, notably those with long necks and legs, such as giraffes and dinosaurs.