The orbital and rotational motions of the Earth and Moon define our familiar units of time. In these units, geological time is immense, involving hundreds of millions, even billions of years. It is subdivided into practical units in terms of the rock and fossil records. These records were used in the infancy of geology to estimate the Earth’s age, returning false values because of inherently wrong assumptions. We will see how radiometric dating using the decay schemes of various radioactive isotopes gives consistent, reliable ages, and shows that the Earth is around 4.5 billion years old. The workhorse of modern analyses is the mass spectrometer, which can determine the age of a tiny sample, even of a single grain. Radiometric dating can be used in environmental situations, for example to date great ice-sheets and even groundwater.

The solar system originated more than 4.5 billion years ago from a rotating cloud of molecular hydrogen and interstellar dust surrounding a star that became the Sun. Collisions and coalescence of particles in the dust cloud led to the formation of a solar system with eight planets and countless smaller bodies that has fascinated mankind since prehistoric times. Our knowledge of the solar system exploded in the recent era of space exploration, and its complete description deserves a library on its own. This chapter provides brief descriptions of the orbits and physical properties of the major planetary bodies. These exhibit natural phenomena originally studied on the Earth, such as gravitational and magnetic fields, seismicity, and tidal motions. They can be understood with geophysical concepts and techniques introduced in later chapters.

Previous chapters in this book have focused on domestic (or municipal) law within Hong Kong. This chapter examines the interface between Hong Kong law and international law and Chinese law (PRC law). It looks at the distinct international legal personality that Hong Kong possesses, Hong Kong’s engagement with international entities and the application of international law in Hong Kong. Previous chapters have discussed certain aspects of the interface between Hong Kong and the PRC legal system, and this chapter builds on this by focusing on mutual legal assistance between the two legal systems, access to the Mainland market for legal services from Hong Kong and cross-border crime.

With the increasing popularity of alternative methods of resolving disputes to lessen the burden on courts, a separate chapter must be dedicated to this topic. One may not typically think of alternative methods of resolving disputes as part of the legal system, but this chapter shows otherwise. Particularly with the Civil Justice Reform, alternative dispute resolution has played and will continue to play an even larger role in solving legal disputes in Hong Kong. The two main methods of alternative dispute resolution, namely mediation and arbitration, are examined.

This chapter looks at law at an abstract level and the fundamental questions of ‘What is law?’ and ‘Why have laws?’ are explored by discussing the functions and concepts of law. This chapter examines the macro and micro functions of law, as well as the major perspectives of law including natural law, legal positivism, sociology of law and critical legal theory. It concludes by exploring various classifications of legal systems and the way in which the law is divided within them, such as the difference between the common law and civil law systems, national and international law, substantive and procedural law, and public and private law.