"Version: 20190101"--Title page verso.Includes bibliographical references (pages 27-28).1. Introduction -- 2. Background -- 2.1. Theory -- 2.2. Methods of gravitational wave detection -- 2.3. LIGO detector description3. Current directions -- 3.1. Noise sources and strain sensitivity -- 3.2. Gravitational wave searches -- 3.3. Gravitational wave astronomy4. Outlook -- 4.1. Ground-based detectors…