1. Introduction; 2. Gravity: The Pull of the Earth; 3. Case Studies in Gravity; 4. Magnetometry: Finding Buried Magnets and More; 5. Case Studies in Magnetometry; 6. Waves: Some Basic Concepts; 7. Electromagnetic Induction: A New Frontier; 8. Case Studies in Electromagnetic Induction; 9. Ground Penetrating Radar: A True Wave-Based Technique; 10. Case Studies in Ground Penetrating Radar; 11. Geotomography: Holograms within the Earth; 12. Case Studies in Geotomography; 13. Electrical Resistivity Tomography: Imaging with Electricity; A. Quick Reference; B. Glossary