Mario Campanelli is an experimental particle physicist with decades of experience on the world's highest energy colliders. In 2007 he joined the faculty of University College London to work on the ATLAS experiment at CERN, where he mainly studies the properties of strong interactions. In 2018 he was nominated professor at UCL. He has 25 years of experience in teaching graduate- and undergraduate-level courses. Antonio d'Alfonso del Sordo is a mathematics and physics student in his third year at UCL. He has volunteered as a maths and physics tutor in London high schools through UCL, and worked as a student ambassador for his department, as well as mentor for first-year students. Camilla Tacconis will soon graduate from University College London with a BSc in physics. She aspires to become a researcher in solid state physics, and one day use this textbook to lecture on classical mechanics at University. Enrico Caprioglio is a third-year theoretical physics student, graduating in 2020. He has great experience in science communication, having worked at the London International Youth Science Forum for four years. Lodovico Scarpa is a theoretical physics student who dreams of becoming a researcher. His interests lie in the fields of (loop) quantum gravity and quantum information. Muhammad Tayyab Shabbir is a third-year undergraduate student at University College London. Tayyab has a background in the English and Pakistani education system and used this experience to make his contributions to the book accessible to students from all educational backgrounds. Sheila María Pérez García is a joint honours mathematics and physics student currently in her third year of study. She established a strong mathematical foundation in the book on which the more complex physical concepts rest.