"The Hidden Reality" reveals how major developments in different branches of fundamental theoretical physics -- relativistic, quantum, cosmological, unified, computational -- have all led us to consider one or another variety of parallel universe.

Trace the growth of physics from philosophy, as questions about the nature of reality got rigorous answers starting in the Scientific Revolution. Then, see how the philosophy of physics was energized by a movement called logical positivism in the early 20th century in response to Einstein’s theory of relativity. Though logical positivism failed, it spurred new philosophical ideas and approaches.

If the point of physics is to explain reality, what counts as an explanation? Professor Gimbel goes deeper to probe what makes some explanations scientific and whether physics actually explains anything. Along the way, he explores Bertrand Russell’s rejection of the notion of cause, Carl Hempel’s account of explanation, and Nancy Cartwright’s skepticism about scientific truth.

Consider the weirdness of time: The laws of physics are time reversable, but we never see time running backwards. Theorists have proposed that the direction of time is connected to the order of the early universe and even that time is an illusion. See how Einstein deepened the mystery with his theory of relativity, which predicts time dilation and the surprising possibility of time travel.

Compare proof for the reality of atoms with evidence for the existence of Santa Claus. Both are problematic hypotheses! Trace the history of atomic theory and the philosophical resistance to it. End with Bas van Fraassen’s idea of “constructive empiricism,” which holds that successful theories ought only to be empirically adequate since we can never know with certainty what is real.

Taught by Professor Lawrence Weinstein of Old Dominion University, this course explains the science, history, hazards, applications, and latest advances in nuclear physics. You learn the principles of radioactivity, how nuclear bombs and reactors work, the uses of radiation for cancer treatment and medical imaging, what makes some forms of radiation dangerous, plus you tour a linear accelerator.

See how the strong and electromagnetic forces shape the nuclei of all atoms. Focus on the curve of binding energy, which explains why heavy nuclei are prone to fission, releasing energy in the process, while light nuclei release energy by fusing. Visit some classroom lab equipment to explore the principles that govern particle accelerators, which are used to probe the structure of nuclear matter.

Survey the sources of radiation in the world around us, bombarding us from the sky (cosmic rays), found in the ground (uranium and other naturally occurring radioactive elements), zapping us in medical procedures, and found in consumer goods. Look at some long-discontinued radiating products such as shoe fluoroscopy and Radithor, an ill-advised radium-laced health tonic.

Now open the hood to see how the nucleus works. Start simple with a hydrogen atom, which has a nucleus of one proton orbited by a single electron. Build from there, adding neutrons and more protons, forging elements and their isotopes and seeing how the nucleus behaves much like a liquid drop. Then use the Fermi gas model to refine your understanding of nuclear structure.

Take a behind-the-scenes tour of the Thomas Jefferson National Accelerator Facility in Newport News, Virginia, where Professor Weinstein and his colleagues use high-energy electron beams to probe the structure of the nucleus. Dr. Weinstein also explains other types of particle accelerators and their purposes, including the Large Hadron Collider in Europe.