| Imagine a textbook in which the illustrations are working models of the objects being studied. Now suppose that the reader could change the system parameters while the model is running. Further, let's imagine that in this textbook the text may be edited, added to or written from scratch by the reader and that the new physical systems may be created to illustrate the principles expounded in the text... and that these new systems may be studied and modified by future readers. This is the paradigm upon which we base our run-time books, including the virtual laboratory in the book as embedded models. Physics-T is such a run-time book. The letter T in the title reflects the fact that this book covers topics that provide a Transition from first year physics courses to more advanced subjects for the physics student or a Taste for the curious non-physicist of those topics usually reserved for physics professionals. The lessons are not rigorous treatments of the topics covered but serve to make some of the concepts of advanced physics accessible to the generally educated public. We aim to make the conclusions seem reasonable, not inevitable. We hope that the physics student would come away with a sense for where the advanced courses are going so that he or she might not lose sight of the goal while struggling with the details. We also hope that non-physicists will gain some insight into the inner workings of the universe. The run-time technology that powers Physics-T is a next logical step in computer-aided education. In the beginning there were printed textbooks with static pictures and graphs that just lay there on the page. Then there were computer-aided texts that were basically just electronic page-turners. Next came multi-media presentations where animation, video, audio and all sorts of snappy pictures were presented along with the text. Even the slickest multi-media presentation though is frozen at the time the program is produced, at compile-time, as the programming people say. All the reader can do is choose a path through material that has been prepared for her. When our book programs are running, at run-time as it were, the reader can get into the underlying algorithms and make changes to the displays that serve as our illustrations, fundamentally changing the program as it runs to illustrate ideas that the author may not have thought of. Practically infinite variation is possible. Table of Contents (In which all is revealed...) Introduction - where we explain how this run-time book thing works and the goals of Physics_T are set forth. This is a good place to start if you are new to the program. The Free-Body Review dips back into material presented in Physics_1, exercising the free-body diagram to remind us of the power of Newton's laws in predicting the future. The Nature of Space is a first look at some of the concepts that will be useful in later lessons. In this lesson I do a lot of talking and waving my arms and not much solid science. In Some Relativity we follow a bit of Mr. Einstein's thinking when he asked himself what would be the consequences if 1 plus 0.5 was sometimes 1 rather than 1.5. Here we introduce the notion of spacetime replacing the ideas of separate space and time, the interval between events replacing the distance between objects and worldlines replacing trajectories. In the Speed of Gravity we explore a paradox exposed by our reasoning in Some Relativity. As usual resolving an apparent paradox requires a re-examination of our common sense. In Some More Relativity we try to salvage Newton's law of universal gravitation, including its implication of instantaneous communication between objects engaged in a gravitational interaction, in spite of the difficulty dredged up in the Speed of Gravity. After all it does correctly predict the observed orbits of all the planets in the solar system except for that of Mercury. |
