In the mid-90s, students studying engineering at Dordt College (now Dordt University) took three semesters of physics using a textbook authored by David Halliday, Robert Resnick and Jearl Walker. As one of those students, I loved how each chapter started with a puzzling question that drew me into engaging the material, like “What size is…
The standard models that physics uses to explain the cosmos have some unresolved issues. If we consider only ordinary matter, for example, galaxies are not heavy enough to prevent them from spinning apart, given how fast they rotate. There is simply not enough matter-based gravity to hold them together. This problem with galaxies is one…
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