It is something like the "Holy Grail" of physics: unifying particle physics and gravitation. The world of tiny particles is described extremely well by quantum theory, while the world of gravitation ...

In the quest to unravel the mysteries of the universe, physicists are revisiting a 150-year-old theory that could illuminate why matter prevails over antimatter. This knot hypothesis, originally ...

In the Fall I'll be starting teaching again, after a semester away on sabbatical and then enjoying teaching relief during my first semester at Penn. I'll be teaching a course that I truly love, and ...

Can a theory that isn’t completely testable still be useful to physics? What determines if an idea is legitimately scientific or not? This question has been debated by philosophers and historians of ...