In many ways, black holes are science’s answer to science fiction. As strange as anything from a novelist’s imagination, black holes warp the fabric of spacetime and imprison light and matter in a gravitational death grip. Their bizarre properties make black holes ideal candidates for fictional villainy. But now black holes are up for a different role: heroes helping physicists assess the real-world existence of another science fiction favorite — hidden extra dimensions of space. Astrophysical giants several times the mass of the sun and midget black holes smaller than a subatomic p... (p. 22)

Were the Earth a crystal ball, you might gaze 2,900 kilometers down to its outer core with a telescope. The Earth, though, is frustratingly opaque — to light. Most knowledge of the planet’s internal structure comes from studying seismic waves, which give a kind of ultrasound image. Inferences about Earth’s internal chemistry rely on the elements found in near-surface rocks, meteorites and the sun. Recently, geoscientists have developed a new tool for probing the Earth’s innards. Borrowing a page from astrophysics, they are using the curious subatomic particles known as neutr... (p. 16)

Science fiction movies and books are full of parallel universes. In a typical scenario, as in the movie Sliding Doors, something happens in one universe—like a woman misses a train—but in a parallel universe, the same woman catches it, setting in motion diverging life paths. Or, as in Isaac Asimov’s imaginative novel The Gods Themselves, alien inhabitants of a parallel universe with different physical laws exchange energy with our universe and send coded messages to Earth. Even without any real-life alien messages to decipher, though, many cosmologists believe that ther...