# Timothy Brandt

### Dating the Earth, the Sun, and the Stars

“How big” is almost always an easier question to answer than “how old.” Though we can measure the sizes of animals and plants easily enough, we can often only guess at their ages. The same was long true of the cosmos. The ancient Greeks Eratosthenes...

### The Mystery of the Gamma Rays from the Galactic Center

Five years ago, NASA’s Fermi Gamma-ray Space ­Telescope saw more gamma rays than expected from the area around the center of our galaxy. Many scientists suggest that the extra gamma rays could be from the annihilation of dark matter particles. This...