Why do onion fumes make us cry? The answer involves volatile sulfur compounds, an enzyme, your eyes’ natural defense system, and a chemical called syn-propanethial-S-oxide — and it is more interesting than you’d expect.

Phantom kangaroos — sightings of kangaroos and wallabies far outside their native range in Australia — have been reported across the United States, Europe, and beyond for over a century. Nobody has a satisfying explanation.

The physics of rainbows — refraction, reflection, and the dispersion of light — is one of the most beautiful demonstrations of optical science in the natural world, hiding in plain sight above every rainy sky.