Noctilucent clouds were once thought to be a fairly modern phenomenon. A team of researchers recently calculated that Earth and the entire solar system may well have passed through two dense ...

Astrophysicists calculate the likelihood that Earth was exposed to cold, harsh interstellar clouds, a phenomenon not previously considered in geologic climate models. Around two million years ago, ...

Around two million years ago, Earth was a very different place, with our early human ancestors living alongside saber-toothed tigers, mastodons, and enormous rodents. And, depending on where they were ...