NASA has recently published a detailed timeline of the "Big Bang" and the events following over the course of over 13 billion years. This timeline, based on the most data received by  NASA's Wilkinson Microwave Anisotropy Probe (WMAP), shows that, after the first micro-fraction of a second following the "Big Bang" (in which matter expanded at a speed faster than light, paradoxically enough), the universe expanded relatively slowly. One of the most interesting findings was that matter began coalescing into stars early on - perhaps only 400 million years after the initial explosion.

Since star formation leads to the appearance of planets and ultimately (though theoretically, at this point) life itself, and life on Earth covers less than half of the time, one might speculate how many ecosystems have risen and fallen, or may exist yet in our universe.