When we think of time, we think of our daily schedules or maybe a lifetime. But the human mind has a hard time grasping the history of the universe, and the relative blink of an eye that humanity has been around. The 300,000 years that homo sapiens has existed is the main focus of what we call history, and that seems like a long time.
Alex Gorosh and Wylie Overstreet built a timeline of the universe out in the Mojave desert, the only place they could build something that big. But the history of mankind had to be built to a different scale than the 13-billion-year history of the universe before we came along; otherwise, all of human history would be too small to even label. This video tries to explain the concept of that long, long time. (via Kottke)