I wrote a blog post for Scientific American’s Observations blog about a video that shows how scientific inventions over the past two millennia led to the population explosion we have today. On a digital map of the world, the video adds a yellow dot every time another million people are added to the Earth. The dots are slow to appear for most of the video’s running time, even with the help of inventions that spread civilizations across the globe–like the magnetic compass and nitrogen-based fertilizer. Occasionally they disappear–several are snuffed out in Europe during the Black Death. But after the industrial revolution, the dots pop and sparkle like the Rockefeller Center Christmas tree. Check out the post and watch the video here.