In the 1970s, some forward-thinking NASA scientists put an Earth-observing satellite into orbit. At an altitude of 570 miles, it photographed the entire planet every 18 days, circling Earth 14 times a day and sending the data back to ground stations.
Forty years later, this satellite and its successors have created the longest continuous record of our planet's surface. By stringing the images together, NASA and the US Geological Survey have shown how rapidly and how profoundly humans are changing the face of Earth.
In this time lapse showing the massive growth of Las Vegas, vegetation appears red because the images were partially gathered through infrared sensors. Golf courses and lawns jump out, foretelling the city's water scarcity problems. Off of Lake Mead an artificial lake appears in the 1990s, and developments form alongside it. This is Lake Las Vegas, where Celine Dion lives.
Check out the video above to see what 40 years of satellite imagery reveal about humanity's global footprint.
Read more: 15 before-and-after images that show how we're transforming the planet