London and surroundings photographed from the International Space Station

© NASA

London and surroundings photographed from the International Space Station

Greetings, Earthlings! It’s World Population Day. And to get you thinking about just how many of us there are walking around on this planet, take a look at this photo of London, England. Taken by the International Space Station as it passed over the urban center all lit up during the night, it shows how thoroughly we humans have transformed the space around us. Our current population is more than 7.4 billion and counting. The United Nations, founding organization of World Population Day, hopes that the observance prompts conversations about how to keep life on Earth sustainable as our numbers increase.