In the years 1972 and 1973, our nation launched a series of probes into outer space, the most important ones called Pioneer 10 and Pioneer 11. Knowing these space probes had the potential of making it out beyond our solar system, soaring silently onward into the deepest recesses of space, the scientists at NASA figured they had an obligation to say something about who we are, this people who had created that technology. In the event that some alien race, dwelling on some world yet undreamed of, should take possession of one of the Pioneer probes, what should we tell them about our greatest achievements as a race?

A committee of scientists, led by the astronomer Carl Sagan, set to work. They decided on a plaque of anodized aluminum, with certain images carved into it. There was a picture of the spacecraft itself, with nude figures of a man and a woman standing in front of it — drawn to scale, so the extraterrestrials would be able to tell how big we are. Then, there was a series of lines and symbols, meant to communicate information about where in the Milky Way Galaxy our planet Earth is located.

If that message is ever read by alien creatures, it’s not likely to be for a very, very long time. By the time either of those slow–moving spacecraft reaches even the nearest star to our solar system, no fewer than 40,000 years will have passed.