Humans have sent into space enough evidence of our existence that intelligent extraterrestrial life may indeed find us before we find it. In 1974 astronomers used the Arecibo Radio Telescope in Puerto Rico to beam a short radio message toward Messier 13, a globular cluster of hundreds of thousands of stars about twenty-five thousand light-years away from Earth. Radio and television signals have been emanating from broadcast towers for about half a century. There are also physical objects that have gone beyond the orbits of the planets in our solar system, such as Pioneer 10, Pioneer 11, Voyager 1, and Voyager 2. Onboard those spacecraft, astronomers have installed pictures and audio recordings about our solar system, our planet, and ourselves.