When you imagine an alien, what do you think of? A green, slimy creature with jagged teeth? Or maybe a cute little E.T.-like figure?

Generally, we envision aliens as somewhat like us -- slightly more bizarre or fearsome versions of ourselves, but humanlike nonetheless. These perceptions reflect our own fears and desires and imaginings.

Now, thanks to nonprofit studio Blank on Blank , we can listen to astronomer Carl Sagan explain why it makes perfect sense that humans would "project their hopes and fears upon the cosmos." Blank and Blank recently published author Studs Terkel's 1985 interview with Sagan as part of its "Experimenter" series.