We're not sure if there's anyone out there to receive them, but we earthlings have been sending messages into space for 40 years now. We've sent radio broadcasts, plaques engraved with pictures, and even a gold-plated record album. So far, we haven't gotten any return messages, but METI (Messaging to Extra-Terrestrial Intelligence) enthusiasts are still coming up with new ways to tackle the two crucial questions raised by this kind of endeavor: How should we send the message? And what should it say?

The first question is technical, concerning the durability of materials, the means of transmission, and the distances to travel. The second is more complicated and far more interesting. A message like this is also a declaration: "This is what we find important. This is who we are."

The Earth Tapestry project aims to create a message that represents a shared, global answer to these questions through an online vote. Pairs of landmarks like Red Square, Machu Picchu, the Lascaux Caves, and others around the world (180 total) are presented along with the questions on eight different parameters: Which is more awe-inspiring? Information-rich? Famous? Noble? Ingenious? Delightful? Durable? Irreplaceable?

The plan is to create a laser engraved disc of a map of the earth along with a legend giving coordinates of these places and what we think about them. It will be sent to the moon on an Astrobotic Technology lander next year.

The director of Earth Tapestry, William Alba of Carnegie Mellon University, says the moon, being "the border between the terrestrial and celestial, between us and the rest of the universe" is a good place to put this information capsule. Not only might extra-terrestrial beings discover it, but humans from the future might as well.

There is also an art installation planned. Alba says they "will continue to take votes over the next year and a half. We plan to fill a space with images of the locations so people can get a sense of what's important to them and people around the world." Earth Tapestry images will be displayed for durations that accord with their rankings in the voting.

There are many other ways to give a sense of what humans find important, of course, but for Alba, landmarks of the world is a good arena for a trial run, to make "a kind of playground or sandbox to think about what do we think is important about ourselves as human beings and how do we decide that together. Place draws people's attention to the globe as a whole. They'll think about where they are and where other people are."

You can cast your vote at earthtapestry.org.