From Zocalo, was it inevitable that human beings came to exist on Earth? We could prove this definitively if we were to meet space aliens who looked just like us, with a fossil record just like ours, says Neil Shubin. From Skeptic, Michael K. Gainer on the physics of UFOs: How realistic is it for spacecraft to travel interstellar distances to Earth? (and more). Who should extraterrestrials speak to? Alternately, if Earthlings were space bound and found a pre-spaceflight civilization, who should talk to them? Crazy far — to the stars, that is; will we ever get crazy enough to go? Internet visionary Esther Dyson is ready for liftoff. Frank White on the time for a world space policy. Sky mining: Robin McKie on how exploiting off-Earth resources could pave the way for human exploration of the Solar System. Dan Allosso on the history of our place in the universe.