The search for'another Earth' has been a staple of science fiction for decades, and now a group of astronomers hope to discover one on our galactic doorstep. Alpha Centauri is a triple star system just over four light years from the Earth, split into a pair of sun-like stars known as AB, and a red dwarf called Proxima Centauri. So far planets have only been found orbiting Proxima Centauri, but experts from the University of Sydney and Breakthrough Initiatives believe they will find a world orbiting the larger binary pair using a new privately funded telescope. Known as the Toliman mission, it will launch in 2023 and scan Alpha Centauri AB for worlds in the habitable zone, where liquid water can flow on the surface. The team hope to be able to say whether there are habitable worlds orbiting either or both of the binary stars by the middle of this decade.

Machine translation of human languages (for example, Japanese, English, Spanish) was one of the earliest goals of computer science research, and it remains an elusive one. Like many AI tasks, translation requires an immense amount of knowledge about language and the world. Recent approaches to machine translation frequently make use of text-based learning algorithms to fully or partially automate the acquisition of knowledge. This article illustrates these approaches. Anyone who has taken a graduate-level course in AI knows the answer.

An illustration shows what a visitor might see if they could stand on the surface of the Earth-size planet Proxima b. Just a few months ago, astronomers revealed that there is an Earth-size world orbiting Proxima Centauri, the next star over. Now, a team of astrophysicists thinks there's a way to pay that planet a nice long visit sometime in the not-so-distant future. The method involves something similar to the Breakthrough Starshot Initiative, a plan unveiled last year that would send a fleet of small spacecraft toward the three stars in the Alpha Centauri system, which includes Proxima. Propelled by a giant laser, those tiny spacecraft would zip through the system in a matter of moments, furiously snapping photos, gathering data, and somehow relaying that information back to Earth.

This artist's impression shows the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image between the planet and Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface. It was just over 20 years ago--a blink of a cosmic eye--that astronomers found the first planets orbiting stars other than our Sun. All these new worlds were gas-shrouded giants like Jupiter or Saturn and utterly inhospitable to life as we know it--but for years each discovery was dutifully reported as front-page news, while scientists and the public alike dreamed of a day when we would find a habitable world. An Earth-like place with plentiful surface water, neither frozen nor vaporized but in the liquid state so essential to life. Back then the safe bet was to guess that the discovery of such a planet would only come after many decades, and that when a promising new world's misty shores materialized on the other side of our telescopes, it would prove too faraway and faint to study in any detail.