Whittier called them "the saddest words: it might have been." But turn it around and you'll find places we create to replace the world we live in -- past, present and future. On To the Best of Our Knowledge, other worlds. Scientist Brian Greene looks at the physics of the multiverse, and...Read more





Scientists are launching one of the most audacious projects ever conceived: a detailed map of the human brain, neuron by neron, synapse by synapse. For some scientists...