Wouldn’t it be really, really nice to get places really, really fast? That’s the promise of the hyperloop, a transportation idea popularized in the 21st century by none other than its Chief Engineer/Magician/Dreamer, Elon Musk. Five years after Musk wrote a white paper on the concept of a maglev train inside a frictionless, air-free tube, hyperloop has become a sort of legitimate business. Four companies with more than $300 million in funding are competing to build the first real one.