LOS ANGELES (AP) - Last week, billionaire entrepreneur Elon Musk released sketch plans for a "Hyperloop" that he hopes one day will shoot capsules full of people at the speed of sound through tubes connecting Los Angeles and San Francisco.
Musk also urged the public to question, modify and, ultimately, perfect his proposal.
From tinkerers to engineers, the race is on.
One firm hustled out a model using a 3-D printer, while another is testing a virtual Hyperloop with sophisticated computer software. People for the Ethical Treatment of Animals wants ad space inside capsules, and in San Francisco, enthusiasts who want the concept to become a reality will meet over beers.
Meanwhile, Musk himself has shelved the project and returned to his established future-is-here transportation ventures - luxury electric car maker Tesla Motors and the rocket-building company SpaceX.