I was feeling a bit nostalgic, so I thought we could look back at the world before "the fifth mode" changed everything. (Make sure to check out the post script. It may be the best part.) From Forbes:

Hyperloop Is Real: Meet The Startups Selling Supersonic Travel

Bruce Upbin

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The majestic Senate majority leader suite in the U.S. Capitol was still Harry Reid's in September when he eagerly scooched his leather chair across the Oriental rug to gaze at something that, he was told, would change transportation forever.

Former SpaceX engineer Brogan BamBrogan (yes, that's his legal name) pulled out his iPad for a preview. Two business partners, the half-billionaire venture capitalist Shervin Pishevar and former White House deputy chief of staff Jim Messina, carefully studied the powerful senator's reaction. Even Mark Twain, a onetime riverboat pilot whose portrait hung over Reid's desk, eyed the proceedings warily.

"What's that?" asked Reid, sitting up, animatedly pointing at the iPad. BamBrogan's home screen showed a photo of a desert plain with dazed and dusty half-dressed people wandering around at sunrise.

"Er, that's Burning Man," the engineer responded, then clued in the 75-year-old politician to the techno-hippie carnival that takes place pre-Labor Day in the Black Rock Desert of Reid's home state of Nevada.

BamBrogan's formal presentation was even wilder, a vision for efficiently moving people or cargo all over the Southwest, to start, and the world, eventually, at rates approaching the speed of sound.

At the end of the 60-minute pitch Reid sat back and smiled. That's when Pishevar leaned in, asking the senator to introduce him to a Nevada businessman who owned a 150-mile right of way from Vegas to California for a high-speed train. Reid said he would, and they shook on it. And thus fell another obstacle in the group's fast-moving efforts to actualize what until recently had seemed not much more than geek fantasy: the hyperloop.

You remember the hyperloop, don't you? It's that far-out idea billionaire industrialist Elon Musk proposed in a 58-page white paper in August 2013 for a vacuum-tube transport network that could hurtle passengers from San Francisco to Los Angeles at 760 miles an hour. Laughed off as science fiction, it is as of today an actual industry with three legitimate groups pushing it forward, including Hyperloop Technologies, the team in Harry Reid's office. They emerge from "stealth" mode with this article, armed with an $8.5 million war chest and plans for a $80 million round later this year. "We have the team, the tools and the technology," says BamBrogan. "We can do this." The 21st-century space race is on.

[Quick aside: (Regular readers, feel free to skip this paragraph—you’ve heard it all before.) Elon Musk did not propose the technology being discussed here in his 2013 white paper. What he suggested was a high-speed train running on an air cushion in a near vacuum—a system so laughably bad that even these guys wouldn’t touch it. They did, however, keep the name. -- MP] 

It's hard to overstate how early this all is. There are dozens of engineering and logistical challenges that need solving, from earthquake-proofing to rights-of-way to alleviating the barf factor that comes with flying through a tube at transonic speeds.

[Quick aside II: If you were listing the actual "challenges" in order of difficulty, none of these would make the top twenty. It's almost as if the author was downplaying the real reasons that this would never rise beyond the level of Dubai tourist attraction, and probably not even manage that. -- MP] 

Yet it's equally hard to overstate how dramatically the hyperloop could change the world. The first four modes of modern transportation--boats, trains, motor vehicles and airplanes--brought progress and prosperity. They also brought pollution, congestion, delay and death. The hyperloop, which Musk dubs "the fifth mode," would be as fast as a plane, cheaper than a train and continuously available in any weather while emitting no carbon from the tailpipe. If people could get from Los Angeles to Las Vegas in 20 minutes, or New York to Philly in 10, cities become metro stops and borders evaporate, along with housing price imbalances and overcrowding. 

It goes on into considerable length after that though I can't recommend reading further.

In case you were wondering what became of the author of the piece.