• The concept is called "O'Neill colonies," named after Princeton physicist Gerard O'Neill who came up with the idea in 1976.
  • In a Tweet on Wednesday, Musk said building them would be "like trying to build the USA in the middle of the Atlantic Ocean."
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Jeff Bezos revealed a vision for human settlements in space earlier this month that verged on science fiction. Fellow billionaire space-missionary Elon Musk said Bezos' plans are exactly that.

At a press conference in Washington earlier this month, Bezos presented plans from his spaceflight company Blue Origin, including his ambition to establish a "sustained human presence" on the moon .

Part of Bezos' space colonization dreams also involve "O'Neill colonies," enormous spinning cylinders taken from Princeton physicist Gerard O'Neill, who came up with the concept in 1976. Bezos said his aim is to house a trillion people in the colonies, which would replicate gravity.

blue origin oneill space colony illustration rendering concept deer dave mosher business insider
Dave Mosher/Business Insider

When asked by a Twitter user on Wednesday what he thought about O'Neill colonies proposed by Bezos, Musk was less than enthusiastic.

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"Makes no sense. In order to grow the colony, you'd have to transport vast amounts of mass from planets/moons/asteroids. Would be like trying to build the USA in the middle of the Atlantic Ocean," he replied.

This isn't the first time Bezos and Musk have sparred over their dual ambitions to colonise space. Musk tweeted about Bezos' Blue Origin presentation at the time, mocking the moon lander's name.

"Putting the word 'Blue' on a ball is questionable branding," Musk tweeted . Bezos also reportedly ribbed Musk during his presentation, pointing out the impracticalities of settling on Mars, Musk's stated destination for his own spaceflight company, SpaceX.

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