The two billionaire tech titans working to make interplanetary human life possible don't agree on how to make that vision a reality.
In the midst of a thread of tweets about the technical aspects of rocketry, one Twitter user asked Musk what he thought about Bezos's idea to use self-sufficient, cylindrical structures that float in space, like those designed by Princeton physics professor Gerard O'Neil. (Earlier in May when Bezos unveiled a Blue Origin lunar lander, he talked about his vision for the O'Neil-like structures.)
Musk does not think Bezos's idea is the best option.
"In order to grow the [space] colony" using Bezos's cylinders, tweeted Musk "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!"
Blue Origin did not immediately respond to CNBC Make It's request for comment.
Bezos has previously talked about his preference for floating space colonies as opposed to having humans live on other planets like Mars, which is what Musk has suggested.
"The space colonies we'll build will have many advantages. The primary one is that they'll be close to Earth. The transit time and the amount of energy required to move between planets is so high," Bezos said at the Yale Club in New York City in February, according to Business Insider.
"Ultimately what will happen, is this planet will be zoned residential and light industry. We'll have universities here and so on, but we won't do heavy industry here. Why would we? This is the gem of the solar system. Why would we do heavy industry here? It's nonsense."
The design of O'Neill's space settlements include two cylinders, each 20 miles long and 4 miles in diameter, according to the National Space Society.
Rendering the interior of an O'Neill cylinder by Rick Guidice, courtesy of NASA.
Musk, meanwhile, wants to "terraform" Mars, or make the surface habitable so people can live there.
While terraforming Mars will be hard and dangerous, Musk sees the Red Planet as the "only realistic option" for establishing a base on another planet, he said in TED talk in 2013. And he has defended the idea even in the face of skepticism.
Fundamentally, going to space is a critical step in the evolution of humanity, according to Musk.
"You want to wake up in the morning and think the future is going to be great — and that's what being a spacefaring civilization is all about. It's about believing in the future and thinking that the future will be better than the past," Musk said.
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