Jeff Bezos has a vision to colonize space with a trillion people. We asked experts to put it to the test.

According to Bezos, leaving Earth would enable the human race to grow and thrive without destroying our home planet.

Business Insider asked four different kinds of experts — from architects to astrobiologists — for their take on Bezos’ plan. Here’s what they said.

Jeff Bezos’s space colonies would look like cylinders

In Bezos’ futuristic fantasy, we’re all kicking back in space stations that look similar to a concept called O’Neill cylinders, named for physicist Gerard K. O’Neill, who first proposed them in the 1970s.

“The vision of Gerard K. O’Neill is inspiring, but it’s absolutely humongous,” said Anthony Longman, an independent architect who put together a concept for space habitats designed to house roughly 8,000 people.

That’s notably larger than the International Space Station, which typically has seven astronauts on board at any given time.

But a space habitat with 8,000 humans is nothing compared to O’Neill colonies that could house several million people and would be about 500 square miles, or as big as San Antonio, TX, inside.

On the outside, these space colonies would measure 20 miles long, four miles wide, and rotate to generate artificial gravity for the humans onboard.

O’Neill thought that we could establish natural ecosystems, bodies of water, and even weather systems inside. From there, we could build farms, transit systems, and bustling cities.

“I’m not saying they won’t be built, but I think it will probably be some hundreds of years before we’re able to build anything at that scale,” Longman said of the O’Neill colonies.

Bezos isn’t suggesting that people will be living in O’Neill space colonies by the end of the century. Even so, that long-term vision is clearly shaping the present-day goals of Blue Origin, and the commercial space race at large.

Both Blue Origin and its biggest competitor in the commercial space industry, Elon Musk’s SpaceX, are developing technologies that Bezos and Musk hope could, one day, shepherd people to new lives outside of Earth.

“I won’t live long enough to see the fruits of this, but the fruits of this come from building a road to space, getting the infrastructure,” Bezos told Fridman.

Challenges of keeping humans happy and healthy in space

There are many issues to address before we can live on giant space stations and colonize the solar system. But to keep it simple, let’s start with the basics: food and reproduction.

Researchers have grown a few crops on the International Space Station, including tomatoes and lettuce. Although these veggies are grown in different conditions, they appear to be just as nutritious as ones grown on Earth, research shows.

However, to achieve the scale of agricultural production necessary for an O’Neill colony, “we need to develop these very safe, closed-loop, self-sustainable agricultural systems,” said Rebeca Gonçalves, an astrobiologist formerly at the European Space Agency whose research focuses on how we might grow crops off-world, like on Mars.

As for human reproduction in space, Adam Watkins, associate professor of reproductive biology at the University of Nottingham, said we have a long way to go.

“Giving birth in space — you just don’t even want to contemplate the logistics and the difficulties that might be associated with that, let alone if there are any complications associated with it,” he said.

As far as we know, no one has ever had sex in space. And we’ve certainly never sent a pregnant person to space. The health risks are too high, Watkins said.

Those risks stand in the way of research that could reveal how space radiation affects a developing fetus. So, scientists aren’t sure what the impact would be.

To eliminate those risks, space colonies would need healthcare systems that are just as equipped to handle reproduction as Earth’s are, Watkins said.

“It’s one thing getting people into space, we can do that. That’s fairly straightforward.” Watkins said, adding that the hard part is “building those entire infrastructure communities where you’ve got those kinds of support structures in place, fully functioning, tried and tested, I think is a very long way off.”

Escaping Earth’s problems may be a ‘dangerous illusion’

Our industrialized presence on the planet is driving climate change, resource scarcity, and a biodiversity crisis. Leaving Earth is a way for humanity to continue on its current path and preserve Earth in the process, according to Bezos.

“We want to use a lot of energy. We want to use a lot of energy per capita. We’ve gotten amazing things. We don’t want to go backward,” he told Fridman.

But Martin Rees, the United Kingdom’s Astronomer Royal who advises the monarchy on astronomical matters, doesn’t think that leaving Earth behind is the best option, he told Business Insider.

Using space as an “escape for the problems we may cause with our own planet,” is a “dangerous illusion,” he said. “We should look after our own planet. It’s the best we’ve got.”

Saving Earth would be far easier than building Bezos’ space colonies, he told BI.

Even if we never make it to space colonies, the work of researchers studying extraterrestrial colonization could benefit us here on Earth. For example, Gonçalves’ research on Martian agriculture could help improve crop resiliency in degraded, sandy soils on our planet, she said.

“I don’t think these O’Neill-type space colonies are going to be nearly as attractive to spend your life on as it is to be living on Earth with its wonderful variety,” Rees said.