Going to space left William Shatner ‘weeping’ with grief

(CNN) - William Shatner — the 90-year-old actor, presenter, spoken word poet, author, and, more recently, the oldest person ever to travel to space — is showing no signs of slowing down.

This fall, he plans to publish a book, called "Boldly Go," which is billed as a sort of philosophical reflection on his life, career, and the "interconnectivity of all things," according to publisher Simon and Schuster. He's also the face of a new coding competition that will offer the winner a chance to travel more than 18 miles high in a spacecraft-esque capsule strapped to a balloon. (Yes, really.)

CNN Business caught up with the "Star Trek" legend this week in a wide-ranging interview. Here's a quick recap.

How he reacted to going to space

Shatner was Amazon founder Jeff Bezos' invited guest on the second-ever crewed flight of New Shepard, the suborbital space tourism rocket developed by Bezos' company Blue Origin. Upon his return, Shatner was visibly emotional. He described viewing the vacuous, black expanse of the cosmos as "seeing death."

"There is Mother Earth and comfort, and then there is ... death," he said at the time.

After the flight, he couldn't stop crying, he said in an interview with CNN Business this week.

"It took me hours to understand what it was, why I was weeping," he said. "I realized I was in grief. I was grieving for the destruction of the Earth."

Shatner said he was profoundly impacted by "Silent Spring," the 1962 book about environmentalism by biologist Rachel Carson.

"It's gonna get worse!" Shatner said of the environmental crisis. "It's like somebody owing money on a mortgage, and they don't have the payments and they think, 'Oh well, let's go to dinner and not think about it.'"

What he thinks about billionaires in space

Companies like Elon Musk's SpaceX and Bezos' Blue Origin — helmed by two of the richest men in the world — are often the target of criticism. Can space exploration paved by the wealthy few ever bring about the type of egalitarianism vaunted by "Star Trek"?

"That's missing the whole idea here," Shatner said. "The whole idea is to get people accustomed to space, like going to the Riviera. It's not a vanity. It's a business."

He also reiterated the goal Bezos has been publicly stating: If we can make space travel cheap enough, we can move polluting industries into outer space, preserving the Earth like a huge national park. (That idea also has its skeptics and critics.)

Why send a software developer to space?

One of Shatner's latest gigs is spokesperson for a competition being put on by Rapyd, a digital payments platform developer. It's called "Hack the Galaxy" and it's calling on developers to solve bi-weekly coding challenges, and the winner can choose between a $130,000 cash prize or the chance to join a 2026 flight conducted by the startup Space Perspectives, which plans to carry customers about 100,000 feet high in a capsule attached to a balloon.

Shatner said he jumped on board with the idea because he wanted "problem solvers" to experience a transformative, high-altitude joy ride just as he did.

"I want to get [these coders] interested in developing the financial community, but then saying, 'Why don't you guys put your minds to carbon capture or, you know, any of the great problems? Hunger? Poverty?'" Shatner said.

Shatner's dinner with Stephen Hawking

Shatner said that he has a new fascination with string theory — a popular idea that attempts to explain quantum physics, or how subatomic particles behave, and how it fits together with more easily observable scientific ideas, like gravity.

For the non-physicists among us, it's incredibly difficult to understand. Shatner said that when he traveled to the UK to interview Stephen Hawking, the famed cosmologist, for a documentary, he wished he'd dived into the topic. But Hawking, who was confined to a wheelchair and used a computer to speak because of a degenerative medical condition, had to have all the questions prepared in advance.

"I was never able to ask him that question" about string theory, Shatner recalled. "But he had said when we made this arrangement, 'I want to ask Shatner a question.' I'm leaning in, you know, we're sitting side by side looking at the cameras...and he laboriously typed out: 'What is your favorite episode?'"

Shatner, for the record, does not have a favorite "Star Trek" episode and didn't give an answer. But Hawking invited him to dinner nonetheless.

"What do you do? At dinner? With somebody who can't talk?" Shatner laughed. "But I had a beautiful moment with him."

For those curious, Shatner also summed up his musings about string theory, which posits that everything in the universe is, at its most basic level, composed of vibrating strings: "I think that we are in vibration with the universe. It's a matter of connecting ourselves."