Aged 90, Mr Shatner became the oldest person to travel to space when he blasted off to the edge of space on a Blue Origin rocket on October 13, 2021.
Now, he has reflected on his voyage in his new book called Boldly Go: Reflections on a Life of Awe and Wonder. An excerpt of it was published in Variety last week.
“It was among the strongest feelings of grief I have ever encountered,” he said.
“The contrast between the vicious coldness of space and the warm nurturing of Earth below filled me with overwhelming sadness.
“Every day, we are confronted with the knowledge of further destruction of Earth at our hands: the extinction of animal species, of flora and fauna … things that took five billion years to evolve, and suddenly we will never see them again because of the interference of mankind.
“It filled me with dread. My trip to space was supposed to be a celebration; instead, it felt like a funeral.”
Mr Shatner flew to the edge of space on the NS-18 mission — the second space tourism flight by Jeff Bezos’s Blue Origin — with three other passengers.
The entire experience, from launch to landing, lasted about 10 minutes.
A fully reusable suborbital vehicle lifts off from a remote desert in west Texas, carrying passengers 106 kilometres above the ground, bringing them a few minutes of weightlessness as well as stunning views of Earth against the darkness of space.
The capsule then descends towards the Texas desert under three parachutes and retro engines, bringing the passengers safely back to the ground.
Mr Shatner’s experience in space is what many astronauts and psychologists call the “Overview Effect”.
It is often described by astronauts as a powerful shift in how a person views the planet and life.
“I learned later that I was not alone in this feeling. It is called the 'Overview Effect' and is not uncommon among astronauts,” Mr Shatner said in his book.
“Essentially, when someone travels to space and views Earth from orbit, a sense of the planet’s fragility takes hold in an ineffable, instinctive manner.
“It can change the way we look at the planet but also other things like countries, ethnicities, and religions; it can prompt an instant re-evaluation of our shared harmony and a shift in focus to all the wonderful things we have in common instead of what makes us different.”