William Shatner reveals in his new book Boldly Go: Reflections on Life of Awe and Wonder that going to space on a Blue Origin flight last year left him with a strong feeling of “grief.”

He writes in an excerpt shared with Variety, “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.”

He added that this feeling, dubbed the “Overview Effect” is not uncommon for astronauts and has been described by Yuri Gagarin, Michael Collins, Sally Ride, and many others