For a show that has aged its characters over many decades, the biggest challenge is not sending people to Mars but making them look believable once they arrive.When Ed Baldwin lands on the moon in October 1971, he is in early middle age. His light brown hair swoops across his forehead. His clean-shaven face is ruddy and, excepting a divot between his eyebrows, unwrinkled. But space can really age a man. By 2003, on Mars, his hair has grayed and receded, and the wrinkles have multiplied and deepened. His skin is sallow, marked with age spots. His cheeks have sunk in.Ed, a highly decorated astronaut, is a central character of the Apple TV+ series “For All Mankind.” He is played by the Swedish actor Joel Kinnaman, who was a few years younger than Ed during the first season, which debuted in 2019. Kinnaman is now 43, but in the fourth season, which premieres on Nov. 10, Ed is in his 70s. Which meant that Kinnaman’s shooting days typically began before dawn, with four hours in the hair and makeup chair.This is one of the myriad hurdles and minor miracles of “For All Mankind,” a series that posits a world in which the space race never ended. From its painstaking aging process to its imagination of an alternative past and interplanetary future, “For All Mankind” is both quiet and wild in its ambitions, a work of science fiction that retains the texture of observable reality. And in this coming season, which shows characters first seen in their 20s now in their 60s and 70s, the crew has had to work harder than ever to achieve plausibility. Sure, you can send men and women to Mars. But can you make them look believable once they arrive?The new season largely unfolds on a base on Mars.Apple TV+“When we were pitching the show, we were like, ‘Oh, this is going to be so great,’” Ben Nedivi, one of the show’s three creators, said during a recent video call. “Now that we’re in Season 4, the challenge has been enormous.”Season 1 began in 1969, when — mild spoilers for the first three seasons follow — in the initial shift from our own timeline, the Russians first land a man on the moon. It ended in 1974, with American men and women having built a lunar base. Season 2, which took place in the ’80s, expanded on this base. Season 3, set in the 1990s, brought Americans, Russians and a lone surviving North Korean to Mars. Season 4 jumps forward another decade. Throughout, the remaining characters are played by the same actors. (The exceptions are characters who first appear as children.)“For All Mankind,” which Nedivi created with Matt Wolpert, his fellow showrunner, and Ronald D. Moore, was always intended as a generational show. Its goal was to take the space race from the 1960s to the present and perhaps beyond, showing exploration and advancement across lifetimes.Sometimes those lifetimes are short. “Space is an insanely dangerous place,” Wolpert said. Otherwise the show’s format requires its characters to age a decade between seasons, without the use of computer-generated effects. (The C.G.I. on “For All Mankind” is for asteroids and explosions, not hair loss.)“The amount of time that Ben and I spend talking about hair and makeup and aging is not something we anticipated,” Wolpert said.“It doesn’t hurt that we’re aging during the show,” added Nedivi, who is visibly grayer than he was when the show debuted. “Trust me, I feel like I’m aging double-time.”From top, Joel Kinnaman in the first, second and third seasons. The makeup artists tried to age the stars subtly.Apple TV+This illusionism began years ago, in the initial casting sessions. Nedivi and Wolpert were looking for actors who were somewhat older than their characters, with the thought that they could be aged down for Season 1 and up beginning in Season 3.During Season 1, the makeup department, led by Erin Koplow, used foundation to give the actors a youthful, dewy look, covering up wrinkles and any discoloration. For the women, makeup appropriate to the era was laid over that. Hair was given extra luster.In the second season, the actors were more or less left alone, though some were given small pieces of what Koplow calls “stretch and stipple,” a latex solution that gives the appearance of fine lines. (The actors are mostly in their 30s, which means they should have fine lines of their own. That’s between them and their dermatologists.)For Season 3 there was more stretch and stipple, more gray hair. Kinnaman, whose character is older than most in the show, was given prosthetic silicone pieces, which created deeper wrinkles. If dark circles or eye bags existed, they were left uncorrected or were even accentuated. And the actors learned to hold themselves differently, better reflecting sore backs and joint pain.Several critics reviewing Seasons 2 and 3 found these interventions insufficient. “The effort to age its stars is negligible at best,” a Vanity Fair writer wrote of the third season. But this was intentional, meant to reflect a natural, gradual process.“With women in particular, it’s really easy to go too far and to make them monstrous with aging,” Glen P. Griffin, who oversees makeup’s special effects and prosthetics, said. “So you have to be really, really subtle.”That subtlety can be thankless: The actors don’t enjoy it; the viewers don’t see it. Griffin and Koplow both described believable middle-age makeup as the hardest part of the job. But this nuance is necessary. Should characters survive, the hair and makeup teams will have to intervene further.Kinnaman’s shooting days typically began before dawn, with hours in the hair and makeup chair.Apple TV+Costuming also helps to age and situate the characters. As with the makeup, the period clothes are meant to murmur, not to shout.“It’s best if they’re not overtly loud,” said Esther M. Marquis, the costume designer for the third and fourth seasons. “There has to be space for the actor to be who their character is. I don’t want to crowd in.”As the characters have aged, the tailoring has changed. “Hollywood loves to get all trim and put together, and that’s not really our show,” Marquis said. The fit in subsequent seasons does not always flatter, suggesting maturity, even subtle weight gain.The few costume pieces that do fit and do shout are the spacesuits, each of which is custom-built. While the suits in the first season were closely modeled on NASA’s designs, by Season 2, Americans had established a permanent base on the moon, outpacing current technologies. For the third and fourth seasons, Marquis had to imagine a suit appropriate for Mars’s climate that could be made mostly from materials and methods available in 2003.“The suit that I was designing had to live in both worlds, a future world and a past world,” she said. “I didn’t want to get too far away from a 2003 reality.”But Marquis did give herself some license, dreaming up a textile that would lead to a slimmer and more pliant silhouette. Most real spacesuits are 14 layers thick. Marquis’s are slighter, as are the astronauts’ backpacks, which would struggle to hold both life support and backup life support systems.“There’s a lot of action in Season 4,” she said. “So the suits had to get lighter.” She noted that the real-world suit designers she had spoken to were also wrestling with the same question.Kinnaman and Casey W. Johnson in Season 3 of “For All Mankind.” In the new season, the spacesuits had to be lighter.Apple TV+The show’s depiction of a different Earth extends beyond crow’s feet and helmets. Its approach to alternate reality is typically subtle. A Mars landing is an admittedly big swing, yet most of the other timeline changes are more restrained. Ted Kennedy skips the Chappaquiddick party. John Lennon survives. Michael Jordan plays for a different team.In each subsequent season, the divergence from our world is greater, a butterfly effect enhanced by the technologies the space race of the show has yielded. Most significantly, the moon’s supply of helium-3 has been mined for cold fusion, effectively solving the climate crisis. (Unscientific viewers like me might have assumed that helium-3 was among the show’s inventions. It’s very real.)This reflects the show’s arguably less subtle message, that something profound was lost when America gave up the space race.“That longing is what inspired us,” Nedivi said. “The show presupposes the idea that actually going out into the unknown and learning more about the world will teach us more about who we are and what we’re capable of.”Since the series’s 2019 debut, the space race has coincidentally begun to run just a little faster. More private companies have launched rockets. The Artemis 3 mission, slated for 2025, plans to land a woman and a person of color on the moon, both for the first time. There is new interest in mining metal-rich asteroids, a Season 4 plot point and another example of the show’s science fiction edging closer to reality.“A lot of the technology that we highlight has become part of the conversation in the real timeline,” Wolpert said. “That’s one of the secret weapons of our show: It’s not about impossible stuff. Nothing in our show is impossible.”Nedivi said “For All Mankind” was intended as escapism, as entertainment. “But if we can encourage further space travel,” he said, somewhat grandly, “that would be a huge plus.”While the show can’t take credit for advancing exploration, it has made at least one contribution to the space program, a small stitch for mankind. Last year, Axiom Space, a private company contracted to supply the suits for the upcoming Artemis missions, contacted Marquis. It wanted her to create a spacesuit cover, a garment meant to cloak Axiom’s proprietary technology during a news conference.“There’s no way they can use it in space because it is black and colored,” Marquis said of the cover. “But it was a wonderful experience.”Axiom has since asked her to design flight suits that real astronauts will eventually wear. In tailoring the flight suits for those astronauts, at Axiom’s Houston headquarters, Marquis was struck with a feeling of déjà vu.“It’s very similar to fitting an actor,” she said. “That’s crazy, right?” More