PLANES SHOT down over Ukraine or gone into thin air. Bitter fighting in Gaza among the globe’s scores of current wars and conflicts. And always the concern about that next violent act that strikes too close to home.

In a world filled with so many disasters and so much turmoil, it is no wonder that from silver screens to mobile screens, from comics shops to toy shops, superheroes are as popular as ever. “When the world gets scary, superheroes sales go up … ,” Brad Meltzer, the bestselling political-thriller author and comic-book creator, tells The Post’s Comic Riffs. “What resonates today is, as we look around at this scary world, we want someone to come save us.”

And to Meltzer, no superhero resonates quite like Batman. It was in the run-up to World War II, in May of 1939, that the Caped Crusader made his debut, in the ominously titled Detective Comics book “The Case of the Chemical Syndicate,” immediately finding an eager national audience. Now, so many thousands of crime-fighting adventures later, DC Comics will celebrate the 75th anniversary of the iconic character by declaring July 23 “Batman Day” – as comic-book outlets around the country partner with the publisher to offer various Bat-birthday collectibles, as well as a new comic written by Meltzer himself.

DC is also timing its Batman event to coincide with the Wednesday-night kickoff of San Diego Comic-Con, the mighty granddaddy of American pop-culture conventions and festivals that draws more than 125,000 fans to the bayside San Diego Convention Center over four-and-a-half days of geek heaven.

And Batman has even had a huge hand in that: Comic-Con — which arose in the wake of the character’s hit ’60s TV show — enjoyed a huge growth spurt in the ’90s as Tim Burton’s Batman movies starring Michael Keaton reignited Hollywood’s interest in superheroes (“After the first Keaton film, everyone at Comic-Con had on a Batman T-shirt,” says DC publisher Jim Lee by phone from California). Burton even acknowledged to The Post at the 2009 Comic-Con that his films had a hand in the event’s march toward becoming massive.

To help celebrate the Batman anniversary, DC Entertainment will have a sizable presence at this year’s Comic-Con. On Thursday, Lee and DC chief creative officer Geoff Johns will share the stage with fellow comics creators Neal Adams, Grant Morrison, Denny O’Neil and Scott Snyder, as well as the Maryland-sprung legend Frank Miller, for the panel “Batman 75: Legends of the Dark Knight.” And on Saturday, Lee and Johns will help spotlight the many incarnations of “the world’s greatest detective,” from the record-setting Christopher Nolan films starring Christian Bale to popular video games and animated shows.

Also on Saturday, DC says it will continue the anniversary celebration by teaming with Random House for books and events at more than 1,000 American libraries.

And to think this was all spawned by a couple of young creators trying to come up with a character to rival the 1938 introduction of Superman — an emergence that sparked the entire multibillion-dollar superhero industry.

IN 1938, THE WORLD’S first popular superhero was launched by Detective Comics, and sales were soon soaring. “As World War II started encroaching on our shores,” Meltzer says, “that’s when Superman took off, selling over a million copies.”

A year after Superman’s birth, the publisher was looking to replicate that success, and an editor tasked Bob Kane with creating another caped crimefighter. Inspired partly by da Vinci’s drawings of flight, Kane rendered a birdlike Bat-Man, then took his idea to artist-friend Bill Finger, who sharpened and darkened the look of “the Batman,” from cape to cowl. In May of 1939, in Detective Comics No. 27 (an issue that has fetched more than $1-million at auction when in top condition), Batman was born.

Soon, with help from teenage writer-illustrator Jerry Robinson — who began as something of a boy wonder himself — Batman had a sidekick (Robin) whose look was drawn from a Wyeth painting; a great villain (the Joker) inspired by a playing card, according to Robinson; and a moody aesthetic influenced by everything from German Expressionist films to the Harry Clarke illustrations for the books of Edgar Allan Poe (Frank Miller not being the first Marylander to effectively help steer Batman toward the darkness.)

Batman has persevered through so many phases, from a film-noir and sci-fi feel to the high camp of the ’60s TV show starring Adam West, to the Dark Knight of a shadowy, tortured psychology as popularized by Miller’s graphic novels and Nolan’s feature films — right up through the casting of Ben Affleck for next year’s “Batman v. Superman” movie. Batman endures by having as many entry points as he has incarnations.

“Through these 75 years, Batman has been fine-tuned by hundreds of writers and artists into honed perfection,” Meltzer says. “He is perfectly defined, and I maintain, the most perfectly defined literary character. The odd part is, although he’s moved from camp, to dark, to self-hating, to self-confidence, you always somehow know exactly what Batman ‘would do.’ There’s a core that never changes.”

“Yet the most beautiful part was that, when you look at that first appearance by Bill Finger and Bob Kane, that core is right there,” Meltzer continues. “It’s not as honed as it is today, but the pieces are there.”

For Batman Day, Meltzer was asked by DC co-publisher Dan DiDio to create a new comic that would rightly celebrate the Caped Crusader’s entire history. “I wanted the story to stay true to that original and honor all the came after,” Meltzer says. “No pressure.”

“Batman has stayed relevant,” DiDio says by phone from DC’s New York offices, “because he is constantly reinvented and reinterpreted by every generation.”

“Dan DiDio and I have pretty regular conversations, always bouncing ideas and talking shop. … ,” Meltzer says. “This time, when he called, he knew he had me. He just said: ‘We’re celebrating Batman’s 75th anniversary. We want to feature the full history, and we’d love you to help us do it by retelling the first story.’ There was too much history in there for me to walk away.”

For the new comic, Meltzer and designer Chip Kidd deconstructed Kane and Finger’s first Batman story, then weaved in a trove of character history. “We took the story apart and then rebuilt it with those original images from the first story,” Meltzer says. “It was like doing a jigsaw puzzle, then flipping it over and seeing there were different images on the back — and that you could put the whole puzzle together in a different way. It nearly killed Chip. And me.”

(On Wednesday, the new comic will also be available for free digital download at

Meltzer and Kidd’s reimagined comic echoes that theme of hunger for superheroes in a scary world, as it alludes not only to young Bruce Wayne becoming an orphan after a theater performance, but also to the multiplex shooting in Aurora, Colo., at a midnight screening of “The Dark Knight Rises.” “First and foremost, that was of course a call to his dead parents,” Meltzer says of a scene in his new Batman story. “But you better believe that those theater shootings were right there, too. For 75 years, Batman has been a cultural shield, protecting us from our deepest fears.”

FOR DC ARTISTS and executives personally, the entry points to discovering Batman were as varied as those of the general public.

For DiDio, the introduction was the live-action TV show that launched in 1966 with all those knowing line-readings and graphic splashes of “BAP!” and “POW!” “I was one of those kids watching on the floor in the ’60s,” says DiDio, who still keeps a toy Batmobile collectible from that era on his office desk.

“It’s important to remember that the TV show wasn’t making fun of the comics of the time — it was directly and faithfully depicting them,” Glen Weldon, author and comics journalist/podcaster for National Public Radio, tells Comic Riffs. “In 1966, Batman was a children’s character, a smiling do-gooding superhero distinguishable from the others only by his costume. He’d been that way for almost 30 years. The TV show took those comic-book adventures and reproduced them exactly for the small screen — but played it deadly straight.”

“That tone was the source of the humor — that decision never to wink or mug, but to invest these children’s stories with life-or-death gravitas — and it’s the reason the show became an international fad, albeit one that burned out quickly,” Weldon continues. “When the show ended, Batman’s sales figures tanked, as well.”

For Lee, the DC co-publisher and Batman artist (“Hush”), it was the comics page that lured him into the Dark Knight’s universe.

“I came into the DC mythology when I was 8 or 9 years old,” says Lee, who was born in Seoul, South Korea, in 1964. “My parents were very much against my collecting comic books — they wanted me to be a doctor.

“In the ’70s and ’80s, it was perceived as a kids’ medium that you outgrew and you threw away when you become a teenager,” says the Eisner Award-winning artist. “My parents didn’t really see the educational upside to it; it was about education and getting good grades and going to medical school.”

Because Lee’s parents kept him “on a tight, lean diet of one new comic book a month,” he fed his comics appetite at the library. “I would read the DC hardcover compendiums and they have decades of reprints,” Lee tells Comic Riffs. “So I had a holistic view of Batman from a very young age.”

“There was a real charm to those stories from the ’50s and ’60s — elements of the Batman mythology that are very appealing to a little kid,” Lee notes of the wealthy playboy turned superhero who has no superpowers. “The Bat-cave and the side cutaways, Wayne Manor and different vehicles and souvenirs. It was a Bat-everything. The fact is, it felt like cool secret ninja society.”

SO BENEATH THE savvy marketing and cool collectibles, why does Batman endure, exactly, as a pop-cultural force?

“Thanks to Bill Finger, Batman was the first comic-book superhero to have a psychological reason to wage war on crime,” says Marc Tyler Nobleman, the District-based author of “Bill the Boy Wonder: The Secret Co-Creator of Batman.” “While he was an original fusion of elements of earlier characters, it was this emotional motive that stood out most. We identify with Batman/Bruce Wayne not only because he has no powers, but also because he has no parents. We emphasize with his empathy.”

NPR’s Weldon, the Washington-based author of the forthcoming book “The Caped Crusade: The Rise of Batman and the Triumph of Nerd Culture,” believes Batman has remained relevant since 1970 because of a crucial reinvention: He gained the psychology of obsession, thanks to writer Denny O’Neil, who was hired to “fix” Batman after the campy TV show’s demise.

“O’Neil’s decision to introduce a note of obsession saved Batman, and indirectly the comics industry, by offering a masculine ideal with whom [capital-N] Nerds could identify, and cherish,” Weldon says.

“Batman was obsessed. Driven. Consumed by his passionate devotion. Nerds read him, and saw themselves — their inner lives — reflected in a dark mirror,” Weldon says. “A dark and significantly more badass mirror. A Batman who was one of them. … It was the first, and remains the most dramatic and influential, reboot of any character in a genre that has come to be synonymous with the term. Without it, the Batmen of Frank Miller, Tim Burton, Bruce Timm and Christopher Nolan would not exist.

“And as this new Batman was introduced, the comics industry began its Great Inward Turn — abandoning the readership of children altogether to build dense Byzantine continuities for Nerds … ,” the author continues. “And none of it would’ve happened — could have happened [in corrective reaction] — if Adam West hadn’t stepped onto that go-go club’s dance floor and done the Batusi [the show’s spin on the Watusi], shaking what his dead momma gave him.”

Meltzer, by contrast, finds value in the constancy within Batman’s creative malleability.

“The ears gets taller, then shorter. The costumer will get darker, then lighter. The utility belt will get pouch-y, then sleeker. But Batman’s character is as stubborn as the man beneath the cowl,” Meltzer says. “He is immovable. He projects sheer will, convincing us we have a chance — even when we don’t. And. He. Will. Not. Change. We, as a people, need someone that committed to an ideal.”

It’s all about the inspiring strength of will and purpose, then, even in a losing battle.

“Batman is the embodiment of the human spirit, but always in a way that he’s never more than human,” Meltzer says. “Every day he goes out, he knows he’ll fail: He’ll never stop crime. He’ll never bring back his dead parents. But every day, he steps into the ring and tries to fight again. Superman may be who we wish we could be. But Batman is who we secretly know we are.”