Two days ago, on October 21, 2015, at 4:29 p.m., Marty McFly and Doc landed here in their future — our present, and now our past. In 1985, the first “Back to the Future” movie came out, and now, 30 years later, we still remember it enough that news articles ran about the date, Toyota had a commercial and people across the world celebrated Back to the Future day. We know it so well. In 1977, the first Star Wars movie hit theaters and became one of the most financially successful movies of all time — 38 years later, we have a new Star Wars movie prepping to hit theaters.

For its 10 year anniversary, Twilight recieved a rewrite by the author with the genders swapped in the book. Next year, “Fantastic Beasts and Where to Find Them” will be released in theaters, the newest film in the Harry Potter universe, 19 years after the first book was published. Jurassic World came out 22 years after Jurassic Park, and a new one is coming out in three years. The Hobbit received three movie adaptations over a decade after the Lord of the Rings movies finished and over 70 years after the book was published. What gives these cultural phenomena such staying power? How can we even distinguish them from the ones that will die in a few years? No one talks about “Twister” anymore, after all, no matter how well it did. It’s largely forgotten.

Many people know the tale of how J.K. Rowling was living on welfare when she wrote the first Harry Potter book and went from literary agent to literary agent desperately trying to find someone who would take it. Nearly two decades later, we still get news articles about each scrap of information she reveals online. George Lucas was so certain that Star Wars was going to do badly that he made a bet with Steven Spielberg, who was also working on a movie, that they would each get 2.5 percent of the others’ profits on their respective movies. Spielberg’s movie is largely forgotten (whatever it was), but he earned millions on Star Wars from that bet.

In short: We can’t tell. Dr. Seuss wrote “Green Eggs and Ham” on a bet. The X-Men were originally a rip-off of DC’s Doom Patrol. What people will love and seek enjoyment from is not something entirely predictable to the people who make that media, and what has staying power to still exist in massive popularity 70 years later is completely unpredictable. Will the Hunger Games have staying power? Once Stephenie Meyer isn’t around to release new versions of Twilight, will that die down, as well? Will this new Star Wars movie even be good?

Waiting is the only thing that can answer those questions, unless you happen to have a DeLorean. And if you do, can I borrow it, please? I didn’t manage to catch Doc on his trip, and I’ve always wanted his autograph.