Well, everyone knows the 1989 Rick Moranis classic Honey, I Shrunk the Kids isn’t connected to the Marvel Cinematic Universe.
What this theory presupposes is…maybe it is?
Like all of the best fan theories, this one comes from Reddit, specifically the r/FanTheories subreddit. User angruss points out that Scott Lang’s initial understanding of time travel is based on Back to the Future, and that Tony Stark has to correct his misconceptions.
The other key quasi-scientific concept in Lang’s life is, of course, Pym Particles. Discovered by Hank Pym, they can alter the size and mass of objects or living things. They’re what turns him into Ant-Man. It would make sense that he also rely on movie-level logic to explain their functioning.
In Honey, I Shrunk the Kids, inventor Wayne Szalinski explains how his shrink ray works thusly: “All matter is made up of not only density but of empty space, and if we can proportionally reduce the amount of empty space in any given object, we can, thereby, shrink the object.”
This is pretty much the same way Pym explains the mechanism to Lang. It’s as if he chose an explanation that he knows Lang will accept and one that will allow Pym to keep the real mechanism—a complicated and closely held secret if there ever was one—a secret.
If true, this would mean that the audience would also not have gotten the real explanation, suggesting that future chapters of the MCU could provide more and more accurate details.
In the meantime, you can watch both Honey, I Shrunk the Kids and Avengers: Endgame on Disney+.