There is a vast array of fan theories circulating the web about how Earth’s mightiest heroes will defeat Thanos in the upcoming Endgame, and many of those theories center around Scott Lang (aka Ant-Man) and his ability to navigate the Quantum Realm. The Quantum Realm–or the Microverse as it’s referred to in the comics, but it can’t be referred to as such in the films due to copy right issues–is a dimension in which one can move between parallel universes/dimensions. One can go into the Quantum Realm through the Earth dimension using Pym Particles, which is the technology the Ant-Man suit uses to manipulate size and mass. The subject of going “subatomic” can get really confusing with its references to energy, physics, and time, but I’m going to do my best to simplify its purpose and impact on the MCU.
The Quantum Realm has been referenced in a few films thus far, but its existence has impacted the Ant-Man franchise the most. The Quantum Realm as described by Hank Pym is a bit different than its comic-based reference of the Microverse. The Microverse is very complex and complicated in terms of its purpose, and it houses parallel universes and new galaxies. Both heroes and villains have used Pym Particles and traveled to the Microverse since its inception in Tales of Astonishment #26 in 1943. Groups like the Fantastic Four have even been trapped in the Microverse at the behest of Doctor Doom. As seen in Ant-Man and the Wasp, Hank Pym is able to travel into the Quantum Realm to save Janet van Dyne, and it is a very odd place to say the least.
Time and space are not the same in this dimension, so the vortexes it creates are very unstable. Time travel is possible through the Microverse since it is an Earth dimension, but the parallel nature of the dimensions does not always ensure the same time line. These time jumps are referenced in the films as “Time Vortexes,” and navigating them appears to be challenging according to van Dyne’s Wasp. Basically, you shrink yourself so small that you can pass through time.
Since there are different realms in the Microverse, there is even a group called the Time Travelers who oversee the well-being of it. It’s a really choppy story line, but this “group” watches over the dimensions/planets within the Microverse. Albeit secondary characters to much larger Marvel plots featuring protectors and overseers of the universe, the Time Travelers can see possible futures and protect Earth and other galaxies. But, hey, the Guardians of the Galaxy have also used time travel to save the galaxy, so anything is possible.
Those who spend too much time in the Quantum Realm or are exposed to Pym Particles too often suffer some bizarre side effects. In a nutshell, one’s molecular code (i.e. what makes people exist/live) is altered. Looking back to the film Ant-Man and the Wasp, Janet van Dyne was stuck in the Quantum Realm for decades, and such exposure seems to have given her true super powers. She communicated with Scott telepathically, who was also exposed to the Quantum Realm in the first Ant-Man film; and she was able to heal Ghost by her touch. Ghost (aka Ava Starr) was exposed to a large amount of Quantum energy as a child, and such exposure mutated her molecular presence. The reason why she can go through walls, become invisible, and manipulate time is because her Earthly body is existing in multiple dimensions at any given time. Since Ant-Man and the Wasp ended with that post-credit snap scene leaving Scott in the Quantum Realm, we really don’t know if Janet van Dyne has similar abilities to Ghost, or with Scott suspended in the realm, if such exposure could give him more mutated powers, as well.
All of this information leads us to Scott Lang’s presence and role in Avengers: Endgame. How was he able to escape the Quantum Realm by himself? We know that Janet van Dyne was unable to get out by herself, and she was the daughter of a brilliant scientist and married to the man who conceptualized the theory. Janet is also an intelligent scientist herself in some comic lines, so she should have been able to escape more successfully than the ex-convict, tech expert Scott Lang. (No offense, Scott.) What makes fans believe Scott Lang is the key to reversing Thanos’s snap is his ability to travel through the Quantum Realm. As I mentioned earlier, the Quantum Realm is a dimension that operates evenly to Earth’s existence. If he were to time travel, it would be due to his subatomic (i.e. his mass size in relation to atoms) state bypassing our perceived time. Scott could, theoretically, figure out a way to navigate time in his subatomic state and pop out whenever/wherever he wants on Earth. Such concept is plausible, and it has even been discussed in other Marvel films. For example, The Ancient One tells Doctor Strange that what he perceives as our world is very small, and that there are other dimensions far greater and more powerful than time. Albeit subjective, there are even fans who believe Strange experiences this Quantum dimension in the film.
Theories, theories, theories. Those are all we have until the early premiere showings on April 25th; however, it will be really interesting to see how Scott was able to make it to Avengers headquarters and escape the Quantum Realm.