UPDATE: Watch the Avengers: Endgame trailer here.

What part could Ant-Man and the Quantum Realm play in the events of next year's Avengers 4? The mid-credits scene in Ant-Man and the Wasp deliberately tied into Avengers: Infinity War, and left Scott Lang in a nightmarish situation. Both promotional artwork and set photos have already teased that he'll appear in Avengers 4, though, so it's safe to say that he finds a way out.

Ant-Man and the Wasp focused on the investigation of the Quantum Realm. Described in Ant-Man as "a reality where all concepts of time and space become irrelevant," the Quantum Realm remains a mysterious yet hazardous environment. The best account of just what the Quantum Realm really is was given by quantum physicist Spiros Michalakis, one of Marvel's consultants, who conducted an interview with Nerdist back in 2015. He said the physical laws we see in the universe – laws of time and space, including gravity and the speed of light – are simply trends in quantum mechanical probabilities. If you shrink all the way down, they all disappear. As Nerdist noted:

"If Ant-Man can shrink down to the smallest of the small, he will enter this nothing, this non-reality. All of time and space will be open to him. He could literally change the universe around him Dr. Manhattan-style. And he could traverse time at will."

Related: How Ant-Man and the Wasp Connects To Infinity War

The mid-credits scene of Ant-Man and the Wasp saw Scott Lang stranded in the Quantum Realm. He'd headed into the Quantum Realm in order to obtain more of the mysterious "healing particles" for Ghost, but horrifically this meant he was inside the Quantum Realm at the very moment Thanos snapped his fingers in Wakanda. As horrified viewers realized, that meant Hank, Hope, and Janet all disappeared. There was nobody there to get Scott back out of the Quantum Realm. It's no secret that Scott will ally with the Avengers against Thanos in Avengers 4, we can presume he's going to get out. But how? And what part could his escape play in the plot of Avengers 4?

The Key May Be Time Vortexes

The Quantum Realm seems to be some sort of fractal reality, and it's dangerously unstable. Right before Scott enters the Quantum Realm, Janet gives him two warnings; first, steer clear of the Tardigrades, and secondly, "Don't get sucked into a time vortex. We won't be able to save you."

In science-fiction, a "time vortex" is usually an elaboration of Einstein's theories of relativity. Einstein theorized that the motion of planets in space twists both space and time around them, creating a sort of "vortex," but science-fiction usually takes this idea one step further, postulating the existence of "time vortexes." These are often used to actually travel through time and space.

This can be seen in a number of properties like the BBC TV series Doctor Who, where the TARDIS travels through the time vortex. Even the Stargate franchise has dabbled with time vortexes being created as a result of gravitational interference with wormholes. Now Ant-Man and the Wasp has revealed that time vortexes exist inside the Quantum Realm - and they could potentially give Scott Lang an escape route. If he were to enter a time vortex, he could be transported to anywhere in the universe; he could travel through time; and, in theory, he could even return to normal size too.

No doubt this idea is a dangerous one, and Janet - who's far too scientifically-inclined so would understand the risks - chose not to give it a shot while in the Quantum Realm. Scott, however, is more likely to be desperate to escape, and he's also fairly clumsy, so it's quite possible he could actually get caught in a time vortex by accident.

Next Page: Where (And When) Could Scott Lang Emerge?

Scott Lang Could Emerge in the Future

There have been persistent rumors that there's an unusually large time-jump between the events of Avengers: Infinity War and next year's Avengers 4. Those rumors were supported just a couple of months ago, when 16-year-old Emma Fuhrmann joined the cast of Avengers 4 as an older version of Scott's daughter, Cassie. The simple fact is that, whatever time period Scott arrived in, his first thought would be to check on his family. This curious casting decision raises the possibility that Scott will emerge from the Quantum Realm five or six years after the "snap," returning to a world that's dramatically changed. The aftermath of Thanos's horrific act would have caused chaos on a global scale, with aircraft dropping from the sky as their pilots disappeared, world leaders vanishing while in the middle of difficult and dangerous negotiations, and emergency services decimated. Promotional photos have teased that the Avengers have stepped up to the challenge, becoming a symbol of hope in a world gone mad.

Cassie would have assumed that Scott was another victim of the "snap," given the timing of his disappearance. It's even possible that she's dedicated herself to honoring his memory, becoming a superhero in her own right, which would be true to the comics, fitting with hints from Kevin Feige that Marvel is interested in adapting the Young Avengers concept. Her father's unexpected return would shock her, and no doubt she'd point the returned Ant-Man to his old allies, the Avengers.

Related: Marvel After Avengers 4: Everything We Know About MCU Phase 4

There's abundant evidence that Avengers 4 is actually a time-travel film, and this may well explain how. The moment Tony Stark learns about time vortexes, he'll start trying to work out how to travel in time and avert the "snap." Ant-Man's return would thus inspire the Avengers to change history. There's even a comic-book precedent for this idea; in 1994, Marvel's Age of Apocalypse saw a time-traveler create a dystopian reality in which Apocalypse ruled. The existence of Bishop led Magneto, leader of the X-Men in that reality, to seek to travel back in time and rewrite history. The parallel wouldn't quite be exact, but it would be significant nonetheless.

This Was The Only Way

This adds another dimension to Doctor Strange's decision to hand over the Time Stone to Thanos on Titan. As he crumbled to dust, Strange told Tony Stark this was the only way, clearly implying he'd foreseen one course of events in which Thanos was ultimately defeated, and had carefully manipulated events to ensure that timeline was the one that came to pass. On the face of it, viewers had assumed Strange handed over the Time Stone the moment Tony Stark's life was threatened, and that Stark is particularly important to defeating Thanos. While there's no doubt truth in this, there may be more to the battle on Titan than just that. It's also possible Doctor Strange needed to prolong the battle until the right moment so that Thanos didn't snap his fingers before Ant-Man entered the Quantum Realm, where he may have been protected.

If this is indeed the case, there are now two people who are crucial to Thanos's defeat: Ant-Man and Tony Stark. Ant-Man is important because he proves time-travel is actually possible, but Tony Stark would be important because he'd be the man to develop the time-travel technology, giving the Avengers a shot at rewriting history. That would turn the mid-credits scene of Ant-Man and the Wasp into an absolutely crucial step along the way to next year's Avengers 4.

More: Ant-Man & The Wasp May Have Already Explained Avengers 4's Time Travel

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