Time Travel Mechanics In Avengers: Endgame Explained

Time travel in Avengers: Endgame is a complicated topic. The film's time travel rules differ from those commonly seen in pop culture, such as in Back to the Future or Terminator. In the movie, the Avengers discover time travel as a way to undo the damage caused by Thanos and his Infinity Stones-powered snap. Scott Lang (Ant-Man) accidentally spends five years in the Quantum Realm, where time works differently, feeling like only five minutes have passed. This discovery leads Tony Stark to invent time travel technology, allowing the Avengers to collect the Infinity Stones from the past.

The rules of time travel in the MCU are explained by the Hulk and the Ancient One. According to the Hulk, actions in the past cannot affect future events in one's own timeline because it is no longer truly one's past. The Ancient One further explains that removing something like an Infinity Stone from the past can cause timelines to branch out and create alternate, parallel futures, similar to the multiverse theory.

The Avengers' time heist creates several alternate timelines, and they must return the Infinity Stones to their original timelines to maintain their integrity and prevent accidentally dooming those alternate realities. Captain America's decision to live out his life in the past with Peggy Carter also creates an alternate timeline.

The Avengers time travel through the Quantum Realm

The Avengers' time travel through the Quantum Realm is made possible by Ant-Man, who, after being trapped in the Quantum Realm for five years, returns to the Avengers headquarters with a plan to collect the Infinity Stones. Ant-Man theorises that because he was able to jump forward in time, the Avengers could travel back in time with ease.

To enter the Quantum Realm, the Avengers use Pym Particles to shrink to subatomic size. Tony Stark then uses his technology to control where they land in time using tiny watches. The Avengers then split up and travel to different points in time to intercept the Infinity Stones.

Captain America, Iron Man, Hulk, and Ant-Man travel to New York in 2012 to collect the Mind Stone, Space Stone, and Time Stone. Iron Man and Ant-Man fail to steal the Space Stone, so Captain America and Iron Man travel back to 1970 to steal it from Tony Stark's father's lab. Thor and Rocket travel to Asgard in 2013 to collect the Reality Stone, and Nebula and Rhodes travel to Morag in 2014 to find the Power Stone. Meanwhile, Black Widow and Hawkeye travel to Vormir in 2014 to find the Soul Stone.

The Avengers' time travel through the Quantum Realm is based on the "Many Worlds Theory" or "Multiverse Theory", which posits that the universe we know is just one of many parallel universes. Thus, any changes made in the past by the Avengers create a new timeline, branching out from the original, without affecting their main timeline.

Pym Particles allow the Avengers to enter the Quantum Realm

Pym Particles are subatomic particles that can alter size and mass. They were discovered in the 1960s by Dr Henry 'Hank' Pym, a scientist and the creator of Ant-Man. The particles can be used to shrink or grow an individual or object.

The Pym Particles allowed the Avengers to shrink to subatomic size and enter the Quantum Realm, thus enabling time travel. Pym Particles were used by the Avengers to go back in time and collect the Infinity Stones before Thanos could.

The Avengers had a very limited supply of Pym Particles, which were stored by Hank Pym before he vanished as a result of Thanos' snap. The particles allowed the Avengers to make one trip each, with the exception of Iron Man and Captain America, who had to make an extra trip to the 1970s.

Captain America and Iron Man travelled to 1970 to retrieve the Tesseract and more Pym Particles from Hank Pym, who was working as an enhanced operative for S.H.I.E.L.D. at the time. Captain America took four vials of Pym Particles: two for him and Iron Man to return to the present, and two more for an unknown reason.

The Pym Particles were essential to the Avengers' plan to undo Thanos' snap, allowing them to enter the Quantum Realm and travel back in time.

Tony Stark invents a special time GPS to navigate the Quantum Realm

In *Avengers: Endgame*, Tony Stark invents a special time GPS, or Time-Space GPS, to navigate the Quantum Realm. This device allows its user to safely and accurately move through time and space using the Quantum Realm.

The Time-Space GPS is a wrist gadget that enables accurate displacement through time and space. The user inputs the desired date and location, and the nanotech Advanced Tech Suit materialises around the wearer's outfit. The user is then shrunk down using Pym Particles, enters the Quantum Realm, and is navigated through it by the GPS, eventually emerging at their chosen destination.

Tony Stark's invention of the Time-Space GPS is a significant development in the film, as it provides the Avengers with a means to navigate the Quantum Realm effectively and travel to their desired locations in alternate timelines. This enables them to retrieve the Infinity Stones and attempt to undo the damage caused by Thanos at the beginning of the film.

The Time-Space GPS plays a crucial role in the plot of *Avengers: Endgame*, facilitating the Avengers' time heist and their efforts to save the world.

The Ancient One explains how removing Infinity Stones creates alternate timelines

The Ancient One explains that the Infinity Stones are responsible for the flow of time in the universe. Removing a stone from a timeline via time travel would create an alternative reality without that stone, which would be bad for that reality. She gives the example that without the Time Stone, her world would be overrun by forces of darkness and millions would suffer.

The Ancient One insists that the Avengers must return the Infinity Stones to their original places in time to maintain the reality of each universe they visit. It is fine if they create separate timelines, but if they deprive one timeline of the Infinity Stones, then they break that timeline.

The Avengers' time travel through the Quantum Realm is based on a popular time travel theory in the field of quantum physics. David Deutsch's "Many Worlds Theory" or "Multiverse Theory" argues that the universe we conceive of as our own is just one of many parallel universes. If something is changed in the past, a new timeline is created, branching out from the original timeline.

The Ancient One's explanation of time travel is proven wrong in the TV show Loki. In the show, the TVA (Time Variance Authority) arrives and quickly resets any branched timelines, which then cease to exist. The Infinity Stones are not necessary for the universe's functioning but are instead necessary for Kang's Sacred Timeline to come to fruition.

Captain America must return the Infinity Stones to their original timelines

In *Avengers: Endgame*, time travel is based on the Many Worlds Theory or Multiverse Theory. This theory, as explained by David Deutsch, argues that the universe we conceive of as reality is just one of many parallel universes. Thus, when something is changed in the past, a new timeline is created, branching out from the original timeline.

Captain America travels back in time to return the Infinity Stones to their respective timelines. He returns the Time Stone to the Ancient One, the Power Stone to Morag, the Reality Stone to Asgard, the Soul Stone to Vormir, the Space Stone to a military lab in New Jersey, and the Mind Stone to Loki.

By returning the Infinity Stones to their original timelines, Captain America ensures that the realities of each universe are maintained and that no timeline is broken or deprived of the Infinity Stones that maintain its existence.

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