At the end of Avengers: Endgame, Captain America dons his quantum suit and travels back in time to return the Infinity Stones to their proper locations throughout history.
He returns to the present several seconds later, having aged many decades in almost no time.
How is this possible?
When Captain America stepped into the time machine, he was 105 years old. When he returned to the present, he was 180. He appeared as a man in his 70s or 80s due to the natural effects of aging, which the super soldier serum in his bloodstream slowed, but did not stop.
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How Did Captain America Get Old in Endgame?
Captain America was older than he looked throughout much of the Infinity Saga. After crashing an armed Hydra bomber into the Arctic in 1945, he was frozen in the ice for 66 years, which preserved his body as though he were in cryostasis.
That means when S.H.I.E.L.D. rescued him, he was a 93-year-old in a 27-year-old body.
Over the next several years, he fought as one of the Avengers, still aging slower than normal. This was because of the super soldier serum in his bloodstream.
He was 105 years old at the end of Endgame when he stepped into Tony Stark’s time machine.
Once he finished returning the Infinity Stones, he didn’t return to the present right away. Instead, he went back to 1948 to live the life he missed out on while he was frozen.
From there, he aged slowly over the next several decades. He didn’t revert to the age he would have been in the 1940s–instead, he was 105 when he returned to 1948 and continued to age until he returned to the present.
Though only a few seconds passed in real time, Cap lived his life between 1948 and 2023 over again, returning to the present when he was about 180 years old.
He showed signs of his advanced age upon his return to the present because, though the serum slowed the aging process, it could not stop it.
That said, he looked pretty good for 180, as he appeared to be in his 70s or 80s physically.
How Did Captain America Go Back in Time Without Changing the Future?
It is typically accepted in fiction that, if you travel back in time, you change the future. Robert Zemeckis and Bob Gale explored this concept in the Back to the Future movies.
However, the Marvel movies are not Back to the Future, and they have their own set of rules regarding time travel.
Early in Endgame, Bruce Banner states history is set in stone and nobody from the future can change it. The time traveler’s past, present, and future all become relative to whatever spot they are occupying in history.
Only the Infinity Stones can affect past or present events when removed from their proper places in history.
This explains why Thanos could destroy half the universe when he had the Stones, and why the Hulk could snap that half back into existence after the Avengers collected them.
It also allowed Captain America to travel back in time without altering the course of events. He originally did this to return the Infinity Stones, which ensured no one like Thanos could erase time and history ever again.
Once the Stones were back in place, he was free to travel to any part of history without changing the future. Even if he wanted to change things, nothing he could have done would have had any effect because the past was set in stone.
Did Captain America Go Back in Time to Be With Peggy?
When Cap traveled back to the 1940s, it’s likely his primary motive was Agent Peggy Carter.
He fell in love with Carter in Captain America: The First Avenger. But when he crashed the plane in 1945, he was presumed dead, so he missed out on the life he would have lived with Carter.
At the end of Endgame, he took advantage of the opportunity to go back and live that life. In the final scene, we saw a young Steve Rogers and Peggy Carter finally getting their dance.
![Steve and Peggy Dance // Ending Scene | Avengers: Endgame [Open Matte/IMAX HD]](https://i.ytimg.com/vi/IztjGOPMCwU/0.jpg)
Of course, this brings up an interesting question. If Steve could travel back in time without changing anything, then he would have still been frozen in ice all those years. How does the movie account for this?
There isn’t a clear answer–in fact, the directors and the screenwriters have differing opinions.
Directors Joseph and Anthony Russo claim Cap’s time travel took him into an alternate timeline, allowing him to live in a separate reality without affecting the main timeline. He then reentered the main timeline to pass on the shield and say goodbye to Sam and Bucky.
Screenwriters Christopher Markus and Stephen McFeely stated Steve traveled back in the main timeline and there were “two Caps” during those decades–one frozen in ice, and one living the good life with Peggy.
Regardless of whether the directors or the screenwriters are correct, Captain America got the happy ending he deserved–without changing the past or future. And he enjoyed a beautiful life.
Conclusion
Captain America appeared to age rapidly in only a few seconds at the end of Avengers: Endgame, but he lived several decades of his life in those few seconds. Thus, when he returned from time traveling, he was showing the effects of a natural aging process.
Sarah Hood is a freelance content writer and editor with a love for all things Star Wars. When she’s not writing, she enjoys cooking, singing, and spending time in the great outdoors.