One of the easiest ways to determine where you are in the Marvel Cinematic Universe is by looking at Black Widow's hair. From her moppy red curls in Iron Man 2 to the new blonde disguise in Avengers: Infinity War, no one changes their locks more than Natasha Romanoff.
Based on the first trailer for Avengers: Endgame, Black Widow/Natasha Romanoff (Scarlett Johansson) seems to be keeping her blonde look from Infinity War. However, one eagle-eyed redditor has noticed that there's more than meets the eye to her upcoming hairstyle.
First, they use this image to show that Natasha appears to be rocking the exact same hairdo from Infinity War. This is extremely uncommon for the character, who always comes into a new movie with at least some hair alterations. However, the redditor notices a change as the trailer progresses...
"But here, as she greets Hawkeye in the middle of an Asian country (maybe Japan) her hair looks like it is braided and long," they point out. This is an excellent observation as the hair seen in the first image would be too short for the style seen in the second photo.
Finally, the redditor includes the concept art image, which shows Black Widow going back to her roots (pun intended!).
"Maybe she colours it or something, but does this mean that Endgame starts with the aftermath of the decimation and then we have a time lapse of a few years (or maybe some months?)."
Since the concept art shows her hair as both longer and darker, this could definitely indicate a time jump. Many speculate the movie will take place a couple of years after the events of Infinity War, but that doesn't mean we won't see the immediate aftermath before jumping ahead.
The redditor also points out that Hawkeye's look in the concept art doesn't quite match with the trailer either, however, they suggest that maybe "he reverts back from Ronin to Hawkeye after the time lapse." Of course, there's always the possibility that this was early artwork that eventually changed.
While some fans think this hair/time jump theory could be true, other commenters weren't quick to buy it. /u/Wakaflockaisaac points out that it's possible Marvel "could have edited/shot some scenes for the trailer with Natasha having different color hair to throw of the fans."
/u/XOpelX writes that people are "focusing on her hair WAY too much" and that the mysteries of the upcoming films won't be solved by hair styles.
However, some people think these observations are definitely pointing us in the right time jump direction. "I think you're pretty spot on with this theory," writes /u/FundoBundo.
Whether or not these Black Widow hair changes are important, we can all agree on one thing: Scarlett Johansson is capable of pulling off pretty much any hairstyle.