While testing weapons with the United States Army in Journey into Mystery #86 (Sep 1962), Thor witnesses a time traveller from the future who steals a cobalt bomb and disappears in to the future, leaving only a fragment of strange metal. In desperation, Thor summons Odin, his father in Asgard, who appears and tells him all he needs to do is attach a fragment of metal to his hammer and spin it as fast as he can.
Odin also asks his son if he had forgotten that his hammer can spin faster than the speed of light and breach time. There’s still some is-Thor-a-persona-of-Don or does-Thor-have-gaps-in-his-memory stuff going on here.
Anyway, now Thor can travel through time?
After battling the “Tomorrow Man” and recovering the cobalt bomb, he disappears into the past again to wrap up the adventure.
[Editorial: I’m putting the blog on pause again until I can build up some a large-ish backlog again. Even after changing the posting rate to only three times a week, I still find it hard to keep up with regular life. But I made it well into the start of the Marvel Age – we got to see the debut of the Fantastic Four, The Hulk, Thor, Ant-Man, Namor, Doctor Doom, and Spider-Man! That’s a nice teeming Marvel Age, but it’s just getting started. Coming up in the next volume of posts we will see: Captain America, Iron Man, and regular tales from Spidey and the start of all those wonderful character cross-overs]