One of the things about Captain America's shield other than it being indestructible is that it always comes back to him when he throws it. I know this is a comic book movie and considered canon, but doesn't that defy the laws of physics? Is there a logical explanation for the shield coming back to him, or is it just because he's a superhero and it's been that way since the beginning?
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The sun is shining... but the ice is slippery.
The ultimate answer is that the shield does whatever the writer's (whether comic book or film writers) need it to do for the story, regardless of real world physics. It's a comic book item, after all.
As for in world explanation, I think the idea is just that Cap is just that smart and has practiced with it so much that he's able to pretty much instantaneously perceive and calculate how (at what angle, with the appropriate amount of strength) to throw the shield so that it's trajectory will have it ricochet off of objects (or people) in such a way that it will return back to him. I would think that he's probably one heck of a pool player.
There's also the fact that it's made from a fictional metal (that's completely vibration absorbent). Some have speculated that because of this, it's able to store the energy from the vibrations and when Steve throws it, some of this stored energy is used in how it behaves when thrown.
Nillindeiel
Agent Hill: ...Then aliens invaded New York and were beaten back, by among others, a giant green monster, a costumed hero from the 40's.... and a god.
Agent Ward: I don't think Thor is technically a god.
Hill: Well...you haven't been near his arms.
~Agents of SHIELD; Season 1 Episode 1 "Pilot"
Right but it doesn't "come back to him" like Mjolnir comes back to Thor. It's more that (as Nillindeiel says) that he's good at throwing it such a way that it comes back in his direction. Also adding to that, he's agile and quick enough to intercept it. There have been several examples of him throwing it where he had to go get it after - either due to someone deflecting it (Loki, Bucky) or just due to how he used it (stuck in a wall or door).
But yeah, it's a combination of all of that. He's good at throwing it (he's thrown other things with similar accuracy), it's made of fictional metal with very unique properties, he's good at catching it etc.
Reading my signature constitutes admission that I am correct. (Too late)
Right but it doesn't "come back to him" like Mjolnir comes back to Thor. It's more that (as Nillindeiel says) that he's good at throwing it such a way that it comes back in his direction. Also adding to that, he's agile and quick enough to intercept it. There have been several examples of him throwing it where he had to go get it after - either due to someone deflecting it (Loki, Bucky) or just due to how he used it (stuck in a wall or door).
But yeah, it's a combination of all of that. He's good at throwing it (he's thrown other things with similar accuracy), it's made of fictional metal with very unique properties, he's good at catching it etc.