Through the Wormhole
The Movie: Loki opens a giant wormhole in order to transport his invading army, and Black Widow closes it just in time for Iron Man to fall back through after getting rid of the bomb.
Real Life: Well, this is not really a "real life" situation because we know next to nothing about wormholes. However, what we know about them — ie, that they are punctures in spacetime — suggests that opening and closing one of enormous size above Manhattan would be kind of risky. This tear in the hyde of the universe appears to be located in low orbit, and would likely cause a huge pressure gradient, sucking our atmosphere and perhaps even people into the vacuum of space on the other side. Maybe the Asgardian gods know something we don't know about the theory of relativity, but since Loki doesn't even know how to keep his distance from the Hulk, we doubt it.