Which one? I have a couple.

[The grass is green, the sky is blue, and intimidation tactics cause Tony Stark to act like an adolescent.]

And the short answer is that our native realities are experiencing waveform decoherence caused by an extradimensional anomaly. The ship was designed to stabilize the waveforms, which includes rounding up everyone who's been - slipped loose, for lack of a better metaphor.