system
Given the following post, respond as if you're commenting on Reddit:
human
[Avengers] What is the origin/ purpose of the Tesseract? How did it end up on Earth, and why hasn't anyone from Asgard come down to retrieve it?

A friend and I were watching Avengers the other night, and she would not stop asking about the tesseract. Any help would be much appreciated.
gpt
With regards to it's origins, the tesseract is almost certainly an alternate/cinematic universe incarnation of the "Cosmic Cube", a number of which can be found in the mainstream Marvel universe. From Wikipedia:

>The Cosmic Cube is a containment device created by various civilizations throughout the Marvel Universe at various times, including the Skrulls...

>These matrices—which may or may not actually be shaped like a cube—are suffused with reality-warping energies of unknown composition that comes from the realm of the Beyonders. 

Additionally, you'll notice that someone from Asguard did come to retrieve it. His name was Loki and he was the main antagonist for the film.

Odin, of course, cannot be personally responsible for every powerful artifact in the Marvel Universe. He simply takes them into his possession whenever necessity requires that they be protected. In so far as the tesseract is not used for substantial, world altering harm, Odin has no reason to retrieve it.