Slipspace

From ILB

Slipspace appears to be a dimension which runs parallel to ours, but with altered laws of physics. Slipspace travel involve slicing a hole into the slipstream, travelling through it, and slicing a hole back into normal reality. Covenant warships are much more precise about this than our own ships. Slipspace also can have odd effects on time itself. It can also be used to broadcast messages.

More on Slipspace via Halo Library (http://library.psyjnir.net/?id=100).