why was Loki able to see what was happening on earth, but THOR could not?

why was loki able to transport himself to earth and Jotunheim, but THOR could not?

how did loki survive the fall, but then THOR needed dark magic to get back to earth?

@THORSON: Dark matter not dark magic also the answer to all your questions is cosmic cube

First, Loki was sitting on Odin's Throne, which allowed him to see what was happening on Earth, it was not in Loki's powerset to do so, but it is a property of Odin's Throne.

Loki transported himself to Jotenheim and Earth via the Bifrost bridge, which Thor utilized as well. The difference was Loki had Odin's spear so he was able to use it by himself, and did not reeuire Heimdall's aid.

Loki fell into a Vortex which transported him to another realm. He required the Cosmic Cube (the tesseract) to return. The Asgardians were cut off from Earth because of the loss of the Bifrost and therefore, as Loki elludes to in Avengers, required a great deal of magic and energy to transport Thor to Earth, but it was a one way trip, Odin could not bring him back and Thor (in the movies, because in the comics Mjolnir can take him anywhere nhe needs to) lacks the powers to do it on his own, so Thor had to get the cube back from Loki in order to go back to Asgard.

@Enyalios: oh makes sense. thank you.