1. Why did Loki travel underground to meet the dwarfs?
Answers
Answer:
Good observation, let me try to explain this to you based on my understanding of it.
Space travel through Tesseract is based on Quantum Tunneling effect, where when you have a high density mass/energy concentrated in a small point, the space-time continum around that point gets wrapped, connecting two far away point, just like folding a paper to connect two points rather than drawing a line to connect them.
Tesseract is a 4 dimensional entity (now they made an infinity stone that can have same power as Tesseract) which is used to connect two points any where in a 3 dimensional universe. It generates a high density energy to warp the space to do so. It generates energy blasts by exitation due to electric field as shown in “Captain America: The First Avenger” when Stark get blasted when experimenting with Hydra weapons.
Loki triggered this high density energy to connect his location in space to earth, as you remember although he did that, he was not able to stabilize the portal causing the shield facility to collapse due to gravitational pull, and that is why they needed Selvig to stabilize the quantum tunnelling effect using Iridium.
How it points to the exact desired points in space as needed by Loki or anybody for that matter is beyond me. It is the correct answer.Hope this will help you.