So where is TNT supposed to take place

[MeetyourUnmaker]

So in the middle part of the wad there is a skybox with three different galaxies. So how is this even physically possible to be so far from Earth?

[Catpho]

Teleporters + Artistic licence

[StevenC21]

The only right answer @Catpho.

[Nevander]

I think it is some kind of distant universe and planet with mining operations going on, based on the level styles and some names.

[Jaws In Space]

From the story text. "The UAC's base was set up on one of the moons of Jupiter, hoping that the increased distance would enhance Earth's safety if something went wrong."

[Impboy4]

It's Io, the closest Galilean moon to Jupiter. Where do you think all that lava in most maps came from? 

[Deleted_Account]

The setting of TNT Evilution is set on Io. Remember there's lot of artistic creativity here, like how Phobos apparently has a misty white sky with mountains covered in lichen or moss.

[DynamiteKaitorn]

TNT is set on an unknown planet called: Trinitrotoluene