"I travel through space."
Translation:Ik reis door de ruimte.
Space in the meaning of outer space always has de in front of it. If it is preceded by een, then it is a room and if there is no article in front, it can be any kind of space (except outer space): space between two object, space in a house, space between the winner an number two and also a meaning not bound do physical space but linked to space/freedom to move and act.
De ruimte can also mean the room but this will normally be made clear because of context. Without context it will usually mean outer space.
"Space" could also be translated without the article ("de/een"), right? For example:
I travel through space and time. Ik reis door tijd en ruimte.
Why wasn't "Ik reis door ruimte" an acceptable translation of "I travel through space"?