The lyrics are basically saying; how can we even try to understand the complexities of the universe when we can't even begin to understand the complexities of ourselves. People try to learn everything they can, about the Earth, the universe, and newly discovered life forms, but in their quest for knowledge they skip the subject of themselves. There's an emptiness inside our heads that no-one dares to dwell means where our emotions are. No one deals with how they feel or sorts out their emotions because it's hard, confusing, and painful. Many people decide to leave that space numb and unoccupied because it's easier to not feel at all than dealing with the complications of emotions, hence the emptiness inside our heads. For a lot of people though, that could easily be changed to hearts.