What is that invisible thing?

I don't know which school year would be most related to this legendary anecdote, perhaps the greatest probability would be the beginning of high school, or some year of elementary school, and if they were galaxies I wouldn't know the distance between them either, the moon appears to be close, but it is far away, just look at it and realize the contradiction, inexploitable for anyone who doesn't have a spaceship, I myself don't need an X on the ceiling to know where the ceiling is, no one knows exactly if the universe has a ceiling, but everyone needs a roof, walls, windows, doors, ... Home.

What is this white doing here? reaLLy??