In the final chapter of the book, Sophie's World, we learn that stargazing is a form of time travel and thanks to this concept the book is better understood by the reader. Albert tells his daughter Hilde that when we look at a star we are looking at what that star looked like millions of years ago because it takes millions of light years for it to reach our eyes. It works the same for someone in another planet that is for example four light year away, if he were to be watching me with a telescope, he wouldn't see me writing this blog, he would see a thirteen year old boy doing whatever I was doing back then, he would be looking at the past not the present. Therefore, this concept makes the reader assume that Alberto and Sophie are many light years away from Albert and Hilde, which explains why Sophie and Alberto can see Hilde and Albert but cannot be seen by them. When observing Hilde, Sophie is actually looking at what Hilde used to look like, at her past, when in the present Hilde does not exist anymore.
I think that time is a very complex idea because it makes me doubt existence. If I am looking at an object close to me it means I am looking at the past or how the object looked many years back, so this means I can never see the present, so how can I be sure that anything really exists. This is something that really scares me and is something that is left unanswered in the book because I keep wondering who really existed, Hilde or Sophie?