How to imagine nothing (a method for a programmer or a mathematician)

Motivation:
Many times people ask themselves "what was before?" For example: what was before the beginning of the universe or what was before the beginning of time. A possible answer is "nothing". However, it is very hard to imagine and understand "nothing" for a human being always surrounded by something and immersed in seemingly continuous time-space. Therefore, I propose this mental experiment to imagine "nothing".

The idea:
Imagine a graph in mathematical sense, or a list in programming sense. 
What is a graph? It is a set of nodes connected by edges. Or, what is a list? It's a set of nodes connected by arcs. But when we imagine them for ourselves we very often see (in our minds, on a sheet of paper or on a computer screen) a set of circles connected by line segments (edges) or circles connected by arrows (arcs).
Now answer this question: What is *between* the nodes of a graph or a list? 
Let's go over intuitive answers. 
- If you recall a sci-fi movie when a time-space traveler progresses from node A to node B of some future (alines'?) transportation system, the movie makers often depict it as falling through a colorful well or something like a roller-coaster. But this is not a correct imagination or intuition for answering what is between the nodes of a graph or the objects on a list because the movies apparently show something, while there is nothing between the nodes (the A and B) which belong to a graph.
- Let us return to our way of visualizing graphs/lists on paper, computer screen, and in our minds (?). It is easy to answer what is between the nodes. It is the space between the nodes that is left on the piece of paper or on the computer screen. So the threads of cellulose in the sheet of paper, pixels on the screen or silicon in computer memory are between the nodes? Is this an answer? It seems ridiculous. But how have we come to this point? We made the space between the nodes (on paper, on the screen) intentionally so that nodes do not overlap and are distinguishable. But this is a false answer (to the question what is between the nodes) because we underlaid space (e.g. 2-D space of the sheet of paper or computer screen) where it does not exist. Or, in other words this space between the nodes does not belong to a graph/list. It is just a medium conveying the concept of a graph/list which imposes a false impression that there is something between the nodes. 
So what is between the nodes of a graph/list? There is nothing.
This way of thinking can be extended to any type of discrete objects. Now you know what is nothing.

What a "revealing" thought seems to be passed in this mental experiment? 
- You can imagine this type of nothing (nothing as nothing vs nothing as something (e.g. number 0, or a neutral element of some operation or material void of the cosmos)).
- You can realize that some questions of type "what is between?", "what was before?" are as irrelevant as asking what is between nodes of a graph.
- Moreover, such questions can be dangerous if we unconsciously try to extend our intuitive unification of some idea (the graph) with the medium conveying the idea (paper, pixels, computer memory).

Conclusion
Try remembering about it when you ask "what is between?", "what was before?" and a possible answer is "noting".

MD, 15th of July 2015