how does zero represent the absence of things?

Answer 1

Zero does not represent the absence of things. It represents the presence of nothing.

Zero represents a real quantity that lies somewhere between 0.00000000000000001 and - 0.00000000000000001.

- 0.00000000000000001 better represents the absence of things than zero does. The number "- 1 x 10(^6)" represents the absence of a million more things than zero ever did.

The absence of things is really the absence of strings, when you get right down to it: Like before the Big Bang. A very long time ago indeed.

Answer 2

Because it does. That's what it is defined as representing. Your question is like asking why red is red or why two represents a pair. It's just what the term was defined to mean.

Answer 3

That's just the way it was set up, long ago when someone figured a way to enumerate things.
Zero = null.
Nothing.
Zip.
Zilch.
Nada.