system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why was it so groundbreaking that ancient civilizations discovered/utilized the number 0?
gpt
To go a bit against the others here:

The fact that people discovered, that "nothing" can be expressed as a number - that you can also calculate with - is not obvious and very revolutionary.

It shows a new level of abstract thinking that actually leads to mathematics as something different than just "counting things". That a number substracted from itself equals 0 seems painfully obvious to us now, but imagine having to do math without this simple operation.

The decimal system is nice, but a very similar system is also possible without 0 - the Roman numerals just are exceptionally confusing. There is nothing stopping people from expressing (for example) 2437 as "2D4C3B7A" and 3004 as "3D4A" and some cultures used systems that were conceptually similar.