General Knowledgespeaking topic
The number zero went uninvented for thousands of years; the Romans built an empire but had no symbol for writing 'nothing.' Writing nothingness down as a thing turned out to be one of humanity's hardest ideas. Why was naming something that does not exist so difficult, and how did civilizations that never managed it still thrive?
— history of mathematics, the invention of zero
practice with this topic
Set the timer (5-30 min), take 20 seconds of prep if you like, start talking. Jot your thoughts onto the sticky-note board.
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