Ballpark — May 21, 2026
Answers to that day's 5 daily estimation questions.
About how many sleep cycles does a typical person go through in a night?
~5 cycles
Sleep cycles are often ~90 minutes, so many people get 4–6 per night.
Teeth a snail has
14,000 teeth
Snails use a radula to scrape food.
Cells in the human body
37 trillion
Recent estimates suggest roughly 37 trillion human cells.
Weight of the Great Wall of China
50 million tons
Equivalent to over 100 Burj Khalifas.
Years a plastic bottle takes to decompose
450 years
PET plastic breaks down into microplastics but never truly disappears.