A million seconds is 12 days. A billion is 32 years.

Humans feel the difference between 1 and 10, but not between a million and a billion. Drag the ruler, lock in your guess, then see how far off a typical brain is. Eight questions, one rule: guess first.

Why the ruler is logarithmic

Each tick on the ruler is ten times the one before. Your error is measured in decades, powers of ten: guessing 3 million for 30 million is one decade low, the same miss as guessing 300 for 3,000. A guess within 0.1 decade (about 26% either way) counts as a bullseye. Scoring is 100 points minus 33 for every decade you are off, never below zero.

The ladder that breaks intuition

Sources

• Seconds per year: 365.25 days x 86,400 s = 31,557,600 s (Julian year, IAU).
• Earth-Moon mean distance 384,400 km: NASA Moon Fact Sheet.
• Human brain neurons, about 86 billion: Azevedo et al., Journal of Comparative Neurology 513, 2009.
• Sunlight travel time: 1 AU = 149,597,870,700 m (IAU 2012) divided by c = 299,792,458 m/s gives 499 s.
• Human cells in a body, about 30 trillion: Sender, Fuchs and Milo, PLOS Biology 14(8), 2016.
• Living languages, 7,164: Ethnologue, 27th edition (2024).
• Light-year 9.4607 x 10^12 km and Earth mass 5.9722 x 10^24 kg: IAU / NASA Earth Fact Sheet.