# Exponential: Carbon-14 Half-life

Some things grow or decay in an exponential way. This means that for every time unit (e.g. a day) the metric changes with ± the same percentage. If you can say "it doubles every _ days" => this means it has exponential growth/increase! If you can say "it drops to half every _ days", it has logarithmic decay/decrease!

### Logarithmic decay

• 2 → 1 = multiply by 0.50 (or -50.00 %) in 5730 year(s)
• multiply by 0.988 (or -1.2 %) in 1 century
• goes ÷ 2 every 57.26 century(s)
• goes ÷ 5 every 132.96 century(s)
• goes ÷ 10 every 190.22 century(s)
• goes ÷ 100 every 380.44 century(s)

### Extrapolation of data points

 start point 2 data point after 14.32 century 1.682 interpolation after 28.63 century 1.414 interpolation after 42.95 century 1.189 interpolation after 57.26 century 1 data point after 71.58 century 0.841 extrapolation after 85.89 century 0.707 extrapolation after 100.21 century 0.595 extrapolation after 114.52 century 0.5 extrapolation after 128.84 century 0.42 extrapolation after 143.16 century 0.354 extrapolation after 157.47 century 0.297 extrapolation after 171.79 century 0.25 extrapolation