## Power of Exponential Growth

Appropriate Level:  Algebra 2 (with logarithms)

The Question:  Suppose you start with an object that has the mass of a proton.  If this object doubles in mass every five minutes, how long will take for it to grow to the mass of the current universe?

Ask for guesses.  Will it be a few hours?  A few years?  A few millenia?  Much longer?

If you wish, give them the following estimates:  Google says the mass of a proton is about $2 \times 10 ^{-27}$ kilograms.  The wikipedia page on the “Observable Universe” says it has a mass of about $2 \times 10 ^{53}$ kilograms.