22. Science Club: Exponentials


1. Connie: OK, so much for relationships. What’s our science topic, Liza?
Liza: Well, Connie, this week I researched the exponential function.
2. Liza: It describes everything that grows at a constant rate.
Gigi: Like weeds?
Connie: Or people?
Brooke: Or money?
3. Liza: Right. Whatever grows will double in a time that is 70 divided by the growth rate.
4. Liza: For example, Brooke, if your money earns 5% interest a year, you’ll have twice as much of it in 14 years.
Graphic: growth rates and doubling times for population, oil and savings.
5. Liza: Every doubling time produces exactly as much all the growth that came before, no matter how long ago it began.
Graphic: doubling squares and rectangles.
6. Liza: But some things don’t grow. There’s only so much oil, and we’ve been using 3.5% more of it every year for a century. Now half is gone. How long can this continue?
Gigi: Another century?
Connie: No, 20 years.
7. Liza: Right, Connie. Same story for coal, phosphate and fresh water. Industrial growth could be over in a generation.
8. Brooke: So what will we have then?
Gigi: Each other.
Connie: Aaand we’re back to relationships.

Posted on July 16, 2009 at 12:00 am in Comics and tagged with , . Follow responses to this post with the comments feed.