Unit 7

Viruses (like COVID): (as well as many email and computer viruses) can spread at ever increasing rates, exponentially, causing major widespread infected areas.

Medicine: When calculating medicine doses, they are calculated based on people's masses. A small child will receive less than a heavier adult, but it also takes into account the exponential decay or half-life of the medication, measuring how quickly it will take for the medicine to no longer be in the person's system.

Investments: Investments can grow exponentially but they can also decay exponentially. We can calculate this growth and decay with exponential functions.

Credit Card Debt: Compound Interest works against people with a Credit Card debt they do not pay off, because the debt grows faster and faster each billing period and can quickly become out of control.

Bacteria: Bacteria grows at an exponential rate. This growth can be estimated using exponential equations.

Google PageRank: Google gives every page on the web a score (PageRank) which is a rough measure of authority / importance. This is a logarithmic scale, which in my head means "PageRank counts the number of digits in your score".

Richter Scale: Richter scale and Decibel. The idea is to put events which can vary drastically (earthquakes) on a single scale with a small range (typically 1 to 10). Just like PageRank, each 1-point increase is a 10x improvement in power. The largest human-recorded earthquake was 9.5; the Yucatán Peninsula impact, which likely made the dinosaurs extinct, was 13.

Decibel: Sounds can go from intensely quiet (pindrop) to extremely loud (airplane) and our brains can process it all. In reality, the sound of an airplane's engine is millions (billions, trillions) of times more powerful than a pin drop, and it's inconvenient to have a scale that goes from 1 to a gazillion. Logs keep everything on a reasonable scale.