# What is the math behind human growth

## What does exponential growth mean?

When assessing exponential growth, people are overwhelmed. The corona pandemic is a good example of this.

Growth processes are omnipresent - in nature as well as in social systems. If you analyze these processes mathematically, you will find two fundamentally different dynamics. With linear growth there is a fixed increase in every unit of time. This is the case with knitting - every minute a sweater grows up to 111 (world record!) Stitches. With exponential growth, on the other hand, the growth increases over time. B. The number of yeast cells doubles every few hours - one cell becomes two, then there are soon four, eight, 16, 32, 64, 128, 256, 512, 1024, etc.
The Covid-19 virus is currently spreading exponentially: The number of infected people in Austria is currently doubling every two days and eight hours. Within just four weeks, their number can rise from the current 602 (as of Saturday, 8 a.m.) to more than a million, as researchers at the Complexity Science Hub Vienna have calculated these days. The fiendish thing about exponential functions is that the growth is barely noticeable at first - it lags significantly behind linear growth for a while, but then shoots up.

However: Unlimited growth is not possible in a limited world - at some point you come up against limits (the title of the Club of Rome report “The Limits to Growth” also referred to this). This means that the increase will weaken at some point ("saturation effect").

The central question is where these limits are. Many global problems are in the middle of an exponential growth phase - such as energy consumption, urban growth or ocean acidification. The same currently applies to the corona pandemic. At least with us. Because data from China or Singapore (where Covid-19 was rampant almost two months earlier) show that the number of new infections is now falling significantly - partly because of the drastic measures, but partly also because more and more people have already built up defenses .

In evolution, humans have learned to correctly assess the dynamics of linear growth. Exponential growth, however, overwhelms our point of view: We usually only react when a problem is rapidly worsening - by then it is already quite late to be able to influence the course. In the case of Corona, one hopes to have intervened in time. It remains to be seen whether this assessment is correct.

The author headed the research department of the “press” and is a science communicator at AIT.

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