today I will write about the difficulties of calculating the amount of people on Earth and demographic revolution.
For this month’s physics problems that I want to solve, I need to know how much is the number of people in the world increasing. It is just a part of the problem but necessary for the solution. One can quite easily make some simple assumptions and derive an exponential formula that is for any type of reproducing species but does not account in “human” factors. Some of those would take an effect for a population of animals or plants too of course, simply because you do not have an infinite space and other resources. Just an exponential growth would work (I think) for
bacteria for example because it is simple to have enough food for LOT of them and they won’t care when they are close to each other.
Humanity could be assumed to increase in size in similar fashion during sometimes of its history, for example around the Industrial Revolution when mortality rapidly decreased while natality stayed the same. This did not happen across the whole globe though meaning that in most of the world we were still stagnating. In 21st century the predictions are even worse, the reason is that people in Western world are dying out, meaning we do not have enough babies. The population still increases overall but its thanks to India, Niger or other countries still in the first parts of demographical revolution, that is a part human “evolution” following the decrease and final levelling of natality and mortality. You can read more about that on Wikipedia.
Northern-Western part of the world is dying out. It is probably because people have higher education, which takes longer time and during their career they have less and less time to have and up bring babies. It is fascinating that this effect takes place even in countries with strong religion background, like Poland. I do not find it very sad though, who would think that there could be peaceful dying out?
Disclaimer: I am not a sociologist.
 This is actually more complicated and in a sense factually false. There are four phases to the life of bacteria colony and only the second follows what I wrote originally. In the beginning when you put bacteria into some medium, meaning place with “food”, they will start to grow individually in size. This is called the lag phase and after that follows the log phase which is an actuall explosion in the number of bacteria. Here the numbers do grow exponentionally but after they do not have anymore nutrients or there is just too much waste around they will come into a stationary phase where the population is in balance. In the end you might have the death phase but when the onset starts depends on the medium, bacteria etc. The bacteria can reach the density of several billions of cells per millilitre. That is a lot and does take some time if you start with smaller numbers but this proces CAN NOT go on forever.
Picture: “bacteria: bacterial growth curve”. Illustration. Encyclopædia Britannica Online. Web. 31 Oct. 2017. <https://www.britannica.com/science/bacteria?oasmId=127577>