Friday, April 22, 2016

Alien Appearance

Assuming that aliens do exist somewhere in the universe, how will we compare to them physically? Fergus Simpson, a cosmologist, performed a Bayesian analysis regarding the size of aliens, size of planets, and population sizes. After considering these factors, Simpson holds the belief that we should not be looking at Earth-like planets because our planet is not representative of inhabitable planets as a whole. Instead, we should be looking at planets of smaller size.

According to Simpson, we may make predictions about alien life based on our current Earth. For our purpose, we are naming an individual country as a “group” of people. If we take a look at the number of countries and their population sizes, we notice that more than 50% of humans live in seven countries. Because of this fact, the median person will probably be a member of one of these seven countries. However, the majority of countries have populations less than six million. If we were to take the median country based on population size, the chosen country would not be from one of the seven largest countries. Anytime groups are of different sizes, most individuals will be members of groups of larger size.

However, when it comes to figuring out where we are in comparison to other life forms, we cannot say with 100% confidence which part of the spectrum we are on. All things being equal, a randomly selected person is most likely to be a member of a more populous group, whether we group by race or blood type or by nationality. Whether it involves blood type or race, we are not equally likely to belong in each group. Simpson takes uses this fact and applies it to our planet so as to compare it to all the “other” planets that house alien life. He proceeds to make the assumption that we are a part of a large group.

Countries with high populations tend to have larger land areas. Because Simpson makes the assumption that we are on the higher end of the population size spectrum, he concludes that our planet is also on the higher end of the size spectrum. If we may compare planets like we compare countries, then there is a higher number of smaller-sized planets. Therefore, we should be looking at smaller planets instead of Earth-sized planets, as there are simply a larger number of inhabited smaller-than-Earth-sized planets than Earth-sized planets or larger.

Apart from population size, we may also hypothesize the size of these aliens. If we take a look at common species on Earth, smaller creatures tend to have a higher population size than larger creatures. For example, the population size of smaller ones like an ant is much larger than the population size of a larger ones like a hippopotamus. We may then apply this concept to the sizes of aliens in comparison to human beings. Above, we saw that we may assume that there are more smaller-than-Earth-sized planets. Given this assumption, these planets also have smaller population sizes, so their inhabitants are likely to have a larger physical sizes. So, it is probable that we are smaller in comparison to most alien populations.


- Stephanie Bao