> This is pure experiment Pedantically speaking, it is not an experiment, it is an observation. Experiment is a kind of study where you control independent var

> This is pure experiment Pedantically speaking, it is not an experiment, it is an observation. Experiment is a kind of study where you control independent variable. In this case no cosmic radiation nor seismic activity were not manipulated by scientists. It is the reason why they speak about correlation but not causation. https://en.wikipedia.org/wiki/Experiment#Observational_studies https://en.wikipedia.org/wiki/Experiment#Observational_studi...