PROFESSOR JULIAN G. FRANCO

Not everything goes in Nature. There are some things conceived by our imaginations that we can actually prove to be impossible. In this knol I exemplify that contention by showing how we can use the scientific method through our knowledge of physics and biology to conclusively prove the impossibility of the existence of human-like creatures that are much larger or much smaller than we are. In doing so I will also discuss various aspects related to our understanding of scale, from the microscopic to the astronomical. I will end up the knol with some philosophical implications related to my main conclusion.
 
Introduction
 
I often hear people argue with seemingly convincing logic that the fact that we haven't seen something doesn't mean that it cannot exist and that it might someday suddenly show up. They say that the world is so mysterious and relatively unknowable that pretty much anything goes. This reasoning is applied, for instance, to the weird and exotic creatures that humans throughout history have conceived in their imaginations and have claimed to have seen occasionally. The scientific method and our knowledge of the laws of nature can be used to disprove the existence and viability of these creatures.