twisted_steel2 wrote:Plus, isn't there evidence (a lot of evidence) that we get visitors all the time? Fermi just seems to ignore that.
That depends on how loose your definition of "evidence" is.
@Okie: Most theories on this topic suffer from that. Pretty much all of them that I know of, actually. Human beings are terrible at comprehending things we don't have an existing basis of knowledge or visualization for. We can't even really comprehend what a 4th dimension would be like. 2D is flat, 3D is what we have in the real world; depth. What would a 4th dimension to reality be like? 4D is even referred to as an "abstract concept" in mathematics.
Human beings trying to comprehend what an intelligent alien race would be like is a joke. We're probably more likely to fire a dart out of a cannon and hitting that particular grain of sand on a beach 2 miles away than we are to accurately predict what an intelligent alien race would be like. We might not even be able to see
them. Human eyes are poor by nature's standards, same with all our other physical senses. What if they can only be seen by infrared, or some other kind of light wavelength that the human eye can't see? We could even have this whole planet already populated by an alien race if they exist in a 4th dimension, or have technology that exists within, but separately from, our own.
There are all kinds of crazy possibilities, many of which we can't even come up with in our own heads. You want to know why I'm confident we haven't had aliens in the traditional sense on this planet as of yet? Look at how they're visually portrayed by pretty much every account, anywhere. In broad terms, they are human. They are bipeds with builds similar to human beings. They have two eyes, a nose, a similar-looking mouth, a neck much thinner than the head, similarly-shaped appendages with digits on the end also known as fingers, etc.
Aliens are just humans projecting, right now. A lot of us want to believe.