Larry, I don't trust mass sightings. We all have the same sensory equipment and capable of being fooled by our senses in the same way. Funny thing that the first thing people assume is aliens - that should be only considered after checking out possible earthly causes.
It's not only tyranny of distance but tyranny of time. There are just so many places and times that aliens could be living in that are utterly inaccessible to us - gazillions of miles or billions of years.
Martin, I'm also a fan of "What we know, we don't believe. What we don't know, we believe".
Thing is, science becomes counter intuitive at very large and small scales - people tend to find it unbelievable because physical laws that affect things of our size are different at the scale of the very large and very small.
For instance http://www.thenational.ae/news/uae-n...um-possibility
Bizarre as the info in the article is, it's less wild than the usual religious belief systems ... but the big man in the sky idea seems familiar to us because we have been told about it since childhood. By comparison, quantum mechanics is alien ...