QUOTE(runephoenix @ Feb 11 2007, 05:19 PM) [snapback]1538703[/snapback]
maybe alien technology advances just like ours.
That 'hat' shaped one in your second picture was quite common in pics for the past century.
I think the various shapes and appearance of UFOs is due to several factors:
1) different phenomena at work (not all UFOs are the same thing)
2) advancement in earthly technology mistaken for UFOs
3) more sophisticated technology available to hoaxers