Originally Posted by Trooth

Well it is a UFO, since no one has identified it. Sadly UFO has become to mean "alien" when really it just means what the name says, Unidentified Flying Object.

I would be somewhat amazed if we are the only intelligent and creative beings in the universe and statistics as Tankie says imply we are not. However statistics don't mean we would get visited.

Even allowing for our limited scientific understanding the sheer scale of the universe makes travelling anywhere a hell of an endeavour. Couple that with the time dilation effect of travelling at speed (it may take you a couple of years to get somewhere but in that time your planet and your destination planet have aged thousands) may mean that you have to use generational travel. I.e. we set off, breed along the way, and our descendants get there.

On that basis the aliens are either very much more longer living than us (by an order or two of magnitude), or for some reason lose the whole mission objective that so many of their forebears dedicated their lives to. They only have to hover over Trafalgar Square or the Houses of Parliament (avoiding Torchwood of course) and their work is done, they can then go off and do whatever it is they do when they aren't annoying some drunken redneck in the middle of some forest (as seems to be their hobby).