There are billions of galaxies out there, and thats only what we have found so far! there is many more too. The chances of us being the ONLY living planet would be a miracle, and science is not supposed to ever believe in miracles.
We have only been able to get too Moon and Mars with actual human craft, imagine how many other star systems there are, just by the law of averages there is life in some of them.
There are so many sightings of UFO and aliens over the years by public, police, army, navy, aircraft pilots, and much more. Maybe a lot of them are not true, but I believe some are. I have never seen one myself but I do believe for the simple fact that how arrogant can you be to think we are the only ones.
Now thats not to say they have visited earth, perhaps they haven't, perhaps they have, but you don't know and nor do I . Maybe GSP has really seen a Alien, like millions all over the world, or perhaps it was a vivid dream that he has thought was reality. But you would be very mentally ill to think you know TS.