There has been a rash of reports of UFO's since the year 2012 began. Literally, of course, UFO simply means that something was seen in the sky that couldn't be recognized or explained at the time. But virtually everyone who hears the term UFO immediately assumes the sighting to be some contraption from "outer space", as in coming from Mars, or even farther out in deeper space, and they believe that probably it is "manned."
In 2011 there were 6000 reports of alleged UFO sightings. Most of these were listed as "unexplained." So far in 2012, 36 of 50 states have called in their experiences with "alien" craft sightings, reports totaling in the hundreds. All told, at least 2 dozen countries are known to have reported seeing UFO's. As of now, there are really no verified accounts of extra terrestrial space craft or aliens on record. There just aren't any videos that were taken by sighters or abductees that show clearly that the earth's space is being used as a highway by alien ships.
Here is one thought on the matter. Scientific exploration has seemed to indicate that there is no intelligent life on any of the planets circling the Sun that could build and fly spacecraft to the Earth. That being true, and I believe it is, take a look at the other possibility. The closest star to Earth, besides the Sun, called Proxima Centauri, is about forty trillion miles distant, and many stars have planets in orbit around them and these planets are relatively close to their Sun. Supposing there was such a planet that could support life orbiting Proxima Centauri, consider that if a space vehicle could travel at 60,000 miles per hour, it would take 50,000 years to travel from that planet to the Earth. Even light, traveling at 186,000 miles per second, takes over 4 years to reach the earth. One could make up all sorts of scenarios that might justify the existence of "little green men" from outer space, regardless of that potentially insurmountable restriction on space and time travel from even the closest possible habitable planet. Arguments for such space travel might include the possibility that there are capable life forms that are so advanced that their space ships can travel long enough to reach Earth while their bodies are frozen in some kind of time warp, or maybe that there are such things as advanced civilizations that can travel on beams of light, and take only a bit over 4 years travel time to arrive here at the speed of light. Or maybe it's just our limited intelligence that prevents us from understanding how and why we could have visitors. Are we humans so vain as to think that we are the only beings in the Universe? Or could it be that the craft have shields that mask the reality of their presence, and the occupants are just waiting for the right time and place to make contact and announce their intentions? The only plausible argument that comes to my mind that might suggest some credibility to the existence of some kind of vehicles flying around in the sky, whether they come from outer space or here on Earth, and assuming they could overcome the time and distance problems, is that the government is covering up any and all contacts of any kind that might suggest we are being visited by aliens. Our leaders might be concerned about panic control.
I believe, like Einstein, that these laws of physics are the same in most places, including outer space. To me, based on the time and distance restrictions, it would be an unreasonable conclusion to draw to say there are life-like forms flying around in Earth's air space, remaining just out of reach of verification. From the thousands of alleged sightings, you would think that at least one person, somehow, somewhere, could manage some clear and concrete evidence that the visions observed are extra terrestrial objects, not just some fuzzy objects as seen from a distance in an unclear picture frame. I challenge the UFO sighters, give us something more to go on than sightings of balloons, bright lights, toy flying saucers, kites, and people who just may want to get a little attention in their drab life, and by screaming UFO, they get it. Give us the name of one renowned astronomer who has evidence that there are space craft hovering above us. Is that too much to ask?