The known universe is a very big place and our solar system is not even a speck of dust in this vast cosmos. To assert that the human race is the only intelligent life in this gargantuan universe is simply preposterous, as most religions try to do in their abject ignorance.
The chances of intelligent life elsewhere in the universe are very high and in fact the odds are strongly in favour of other forms of life being as clever, or much more advanced than the human race. Nevertheless, the current physical laws of this universe seem to operate the same everywhere, so the one constraint against successful intergalactic travel is simply that as far as we know, nothing can travel faster than 300,000 kph, the speed of light.
So unless some amazingly advanced civilisation managed to get around this physical constraint and develop Faster-Than-Light transportation, the distances between star systems is too vast for intergalactic travel. Unless the human race is faced with a civilisation so advanced that it has conquered the restraints of physical time and space, then we can safely say that we have not been visited by aliens - yet.
Area 51 is the slang name for a US military base located in the southern portion of Nevada, about 140 km northwest of Las Vegas. Located on the southern shore of Groom Lake, it is supposedly a developmental and testing site for experimental aircraft and weapons. That US military base has always been the centre of attention regarding alien visitations, with rumours about alien spacecraft and even alien bodies being stored there by the US military. This of course is nonsense and the myth was exposed recently by an engineer who worked at this base for many years.
According to Thornton Barnes, a former engineer at Area 51, the reported sightings of UFOs in the 1960s were really light flashes from extremely high-speed experimental jets and aliens are not stored at the super-secret facility. Barnes stated that spy planes being tested at over 2,000 miles per hour at altitudes of 90,000 feet would produce flashes of light that people on the ground thought were UFOs.
Barnes stated that the myth of UFOs flying over the USA and aliens being stored at Area 51 actually helped them keep the classified activities of the military centre secret from the public. He said, "We considered it to be a bonus. The UFO sightings made it easier to conceal what we were doing." In fact, Barnes said, "Area 51 was the most boring place I ever worked."
Barnes made the statement, "We were the UFOs," referring to his and other pilots' activities of flying super-fast jets over the sky of the USA during the early reporting of UFOs. And in reality, that is exactly what they were at that time - 'unidentified flying objects', as to whether they came from Earth or outside of Earth, but definitely 'flying objects'. He added, "People have an imagination - we laughed at it."
In the 1960's there was a rash of UFO sightings by Americans. The US Air Force (USAF) ran an investigative operation called Project Blue Book, where USAF personnel would carefully interview people who claimed to have seen UFOs and investigate alleged sightings of alien spacecraft. In fact, there was even a television series based on this called Project UFO.
In January 2015, the CIA finally admitted that the US government ran disinformation campaigns such as Project Blue Book to cover up the development of the Lockheed U2 high altitude spy plane and the SR-71 Blackbird superfast reconnaissance aircraft. The amazing Blackbird still holds the outright aviation speed record to this day - over 50 years after it came into operation - an amazing feat in itself.
After Colonel Gary Powers was shot down over the USSR in his Lockheed U-2 spy plane, the USA realised that the Soviets had finally developed missiles that could reach the high altitudes where the U-2 operated, so the Americans had to develop a spy plane that could fly faster and much higher than the U-2. All spy flights over the USSR were cancelled until a solution was found.
To supersede the U-2, famed aeronautical designer Clarence 'Kelly' Johnson and his team developed the most amazing aircraft, the Lockheed SR-71 Blackbird, that could fly at over three times the speed of sound at an altitude of over 90,000 feet. The Soviets had absolutely nothing in the way of missiles or aircraft that could reach that altitude or that speed. But the problem for the Americans was that they did not want the Soviets to know about the SR-71 and that they were going to resume secret spy flights over the USSR.
The SR-71 operated primarily out of Beale Air Force Base in Marysville, California and always at night. Locals in adjoining states would see objects travelling through the night skies at amazing speeds, as the SR-71 was put through its paces. Not knowing that the USA now had an aircraft with such amazing performance, people assumed that what they saw were UFOs.
So the USAF decided to run a disinformation campaign to discredit anybody who reported seeing the SR-71 and tried to convince them that they had actually seen UFOs. This campaign, bolstered by the Project UFO TV show, not only fooled the American public and furthered their belief in UFOs, it also achieved its primary objective of fooling the Russians for many years. The SR-71 made countless flights over the USSR, gathering vital intelligence for the Americans and the Russians had absolutely no idea of this for many years.
However, the public hysteria about UFO's, promoted largely by the USAF and the media, caused many people to report UFO sightings, even if they actually saw nothing. Stories of alien abductions abounded, science fiction writers had much material to call upon and Hollywood made hay with ridiculous science fiction movies about alien invasions and little green men from Mars.
But as far as producing one scrap of evidence to show that aliens from another planet or galaxy had visited Earth, nothing so far has been seen.
Many people have cashed in on promoting their cockamamy theories about aliens among us. There are more than enough people on this planet who swallow any ridiculous story without foundation - religious beliefs prove that, so extracting money out of such gullible fools is not very difficult for unscrupulous shysters.
David Icke, an ex-English soccer player, had for years been promoting a theory that shape-changing alien lizards have taken the place of world leaders and important figures and they are secretly manipulating the affairs of this planet. Icke has made a lot of money out of selling his books and recordings about this nonsense and there are many people who really believe that the President of the USA, the Prime Minister of Britain, the Russian, Chinese and even the Australian leader are all alien lizards, even if some of them do act like reptiles and resemble them.
Any alien civilisation that could develop spacecraft that travelled much faster than light, avoided the time dilation properties of such speed and managed to come from distant planets to Earth, would look upon the human race as nothing more than microbes or at the most, cattle. So why would such advanced alien civilisations with such amazing technology try to conceal themselves from us, or even worse, assume the personas of our leaders and manipulate world affairs in secret?
The truth is that such advanced alien races would come here and do whatever they wanted in full view of us, as we would be nothing to them whatsoever. It is doubtful if such aliens would even bother to negotiate with us. Do humans negotiate with lizards in the jungle? Of course not - and we would be lower than lizards to an advanced alien civilisation that had the technology to travel intergalactically. They would not skulk around hiding from us or visiting this planet for millennia without revealing themselves and to think that they would lurk around, too scared to show their faces (if they had faces) is simply ridiculous.
Here is an explanation for all those UFOs that were reported by motorists driving across the Nullarbor Plains from Adelaide to Perth from a retired commercial charter pilot personally known to me.
To imagine that the human race is the only intelligent life in the universe is sheer idiocy, yet many religions and religious leaders postulate exactly that, which shows how completely stupid they really are. Nevertheless, if other civilisations exist and have the ability to travel interstellar distances and they come to our humble speck of dust called Earth, we would certainly know about it in very short order, hopefully if such civilisations did not consider us to be vermin and annihilate us.
So until we actually see such aliens instead of believing raving idiots, conmen and Hollywood scriptwriters, then we can safely say that aliens have not landed on Earth - yet. One wag said it very succintly: "The surest sign that intelligent extra-terrestrial life exists in the universe is that they have deliberately avoided making contact with the human race."