For decades, the U.S .government has dismissed reports of unidentified flying objects, known more familiarly as "flying saucers."   Pilots learned that reporting what they saw could end their careers.  Their sanity could be called into question.

That policy actually created a threat to national security.  Military pilots who were intimidated from reporting what they thought were extraordinary airborne objects could just as easily have been discouraged from reporting actual enemy threats from communist or terrorist nations. 

With the advent of advanced radar and optics, and with millions of people carrying video-capable cell phones, the danger to national security has given way to the far lesser danger of embarrassment to the government.  It may be only a matter of time before coordinated sightings by radar, pilots, and civilian witnesses on the ground become so widespread that official denials will be seen as ludicrous.

Moreover, when the government tells thousands of its citizens, "You did not see what you saw," the trust in government will erode dangerously.

Now that we have admitted that there is a problem — the first step toward solving it — there arises the question: just what the heck is it that so many of our friends are seeing?

The first answer that pops into the minds of many people is space aliens — intelligent life from technologically advanced planets far, far away.

While this answer is not entirely implausible, there are very good reasons to doubt it.  I call this answer the "Superman theory."  "Look up in the sky — it's a bird, it's a plane," it's an intelligently piloted spacecraft.

Birds and planes are so familiar to us that when we see strange objects in the sky, we tend to classify those objects as something within our experience:  birds, planes, stars, meteors, perhaps even "swamp gas."  Flying saucers may not be in our actual daily experience, but most people have some concept of what they might be.  If you ask them, they will likely answer, "manned" space vehicles.

We now can add drones to our list of possibilities as to what UFOs are.  If they are unmanned drones, then, we must ask, are they coming from Iran or from other planets?

Astronomers and other scientists have, for years now, been searching for signs of technological civilizations on other planets.  The discovery that exo-planets are a common feature of the galaxy makes that search seem worthwhile.  So far, however, the search has been fruitless.  We have made the same mistake: to expect the unknown to conform to our experience of the known.  Because our technology broadcasts (unintentionally) radio waves into space, we somehow expect that alien technologies will do the same.  If so, we should detect their transmissions.  Why haven't we?  It is because they might transmit for three or four hundred years, but that is a tiny slice of time, compared to the estimated age of the galaxy.  We are not finding such signals.  We may never.   Any advanced aliens out there have likely moved far beyond that stage.

Experiments in our own laboratories suggest that emerging technologies may soon render electro-magnetic spectrum communications inefficient and obsolete.  Such topics as quantum entanglement are at present considered "far out" physics, but they are, in fact, based in solid science.

Even putting all that aside, there is one glaring inconsistency in most UFO sighting reports:  we can see them.  That should not be possible.  If the space aliens possess technology so advanced that they can cross trillions of miles of interstellar space, with all its hazards, then surely, they possess stealth technology that can make them invisible to all our detection methods.  Even here on Earth, we are capable of amazing stealth, not only in radar, but even in the visible light spectrum.

The inconsistency is that UFOs behave as if they wish to avoid detection, yet, at the same time, they seem clumsy in those efforts.  We see them.  They "run away."  None of that makes sense.

Finally, there is the question: if there are space aliens in our atmosphere, are they hostile?  If they are, then we are helpless against them.  Science fiction movies glamorize heroic battles to defeat the aliens, but we cannot even defend the planet against a potential swarm of giant meteors.  Any advanced aliens could easily redirect a few thousand asteroids to crash into our planet with devastating effect, while keeping themselves at a safe distance. 

What are the UFOs, and why are they here?  The bottom-line answer: they are something we cannot begin to imagine.  Their reasons, if any, are hopelessly inscrutable.