If you want a lack of sense, the counter-argument to the time-frame conundrum is to postulate an essentially immortal civilization that sends out self-repairing and self-creating automated spacecraft to scour the galaxy, or even universe. Therefore the passage of time is irrelevant; the craft - often called robots - can travel for millions of years and beam their results home.
In some variants, the robots can sense the presence of civilizations and send down investigating subcraft, which are the UFOs that get spotted.
And the motherships are NEVER spotted from Earth, ever, in any fashion, and the approach of the smaller ships either, even though we can see many asteroids that are going to come close.
On a more practical note, I once saw a “fantastically swift UFO.” A plane was taking off from a large airport toward the setting sun and reflecting a good amount of light back to me. It moved extremely slowly in angular velocity, so it “hung in the air”. Then it changed its angle, and “disappeared.” Wow, what great speed that UFO demonstrated!!!
Not to get off topic, but you would describe that person as a “experiencing a miracle” or “possessed” or possible a “lunatic” to convey the concept that reality is actually very different from what they are experiencing, possibly being fabricated for them by a wizard or God (or gods).
In fact, I would say that UFOs, virtual reality, multiverses, gods and whatnot all feed into a very real human need to rationalize and explain a universe that we fundamentally perceive to be more complex than we understand. Possibly more complex than we will ever be able to understand.
Unfortunately, while intelligent life may, and probably is real elsewhere in the universe, for another species to visit Earth required them to possess one or more technologies or biological properties that we would consider, for lack of a better term, “magic”.
Immortality
Safely freeze themselves for centuries or millenia
“Generational ship” that can support a self-contained civilization indefinitely
Faster than light travel
Safely manufacture and handle exotic energy sources (like antimatter) in sufficient quantities
Ability to create stable wormholes, warp space or otherwise manipulate physics
Self replicating, self repairing machines
Complex machinery capable of operating reliably in the most extreme environments for longer than machines, if not human civilization have actually existed
People toss these ideas around as if they are realistic engineering capabilities based on any current or speculative human technology or science. In reality, any of these capabilities are literally as plausible as saying “a wizard lives in our engine room”.
As Exapno_Mapcase pointed out above, only the last two technologies are necessary. If we could make long-lasting, error-free, competent self-replicating probes we could cover the galaxy in finite time. The magic could come in designing and building the first one.
Here’s a fairly detailed, recent discussion of some of the problems, initiated by a specialist in materials science and engineering.
Marinko suggests that there would be some resources that could not be replicated in the destination system, such as complex technologies that require rare elements and or microscopic circuits. He calls these elements ‘vitamins’ and says that these resources would need to be carried on-board the spaceship. Self replicating probes would not be possible if the requirement for ‘vitamins’ could not be met.
It seems likely that no self-replicating probes could be successful until the problems of ‘vitamins’ are solved, as well as the problems of self-repair and safe data storage that can resist disruption by cosmic rays and age. We are many centuries - possibly many millenia - from solving these problems.
One solid point makes a point.
Two solid points make a line.
Three solid points make a triangle.
Four solid points make a square.
No solid points make a belief system.
I suspect there are some UFOs that are very experimental aircraft testing different concepts. Pre- prototype. Computer modeling and wind tunnels are great but isn’t there a point where you have to build a full size one and see what it does in the air, at altitude and speed?
There were lots of single-panel cartoons about them, too, but mostly in black and white. I suspect the “little green men” idea got another boost when Frank Kelly Freas’ painting illustrating Fredric Brown’s great short novel Martians, go Home! in the September 1954 issue of Astounding Science Fiction. It was (much later) used as the cover for the paperback edition.
Apparently at some point the USAF took seriously enough the idea that reports of disk-shaped aircraft might be experimental disk-winged airplanes that a number of test versions were built.
I think it was the other way around. The military supported the idea of “flying saucers from outer space” to divert others from looking inward instead of outward.
Disk aircraft were tested before WWII and the Germans were probably interested in the concept, as they were in every other type of experimental aircraft. Some speculate that the foo that the foo fighters fought might be circular or even spherical shaped craft, but no evidence appears to support this.
After the war the U.S. military definitely funded a secret project with the Canadian aircraft firm Avro Canada. A circular craft called the Avrocar was built and tested in the 1950s before the military cut its losses on something that could never work. (One craft got three feet off the ground.) Again, though, the entire aircraft industry, civilian and military, was furiously churning out radically new designs throughout that period. The Avrocar was part of an effort to create VTOL (Vertical Takeoff and Landing) craft that extended into flying cars, which is where I got into them.
The flying saucer craze needed no help from the military. People went crazy all on their own. My reading suggests that the military was completely embarrassed by these reports. Why couldn’t they be found? Because they didn’t exist was not an acceptable answer. So they downplayed rather than boosted the craze. Is that the reason why UFO sightings peaked in the early 50s and then faded as a public fad for more than a decade? Possible but unlikely. More likely is that people moved on to the real world space race as a obsession.