I am referring to alien UFOs; reports claimed to be of aliens and their ships.

Are UFOs real? Are people abducted by aliens who then perform experiments on them?

Why would anyone even consider believing in UFOs? I think it is the incredible number of reports with photos and videos; and reports from abductees who get cancer in the exact spot of their body where the aliens performed the experiments.

Certainly some (many? all?) reports of UFOs are fake. But lets consider the implications if many of them are real:

Consider the ships. There are thousands upon thousands of different kinds of ships having different characteristics. So if UFOs are real, we are being visited by not just one alien species, but many thousands from many thousands of distant worlds.

And why have they not yet released a pathogen to wipe out humanity so they can take possession of our planet? After all, there have been UFO sighting for thousands of years.

Consider the living conditions inside a ship. They are smallish, meaning, the aliens are either small, or cramped. And they need supplies of energy and food and water and whatever else they need to survive.

The physics of the universe requires that: (1) energy is needed to enable physical interactions, and (2) all there is as the building blocks of all life (even alien life) is atoms and electrons and quantum mechanics and energy and etc.

Do the aliens land somewhere on the earth or moon to recharge and to get more resources of chemicals? If so, why do we not find many thousands of little mines all over the earth?

Based on Einstein's theory of relativity: (1) nothing can travel faster than the speed of light, and (2) travelling very fast increases the object's mass and, therefore, the required energy to accelerate the object to that high speed. A consequence of this is that these aliens have been travelling in their tiny ships for thousands or millions or hundreds of millions of years. Why would anyone want to do this?

Also, consider the energy requirements for these ships. Where in their tiny ships do they store the immense quantities of fuel needed for such fast long trips? And ditto for food and heating and etc.

Consider that some of the reports of UFO sightings involve the ships moving in ways that defy the laws of physics. Do we really want to consider the possibility that the physics for these aliens is different?

There are various general explanations for all otherwise unexplained UFOs, such as ball lightening (which can move unpredictably and make fast turns), swamp gas, defects in cameras or lenses, and hoaxes.

Some devote their time and energy to debunk various UFO reports; to demonstrate alternate explanations for what was reported. But with so many UFO reports, how can anyone possibly debunk them all? And some of these reports may not be able to be satisfactorily debunked at all. Are these therefore true? (This is horrible logic, to assume that a report that can't be explained is therefore true. If I claim I saw fairies and you can't prove me wrong; does this mean fairies exist? Ditto for unicorns, gremlins, and etc).

A final consideration: alien civilizations would require sufficient energy and resources to develop their science which would be vastly superior to ours, and to invent and build their ships that have capabilities beyond anything we can even imagine. Compare the requirements for this with earth:

We are likely to run out of cheap fossil fuels long before we can manage to build hundreds of ships with the necessary capabilities so that, we ourselves in the far future someday become aliens to some other fledgling civilization of a far distant planet somewhere.

And consider the source of our fossil fuels: The universe has only galaxies with their stars and planets; and only planets orbiting stars have the environment and resources necessary for life to develop (no life inside of stars or black holes, or in empty space).

On earth, we happened to have a period in the past in which huge numbers of organisms died and were buried in just the proper geological condition so that, millions of years in the future, we of today would have fossil fuels. But these will soon run out, lasting only a couple of hundred years total (out of hundreds of millions of years of multicellular life on earth).

It is unlikely that a miraculous form of sustainable energy will be discovered or invented soon that will supply sufficient energy for us to continue on into the future and to someday ourselves become aliens. Rather, it is highly likely we will experience global civilizational collapse once the oil runs out, and humans will descend into a permanent dark age having farming using horses, and using trees for fuel and charcoal.

For those planets having life, perhaps some of them would have a similar geologic history as earth, and there would arise a species of life similar in capabilities to humans. But eventually, just as for us here on earth, their easy cheap energy resources would run out. Likely, every world like ours would come to the same conclusion — permanent global civilization collapse.

Another explanation for UFOs given by Christians is: that they are demonic apparitions. (Does that mean that a particular unexplained UFO sighting is demonic until someone discovers another explanation, and then it is no longer demonic?)

But if you claim that anything you can't explain is merely a demonic apparition, you have rendered scientific knowledge and investigation useless. Why seek non-demonic explanations for anything if everything is demonic?

So my conclusion is, therefore, that there are no alien UFOs; every report has a naturalistic explanation. (But we may not be able to determine the explanation.)