June 25, the U.S. Department of Defense will release a report on UAPs (unidentified aerial phenomena), a term now preferred to UFOs (unidentified flying objects).

A number of unusual sightings since 2017 prompted Congress to ask for a report. According to space industry reporter Leonard David, the justification is airspace safety and control, not an effort to support or refute claims about alien spacecraft: “The report’s firmest conclusion, it seems, is that the vast majority of UAP happenings and their surprising maneuvers are not caused by any U.S. advanced technology programs.” That might mean, for example,

UAP are entirely homegrown products of revolutionary and clandestine technological advances, whether by other countries now challenging American airspace or by the U.S. itself as part of some supersecret domestic program meant to detect flaws in the nation’s defenses? The mind boggles.

Leonard David, “Experts Weigh In on Pentagon UFO Report” at Scientific American (June 8, 2021)

Reason enough for investigation. The UFO rumor mill is powered, in part, as David notes, by the military habit of assuming that everything is classified unless otherwise noted. That naturally creates the impression that “the Pentagon is hiding something.”

Of course, that’s true. The Pentagon is always hiding something! What not necessarily true is that whatever the Pentagon is hiding has any intrinsic importance for the rest of humanity. But we shall see.

Recently, a number of experts offered opinions as to whether aliens exist. Four out of five experts polled at The Conversation believe that they do: Here’s one pro from planetary scientist Helen Maynard Caseley:

I’m of the opinion that it’s only a matter of time before we find something that resembles biology somewhere other than on Earth. This is because we’re increasingly finding various potential pockets in our solar system that may be hospitable to life as we know it. For instance, consider the under-ice oceans of Europa and Ganymede (two of Jupiter’s large moons): these are places where the temperature is just right, there is access to water and to minerals, too. Then again, that’s viewing things with a very Earth-like lens, and of course alien life could be very different to our own.

Chynthia Wijaya and Noor Gillani, “Do aliens exist? Five experts give their opinions” at The Conversation (June 13, 2021)

Only one way to find out. Meanwhile, the con, from astrobiologist Martin Van-Kranendonk:

If we use purely empirical data and assume the question refers to any type of life outside of Earth that is not related to human activity, then the answer — as far as we know — must be no.

But, of course, our knowledge relating to this question is finite; we have not investigated every corner of the universe for signs of life and we do not even know what may constitute life in another chemical system, as there is no agreed-on definition of carbon-based life even here on Earth.

Chynthia Wijaya and Noor Gillani, “Do aliens exist? Five experts give their opinions” at The Conversation (June 13, 2021)

Van-Kranendonk has a point. It’s not clear whether viruses here on Earth, for example, should be considered life forms. Depends on one’s definition of life.

Some, including physicist Mark Buchanan, hope we never find out. Citing a group of astronomers, he wrote,

“Chances are, we should all be grateful that we don’t yet have any evidence of contact with alien civilizations,” Buchanan writes.

“Attempting to communicate with extraterrestrials, if they do exist, could be extremely dangerous for us.

“We need to figure out whether it’s wise — or safe — and how to handle such attempts in an organized manner.”

Jon Lockett, “Alien contact could ‘end life on Earth,’ scientists warn” at New York Post (June 14, 2021)

Well, we can safely predict that June 25 will see a flurry of renewed interest.

In the meantime, you may also wish to read current theories as to why we don’t see extraterrestrials:

1. Are the Aliens We Never Find Obeying Star Trek’s Prime Directive? The Directive is, don’t interfere in the evolution of alien societies, even if you have good intentions. Hence the Zoo hypothesis. Assuming the aliens exist, perhaps it’s just as well, on the whole, if they do want to leave us alone. They could want to “fix” us instead…

2. How can we be sure we are not just an ET’s simulation? A number of books and films are based on the Planetarium hypothesis. Should we believe it? We make a faith-based decision that logic and evidence together are reasonable guides to what is true. Logical possibility alone does not make an idea true.

3. Did the smart machines destroy the aliens who invented them? That’s the Berserker hypothesis. A smart deadly weapon could well decide to do without its inventor and, lacking moral guidance, destroy everything in sight. Extinction of a highly advanced civilization by its own lethal technology may be more likely than extinction by natural disaster. They could control nature.

4. Researchers: The aliens exist but they are sleeping… And we wake them at our peril. The Aestivation hypothesis is that immensely powerful aliens are waiting in a digitized form for the universe to cool down from the heat their computers emit.

5. Maybe there are just very few aliens out there… The Rare Earth hypothesis offers science-based reasons that life in the universe is rare. Even if life is rare in the universe, Earth may be uniquely suited to space exploration, as the Privileged Planet hypothesis suggests.

6. Does science fiction hint that we are actually doomed? That’s the implication of an influential theory, the Great Filter hypothesis, as to why we never see extraterrestrials. Depending how we read the Kardashev scale, civilizations disappear somewhere between where we are now and the advanced state needed for intergalactic travel.

7. Space aliens could in fact be watching us. Using the methods we use to spot exoplanets. But if they are technologically advanced, wouldn’t they be here by now? The Hart-Tipler conjecture (they don’t exist) is, of course, very unpopular in sci-fi. But let’s confront it, if only to move on to more promising speculations.

8. Is the brief window for finding ET closing? According to some scenarios (the Brief Window hypothesis), we could be past our best-before date for contacting aliens. Of course, here we are assuming a law of nature as to how long civilizations last. Can someone state that law? How is it derived?

9. What if we don’t see aliens because they have not evolved yet? On this view, not only did we emerge during a favorable time in the universe’s history but we could end up suppressing them. The Firstborn hypothesis (we achieved intelligence before extraterrestrials) lines up with the view that humans are unique but sees that status as temporary.

10. The aliens exist—but evolved into virtual reality at a nanoscale. That’s the Transcension Hypothesis, the latest in our series on science fiction hypotheses as to why we don’t see extraterrestrials.
    On this view, after a Singularity the ETs become virtual intelligences, exploring inner space at an undetectably small scale.
11. Is intelligent life in the universe living in interior oceans of planets and moons? The Ocean Planets Hypothesis is that intelligent beings may flourish in the interior oceans of the moons of gas giant planets — or within exoplanets — but they are trapped there.
    If intelligent life forms are trapped in the interior oceans of rocky moons and planets, Earth is a special planet—much better suited to space exploration.
12. Is real-world space travel just too daunting for ET? That’s the Percolation Hypothesis as to why we don’t make contact with aliens. They can’t overcome the laws of physics, any more than we can. If there is a purpose behind the universe, maybe the aliens and we weren’t intended to meet. That’s worth considering, given the physics barriers.

13. The Aurora Hypothesis: ET could risk only rare contact with us. Given the difficulties and risks of space travel, extraterrestrials with advanced technology may have visited Earth only one in a million years, researchers say. After centuries of modern science, we are just now looking for fossil bacteria on Mars, not without risk. ET may be in the same position.

14. The Dark Forest Hypothesis: What if the extraterrestrials can’t afford to take chances with us? That’s the Dark Forest Hypothesis, riffing off the title of one of famed Chinese sci-fi author Liu Cixin’s novels. The Dark Forest Hypothesis assumes that we can use sociology to figure out what extraterrestrial intelligences might be like or might want. But can we?