Ask A Genius 1358: Are UFOs Evidence of Alien Life? Scientific Plausibility and Public Belief

Author(s): Rick Rosner and Scott Douglas Jacobsen

Publication (Outlet/Website): Ask A Genius

Publication Date (yyyy/mm/dd): 2025/04/16

Scott Douglas Jacobsen: Between June 14 and June 24, 2021, the Pew Research Center surveyed 10,417 U.S. adults. The survey found that 65% believe intelligent life exists on other planets. Additionally, 51% consider UFO sightings reported by military personnel as probable or definite evidence of extraterrestrial life. Specifically, 40% said “probably,” 11% said “definitely,” while 47% believe these sightings are not evidence of alien life—furthermore, only 10% view UFOs as a significant national security threat.

Rick Rosner: This is different from things like Sasquatch or flat Earth theories because there is a reasonable scientific basis for believing in life on other planets. As our telescopes have improved, we have learned that most stars have planetary systems, and on average, there is at least one planet per star. It is not uncommon. Many stars, including binary systems, have multiple planets.

Binary star systems can complicate planetary formation but not necessarily prevent it. The Milky Way galaxy alone contains an estimated 100 to 400 billion stars. 

Jacobsen: In the observable universe, there are approximately 2 trillion galaxies, which amounts to roughly 10²³ stars.

Rosner: The Drake Equation allows scientists to estimate how many stars might host planets capable of supporting life. For instance, if 90% of stars have planets, and around 20% of those planets are in the habitable zone—where liquid water can exist—then only a subset will be rocky planets, not gas giants. Rocky planets require specific conditions during system formation, such as certain collision patterns, to form a solid surface.

Life as we know it likely also requires a planetary magnetic field, which usually depends on a rotating iron or metal-rich core to shield the surface from harmful cosmic radiation. Even using conservative assumptions, starting with 10²³ stars and applying these filters, we still have the strong possibility that billions of planets could support life. Assuming Earth hosts the only life in the universe seems statistically unreasonable.

Beyond the Drake Equation, the sheer diversity and randomness in how solar systems form suggest that life-supporting conditions are not uniquely rare. It is plausible that planets capable of sustaining life—whether similar to Earth or different in nature—exist in large numbers throughout the cosmos.

It seems likely that there is life elsewhere in the universe. Once life emerges, the next step is considering the odds that it survives long enough and evolves into intelligent beings capable of developing technology. I think it is probable that millions—likely far more—of planets have hosted technological civilizations, either currently or at some point over the billions of years the universe has existed.

And I believe you cited the statistics—approximately two-thirds of Americans believe in life on other planets. 

Jacobsen: The short version is that 65% believe in intelligent life elsewhere, and 51% believe military-reported UFOs are evidence of that.

Rosner: So, it is reasonable to believe that life exists on other planets. What is not reasonable is the idea that such lifeforms are actively visiting Earth or that we are encountering their spacecraft in our atmosphere.

Jacobsen: One slight trend is noteworthy: In 2012, a National Geographic poll found that 36% of Americans believed in UFOs. By 2023, an Ipsos poll recorded that number at 42%. It was not a massive shift, but it was still a noteworthy increase.

Rosner: Now, I do not believe that UFOs are alien spacecraft visiting us. First, there is no evidence—and no theoretical basis within physics—to suggest that any object can travel faster than the speed of light, or even near it, in a practical spacecraft.

Light itself is the only thing we know that can travel at light speed. In theory, one might imagine sending pulses of light that could be used to assemble something elsewhere, but even that seems highly implausible.

Technologically, it is tough—bordering on impossible—to send any spacecraft at even 10% of the speed of light. Moreover, at those speeds, any impact with debris would be catastrophic. Even a dust particle could cause an explosion equivalent to a nuclear detonation unless the craft has extremely advanced shielding or an electromagnetic deflection system.

However, for the sake of argument, let us say an advanced civilization managed to build spacecraft that travel at 20% ofthe speed of light. Even then, stars are separated by several light-years. Our closest stellar neighbour, Alpha Centauri, is about four light-years away. At 20% light speed, reaching it would still take 20 years.

This raises serious doubts about the practicality of interstellar visitation, especially at a scale that would lead to the kinds of encounters described in UFO reports. The odds that a technological civilization not only exists but has developed interstellar travel, chosen to visit Earth, and done so repeatedly in ways we cannot reliably detect or document—all of that seems extraordinarily improbable.

Let us say, for the sake of simple math, that one in a million stars has a technological civilization orbiting it. That would mean, on average, the nearest such civilization is about 100 stars away—which translates to roughly 400 light-years from us. Even if a spacecraft could travel at an implausibly high speed—say, 20% of the speed of light—it would still take 2,000 years to reach us.

And that assumes extremely optimistic engineering capabilities. Maybe such a civilization could build robotic probes that search for radio signals or signs of life—machines that can replicate themselves using local materials. These are called von Neumann probes. The idea is that they could spread through the galaxy exponentially, building more probes as they go.

However, that seems like a dubious and wasteful endeavour. Would a civilization want to announce itself across the galaxy that way? And even if it did, at 20% light speed—which, again, is highly unlikely—it would still take thousands of years to reach us. More realistically, 2% of light speed would be achievable, if at all, which would make the travel time between civilizations about 20,000 years.

At that point, any form of contact becomes incredibly inefficient and uncertain. If civilization is advanced enough to build and launch interstellar spacecraft, it is probably also advanced enough to simulate alien civilizations from home. Within the next century, we will likely be able to simulate the entire process of evolution, from single-celled organisms to intelligent beings and technological societies—all without ever leaving our planet.

So, it seems unlikely that a rational civilization would physically visit us. The time, energy, and resources required would be astronomical, and for what? To find yet another primitive, chaotic civilization?

I’ll admit one possibility—an irrational or eccentric civilization might do it. Maybe they have an enormous arts budget and decide to fund some massive, absurd gesture, like spending the equivalent of a quadrillion dollars and 100,000 years to send a spacecraft to some random planet just for curiosity or spectacle.

There was a movie—I think it was Explorers—in which a group of kids made contact with alien visitors using some kind of tech. At the end of the movie, it turns out the aliens were also just kids who stole a spaceship—that scenario I can buy: some reckless, immature civilization deciding to do something this ridiculous.

However, most civilizations would not be that reckless. The likelihood of any civilization spending such vast resources to reach us seems extremely low. I do not believe civilizations are actively scanning the galaxy to make friends. More importantly, there is no universal “start time” for civilizations. They do not all arise at once—some begin early, others late. Timing alone makes synchronous contact improbable.

Civilizations can arise billions of years apart. If you send spacecraft out into the galaxy, you could easily encounter a civilization two million years older than yours—and such a civilization might not want you to exist. If they are much more advanced, they could easily obliterate you. So, I do not think civilizations are casually sending out spacecraft, with one possible exception.

Jacobsen: What is the exception?

Rosner: Nearly every galaxy we have observed—probably over 99%—has a supermassive black hole at its center. There is a chance that computational capacity increases in the environment surrounding a supermassive black hole. Time dilation, gravitational compression of space, and other relativistic effects might allow for faster or more efficient computation.

The long-term trajectory of advanced civilizations is to become computation-intensive. If true, the galaxy’s center might be the optimal place to go. It could offer more excellent computational resources, forming a compact, high-efficiency computational hub.

Once a civilization reaches a certain level of physics and technology, it figures out that the galactic center is where it should go. That is where the “action” is in terms of information processing. But we are nowhere near the center.

We are way out on the galactic outskirts. The Milky Way is roughly 100,000 light-years in diameter, and we are located about two-thirds of the way from the central black hole to the outer edge of the visible disk. We are in a relatively quiet and remote region.

Given that, it is unlikely anyone is coming out to visit us. We would also unlikely encounter civilizations travelling inward toward the center, especially within any reasonable time frame.

Over billions of years, if the idea is accurate—that civilizations tend to migrate toward the galactic center—some might indeed pass by us. Maybe some even develop technology to move massive objects closer to the center, like entire planetary systems. However, the odds of such civilization passing near us within a million-year window are extremely low.

And we could only observe space and atmospheric phenomena briefly. Our ability to monitor the sky meaningfully spans just a few hundred years. If you include ancient civilizations like the Chinese keeping astronomical records around the time of Jesus, that could stretch to a couple thousand years.

However, the odds that a passing civilization happened to intersect with us—within the tiny sliver of time during which we have been able to observe anything—are astronomically small. The chance that an advanced civilization would visit or even be seen by us in the last two thousand years is minuscule.

Civilizations would be spread too far apart in space and time. For any real chance of contact, civilizations must send out long-lasting sentinels across vast distances and epochs to increase the likelihood of discovering others. However, I have already argued that such an approach may not be desirable or sustainable.

Jacobsen: So you are saying that, in that context, believing UFOs could represent alien contact is less unreasonable than other fringe beliefs?

Rosner: Yes. Compared to things like ghosts, yetis, or flat Earth theory, the idea of alien life has at least some grounding in scientific plausibility. There is reasonable astrophysics behind the possibility of life elsewhere, even if actual contact remains unlikely.

However, here is the issue—there is very little serious analysis accessible to the general public, or even to most scientists, regarding the probabilities, timescales, or distribution models of extraterrestrial civilizations. Most people do not encounter discussions of average distances between civilizations or timelines for technological development. That kind of modelling probably only occupies the minds of a few hundred or maybe a thousand specialists in the U.S.

So, you can be rational and still hold somewhat unreasonable beliefs about alien contact due to a lack of exposure to this thinking. That is different from people who believe in the flat Earth. One is speculative; the other is delusional.

Jacobsen: Do you have any final thoughts before we wrap for the night? There is more to say—government acknowledgments, secrecy, eyewitness testimony, scientific plausibility, and technological constraints. I’ve got notes on all of that.

Rosner: From what I understand, UFO sightings didn’t really take off until the 1950s when UFO magazines began circulating—selling stories and speculation about sightings. Before that, people did not report them. So there’s an argument that the idea had to be introduced before people began “seeing” them.

You could argue that people were becoming more aware or better trained to spot them. However, I think it is more likely that the magazines trained people to misinterpret ordinary phenomena as UFOs. It is suspicious that the rise in sightings coincided directly with the rise in cultural exposure to the concept.

All right, thank you again.

Jacobsen: Take care.

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