Welcome to The Nonlinear Library, where we use Text-to-Speech software to convert the best writing from the Rationalist and EA communities into audio. This is: I still think it's very unlikely we're observing alien aircraft, published by dynomight on June 15, 2023 on LessWrong.

Some suggest there might be alien aircraft on Earth now. The argument goes something like this:

(1) A priori, there’s no reason there shouldn’t be alien aircraft. Earth is 4.54 billion years old, but the universe is 13.7 billion years old, and within a billion light years of Earth there are something like 5 × 10¹⁴ stars. Most of those stars have planets, and if an alien civilization arose anywhere and built a von Neumann probe, those probes would spread everywhere.

(2) We have tons of observations that would be more likely if there were alien aircraft around than if there weren’t. These include:

Vast numbers of anecdotal reports from pilots.

Videos that appear to show objects with flight characteristics far beyond known human capabilities.

Senators—with access to classified information—raising concerns about unknown craft near military installations.

Rumors from multiple sources that the government has captured, intact alien craft.

(3) So if we agree that:

the prior probability P[aliens] is pretty high; and

P[gimbal video | aliens] > P[gimbal | no aliens]; and

P[Pheonix lights | aliens] > P[Pheonix | no aliens]; and

P[Trans-en-Provence | aliens] > P[Trans-en-Provence | no aliens]; and

P[2021 Pentagon UAP Task Force report | aliens] > P[report | no aliens]; and

P[UAP Task Force member whistleblower alleges US government has intact non-human vehicles | aliens] > P[whisleblower | no aliens]; and

P[Former intelligence official says four people confirm secret US government program to analyze off-world craft | aliens] > P[official | no aliens],

then don’t we have to conclude that the posterior probability P[aliens | everything] is pretty high?

No.

What I like about this argument

First, I agree the prior probability should be pretty high. Say you just told me:

Okay, say there’s a universe with at least 10²⁴ stars, and most stars have planets, and on one planet somewhere life has evolved and started sending stuff to other planets and has an ever-accelerating pace of technological development.

Then I would agree—the odds that there would be alien aircraft on my planet seem good. It seems like we—or our artificial descendants—might well send aircraft to other planets. So why shouldn’t alien aircraft be here, now?

Second, it takes eyewitness reports seriously. There are a huge number of reports by pilots seeing objects accelerating at insane rates with no obvious wings, control surfaces, or signs of propulsion. It’s a mistake to dismiss these as a product of diseased minds or attention-seeking. There are just too many reports—both civilian and military—sometimes from pilots in different planes at the same time, sometimes invisible to radar and sometimes confirmed by radar from multiple sources. Usually, these people make little effort to draw attention to themselves—we only hear about their observations secondhand. They seem serious and well-intentioned.

(I hesitate to mention this, but I even have family members that report seeing something very strange years ago. I respect their intelligence and I don’t think they have an agenda—they barely talk about it and don’t consider it very important. The story goes that I myself saw it, but I was very young and remember nothing.)

Third, I agree that lots of these observations are very hard to explain. Now, of the 510 reports investigated for the 2022 UAP task force report, more than half had mundane explanations—usually balloons or drones. And some of the leaked videos could plausibly be explained in terms of stuff like rotating glare. But other incidents have apparently been measured by different sensors (e.g. vision, radar) or from multiple locations (e.g. a plane and a ship) simultaneously, and just don’t have a cl...