Here’s what looked like a fun, occasional book: a popular summary of a popular topic that’s well-known among followers of science and of science fiction. I bought it to glance through, not necessarily read through. But then I heard the author do an interview on Science Friday a couple weeks ago – here’s the link — and heard him make a couple key points that I wasn’t aware of. So I picked up the book and read it after all.

(Harper, Oct 2023, xviii + 215pp including Notes, Recommended Reading, and Index)

I read his previous book, LIGHT OF THE STARS, back in 2019, which addressed a somewhat more specific topic: what the existence of alien worlds might tell us about humanity’s future. (Quite a lot, when you think about it in the sense of an existence proof.) Here’s that review. He touches on this topic at the very end of this book.

The new book is more pop oriented. When people think about aliens, in what sense do they think about them? The unavoidable answer he explores is: UFOs. Are they ‘real’? Meaning, are UFOs ‘really’ alien spaceships? If so how did they get here, and so on?

Secondarily, he explores what aliens (setting aside UFOs) might be like, given our understanding of the stars and the planets that might be orbiting them; of evolution, of biology. Here’s where the new discoveries of the past couple decades have an impact. I’ll save that for last.

The detailed table of contents can pretty much serve as an outline of the book. So I’ll adopt that, then add comments.

Ch 1: How Did We Get Here?

Debates throughout history; the Fermi Paradox (1950); Drake’s Equation (1961); UFO sightings since Kenneth Arnold in 1947; aliens in pop culture since the 1950s.

Ch 2: So How Do We Do This?

Project Ozma; the idea of habitable zones; Dyson spheres; the Kardashev Scale.

Ch 3: WTF UFOs and UAPs?

The giggle factor: how derision of UFOs almost derailed SETI; hoaxers; unexplained cases; how UFOs became UAPs; what a scientific study would look like.

Ch 4: What If They *Are* Aliens?

How they would achieve interstellar travel; what kind of technology they might have; the notion of interdimensional gateways; why would they be here at all?

Ch 5: Where to Look for Aliens

Abiogensis and the Miller-Urey experiment; the discovery of ocean moons in our own solar system; the revolution in the discovery of exoplanets; the enigma of super-Earths; snowball worlds and ocean worlds

Ch 6: The Cosmic Stakeout

Biosignatures; technospheres and noospheres; technosignatures; alien megastructures; pollution and aliens skies; solar system artifacts; ‘Oumuamua; terraforming

Ch 7: What Will We Fine When We Find Aliens?

Carbon-based? Humanoid? Will we be able to talk with them? Would their ethics be similar? Will biology someday give way to technology? How to think about million-year-old civilizations

Ch8: Why Aliens Matter More than You Think.


Here are the key points I took away. I’ve been vaguely aware of the discoveries of hundreds, even thousands, of exoplanets by the Kepler observatory over the past two decades, but haven’t paid close enough attention to the broad conclusions of that search, which are, according to Frank:

  • Virtually every star examined by Kepler has planets. Usually a similar number to those in our solar system, but virtually never in the same arrangement, where in our solar system the small rocky planets are close in to the sun and the larger gaseous planets are farther out. Many different assortments have been found. (Granted, I imagine Kepler is looking only at stars that might have Earth-like planets – avoiding stars too old or too young – but even so, this result is impressive.) And about one in five such stars has a “habitable” planet.
  • This has great implications on Drake’s Equation, in which one factor in the calculation of the likely number of intelligent species in the galaxy is the proportion of suitable stars that have planets. This factor is now virtually 1, greatly increasing that likely number of species. Similarly, these discoveries inform Stephen H. Dole and Isaac Asimov’s analysis in PLANETS FOR MAN, from 1964, reviewed here, which is a subtler consideration of Drake’s terms.
  • The most common size of planet is the so-called super-Earth: like Earth but larger. In our solar system the ratio of the biggest rocky planet to the smallest gaseous planet, Earth to Uranus, is 1:14. The super-Earths lie within this range. They’re more common than planets Earth’s size. That means we might well discover ETs on those planets that would have higher gravity with attendant differences in biology and even technology.

Two more interesting points:

  • The big shift in trying to detect alien intelligences over the past 60 years has been from sending, and trying to detect, radio signals – this is what Project Ozma was all about, with those radio telescopes in Aricebo, the Very Large Array in New Mexico, and the array in Owens Valley in California, visible from Highway 395 by travelers to the Mammoth ski resort – this is what James Gunn’s novel THE LISTENERS (my Black Gate review here) and Carl Sagan’s novel CONTACT (here) were about – to the more passive attempts to detect “biosignatures” and “technosignatures,” indirect evidence of life or industrialization on those exo-planets, even via pollution in their atmospheres. Another generation of space telescopes will be necessary to detect most of those.
  • Frank makes the interesting point that climate change may be an unavoidable consequence of developing technology.

And of course the biggest takeaway, which Frank’s previous book directly addressed: the actual discovery of alien intelligences on other planets would would give humanity confidence that we might overcome our current problems (climate change, in particular, but also political strife) and mature into a long-lasting civilization. The first confirmed evidence would indicate that we’re not inevitably doomed.

Another interesting point:

  • Frank has a discussion of how planets might swing one way or another, depending on temperature and water availability, into desert worlds or ocean worlds or ice-covered worlds. In my essay I somewhat mocked the idea that a single planet should be entirely jungle or entirely desert (as in Dune), but perhaps such monobiomes are not so implausible after all.

(My one nit with the book is that Frank tries a bit too hard to be casual about what he expects will be difficult subjects for his pop readers. A single example, p 86.8: “As I’ve been emphasizing until you want to smack me…”)

Name checks, aside from the obvious suspects: Olaf Stapledon; Freeman Dyson and Carl Sagan; William Proxmire; James Lovelock; Arthur C. Clarke (for Rendezvous with Rama); Star Trek (“The Devil in the Dark”); Fred Hoyle (The Black Cloud); Stephen Jay Gould; Twilight Zone (“To Serve Man” — he credits Damon Knight for the original story, but he doesn’t Ted Chiang when he mentions the film Arrival); Liu Cixin (his “dark forest” hypothesis); Ray Kurzweil. And the Hayden Planetarium.

This entry was posted in Astronomy, Book Notes, Science. Bookmark the permalink.

Leave a Reply

Your email address will not be published.