Book review: Extraterrestrials

Author: Wade Roush

Publisher: MIT Press

ISBN: 978-0-262-53843-5

Price: £12.99 (Pb) 221pp

Although ostensibly a general book about extraterrestrial life, Wade Roush’s smart little primer on SETI really focuses on the Fermi Paradox. Roush is fascinated by what the Fermi Paradox could mean. Is it telling us that life on Earth is alone in the Universe, or, as Roush wonders, maybe “we’re not looking at the problem the right way”?

What delights me about Extraterrestrials, which is the latest in a long line of smart-thinking and general knowledge guides from MIT Press’ Essential Knowledge Series, is that Roush could have fallen to the temptation to take the easy way out and stick rigorously to the standard party line in SETI. Instead, Roush is insistent on challenging assumptions, asking questions and constantly reminding us that we may need to reframe what it is we’re looking for in SETI if we want to be successful in our search.

One of the methods by which he encourages us to think about SETI in different ways is through analogies. Indeed, the book kicks off with one. The Fermi Paradox asks the question, if extraterrestrial life exists then why is it not here, and why do we see no evidence of it elsewhere? Roush reframes the question by taking us back to 1491, and imagining a summit meeting between the chiefs of various Native American tribes, who in this fictional account have gathered to discuss whether there could be other, unknown, tribes living in distant lands far across the oceans. The chiefs discount the possibility – surely if these other tribes existed then they should have visited America by now. The fact that they had not, reasoned the chiefs, must mean that they don’t exist. 

Of course, the very next year, Columbus would arrive on the shores of the New World.

Another analogy used to interesting effect is what Roush calls ‘On the Porch’. As children, our parents might have taken us to visit their friends or family. As we kids would run around playing, the grown-ups would be sat on the porch, discussing adult stuff to which the children were not privy. Maybe extraterrestrials are like the adults in this scenario, suggests Roush as a possible explanation for the Fermi paradox – they’re talking among themselves ‘on the porch’ while we kiddos run around and try and figure out the Universe. Once we’ve grown up, we’ll be allowed to enter their conversation.

These analogies, and others found in the book, are a trademark of Roush’s breezy style that makes Extraterrestrials highly accessible. With the main text running to just 191 pages (there’s also a good glossary, an impressively long selection of references, and the index), Roush is limited for space and it can sometimes seem like Extraterrestrials is just skimming the surface of  the topic, but as a book aimed at newcomers to SETI, there’s enough there to satisfy beginners while tantalising them with ideas and concepts, which they can then go and learn more about for themselves.

Roush begins with a potted history of various ideas about alien life throughout the ages, from Ancient Greek philosophers to Copernicus and Giordano Bruno, William Whewell and Percival Lowell. There are no surprises here, but it’s an informative read.

There’s enough here to satisfy beginners while tantalising them with ideas and concepts that they can seek out to learn more about for themselves

The next chapter does the same thing for the history of modern SETI. I detect a little bit of hero worship here from Roush – not that there’s anything wrong with that! He gushes over such pillars of the SETI community as Jill Tarter and Paul Horowitz, hailing from SETI’s middle-history of the 1970s, 80s and 90s. But it’s a bit like asking someone to name who their favourite science-fiction authors are, and they reel off the names Asimov, Clarke, Heinlein. Yes, great writers, but science fiction has moved on since then with much more to discover, and it’s the same with SETI. For example, the biggest SETI programme of all time, the currently ongoing Breakthrough Listen project, receives scant mention from Roush. 

Admittedly, you could point that same finger at me for my book The Contact Paradox, although in my defence two-thirds of that was written before Breakthrough Listen was even a thing, and I subsequently looked to incorporate it where relevant. I’d have liked Roush to devote some time to really showing the reader how SETI is still an active, and indeed increasingly thriving, field of research today, with a new generation of researchers taking on the mantle of Tarter, Horowitz, Drake and others.

The book’s title brings to mind not just SETI, but the search for all kinds of life, including microbial life, and where it might live. In that sense, Chapter 3 is the chapter most in keeping with the title of the book. It’s about exoplanets and extremophile life, and does a good job of summarising our basic knowledge about both. Roush raises the Rare Earth argument, and it’s pleasing to see that he is up to date with developments to be able to offer refutations to some of Rare Earth’s more spurious claims.

The final two chapters focus on the Fermi Paradox, and what you take from these chapters will depend on your personal thoughts about the Fermi Paradox, and whether you think it’s a paradox at all. Roush runs through a list of possible explanations for the ‘Great Silence’, and if you’re not convinced by this chapter, then that’s more to do with the quality, or lack thereof, of the explanations for the Fermi Paradox that have been proposed over the years, rather than any fault of Roush’s. Indeed, Roush himself is (sometimes overly) dismissive of many of these possible explanations. While he acknowledges that we haven’t searched enough of the Galaxy to be able to draw any serious conclusions, and that time and space both work against SETI, Roush does still think that life exists out there, but that there’s something fundamental about it that we just don’t understand yet, and that when we do, the answer to the Fermi Paradox will fall into place. 

To highlight this, Roush resorts once more to analogy, telling the story of nineteenth century astronomers puzzling over the orbit of Mercury. They couldn’t explain its orbit because they were missing a key piece of information – the General Theory of Relativity – that wouldn’t be discovered until the twentieth century. 

What the missing piece of information in regards to the Fermi Paradox is, Roush can’t say, but frankly neither can anyone else yet. Maybe it’s a concept that’s already been proposed. Maybe it’s something we haven’t thought of, or learned about, yet. I broadly agree, with a subtle difference. I don’t think it’s necessarily the case that we’re missing a key piece of factual information, but more that our assumptions might be mistaken and are taking us down the wrong track. The missing magic ingredient that Roush is asking for may simply be that we need to make better assumptions as starting points for our search.

Roush thinks that there’s something fundamental that we just don’t understand yet, and that when we do, the answer to the Fermi Paradox will fall into place

Roush is a journalist and academic at MIT’s Knight Science Journalism programme (I used to enjoy reading their blog critiquing science journalism), rather than a SETI scientist, but he’s done a bang-up job with Extraterrestrials. The discussions contained within are mostly accurate, with only the very occasional slip – for example he credits Paul Horowitz as being the pioneer behind optical laser SETI, but optical SETI was first proposed back in 1961 by Robert Schwartz and the inventor of the laser, Charles Townes, and it was first conducted and promoted by Stuart Kingsley in the early 1990s. 

I also feel that Roush places too much emphasis on Avi Loeb’s controversial theory that an interstellar interloper into our Solar System, 1I/’Oumuamua, was a spacecraft with a light sail. The hypothesis did get a lot of play in the popular press at the time, so I can understand why Roush has included it in his discussion. Yet while there’s vague mention of criticism of Loeb’s theory (and Roush himself thinks “the chances are” that it is natural), there’s no mention in the book about how astronomers whose specialist research area, unlike Avi Loeb’s, is to study minor bodies, are satisfied that ’Oumuamua is a natural object.

Roush also takes for granted that SETI signals can cross light years unhindered, and indeed uses this as support for his conclusion. However, electromagnetic signals weaken with the inverse-square law, and the SETI Institute’s Seth Shostak has calculated that if we moved Arecibo to the nearest star system, Proxima Centauri, then it would not be able to detect radio leakage, such as television signals, from Earth because the inverse-square law would weaken them too much. SETI scientists claim that the new FAST telescope in China, and the forthcoming Square kilometre Array, should be able to detect radio leakage from the closest stars, but nevertheless, if there were technological aliens living on a planet orbiting a star 10 or 20 light years away, it’s not impossible that they could have missed our incidental signals.

These points of discussion aside, as primers for SETI go, Extraterrestrials has a lot going for it. Wade Roush’s book covers a lot of subjects in its short length, albeit sometimes fleetingly, but most importantly Roush makes the reader think and ask more questions. I’d undoubtedly recommend Extraterrestrials for people new to SETI – and then once they’ve read it, they’ll be perfectly placed to tackle more in-depth books, like, I don’t know, The Contact Paradox!

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