(2021) Avi Loeb, John Murray, £20 hrdbk, xvii + 220pp, ISBN 978-1-529-30182-4
Though the subject matter is sensational and unbelievable, the author is a respected astronomer at Harvard University, former Chair of its Astronomy Department, and a Fellow of the American Physical Society (the US equivalent of Britain's Institute of Physics). However here he is flying a kite with the – what some consider to be an outlandish – proposal that our Solar System was recently visited by a technological construct built by alien intelligence.
This site's regulars may recall that back in 2017, the first extra-solar object was detected passing Earth orbit. The odd thing about this interstellar visitor was its shape. It appeared to be very long and thin (five times longer than it was wide). This is a most unusual, giant rocket-like shape and cannot be accounted for by known astronomical objects such as rocky asteroids or icy comets. Furthermore, as it came close to the Sun, its course adjusted! It was also a very different from the only other (to date) visitor from interstellar space that subsequently passed by in 2019. This strange, 2017 object was dubbed 'Oumuamua.
Avi Loeb's contention is that 'Oumuamua was not long and thin but hemispherical – a conjecture calculated by another astronomer. Further, he explains that the close-to-the-Sun course adjustment could be due to Solar wind provided the object was very light and not due to cometary venting as is the official view. Loeb rules out cometary venting as no dust was detected with the theorised gas expulsion: dust release always accompanies gas release from comets! Indeed, from size calculations of 'Oumuamua being a thin hemispherical sheet, dark on one side and reflective on the other, it would be possible for Solar wind to nudge 'Oumuamua in exactly the way that was observed.
Essentially Avi Loeb's case fits the bill, whereas the accepted view simply does not satisfy all the observations made. But his case only works of 'Oumuamua was extremely light and that it was in essence a light sail. Large light sails are not found in nature and so Avi Loeb concludes that 'Oumuamua must have been constructed by technological extraterrestrials!
Having read Extraterrestrial, and in preparation for this review, despite being in SARS-CoV-2/CoVID-19 lockdown without internet access, I nonetheless discovered I had two 'Oumuamua papers in my academic collection on my server. One of these was the Nature paper that ascribed 'Oumuamua near-Sun course correction to cometary-like out-gassing(1), out-gassing which Loeb notes was never observed, and a pre-print of Loeb's own paper with Shmuel Bialy, putting forward the case for 'Oumuamua being a light sail. (2). So, in addition to having another (more academic) version of Loeb's take, I had the alternate view that 'Oumuamua was a body that had some volatiles that out-gassed when close to the Sun, so altering its course.
Using the Nature paper as a foil to test Loeb's seemingly outlandish light-sail hypothesis, I note that the Nature paper too says that there was no out-gassing dust was observed from 'Oumuamua and yet there should have been dust seen if there was the hypothesised out-gassing they calculated. To get around this the Nature paper's authors claim that the material being out-gassed was 'atypical'. This basically means it was inexplicable unless you put it down to the unknown extra-Solar conditions of the object's origin. In short, the Nature paper does not provide a fully satisfactory explanation. Loeb's light-sail hypothesis therefore has a certain viability: given what we know, it is not entirely implausible. This remains so even with the Nature paper presenting, and rigorously dismissing, seven alternative explanations (but Loeb's light-sail hypothesis was not one of them).
The bottom line Loeb is not some sort of von Daniken eccentric peddling a ludicrous theory but a serious astronomer who just happens to have an hypothesis that is very exotic but does seem to best fit the facts. As he himself notes, it is only because he is advanced in his career, and recognised for his body of astronomical work, that he is able to think outside the box of accepted view without undue professional repercussions.
Extraterrestrial, is written at the easy end of the New Scientist magazine level of science writing and so will be accessible to a potentially wide readership. It certainly fits the bill for this site's target audience: scientists who also enjoy science fiction in their spare time, as well as SF lovers who happen to like popular science.
However, importantly Extraterrestrial is more than the presenting of an exotic idea; it is a rallying cry against the constrained, conservative culture that permeates science. This is something that is very real and I too have come across quite a lot in my own career, especially over the many years I spent presenting biologists' views to policymakers. Policymakers want clear guidance. In most cases, they do not want or need significance down to the last decimal place but a workable option. Conversely, scientists (that aren't associated with any vested policy interest) don't like sticking their head out of the trench, don't like controversial issues, and really just want a peaceful life. It also manifests itself in dogmatic belief that refuses to consider the non-traditional. An example might be that dinosaur pigments are detectable today (3). Some referees refused to believe it despite the lab evidence. I have also personally encountered it having been told off in the early 2000s by a Government Scientific Advisor for saying that we were unlikely to keep human-induced global warming below 2°C above pre-industrial. This led me to my 2009 'Climate Crunch' essay and then logging subsequent work by others that pointed to the same likelihood (including a warning by a subsequent Scientific Advisor).(4) What irony.
I mention the above to illustrate that conservative thinking in science is not restricted to whacky astronomical ideas. Within astronomy, Avi Loeb provides examples. For instance, the idea that an easy way to detect exoplanets might be to look for signs of hot Jupiters where a massive gas giant orbits close to its star so as to induce a more noticeable wobble. This notion was presented in 1952 by the astronomer Otto Struve but was dismissed as it was thought that gas giants would not exist close to a hot star and form (and stay) further out. Only in the 21st century were hot Jupiters found to exist in work that attracted the 2019 Nobel prize for Physics. Yet over half a century of possible progress in this area was lost!
For an example of the standard science coverage of 'Oumuamua, check out the interesting and worthy (but nonetheless staid) PBS Space Time YouTube channel and its episode on 'The Origin of 'Oumuamua, Our First Interstellar Visitor'.
In Extraterrestrial, you can sense Avi Loeb's frustration at an astronomical community that fails to engage (scientifically challenge and present alternates to the total assemblage of evidence he presents) with the hypothesis he raises. He also makes a plea for a survey for lightsails as technosiganures in the Solar System, which is warranted, irrespective of whether ‘Oumuamua is one of them.
I suspect many non-astronomical scientists who also read SF were intrigued by the news of ‘Oumuamua, and its odd long cigar shape, had their own thoughts on the subject: I know I did.(5) So many will be intrigued by Extraterrestrial: The first sign of intelligent life beyond Earth. This is a book that deserves to be read and not dismissed out of hand. And if some pick up on the need for the science community to be more broadminded (without losing science sensibilities) then that will be no bad thing.
Notes and references
1. Micheli, M., Farnocchia, D., Meech, K. J. et al (2018) Non-gravitational acceleration in the trajectory of 1I/2017 U1 (‘Oumuamua). Nature, vol. 559,p223–226.
2. Bialy, S. & Loeb, A. (2018) Could Solar radiation pressure explain ‘Oumuamua’s peculiar acceleration? Astrophysical Journal Letters. arXiv:1810.11490v2.
3. Pan, Y., Zheng, W., Moyer, A. E. et al (2016) Molecular evidence of keratin and melanosomes in feathers of the Early Cretaceous bird Eoconfuciusornis. PNAS, E7900–E7907. doi/10.1073/pnas.1617168113.
4. Sir Robert Watson (former Chair IPCC and Chief Science Advisor DEFRA) "Science adviser warns climate target 'out the window' -- BBC News" -- August 2012.
5. My own initial (wild) thoughts on ‘Oumuamua. I have not aired these before as, while I was interested in the news of ‘Oumuamua being a very oddly-shaped visitor from beyond our Solar system, I am not an astronomer and, among other things, do not know which numbers to crunch: it is always best not to publicly proclaim on matters outside of one's area of modest expertise. Yet, it is not unreasonable to expect any scientist with a seperate interest in SF, not to have thought about the 'Oumaumau news: indeed, it'd be strange if they didn't. So from my own perspective of astronomical ignorance, I had casually, yet wildly, mused whether it might have been the giant, largely empty, ion motor and fuel section of a probe being inserted into our system having decelerated from a significant fraction of light-speed (possible with large, theoretically possible to us humans but yet-to-be-built ion motors)? Being largely empty, its lightness might make it more susceptible to Solar wind near the Sun, and if it did contain fuel some of this might have vented if any remnants warmed near the Sun and so explain the course correction. Such fuel would be pure and so not contain dust hence explain the absence of dust normally associated with cometary out-gassing. Being part of a targeted probe would also explain the statistical (what is known as Monte Carlo) random chance of observation of such an object at such a distance over the few year's we have had the detection capability. If it were random alien space junk then the numbers of such bodies out there would have to be literally astronomical to find one coming so close to the Sun within the observational time frame of a few years. However, I am not an astronomer and I am sufficiently grounded to realise that my idle thoughts are more likely to have arisen from my being an SF fan boy as opposed to science training. I do though note that this wacky notion also fits all the data we have on ‘Oumuamua just as well as Loeb's. Further, with a century or so's worth of commercial radio broadcasts, we would have been noticeable to another technological civilisation up to a hundred light years away. Assuming it takes a decade for an advanced interplanetary space-going civilization to assemble an 'Oumuamua probe mounted on an 'Oumuamua-sized fuel tank and ion motor and a year to get to a tenth the speed of light (necessitating an acceleration of a heck of a lot less than an Earth gravity) and a year to decelerate, then such a probe could have come as far away as seven light years. Go to 20% the speed of light and that doubles the range. A powerful ion drive would emit a powerful radiation, but in a very focussed way so that unless it was directly pointed at the Earth during the probe's deceleration phase, it would be invisible to us. Perhaps we should now be looking for a small probe knocking about the inner system? (But perhaps best not to take this idle rumination too seriously.)
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