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Book Review: extraterrestrial The First Sign of Intelligent Life Beyond Earth


I don’t normally do book reviews but since someone wanted to get my thoughts on this one, I thought I would share with a broader community.

Source material

Extraterrestrial: The First Sign of Intelligent Life Beyond Earth: Loeb, Avi: 9780358278146: Books

Let’s get into it

This book is mainly about what to make of the very unusual sighting of an object which came from outside our solar system in 2017, dubbed ‘Oumuamua.

This book is written at a very simple level – perhaps fifth grade or sixth grade? So I guess it’d be a great addition to a middle school library. I was aching for some more details.

I’m actually ready and willing to ‘believe.” For me the main thing was the paucity of facts presented.

The biggest failing of the author is to fail to be so guarded! Professor Avi, you are uniquely qualified to spin any plausible story about this object. Surely you have thought of many origin stories for this thing. Why not share them? This is a book, after all, not a scientific publication. We won’t peer review you for daring to create a plausible backstory for this object.

For me to make my points I have to give some background so everyone sees what I am seeing.

Professor Avi has this super cool lightsail project. Something like 10 GigaWatt lasers are required to send a super slender light sail up to 1/10th the speed of light.

An aside. Wouldn’t a multi Gigawatt blast create a plasma out of the atmosphere, thereby transferring its power to the air rather than the target lightsail? Maybe you overcome that by spreading the laser over a wide area. or using micosecond blasts. Not sure. And what about the reflecting rays? Can they be adequately disbursed to avoid singeing the earth?

But I digress. Sending any macro object to any fraction of the speed of light is wondrous. And dangerous. By conservation of energy I have to assume the thing at that speed would have 10? 100? gigajoules of energy (I will do the math later). Imagine the consequences of an earth-like planet being “visited” by one of those things. Either cataclysmic, or at least terrifying to those lifeforms. Yes, I know the odds of collision are infinitesimal. But they are not zero. And no way can these things be aimed with such precision to avoid that scenario altogether. Not to mention the idea is to send thousands or millions of them out. Welcome to mankind, extraterrestrials, we like to announce our entrance with a bang!

For instance, ‘Oumuamua, though it comes from outside our solar system, is at the local system of rest of the nearby stars. So that is pretty remarkable, and it means its speed is not anywhere close to a fraction of the speed of light, unlike Prof Avi’s lightsails. Why is that? This particular civilization felt they could wait around thousands of years?? Or did it start out at a fraction of the speed of light and then get decelerated as it neared its target? And if so, by what force?

And when I learned it sped up as it zoomed around the sun, I immediately thought of the analogy of our space missions which sometimes use giant planets like Jupiter to pick up speed and slingshot away faster than they had been going. Was ‘Oumuamua purposely aimed near to our sun for its boomerang effect? But it was tumbling like every eight hours. Should lightsails do that? Or does that show if it was a lightsail, it was no longer fit for purpose – inactive space junk? ‘Oumuamua trajectory deviated in the manner a lightsail might. But if it was slowly tumbling, how is that compatible with that statement? Aren’t lightsails only good for catching rays from one orientation? I actually don’t know but that’s what I would naively assume.

And it came from somewhere. if you reverse its trajectory, where did it come from? Was it an area with an inhabitable exoplanet?? Is that area receiving heightened scrutiny from SETI and company??

Going back to these lightsail things travelling at a good fraction of the speed of light, if one were to whip past us, would we even have a chance to see it? I believe it would be effectively invisible to us. How would they fare when colliding with space dust?

A manufactured lightsail would have great symmetry. The brightness profile was not a nice sine function, though close. What is the lightsail shape we can assume given the observed brightness profile fluctuation? A partially destroyed lightsail, perhaps? Where is the artist’s rendering of that?

So you see my point now? Don’t make me speculate. You’re the expert. Your speculations will be grounded in better science than anything I can dream up. So I guess Prof Avi, despite being a maverick in many ways and bucking current scientific thinking in promoting this as a thing created by alien life, reverted to the usual scientist’s conservatism in not making unprovable statements. And we are worse off because of it.

The great filter

And this term bothers me. It reads poorly. The first I heard it was from a fellow reader, and, even though I was familiar with the concept, I had to ask for a definition. A good term of art is self-explanatory. This is not a good term. Advanced civilizations probably last for only a few hundred or at best a few thousand years before they self-destruct. Looking at ourselves, we’re probably only going to get a few hundred the way we’re going. And this is supposed to be the great filter or something? I don’t have a better term, but far more clever people could come up with one I am sure. Like inevitable self-destruction, except something with more of a ring to it.

So I was asked, if this comes from an advanced civilization, is this a cause for hope, or a cause for despair? To argue the despair first, we got space junk from an advanced civilization. Probably they died out and we are left to do astroarchaeology on their junk. Not so great. But I am more hopeful. It’s incredibly difficult to target another star, they managed to do it. Maybe their lightsail had an accident or something. No worries because they sent out millions more like Prof Avi proposes to do. And, the main thing, we overlapped with them! We were advanced enough to detect another’s technology. Mostly because of the self-destruction tendencies, and the randomness of when advanced life forms, we’re not going to have any overlap with the vast majority of our fellow aliens. Their time in the sun was either way in the distant past, or will occur way in the future. That we overlapped in any way at all, probably means there are very, very many advanced civilizations, even in our stellar neighborhood, such that we had decent odds of intercepting and overlapping with one. And that gives me awe and excitement to learn about this advanced life. The hope comes from the viewpoint that these beings aren’t threatening to us. I have a naive belief that they would be trained in cultural sensitivities a la Star Trek The Next Generation or something as opposed to Independence Day, and decide not to wipe us out, nor to alter our technology (much), but more to observe us from afar. So on balance this encounter makes me hopeful.

Any insight if this was a civilization which reached the singularity? I.e., where it transferred its organic intelligence to a program in silicon or some other infinitely long-lasting, purpose-built medium??

So yes I am convinced the simplest explanation is the best one, and prof Avi’s hypothesis is by far the simplest. It raises a few questions which I would have preferred answered. And I was dying for more speculations. The speculations of an insider is worth 100 times the speculations of an outsider such as myself who doesn’t know what they don’t know!!


Prof Avi devotes a lot of time to philosophy. That’s all good. I didn’t learn too much from it, but I suppose others could find it useful. I don’t have an issue with it.


If I were really responsible, I’d do research, or at least read the darn book reviews on Amazon or get an answer to some of my questions on Quora or something. Probably a lot of my questions are addressed. But my time is not infinite and I’m not trying to impress anyone. As I learn more in the course of my ad hoc reading I will revise this blog with better information. And one more thing about my personal philosophy, I am writing this based solely on self-reflection and readings I’ve absorbed from years ago. I consider active research “cheating” in this regard, and I will inevitably be swayed and biased by the first educated opinion I come across.

Before reading this book, I was aware of this object from 2017 and that it was special, just based on my general reading of science news. It was only from this book that I realized how compelling the extraterrestrial case was.

Prof Avi took a few facts and made a book out of it. He should probably create a fictional but plausible back story for this object and make another book that addresses some of these basic questions.

February 2022 update

They have just discovered signs of a third exoplanet around Proxima Centauri, our nearest neighbor in the galaxy! That’s exciting. The place is only four light years away. Maybe a lightsail craft will visit it within our lifetimes.

Reference and related

Extraterrestrial: The First Sign of Intelligent Life Beyond Earth: Loeb, Avi: 9780358278146: Books

My cheese grater image of the 2017 eclipse.

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