I’m trying to identify a science fiction novel I read about five years ago. I do not remember the author, or the title, or even most of the plot(!), but one minor background scene was very vividly described, and made a big impression on me. It concerns the phenomenon of total solar eclipses.

In this scene a character was musing on the implausibility of these eclipses. Although the Earth is an ordinary planet, and the Sun is a quite ordinary star, the coincidence of the Earth having a large moon whose diameter precisely matches the apparent diameter of the Sun to just about blot it out at an eclipse is far more improbable. It is not even a permanent situation - the Earth-Moon distance increases every year, and so in a few tens of millennia total eclipses will not occur any more. He made the point that as this is such an unusual situation, that if aliens exist, and if aliens have a concept of tourism (visiting strange and exotic locations for fun), then one point on their itinerary would surely be to view a total eclipse on Earth. With that in mind, a cheap and easy way to search for extraterrestrials would be to go to solar eclipses, and look out for eclipse-viewers of unusual appearance - they could be aliens in disguise.

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    Not entirely a match, but one of the Foundation books had Earth being very unusual because of the relatively large size of its satellite. Dec 6, 2020 at 21:31
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    Wouldn't any species with the ability to easily visit other solar systems also be able to easily sit in a ship at the relevant distance from any planet/dwarf planet/satellite/&c and see a perfect eclipse that way, without all the bother of locating and travelling to rare systems such as ours?
    – gidds
    Dec 7, 2020 at 18:04
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    but in a spaceship you don't "listen to the animals nearby fall silent and feel with their own skins the sudden chill in the air that comes with totality..." Dec 7, 2020 at 19:15
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    Isaac Asimov mentioned this in one of his essays in F&SF: "The Triumph of the Moon". I believe the "triumph" is the coincidence that the sun is 400 times the Moon's diameter and 400 times farther away; anything else and we wouldn't get the "ring of light" type of eclipse. Dec 9, 2020 at 2:54
  • Clara, note that this is a very common observation. There are hundreds of articles about this, and it is a favorite of UFO / "ancient astronaut" / "aliens seeded Earth" theories, books, articles, etc. Note that even about the most famous scifi book/movie of all, 2001 Space Odyssey, suggests this by emphasizing the alignment. Really it's a "trope", there's no "specific" story this happens in. (although I guess, we could find "your" one!)
    – Fattie
    Dec 9, 2020 at 13:49

2 Answers 2


I believe you are looking for the novel Transition by Iain M Banks. It was published in 2009 and features a passage very much as you describe. From the prologue...

So lets think about eclipses for a moment. Even if we haven't seen an eclipse personally, we've seen phoptographs in magazines or the footage on television or youtube. We are almost blasé about them; they are just stuff that happens on our planet, like weather or earthquakes only not destructive, not life threatening.

But think about it. What an incredible coincidence it is that our moon fits exactly over our sun. Talk to astronomers and they'll tell you that Earth's moon is relatively much bigger than any other moon around any other planet. Most planets, like Jupiter or Saturn and so on, have moons that are tiny in comparison to themselves. Earth's moon is enormous, and very close to us. If it was smaller or further away you'd only ever get partial eclipses; bigger or closer and would hide the sun completely and there'd be no halo of light round the moon in totality. This is an astounding coincidence, an incredible piece of luck. And for all we know, eclipses like this are unique. This could be a phenomenon that happens on Earth and nowhere else. So hold that thought eh?

Now supposing there are aliens. Not E.T aliens - not that cute or alone. Not Independence Day aliens - not that crazily aggressive - but, well, regular aliens. Yeah?...

It goes on to talk about how these aliens go exploring the galaxy but are keen to visit earth to see the an eclipse.

But what I want to propose to you is that, as well as all those other wonders, they want to see that one precious thing that we have and probably no one else does. They'd want to see our eclipse. They'd want to look through the Earth's atmosphere with their own eyes and see the moon fit over the sun, watch the light fade down to almost nothing, listen to the animals nearby fall silent and feel with their own skins the sudden chill in the air that comes with totality...

...So that's where you look for aliens. In the course of an eclipse totality track.

This is roughly pages 7 to 9 in the prologue of the paperback version published by Orbit. It is as you say, only a short scene within a much larger and complex novel.

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    Yes, it was "Transition" - I've looked through it now and I remember the transitioning between realities with aid of a drug. Not one of Banks' stronger works I think, but I'll reread it. Thanks! Dec 7, 2020 at 7:49
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    @NeilMeyer "... earth is tiny when you compare it to Mars ...". [Citation needed]
    – Zano
    Dec 7, 2020 at 17:17
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    Sorry not Mars, just jupiter
    – Neil Meyer
    Dec 7, 2020 at 17:19
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    Jupiter has five moons that are big enough to occult the Sun (Io, Europa, Ganymede and Callisto, plus smaller and closer Amalthea) and the shadows of the first four on Jupiter are visible to Earth telescopes; these should count as solar eclipses. The other 70+ moons of Jupiter transit the sun. So the coincidence is not that Earth's Moon is large but that it is currently just the right size and distance away for some solar eclipses on Earth to be total and others annular.
    – Henry
    Dec 7, 2020 at 17:49
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    Why does the size of the planet matter? Shouldn't it just depend on the moon having the right size, distance, and orbit (to intersect the ecliptic)?
    – jaxad0127
    Dec 7, 2020 at 17:50

This might be Illegal Alien (1997) by Robert J. Sawyer.

One of the aliens says:

"Incredible? No. Unlikely perhaps, but, then again, no more unlikely than the coincidences of sizes and orbits that makes possible the kind of perfect total solar eclipse we observed from Earth's surface. Of all the inhabited planets in the entire universe, Earth may be the only one that enjoys such a spectacle."

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    Hmm. This is almost definitely what I'm remembering, but digging a bit further it's not a complete match. I'll leave it up for now in case nobody finds anything better.
    – DavidW
    Dec 6, 2020 at 20:44

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