Nemesis by Isaac Asimov was an enjoyable tale about how a small self-contained settlement leaves the Solar System to orbit another star. The story has two timelines that alternate, one in the present and another from fifteen years ago that slowly approaches the present. The intersection is well done and I enjoyed the story for the most part. However, there are a few scientific things that bugged me, so inside of doing a review I’m going to deal with the science concepts discussed in the book from a present day perspective.
The biggest issue I had with the story was the name. As soon as I saw the title was Nemesis, I immediately jumped to the Nemisis theory which posits that there exists a rogue star which enters into our solar system at a set interval. Knowing that it’s rumoured to take millions of years per orbit, that it would have to be more massive than Jupiter to sustain nuclear fusion (and thus make it a star), and that the closest star is roughly 4.3 light years away, it all seemed rather unlikely. Why? First, Nemisis would have to be on a highly elliptical orbit, passing inside our solar system at its closest point yet be very far away otherwise to maintain its million year orbit. Next, it would have to stay gravitationally bound in order to have this periodic orbit. Third, it would need to go unnoticed to the point that present day astronomy has not detected it.
Asimov drops almost all of these problems by the wayside. It’s named Nemesis because it’s found to be closer than Alpha Centauri, not because it’s going to destroy Earth. It’s discovery still bothers me though. This is a star that’s two light years away from us, yet no one has measured it’s parallax before. The first successful stellar parallax measurement was in 1838 of a star more than 10 light years away. Granted, the star is hidden behind a dust cloud which dims the already dim star further which might make it so that people overlooked it, but it’s so close that people would have had to see it’s annual parallax movement. Did they mistake it for an asteroid? Maybe, but then they would have seen it return to its original position at the end of the year, removing that possibility. No matter how you look at it, we should have seen it before now.
I have to praise Asimov for some things though. Nemesis does not orbit our Sun but instead is haphazardly moving through the Milky Way and will just happen to intersect our solar system this one time. In making the name and purpose of Nemesis work he’s done two things right, though I still dislike that no one discovered the star for so long.
What about the solar system that Asimov describes? As we’ve studied solar systems besides our own, we continue to find more and more with large gas giants orbiting closer than Earth orbits the Sun, which is in sharp contrast to our own solar system. This is partly due to selection bias (it’s easier to detect large planets than small ones), but it still shows a predominance for large, close planets due to the sheer number of them.
Further, moons will become tidally locked with planets, just like our moon is tidally locked with Earth, and planets will become tidally locked with their stars, just like Mercury is tidally locked with the Sun. The orbital period of roughly one Earth day is also in line with our solar system, as Jupiter has at least four moons that orbit it in less than a day. However, Jupiter’s largest moon is only 40% as wide as Earth, unlike Erythro which is larger than Earth. Besides this last point, everything else has a president and seems plausible.
The last point to touch on is how habitable the planet would be. Earth varies by roughly 5 million km over its entire orbit, and the larger temperature variation we feel is not from distance but from our axial tilt which cause the seasons. Nemesis is dimmer than the Sun so Erythro cannot vary as much in it’s orbit, but because it has no axial tilt then this isn’t much of an issue. It seems quite plausible that Erythro would be habitable and stay that way.
This brings us to hyper-assistance. First off, I have no great issue with exceeding the speed of light. There have been a lot of discussions over the years as to how it might be possible, and there are some theories that look similar to Star Trek’s Warp Drive. I also like how the first version of hyper-assistance requires that your overall trip not exceed the speed of light while the final version allows you to forgo this restriction.
Hyperspace is a little stranger. It’s quite possible that hyperspace has different laws than normal space and that they didn’t know of these rules when they first set to work. Perhaps even the first tests didn’t show them, and there was no obvious proof until the first human flight. But then why did Chao-Li Wu find something that everyone else missed for over a year? It’s just like how Einstein discovered relativity because he was annoyed by a lack of explanation of various phenomena; Wu may also have been bothered by the lack of a path in hyperspace, causing him to develop his own theory that better explained all of hyperspace theory, just like Einstein better described gravity.
Now should hyperspace have negative gravity? Maybe. Here I think Asimov is drawing on antimatter. One idea behind antimatter is that it’s negative energy travelling backwards in time, like matter is positive energy travelling forwards in time. In order to make antimatter work we have to flip two things to negative, and the same idea is applied to hyperspace.
And that’s it! Overall the science is within reasonable bounds, though the time it took to discover Nemesis still bothers me. Now that I’ve gotten all that off my chest, I can go read something else.