Before writing Nomad, I spent months talking to astronomers and astrophysicists to build up the science behind the encounter I envisioned. At first, the physicists said the event would totally destroy the Earth, but slowly, I managed to piece together a physics-based scenario where it was possible life could survive on the surface—otherwise it wouldn’t make for much of a story!
It might seem that the events unfolded extremely quickly when Nomad made its final approach, but I carefully modeled the tidal forces affecting the Earth accurately in time and magnitude. Tidal forces are inverse cubically proportional to distance, which is why the sun only exerts half of the tidal force on the Earth that the moon does, even though the sun is almost thirty million times its mass (and four hundred times further away—so 400 x 400 x 400 equals sixty four million, and thirty million divided by sixty-four million gives us the one-half tidal force of the sun versus the moon).
In the end, I managed to convince a team of post-graduate researchers build a full three-dimensional gravity simulation of the entire solar system to lob my Nomad black holes through the middle of. All of the elements of the story—all the forces involved and the paths of the planets afterward—are based on real-world physics. If you want to see me run this simulation, and see Saturn and Earth on their collision course after Nomad, just search for “YouTube Mather Nomad Simulation” or click the link below: https://www.youtube.com/watch?v=X11yMkLUzCY.
There have been many books and movies illustrating the idea that the Earth is part of the ecosystem of asteroids and comets, planets and even our Sun, and that from time to time, an object may hit the Earth, or the Sun may flare, triggering catastrophic events. But what hasn’t been explored as much is the effect of an ecosystem on a much larger scale—the effect exerted on the Earth by objects in our interstellar and even intergalactic neighborhood.
It might sound farfetched, but it isn’t.
In fact, much of the events we’d attributed previously to chance, like the asteroid impact that wiped out the dinosaurs, might not be random at all, but the direct result of the interstellar interactions the Earth has with passing stars (still random, but on a much larger scale). In school, we’re taught that the closest star, apart from the Sun, is Proxima Centuri, at just over four light years of distance. It may seem like the interstellar neighborhood is static.
But it’s not.
In February of 2015, researchers were dumbfounded to discover that just 70,000 years ago, near enough in time that our direct ancestors would have seen it, Scholz’s star, a red dwarf, passed about a half light year from us. This led to a flurry of data crunching, leading scientists to discover that, for instance, four million years ago, a giant star, more than twice the mass of the sun, passed less than a third of a light year from us, and in just over a million years from now, another star will pass at just over a hundredth (yes, a hundredth) of a light year from our sun, grazing the solar system itself and possibly affecting the orbits of the planets.
Now scientists are saying that Sedna, the 10th planetoid of the Sun, the one after Pluto, isn’t even an original planet of our Sun. It was captured from a passing star over a billion years ago, when our solar system collided with an alien star’s planetary system. Hundreds of objects in the Kuiper Belt, the collection of planetoids past Uranus, are believed to have been captured from passing stars. So we are continually mixing together with others stars and interstellar objects, and not on a time scale of billions of years, but on a regular basis every few million years—some scientists now even think that alien stars transit our solar system’s Oort cloud as often as every few hundred thousand years (http://www.bbc.com/news/science-environment-31519875 ) A change in Earth’s orbit might have triggered one of the biggest global warming events in its history (http://www.dailymail.co.uk/sciencetech/article-2125533/Global-warming-55m-years-ago-triggered-changes-Earths-orbit.html). And scientists now think that a massive ice age, started 35 million years ago, might have been also been caused by another shift in Earth’s orbit, and that this same event disturbed the asteroid belt enough to precipitate several large asteroid impacts, one of which formed the Chesapeake Bay. Some now believe these sorts of events might have been caused by the gravitational effect of a passing star.