The winter is coming. Here on Earth, we can accurately predict when it will come, how long it will last, and even how severe it will be. But in the world of the continents of Westeros and Essos, the epic series by George R. R. Martin is not like that. Imagine living in a world where the seasons are unpredictable: their duration, approach and severity are completely unknown. There can be months, years, or decades between winters, and they can be mild, harsh or disastrous, lasting for years. Although the Earth has never experienced such chaos, Pluto's outer satellites are still as, as shown by the satellite "New Horizons". Now we can scientifically prove that the world from "A Song of Ice and Fire" may not be so fantastic … if the world of Westeros is a satellite orbiting a giant double planet, theoretical physicist Ethan Siegel believes.
Binary planets, in theory, can be of very different sizes and orbital distances. Any smaller worlds that revolve around them at a decent distance will maintain a stable orbit, but rotate and wobble chaotically.
It may seem as if nature itself has rebelled against you. The planets revolve around their axis, revolve around their parent stars in an ellipse, and any changes that occur in their orbits are either extremely gradual or immediately catastrophic. Unless there is a collision or major interaction with a massive body nearby, the only orbital changes will be associated with precession, slow rotation deceleration and planetary motion around the Sun. The time of year is determined by the combination of your axial tilt and distance from the Sun, and that's it.
Earth in orbit around the Sun and its axis of rotation. The seasons of all the worlds in our solar system are determined either by the tilt of their axis, or by the elongation of the orbit, or both.
At first glance, the conditions are quite ordinary and many planets get along well with them. But each of them has serious flaws in describing the world on which Westeros could be:
- If the planet is in a binary system of stars, it will belong to two stars. This solution is dynamically unstable and could throw the planet into interstellar space.
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- If a swarm of large planets passes by, periodically shaking the planet's orbit. Such gravitational intruders, if large enough to change their orbit, are likely to render the world uninhabitable due to orbit changes.
- If a world that changes its orbit like the satellites of Saturn Janus and Epimetheus is located nearby. However, in this case, two stable probabilities will be presented, and not chaotic, unpredictable winters like those shown in "Game of Thrones".
This image, taken by the Hubble Telescope, shows all five of Pluto's moons orbiting this dwarf planet. Orbital paths are added by hand, but are in resonance 1: 3: 4: 5: 6 and all rotate in the same plane with a deviation of one degree. The four outer satellites outside of Charon are constantly dangling instead of rotating around one specific axis.
But there is an option that will work, and an example of this is right before our eyes. Somewhere far beyond Neptune lies the Pluto-Charon system, which will provide us with a suitable site. Pluto and Charon are locked to each other, but immediately behind them are four other moons: Styx, Nyx, Cerberus, and Hydra. If Pluto and Charon merged into one mass, all four of these moons would be tidally blocked, that is, they would always look at their parental world with one side. If we replace this single world with a double one, in which objects of comparable and greater mass than the outer satellites, they will all dangle chaotically.
To get the world of Westeros, we just need to increase it all. Instead of a small asteroid-sized object floating around a binary system of dwarf planets, we need an Earth-sized object orbiting two gas giants. If, say, a planet the size of Saturn with super-Earths nearby, or a massive gas giant that revolves around Jupiter's solid core, any satellites of these binary worlds - even satellites the size of Earth - inherit chaotic dangling behavior. Night and day in such a world will not go anywhere, since it will rotate rapidly relative to the Sun, but the axis of rotation will behave in an unpredictable way. This will result in variability in seasons and lengths of day and night, and possibly lead to years of darkness.
A planetary collision early in the formation of the solar system could result in double planets, possibly even a pair of giant worlds. Any satellites near them will rotate rapidly and also dangle due to mutual gravitational effects.
There are several ways to create such a dense, massive binary object, but the simplest of them would be a massive collision of two young gas giants in the first 100 million years of the solar system's formation. With certain parameters of the orbit, a large gas giant with a small but massive companion planet - several times heavier than Earth, can form. The gas giant and its massive companion will be tidally blocked, providing the outer satellites with stable orbits with unstable rotational axes. In such a system, an orbit around the two of giants can take only 24 hours (like the moon of Saturn Mimas), but changing the axis of rotation will lead to the fact that the seasons will be wildly unpredictable.
From the surface of the world revolving around the giant double planet, it will be possible to observe the two worlds alternately, and sometimes simultaneously. One will be larger than the other. It will be beautiful at night.
If you lived on such a planet, you would know for sure that winter is coming. There may even be areas like the North that are consistently colder than the rest of the continent for tens of thousands of years. But how long the winter lasts after the onset, how severe it will be, it will not be determined by magic, but by the gravitational attraction of the Sun and the twin planets around which your world revolves. And it's not just about winter. With the help of geoengineering, we could create a planetary system that would reign in an eternal summer that Westeros could only dream of.
Ilya Khel