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Good news! our planets are safe

The solar system is stable for at least 100,000 years

Image by TOPIA

It’s nice to have a feel-good story every once in a while, so here’s one to hold off the existential dread: the Earth isn’t likely to get flung off into deep space for at least 100,000 years

In fact, all of the Solar System’s planets are safe for that time frame, so there is good news all around, for you and your favourite planetary body.

Maybe it’s worth backing up a little bit. The likelihood of Earth, or any planet, being bumped from its orbit is always slim. As Newtonian physics tells us, an object in motion remains in motion unless acted upon by another force – and for something the size of a planet, it would take a significant force to push a planet off track. But there are examples of planetary reshuffling in the Solar System’s own history. One of the most broadly accepted models of Solar System formation, the Nice model, describes how the outer planets migrated early in the Solar System’s history, and would have wreaked havoc on the inner rocky worlds, possibly displacing or even swallowing smaller proto-planets in the process.

The Solar System is a busy place – luckily, most of the objects are tiny | Credit: NASA/JPL-Caltech

But now, researchers have done the math to show that such a migration is unlikely in the next 100,000 years. Angel Zhivkov and Ivaylo Tounchev from the Department of Mathematics and Informatics at Sofia University in Bulgaria used computer calculations to determine that the planets are likely to remain stable. Their eccentricities (how much their orbit differs from circular) will stay small, as will their inclination (how far above or below the plane of the Solar System they travel). Similarly, the semi-major axes (the radius of the longest part of an elliptical orbit) will not change significantly for any of the planets.

The Semi Major Axis of a planetary orbit | Credit: Sndeep81/Wikimedia Commons

Even downgraded dwarf planet Pluto was included in this study, and diehard Pluto fans will be happy to know that it too is likely to do little more than oscillate a bit over the next 100,000 years.

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So what happens after 100,000 years? The farther you go in time, the harder predictions become, as the real Universe is always a little chaotic, but Zhivkov and Tounchev believe that “with simple additional reasonings and evaluations… the Theorem could be proven for one million years.” There’s not likely to be trouble in that timespan either. And, if you’re really worried, all it would take is some additional computing power beyond what was accessible to the researchers, and “the stability of the solar system could be proved for the next five billion years,” they say.

The true colours of the planets

Of course, the model isn’t perfect. It doesn’t take into account relativistic effects, and the math assumes that the planets are point masses, which, of course, in real life they are not. But perhaps the most glaring omission from the calculation are the millions of smaller bodies in the Solar System: asteroids, comets, and everything in between. On their own, the gravitational effects of these objects are negligible, but as a collective, over billions of years, they certainly could jiggle the planets around a bit. Including them all in the model would be a monumental task, and one with diminishing returns. It’s not something that should keep you awake at night.

What’s so good about this?

Thankfully something is stable right now. Earthlings, Martians, and Jovians alike: take a breath and enjoy the ride. The next 100,000 years around the Sun are going to be smooth sailing. Don’t forget the sunscreen!

If you want proof, read the research on ArXiv. Subscribe to Universe Today’s weekly email newsletter for more spacey news like this.

Meet the writer

Scott Alan Johnston is a science writer/editor at the Perimeter Institute for Theoretical Physics, a contributor at Universe Today, and a historian of science. He is the author of The Clocks are Telling Lies, which tells the story of the early days of global timekeeping, when 19th-century astronomers and engineers struggled to organize time in a newly interconnected world. You can follow Scott on Twitter @ScottyJ_PhD

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