Buzz
The image portrays the orbits of the planets as neat and unchanging, but is it possible that chaos theory could upset that perfect order?A word of caution: If the mention of the "Butterfly Effect" causes you to roll your eyes, you might want to stop here. But if you're intrigued by the unpredictable and dark mysteries of the universe, keep reading.
We are all familiar with the image of planets orbiting the sun in a calm, orderly manner. In fact, their movements are so precise that astronomers can predict orbital events—transits, eclipses, and alignments—with incredible accuracy. Need a list of solar eclipses over the next 10,000 years? It's available.
Now, let's imagine looking billions of years into the future. How do those ancient astronomical tables hold up then? Not very well, when you factor in chaos theory. According to chaos theory, small changes in a complex system can lead to massive, unpredictable outcomes. This is the famous butterfly effect: a butterfly flapping its wings in South America can trigger a storm halfway across the world, in Brisbane, Australia. Some scientists argue that chaos theory could govern the solar system's future evolution, and in billions of years, Earth could potentially collide with either Venus or Mars.
The researchers behind this theory, Jacques Laskar and Mickaël Gastineau, published their work in a 2009 issue of *Nature*. At the time, they were affiliated with the Paris Observatory. Interestingly, they did not rely on the observatory’s telescopes for their research but instead used the power of computers, including the JADE supercomputer at the National Computing Center for Higher Education and Research (CINES).
The computing resources may seem excessive, akin to a scientist's version of a muscle car, but when you realize the calculations they were attempting, it all makes sense. They were applying Newton's universal law of gravitation to their research.
You’ll recall that Sir Isaac told us that a universal gravitational force exists between any two objects. This force is proportional to the masses involved and inversely proportional to the square of the distance between them. He also proposed that the Sun’s gravitational pull is what keeps the planets in orbit. However, based on Newton's own law, all objects in the solar system, from planets to moons to asteroids, exert gravitational forces on each other. Could this complex interaction lead to the instability of the solar system over time? In the short term, no. Even over extended periods, most astronomers believed the solar system would stay stable.
Then, a handful of eccentric cosmologists began to speculate whether chaos theory could be applied to planetary orbits. If so, might tiny variations in planetary movements become amplified over time, eventually leading to dramatic shifts? How long would this process take? Thousands of years? Millions? Billions?
Computer Code and Chaos
To resolve this question, one must take into account the movement of all the planets and the forces acting upon them during that movement. Next, the solar system would need to be run like a clock, allowing the planets to cycle through hundreds of thousands of orbits. During this process, crucial data on each planet would need to be collected. A key factor in this analysis is orbital eccentricity, which measures how much a planet's orbit deviates from a perfect circle. Eccentricity is critical because it determines whether two planets might share the same orbit and possibly collide.
Do you think you could simulate such a scenario in your mind or with a simple model of the solar system? Probably not. However, a supercomputer can do this, which is why Laskar and Gastineau used the JADE supercomputer for their work. They inputted 2,501 orbital scenarios, each one tweaking Mercury's orbit by a few millimeters [source: Laskar and Gastineau]. They chose Mercury because it is the smallest planet and the easiest to influence, and because its orbit interacts with Jupiter’s, causing ripples throughout the entire solar system.
For each hypothetical scenario, they followed the movement of all planets for over 5 billion years, the sun’s estimated lifespan. This allowed the supercomputer to carry out the intricate calculations. Despite the power of the JADE computer, each calculation took four months to complete.
Fortunately for life on Earth, the solar system remains stable in 99 percent of the scenarios run by the French duo, meaning no planets collide or are ejected from their orbits [source: Laskar and Gastineau]. However, in 1 percent of the cases, where orbital chaos has the largest cumulative impact, Mercury’s orbit becomes eccentric enough to trigger catastrophic changes in the solar system. Some of these disasters only affect Mercury, which could either crash into the sun or be flung out of its orbit. Other scenarios, more troubling, see Earth colliding with either Mars or Venus. A collision with Venus would unfold in five stages, each illustrating the build-up of orbital chaos [source: Laskar and Gastineau]:
- Initially, an interaction between Jupiter and Mercury in about 3.137 billion years causes Mercury's orbital eccentricity to grow. This transfers noncircular angular momentum from the outer planets to the inner ones.
- This momentum transfer destabilizes the inner planets, making the eccentricities of Earth, Venus, and Mars grow larger.
- Earth has a near miss with Mars, further destabilizing Mars’ orbit.
- Subsequent resonances, or synchronized, reinforcing interactions, between the inner planets reduce Mercury’s eccentricity but increase the eccentricities of Venus and Earth even further.
- Venus and Earth continue having near misses, and eventually, at 3.352891 billion years, they collide in a massive explosion that annihilates both planets.
When it comes to orbital instability, its effects are often invisible in the short term. However, astronomers have found other signs indicating the instability of planetary motion. In February 2012, the European Space Agency's Venus Express spacecraft, while attempting to observe surface features of Venus that had been identified by Magellan 16 years prior, discovered that these features were displaced by 12 miles (20 kilometers). This suggests that Venus’s rotation may be slowing down. The high atmospheric pressure and intense winds on the planet could be causing friction that affects the surface, which might lead to one Venusian day lasting nearly 250 Earth days [source: Atkinson].
Perhaps Not After All
An artistic rendering of Dawn orbiting the asteroid Vesta. Astronomers are keenly interested in the possibility that this massive asteroid might someday collide with its asteroid neighbor, Ceres.
Image courtesy of NASA/JPL-CaltechIn 2011, as NASA's Dawn spacecraft entered orbit around Vesta, Laskar examined the chaotic interactions between Vesta and the asteroid Ceres, as well as the dynamics between these asteroids and the planets. His findings showed that even the smallest errors in measurements could be amplified by these interactions, making it impossible to predict planetary orbits -- and the possibility of collisions -- beyond 60 million years into the future [source: Shiga]. While collisions between Vesta and Ceres seem probable, the fate of the planets remains highly uncertain.
So, what can we make of all this seemingly paradoxical information? First, the solar system is brimming with objects that, according to Newton's laws, exert gravitational forces on each other. Second, these forces can significantly alter planetary orbits, even if these changes are not measurable in the span of human history. And lastly, here's a fun thought: the universe doesn't create or destroy worlds gently, but instead does so through intense and violent processes.
In fact, astronomers have observed other solar systems facing catastrophic destruction. In 2008, a team from the Harvard-Smithsonian Center for Astrophysics detected a Saturn-sized planet orbiting a star in the Centaurus constellation, emitting far more heat than its size should allow. The scientists now believe that this giant planet is still radiating immense heat from a collision with a Uranus-sized protoplanet that occurred in that star system's recent history.
In 2009, NASA's Spitzer Space Telescope captured the aftermath of a dramatic collision between an object the size of our Moon and one the size of Mercury, located about 100 light-years away in the constellation Pavo (the peacock). Spitzer's instruments detected the unmistakable signatures of amorphous silica, a substance that forms on Earth when meteorites crash into the surface.
Even if our solar system manages to avoid orbital chaos and the collision of inner planets, we may still face a grim fate. In 5 billion years, as the sun runs out of fuel, our once-comfortable corner of the universe will become increasingly inhospitable. Not long after, we’ll be consumed by the expanding star, swallowed completely. Whether it’s a chaos-driven collision or the death of our star, our small blue planet won’t go out quietly, but with an explosive bang.
