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The three-body problem is a physical problem that puzzled Isaac Newton.
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It describes the orbits of three bodies, such as planets or stars, that are caught in each other’s gravity.
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The problem is unsolvable and led to the development of chaos theory.
Although Netflix’s “3 Body Problem” is a science fiction show, its name comes from a real math problem that has puzzled scientists since the late 1600s.
In physics, the three-body problem refers to the motion of three bodies caught in the gravitational grip of one another — like a three-star system.
It may sound simple enough, but when you dig into the math, everything spins very quickly.
Two-body vs. three- and multi-body systems
A simpler version is a two-body system like binary stars. Two-body systems have periodic orbits, which means they are mathematically predictable because they follow the same path over and over again. So, if you have the initial positions and velocities of the stars, you can calculate where they have been or where they will be in space in the distant past and future.
However, “resulting in a third body that is close enough to throw in an interaction,” Shane Ross, professor of aerospace and ocean engineering at Virginia Tech, told Business Insider. In fact, it is almost impossible to predict precisely the orbital paths of any system with three or more bodies.
While two orbiting planets may look like a Venusian diagram with overlapping ovoid paths, the paths of three interacting bodies are often like tangled spaghetti. Their trajectories are usually less stable than two-body systems.
All that uncertainty makes the so-called tri-body problem largely unsolvable, Ross said. But there are certain exceptions.
The problem is three bodies over 300 years old
The three-body problem goes back to Isaac Newton, who published his “Principia” in 1687.
In the book, the mathematician noted that the planets move in elliptical orbits around the sun. But Jupiter’s gravitational pull seems to have affected Saturn’s orbit.
The three-body problem didn’t just affect distant planets. Trying to understand the variations in the moon’s movements caused Newton a literal headache, he complained.
But Newton did not fully understand the three-body problem. And it remained a mathematical mystery for almost 200 years.
In 1889, a Swedish journal awarded the mathematician Henri Poincaré a gold medal and 2,500 Swedish crowns, about half a century’s salary for the professor at the time, for his essay on the three-body problem which laid the foundation for a whole new mathematical theory on called. chaos theory.
According to chaos theory, when there is uncertainty about the initial conditions of a system, such as the mass or velocity of an object, that uncertainty becomes apparent, making the future increasingly unpredictable.
Think of it as taking a wrong turn on a trip. If you turn left instead of right at the end of your journey, you are probably closer to your destination than if you made the mistake at the start.
Can you solve the problem by three bodies?
Splitting the problem into three bodies would help scientists track the movements of meteors and planets, including Earth, in the future. Small movements of our planet can have a big impact on our climate, Ross said.
Although the three-body problem is considered mathematically unsolvable, there are solutions for specific situations. In fact, a few have been discovered by mathematicians.
For example, three bodies could orbit stably in a figure eight or evenly spaced around a ring. Both are possible depending on the initial positions and velocities of the bodies.
One way researchers look for solutions is “constrained” three-body problems, where two main bodies (such as the sun and Earth) interact and a third object with a much smaller mass (such as the moon) contributes less gravitational. In this case, the three-body problem looks a lot like a two-body problem since the sun and Earth make up most of the mass in the system.
However, if you’re looking at a three-star system, like the one in the Netflix show “3 Body Problem,” it’s much more complicated.
Computers can run simulations much more efficiently than humans, but because of the inherent uncertainties, the results tend to be approximate rather than exact.
It’s also critical to finding solutions to three-body problems for space travel, Ross said. For his work, he enters data about the Earth, the moon and spacecraft into a computer. “We can build a whole library of possible trajectories,” he said, “and that gives us an idea of the types of motion that are possible.”
Read the original article on Business Insider
