If you've been looking for a new Netflix obsession like me, chances are you're considering 3 Body Problem, the sci-fi series based on the hit books by Liu Cixin. The eight-episode show, from Game of Thrones creators David Benioff and D.B. Weiss, and True Blood writer Alexander Woo, begins in ‘60s China where a young woman makes a fateful decision that has endless repercussions across space and time. 3 Body Problem follows 'The Oxford Five;' a team of scientists who race to save humanity from the dangerous consequences.
Much of the show centres around the real science of the ‘Three Body Problem,’ therefore blending fiction with the reality of principles relating to astrophysics. But some of it can certainly be a little, well, mind-boggling – unless you have a scientific background and know what's going on. I spoke with Kate Pattle, Lecturer at University College London in the Deptartment of Physics & Astronomy, to simplify said science and to distinguish fact from fiction. Keep reading to discover the answers to the questions you've been wanting to ask.
What is the three Body Problem (in simple terms)?
Let's start with the basics: what exactly is this term and how is it used within astrophysics? Kate explains that “it all goes back to Isaac Newton’s theory of gravity.”
“For a ‘two-body’ system - two objects that feel each other’s gravitational pull, like the Sun and the Earth, or two stars orbiting one another - Newton gave us a straightforward mathematical solution for how the pair of objects will move. If we know where the objects are now, and how fast they’re moving, we can accurately predict will be at any time in the future.”
The problem is when a third object is added into the equation, which is when predictions become a lot more difficult.
“For any number of objects more than two, even though Newton’s laws of motion apply to the system, we don’t have a simple equation that describes how the set of objects will behave. We call this the ‘three-body problem,'” Kate explains. “If there are three objects, for example, three stars, feeling each other’s gravitational pull, we generally can’t predict their future behaviour.”
“The system can be what we call 'chaotic' - which means a very small change in where the three bodies are right now can produce huge changes in where they will be in the future. It’s like forecasting the weather, which is also a chaotic system: the weather forecast will probably quite accurate for tomorrow, but by next week, we have very little idea of what’s going to happen, and for next month, we have no idea. When predicting the future of three-body star systems we predict over thousands or millions of years, rather than over days or weeks for the weather, but the principle is the same.”
Can the Three Body Problem be solved, and how close have experts got?
With such a complicated, ‘chaotic’ problem, is this something that can ever be practically solved? Well, the answer is a sort of ‘yes and no’. Kate says:
“There have been many attempts to solve the three-body problem, and what are called ‘series solutions’ have been found - these solutions are mathematically beautiful, but require you to be able to sum to infinity to get a perfectly accurate answer. There are no solutions that work in every case that can produce a perfectly accurate prediction for a three-body system in a finite amount of time. There are a few entirely accurate solutions for particularly special cases - for example, if the stars were moving in a figure-of-eight pattern - but patterns like this are very unlikely to be seen in real star systems.”
That doesn't mean that astrophysicists aren't continuing to try, however. “Generally, we use computers to produce approximate solutions by taking very small steps: we predict where the stars will be a very short time into the future - for which our ‘forecasting’ should be accurate - and then make a new prediction based on our answer, and then keep going like that."
However, says Kate, this only works for a while, then breaks down “just as the weather forecast does – although we are predicting over thousands of years, rather than days or weeks.”
It also depends on the circumstances: “When the third body is much lighter than the other two - like the Moon, in the Sun-Earth-Moon system, for example - we can produce an extremely good approximation to the real solution for a very long time into the future. But if all three bodies have about the same mass - such as in the Trisolaris system in 3 Body Problem - it is much harder to make accurate predictions for where the stars will be in the future.”
What would happen if there was a civilisation living on a planet within a three-body star system?
So, what exactly would happen if something like the story in Netflix's 3 Body Problem actually did happen? Would it cause destruction and chaos? Well, it sounds as though it sort of depends on the circumstances. “There’s nothing inherently bad about living on a planet in a triple system, provided that it’s a stable system,” notes Kate.
“The nearest star system to our own, Alpha Centauri, is an example of this. Stable triple systems are typically what we call ‘hierarchical triples’ - there are two stars locked together as a close pair, and a third star which is much further away, which orbits around the central pair as if they were one star. In these cases, planets can quite happily orbit around any one of the three stars (circumstellar orbits), or around the central close pair (circumbinary orbits), or around all three stars at once (circumtriple orbits) - and examples of all three cases have been found. Sometimes these planets are even found in ‘habitable zones’, which means that the conditions are right for them to have liquid water on their surfaces - which is necessary for life as we understand it.”
However, if the triple system is not stable, Kate says that the outlook is indeed “a lot less cheerful.”
“Generally, unstable triple systems like the one in 3 Body Problem are probably short-lived, in astrophysical terms – so with lifetimes measured in millions of years, rather than the 10 billion (10 thousand million) years that our Solar System will live for. We expect an unstable three-body system to usually quite quickly disintegrate (again, by ‘quickly’, we mean over thousands of years, at least!), with one of the stars being thrown out of the system entirely. It’s unlikely that a planet could live in an unstable triple system for the billions of years needed for multicellular life to evolve, let alone for long enough for an advanced civilisation to develop.”
This would ultimately result in dire consequences for said civilisation, meaning alternate ways of living would need to be found pretty promptly. “If you were living on a planet in an initially stable triple system that became unstable, it would probably be the end of your civilisation if you didn’t act.”
Kate continues, speaking of solutions: “If your civilisation had developed interstellar travel and you knew about a planet in a stable orbit around a single star to go to - like the Earth, for example - you would certainly want to get there as quickly as you could, as being in an unstable three-body stellar system would likely end with your planet being thrown out of the system and into the depths of space.”
How much of Netflix's 3 Body Problem is realistic, and how much is completely fictional?
If you're worried about a near future that looks like the storyline of 3 Body Problem, fear not. “Although the idea of planets in three-body stellar systems is plausible, most of what happens in the show is completely fictional - and it wouldn’t be a very good story otherwise,” says Kate.
“We know that many stars have planets around them, and that many - perhaps most - stars are in multiple systems, so planets in three-body star systems may be quite common. We’ve even detected planets in binary and triple systems, sometimes in places where liquid water could exist - and so where life like our own might be able to exist, as well. However, chaotic triple systems like the one in 3 Body Problem are probably short-lived, so complex life having time to evolve on planets in such systems is very unlikely.”
Kate continues: “We have very little idea about how common life is in the Universe, but the chances of having an advanced civilisation on a planet orbiting a star near our own seem to be quite low. However, if advanced alien life does exist near us, our communication with them would always be limited by the speed of light - it takes more than three years for light waves to reach Alpha Centauri, the nearest star system to our own. Unlike in 3 Body Problem, we can’t communicate faster than the speed of light using quantum entanglement, as this effect doesn’t allow information to be transmitted.”
"Finally, the Trisolarans make use of ‘sophons’ - higher-dimensional supercomputers the size of subatomic particles - to interfere with life on Earth. While higher dimensions are theorised, we have no direct evidence yet for their existence, and even if they do exist, using them in the way described in 3 Body Problem is pure science fiction."
Is 3 Body Problem on Netflix now?
Yes, the TV series came to Netflix on March 21st so is available to watch now. The trailer is available to watch below, in case you still need convincing. Sci-fi fans, this one's for you!
