Astrophysics in The Three-body Problem — Black Hole, Three Spheres and More

The release of the first-ever blackhole photo wiped out all previous depictions of the behemoth in sci-fi novels and movies. It has been 104 years since Einstein first proposed the general theory of relativity, and now the exquisite theory has once again been reconfirmed by time.

When comparing the imaginary worlds with cutting-edge science, the latter is always crazier.” Liu Cixin, the Chinese author of the internationally acclaimed sci-fi novel The three-body problem, has expressed this opinion on various occasions. All of his inspiration and story ideas are already deep-rooted in the profound mine of natural sciences and astrophysics.

Black hole

As an astrophysicist, Ye was strongly against nuclear weapons. She knew this was a power that should belong only to the stars. She knew also that the universe had even more terrible forces: black holes, anti-matter, and more. Compared to those forces, a thermonuclear bomb was nothing but a tiny candle.

According to an equation we learned in high school physics, the gravitation is positively correlated to the mass of the stars, and negatively correlated to the diameter. To put it simply, as the mass of the black hole is so huge, it equals the mass of millions of suns. The gravitational pull of the black hole is beyond imagination. It’s so powerful, even the light can’t escape it.

According to Kip Thorne, the Nobel-prize winning physicist and theory consultant of Interstellar, our three-dimensional world can be imagined as a giant membrane. The black hole is like a tennis ball rolling on the wide blanket, which warps the membrane, with the time and space of our world warped along with it.

an example of a three-dimensional membrane (source: quora)

Generally speaking, the so-called event horizon, is the last place where we can see light, or rather the boundaries of the black hole.

The Three Spheres

The two spheres would stay together and hang there without moving, a symbol for death. If they did had initial movement and didn’t collide, they would orbit around each other under the influence of gravity. No matter the initial conditions, the rotation would eventually stabilize and become fixed: the dance of death.

The three spheres, given initial movements, went through complex, seemingly never-repeating movements. The descriptive equations rained down in a thunderstorm without end.

The mathematics fanatic in the novel Wei Cheng gave the three-body problem a nearly poetic explanation. During his meditation in a Buddhist temple, he saw through the mystery of the cosmos.

Three-body problem is a basic model of astrophysics, that describes the movement pattern of three celestial bodies under the universal gravitation, given random masses, initial position and movement of the “three spheres”.

In the solar system, the earth, sun and the moon can fall into such model. However, the movement pattern cannot always be traced mathematically, so astronomers often dubbed it “chaotic solutions”.

computer simulation of three body movement
computer simulation of three body movement (source: youtube)

In the novel three-body problem, three stars in a nearby galaxy form a three-body problem, and their movement falls into a disorderly pattern, sometimes near and sometimes far. Such chaos brings extreme hot and coldness to the creatures living on the three stars. So they learn to dehydrate themselves in order to survive, and come back to life through rehydration when the climate is favorable.

The three-body civilization is strongly affected by such disorderly movement of the stars, bringing the changes of Chaotic Era and Stable Era.

Multi-dimensional space and quantum communication

Sophon, in the book, was originally a particle that three-body use to communicate with humans, which is made up of protons, and can be extended both low-dimensionally and high-dimensionally. Mind here, the universe in the book can be perceived as a multi-dimensional space.

The prevalent theory is, the world we live in is four-dimensional. The fourth is the vertical axis of time, past, present and future. Steven Hawking used to describe this in a speech entitled Brane New World, focusing on the M theory (Brane theory), “We take it as obvious that we live in the world of three space dimensions and one time dimension, but maybe we are just shadows cast by a flickering fire on the wall of the cave in which we have our existence.”

Plato’s allegory of the cave (source: World Wide Kitsch)

According to the M theory, the universe is 10-dimensional or 11-dimensional. The reason we cannot perceive the other six or seven dimensions is that they might exist in an imperceptible world to humans, whether it’s macro like the multiple layers of possibilities and timelines, or micro, like what’s depicted in the quantum world in Antman.

the kaleidoscopic quantum world in Antman (source: thrillist)

In the first book of the trilogy, Sophon can take any shape or form, just like the countdown numbers that magically appeared in the scientists’ eyes, aiming to disturb the best brains of the earth society, so as to destruct scientific and technological development of mankind. Several scientists committed suicide because of this.

In the third book, Sophon the particle was extended and personified, who serves as a messenger for the earth. It has yet to be discussed why it came to be a Japanese woman called Tomoko. Some say the personification has a political implication related to the anti-Japanese war in Chinese history.

Also, scientifically, it discusses the possibility of quantum communication talking about message transmission between earth and three body aliens. Quantum communication is inspired by the quantum entanglement theory, which Einstein referred to as “spooky action in a distance”.


“You can only take a guess.” Ding Yi looked up and said, “The molecules of this thing are neatly arranged like marching soldiers, and they are consolidated with each other. Do you know how strong it is? The molecules are nailed into place. Even their own vibrations are gone.”

The waterdrop is a cosmic probe built by aliens, made of strong interaction force material (SIM) mentioned in the novel. Its shape, as the name implies, resembles a waterdrop, with an absolutely smooth surface that reflects almost all electromagnetic waves and absolute zero temperature (about minus 273.15 degrees Celsius). Its atomic nucleus is locked by strong interaction force, which makes it invincible.

Waterdrop is the author’s imaginary object, however some say that the hardness of which has a resemblance to a neutron star.

Featured photo credit to