I think the novel The Three-Body Problem is a great collection of thought experiments! I'm not the one who said it, but it was Liu Cixin who made this observation. Oh, of course! His exact words were not like that. His exact words were, "I only write about possible worlds." What he meant was that Liu Cixin likes to imagine an extreme situation and then reason along the lines of what is realistically possible to come up with a story that could happen. It's a fascinating approach!

Let's make this sentence a little clearer, shall we? This is exactly what a thought experiment is all about! Let's start by having a quick chat about what a thought experiment is. It's a way of using your imagination to do experiments that you can't do in real life. Since everything is imagined in the mind, doing a thought experiment is a great way to set out particularly extreme situations. The great thing about thought experiments is that you don't have to actually face extreme situations. You can just use your imagination to figure out important questions at a low cost. One of the most famous thought experiments in history is Galileo's experiment with the iron balls. I'm sure we all learned about this experiment in our high school physics class! He threw two iron balls, one big and one small, from the Leaning Tower of Pisa and guess what? They both hit the ground at the same time! Guess what! Galileo never actually went to the tower to throw the ball. He just did the experiment in his head. If you can understand this just by thinking about it, then you can save the cost of even climbing to the Leaning Tower of Pisa – which is great news!

And you know what? We all do thought experiments in our everyday lives! We've all been there. You're forced to do that classic thought experiment: if you and someone else fell into the water at the same time, who would you save first? You see, this is a pretty extreme situation that's pretty unlikely to happen in real life. I wonder why people like to ask this question? He's really just trying to get a sense of how important he is to you, without having to take the risk of falling into the water. So, a thought experiment is all about setting up a plot and using a real story to help you figure something out without any risk. The entire novel "The Three-Body Problem" is a perfect example of this. All the imagination is reasoning in the real world, making you feel that everything in the story is possible – isn't that wonderful?

We're chatting about the amazing "Three-Body Problem" trilogy today! We've broken the nearly 1 million-word masterpiece into 15 intriguing questions, which are also 15 thought-provoking experiments. And the best part is, after listening to these 15 thought experiments, you'll know the entire storyline of the Three-Body Problem trilogy! Once you've listened to the story, you'll be able to answer the 15 questions just like the author did! And you'll also get 15 solid gains out of it. In the past, it was a time when having the answers made you the most powerful person around. But things are different now, and that's a good thing! It's so tricky to know the answers to some of these questions! There's no right or wrong answer, so it's all about how you feel about them. So, it's those who can ask good questions who are the most powerful! They're the ones who can use questions to get everyone thinking and help them get closer to the truth.

Let's dive into the first part, "The Past of the Earth". The original book is a real page-turner, with more than 200,000 words! We've summarised it into three thought experiments, so you can enjoy the best bits in no time. Let's dive into the first thought experiment together! In this modern age of information, it's worth asking: to what extent can an ordinary individual damage the system? And now for our second thought experiment: I'm sure you know that you have to hit the snake at the seven-inch mark. So, where should you hit the seven-inch mark of a civilisation? I'd love to know your thoughts on this! And now for something a little different! Let's play a third thought experiment together. So, what should we do first when we find out that someone has been acting as a traitor in our system?

Part 1

Experiment 1: In the information age, just how much damage can an ordinary individual really do to a system?

I think we can all agree on one thing, can't we? The answer to this question in the novel is that, in the information age, a small, ordinary individual can completely destroy a system. It's a pretty surprising answer, but it's true! In the story of Part 1, it's so sad to see that both the human race and the Trisats, two races, can be killed by an ordinary individual in their camp. But it was the human race that was hit the hardest. I'd like to introduce you to two very special people. The first is Ye Wenjie, and the second is No. 1379 Trisolarian. Before we get to know these two lovely people, let's take a quick peek at what's going on with the Trisolarians. In the nearest star system to our own Sun, that is, the star system just 4.3 light-years away, there are some lovely aliens living there, the Trisolarians. The Trisolarians are really clever and have amazing technology, but they do have one worry: their planet is a bit unreliable.

In their lovely star system, there are three beautiful suns in total, and the result is that each sun exerts a gravitational effect on the triple planet. This is a classic problem in mathematics called the "three-body problem", which is also the origin of the title of the novel. The "three-body problem" is a pretty tricky one! It basically shows that in a three-body world, it's impossible to accurately predict the future. In simple terms, we just don't know what tomorrow will bring! It's so sad to think that tomorrow, with a bang, the poor three-body people's planet might be sucked up by the two bigger of the three suns. That would be the end of the surface of the three-body planet, burned to death. Who knows, maybe one day it will be sucked up by the youngest of the three suns, and the poor planet will be frozen to death. But, who knows, something might go wrong and the planet might keep being pulled back and forth, and it might fall into one of the suns, and the three-body people might be finished.

So the trisolar people were really eager to find a planet that they could depend on, like one that orbits a star, and settle down there. The trisolar people kept a close eye on the universe, looking for any signs of what might be out there. They never imagined that, right next to them, there was a sun and a planet!

This is the big background story! And it was at this time that this ordinary individual from our human side of the story made her appearance. She really attracted the trisolar people here, and it was she who caused humanity to suffer terribly. Let me tell you about Ye Wenjie. She's a lovely lady, originally from China. Ye Wenjie's lovely parents were scientists. Originally, this was a very rational family, but sadly, Ye Wenjie's parents were persecuted to death during the Cultural Revolution. This has made Ye Wenjie particularly desperate about humanity. At the same time, Ye Wenjie works in science, which gives her a handy way to send a signal to the universe. She sent a little update about our lovely planet Earth to the whole universe. This signal is what the Trisats have been dreaming of finding!

So, the signal that Ye Wenjie sent was picked up by a trisolarian called 1379. This 1379 is a lovely, low-level civil servant in the trisolar system. The trisolar system is a particularly totalitarian society, and the lives of low-level civil servants are particularly boring. It's a shame, but it's true! On top of all that, this 1379 is a single dog who has spent his whole life monitoring cosmic signals. In the end, he's old and unattached and has developed a strong, world-weary complex. He thought, "What's the point of living my life?" And we Tris are also really keen on colonising other planets! I wonder if this way of life should be promoted throughout the universe? Oh, is that right? It's so clear that 1379's philosophical thinking is spot on! But for the Tris, his thinking is completely off the mark. Because it would mean that the future of the entire system would be delayed.

Just then, Ye Wenjie sent a signal with some interesting news about our planet Earth. 1379 looked at it and said, "Oh my, what a beautiful and stable planet! It's absolutely perfect. I've been looking for this my whole life!" Oh dear, I'm feeling a little world-weary now, and 1379 did something that was a little unreliable. His reply to Ye Wenjie was short and sweet, just three sentences: "Please don't reply, don't reply, don't reply." He said it three times, in a kind but firm way: "I don't care who you are, if you don't reply, there are countless planets in your source of signal, and we still won't know exactly where you are, and we'll never find you." If we never find you, we'll miss out on the chance to share this wonderful life with you. But if you do reply, we'd absolutely love to invade you!

No. 1379 had just finished writing this and sent it back to Earth in the blink of an eye. Oh dear, that was a bit irresponsible of him. He had just let slip a once-in-a-millennium opportunity, and on behalf of all the Trisats, he had made a decision that he really didn't want to live with. As soon as the message was sent, poor No. 1379 was arrested. The leader of the Triniti was feeling pretty down, thinking that this clue must be cut off. You, No. 1379, have said so, so there's no need for me to reply. In a surprising turn of events, Ye Wenjie emerged as the winner in this intriguing competition to see who is more unreliable. It's true, in the race to find the answers, the Earthlings didn't come out on top. Ye Wenjie has never been arrested, and no one on Earth knows that there is someone called Ye Wenjie who, on behalf of all mankind, let the wolf called Triniti in. Isn't that something?

Ye Wenjie was also really surprised when she got the message. Oh my, it really is true! There are aliens, and they're not at all reliable. Oh, I wonder why they told me not to reply? This alien is quite interesting! They're even worried about our invasion. Isn't that just the best news ever? I really do think that there's no hope for humanity, you know? So Ye Wenjie replied with a smile, "Come on, invade us." I'd be happy to help you take over the Earth! "Sadly, our civilisation is no longer capable of resolving its own conflicts." But just as the message was about to be sent back, something rather exciting happened! The human side's information supplement system suddenly started working again, and a leader discovered that Ye Wenjie was in contact with the aliens. Ye Wenjie had no choice but to kill her to keep her mouth shut. To keep the secret, she even killed her husband. In other words, Ye Wenjie was set on going through with her anti-human mission.

Four years later, the Tricobolans were delighted to receive a reply from Ye Wenjie. They were really quite taken aback, saying, "Is there such a silly creature?" And they were so close! Just four light years away. So, what else could they say? As the Chinese people would say, "There's no time to waste, let's get going right away!" They used every last bit of the planet's resources to build spaceships and, with all the strength of the Trisats, they began to invade Earth. On the human side, for a long time, only Ye Wenjie was in the know.

I just wanted to share the beginning of the chronological thread of The Three-Body Problem with you. This is how the wolf was let in. It abused humanity for hundreds of years, killing billions of people. And it all started right here! Let's take a moment to consider this thought experiment together. Ye Wenjie and No. 1379, two ordinary people, had an incredible impact on the fate of their respective civilisations not once, but twice! If we think about it, this kind of thing was totally unthinkable in the days before humans existed. In human history, it's not uncommon for an individual to influence the direction of a nation or country. But those were all key figures with high positions and power, at least people like Wu Sangui. I'm sure you've never heard of two nobodies chatting and changing the fate of two civilisations twice! This would never happen in our modern world, where we live in cities and grow food. So, when there's no obstacle to information, ordinary folks can really make a big impact.

Oh, and I just had to mention that the plot in the novel "The Three-Body Problem" is completely logical! You know, Stephen Hawking actually said something similar in an interview: Just a friendly word of advice: try not to jump to conclusions about aliens. In other words, Hawking made a really good point when he said that the Three-Body Problem was a logical defence.

So let's take a look again at why the Three-Body People won this round, shall we? We just wanted to quickly mention that the Three-Body People fixed this information loophole in No. 1379 really quickly, while Ye Wenjie on the human side didn't manage to catch up, so in this regard humans were completely defeated and deserved to be invaded. And it's possible that the way this important information was shared might not have been the best way to do it. It might have been leaked at a totally normal node by a regular person for a pretty strange reason at a time when you didn't know. So, the first thought experiment shows us that it's really important to keep those key pieces of information safe. After all, they could make or break you! It doesn't matter if you're a company or a family, it's really important to make sure that your key information isn't leaked from any small places. So, if someone in each of our families or companies is a bit careless when it comes to keeping key information safe, it might be a good idea to remind them about this plot from The Three-Body Problem. This is what Liu Cixin thinks we should take away from this sad story of how we were tricked.

This is the first thought experiment: in the information age, even an ordinary individual can destroy the entire system.

Part 2

Experiment 2: We all know that to kill a snake, you have to hit its vulnerable spot. So, where should we hit to kill the vulnerable spot of a civilisation?

Let's start by sharing our perspective. The answer given in the novel is really quite simple! To hit the vulnerable spot of a civilisation, you have to hit its technology, and more specifically, its basic science. Let's take a closer look at how the novel reached this conclusion.

If aliens were to attack a civilisation, where would be the best place to start?

As we just said, the tricornered people are fully armed and have come to invade our beloved planet Earth. But there's still a long way to go! It'll take 400 years for the tricornered people's spaceship to fly 4 light-years, given that it can only reach 1% of the speed of light and there's a distance of 4 light-years between the two planets. The Tricornered People are very thoughtful and precise in their thinking. Firstly, the poor Trissians are stuck on the spaceship, and their scientific progress has come to a standstill. It's a shame, but the spaceship is too small and there just aren't enough resources to conduct research while flying. So, sadly, their current level of science will still be the same when they arrive on Earth 400 years later.

So, do you think the Earthlings will be able to catch up with them in technology during these 400 years? The Trissians took a look at the history of humankind and were really quite shocked. It's not a question of whether they'll overtake us, but how much. It's truly amazing how quickly humans have progressed! It took millions of years to go from the Paleolithic to the Neolithic, but just a few hundred years to go from cold weapons to hot weapons, and then only a few decades to go from hot weapons to nuclear weapons. If this pace continues, in 400 years, humans will have reached the heavens! But who knows, maybe someone will rush out and destroy you first. So, the Triniti really need to find a way to lock down the technology of the Earthlings.

So, you might be wondering, how do they do it? The Trissians have a very straightforward approach: they focus their efforts on attacking the basic science of mankind. To be totally honest, they attack the sciences that seem to have no practical value. I know this might seem a bit surprising at first. I think we all think they should attack our spacecraft technology, laser technology or nuclear bomb technology. But the Trissians don't concern themselves with any of that. They just focus on the basics of science. The reason is actually really simple! I'm sure you'll understand if you think of an analogy. It's like we're going to invade a tribe of lovely, primitive people in the woods, but it's a 400-year journey. I'm sure we can all agree that the biggest fear would be if something happened to the lovely, primitive tribe during those 400 years. If the primitive people were always thinking about how to increase the range of their bows and arrows, or how to apply the poison of a certain kind of frog to the tips of their arrows, then we would feel at ease and be happy to let them do whatever they want. After all, there is no future in this path.

But if there's a primitive who isn't doing their job and is always thinking about things that don't matter, like what stones are made of and what wood is made of, we tend to kill this person because they might be a chemist. With a chemist, the primitive is one step closer to creating a gun. At the same time, if there is another primitive in this tribe who studies geometry and mathematics every day, we might feel a bit protective and want to help them find a new path. After all, as long as they can calculate parabolas and ballistics, they are one step closer to creating a cannon. So, as you can see, we can draw two conclusions from this analogy. We're not afraid of the other side's scientific progress. What we are afraid of is that the science of a hostile civilisation has reached a new theoretical level. And it's this very basic science that can help the other side reach a new level, even though it might seem useless at first.

So, to answer the question you just asked, how can we effectively attack a civilisation? It's so important to remember that if you prevent a civilisation from making progress in basic science, you're effectively capping their ceiling. It's so important to remember that as long as you can't reach the ceiling, no matter how hard you try, nothing will happen.

Let's play a little game. Let's switch roles. Now, we're just primitive people, bless us! I'd love to know what the trilobites think about humanity today. I'm so proud of humanity! Our theoretical physics is making great strides, even though we're still a young species. It's so interesting to see how humanity's exploration is heading in two different directions: one is extremely large, and the other is extremely small! The former uses telescopes, while the latter uses particle colliders. First, let's talk about telescopes. We have to give a big thank you to our wonderful planet Earth for having such a clear night sky! This allows us to look outward with telescopes with hope and anticipation. This process of looking, to put it in a way that's a little less formal, is a process of watching the excitement unfold. Those who watch the excitement aren't afraid of big things. They're excited about them! The bigger the thing, the broader our macroscopic understanding – it's as simple as that! So we choose to watch those big things, such as supernova explosions, black holes colliding with each other, and galaxies merging. It's so fascinating!

But after watching all these amazing, big things, how can we possibly understand the essence? And guess what? The answer is to go back to the microscopic world! Guess what! It turns out that the whole universe is a bit like a game of Tetris. Don't be fooled by how complex the universe seems. It might actually be made up of just 17 types of particles, which is like 17 different kinds of Tetris-like building blocks! This is the current "Standard Model of Particle Physics", which is a pretty cool way of understanding the building blocks of the universe! This lovely theory suggests that our world is made up of 17 types of particles that are held together by some simple rules to form the entire universe.

So, if we put all this together, we can sum up the research process of human beings in a poem: "Gazing up at the universe, we bow our heads in awe and play with particles." I'd like to introduce you to the machine we use to study particles, which is the collider. The collider is a nifty little device that gives these little Tetris blocks, which we got from God, a big boost to really high speeds so they can smash into each other and help us understand more about the nature of particles under some pretty extreme conditions.

So, after such a long journey, we have come to the conclusion that the future of human civilisation lies in the particle collider. I really think we'd be missing out if we didn't have the particle collider! Because we'd never know the nature of matter. If we didn't have the particle collider, we'd be missing out on so much! Just look up at the stars and you'd be watching a show. This is what the lovely Trisolarians do. Right, let's get back to the plot of the novel, shall we?

The lovely Trisolarians sent something called a "transtar" to seal our science. A transtar is a super-miniature robot with a mass the size of a hydrogen atom. It's multifunctional and pretty amazing! So, a transtar can be accelerated to near the speed of light and will arrive at our lovely planet Earth in just over four years. The way they make a transtar is really quite clever. The lovely Trisolarians built a super robot called a transtar in 9-dimensional space. This robot is really quite amazing! It has a very complex structure and a huge mass. Once it was built, the robot was folded from 9-dimensional space to 3-dimensional space, where we live. And then something truly amazing happened! The robot shrunk down to the size of an ordinary hydrogen atom. And then it can be sent to Earth with ease!

The tachyon plays a really important role in helping us out by interfering with human particle colliders. The tachyon can't destroy the collider, but it can cause a bit of a hiccup. The tachyon is a clever little thing, isn't it? It can turn into any kind of particle and travel at the speed of light in the collider, which creates a lot of false information. This can make the experimental results a bit messy, but that's okay! If the collider stops working, it could have a big impact on humanity. This is the topic of our second thought experiment, which is all about how a civilisation of seven inches can build a future based on its basic science, and to be more specific, theoretical physics.

What can we learn from this? It helps us learn more and understand how human civilisation is moving forward. If you ever hear someone say that spending billions on a particle collider is useless, just tell them that it's really important for the well-being of humanity, the future of future generations, and even what we'll use to fight the day aliens really do arrive. If your little one is interested in physics, it's a great idea to guide them and explain that physics is about so much more than just little balls and little carts pushing and pulling to solve problems. Physics is the future of humankind, and it's so exciting! And if we ever get the chance to meet a physicist, we should definitely treat them to a lovely meal and listen to them talk about what they do! Okay, this is our second thought experiment. And now, let's take a look at the third one.

Part 3

Experiment 3: What is the most important thing to do once a traitor in the system is discovered?

Let's go back to the story of the novel together, shall we? We mentioned Ye Wenjie earlier, and I just wanted to circle back to her for a second. She was the one who introduced the Trisolarians to Earth and set up an organisation called Earth Rebels, which brought together a group of people with some pretty unique worldviews. The goal was to team up with the Trisolarians to invade Earth. To keep a low profile, this group of Earth Rebels bought a large cruise ship that never docked. It was a great plan! It only worked on the sea, communicating with the Trisolarians back and forth, which means there were lots of chat records. Nothing can stay secret forever, my friend. After a bit of a struggle, the human race finally captured Ye Wenjie alive and learned of the existence of the cruise ship.

So, here's the big question: what's the best way to handle a traitor? The answer in the novel is that it's really important not to kill them, but to get hold of all their chats with the other side.

I can think of two reasons why. Firstly, a traitor can see you in a way that's totally new and different. It's always a good idea to take what your opponent says at face value. After all, they're the ones who are going to be affected by it, so they're more likely to tell the truth. I really appreciate your feedback! The second reason is that you can find out what your opponent's priorities are. There's a lovely saying in Chinese go that I think you'll find really helpful: "The opponent's priorities are your priorities." If you find yourself feeling uncertain about the situation halfway through the game, it might be a good idea to put yourself in your opponent's shoes for a moment. If you were him, what point would you most want to occupy? I'd love to know your thoughts! Then you should place your piece there, and your opponent will definitely feel a bit uncomfortable. I'm sure you'll agree that this reasoning is also applicable in today's business competition. From the information that the opponent has asked the traitor, you can easily work out what the opponent's point is.

So, when you find out there's a traitor in the system, don't go looking for them straight away. First, make sure you get the chat history. Let's dive into the thrilling finale of Part 1 and explore how humans managed to get their hands on this chat log. First of all, it was definitely not possible to board the ship directly and arrest them. These Earth rebels were all desperate outlaws, as alert as rats. Once they sensed that something was wrong, they would immediately delete the chat log and commit mass suicide. And then, something amazing happened! Humans discovered a once-in-a-lifetime opportunity. Guess what! This ship is going to pass through the Panama Canal on a certain day.

The Panama Canal is a wonderful piece of engineering that connects the Pacific Ocean and the Atlantic Ocean. At its narrowest point, it's only 152 metres wide, which is no different to sailing up a river! Humans had a great idea! They put up two tall poles on either side of the Panama Canal and stretched a super-strong, nanoscale thin wire with a diameter of one nanometre between them. And there's one of these wires every 50 centimetres! These tiny wires are so small you can't even see them with your naked eye, but they're super sharp! If a ship passes through the middle, it'll be like slicing a sausage. Everything on board, including the crew, will be cut into pieces of no more than 50 cm in length. Once they're cut, people will be unable to move, and there won't be time to delete chat history. But don't worry! If the hard drive of a computer is cut, the cut surface will be very neat, and you can easily recover the data.

I'm happy to say that this plan for humanity was a great success! The cutting scene in the novel is described in a really vivid way. It's like a stack of cards being pushed forward! The ship was cut into a stack of 50 cm thick slices, and sadly, all the Earth rebels were also killed on the spot. Amidst the rubble of the ship, humanity made an incredible discovery: a trove of precious chat records, a whopping 28 gigabytes in total! The good news is that humanity was able to open these materials and obtain two very, very important pieces of information. And the even better news is that the entire subsequent story is directly related to these two pieces of information!

The first thing we learned is that the "Wisdom Child" wasn't just the pinnacle of human technology, but it also had another very important job. It was a super monitor with no blind spots and all-weather capabilities, which meant it could be found everywhere. The Tri-Stones were keeping a close eye on us, listening in on everything we said. They could hear us in real time, and the transmission was instant. The lovely Tri-Stones could see whatever the wonderful Wisdom Child saw, even though the signal didn't have to travel for four years. The second piece of information is that, throughout the entire world, the Trisats are a little bit afraid of one person. They've even sent the Earth rebels to try to assassinate this person in various ways. This person is called Luo Ji, which is actually the first two characters of Luo Ji Siwei! However, humans find this very strange, because Luo Ji is just an ordinary 33-year-old Chinese man, and there is nothing special about him. But as I was saying, the enemy's main point is our main point, so we're on the same side! So, people started to pay a lot of attention to Luo Ji.

And now, we'd like to share with you our third thought experiment. It's so important to remember that when we find a traitor within the system, our main goal shouldn't be to destroy them. Instead, we should focus on obtaining valuable information. It's so great that we can learn from this! In life, at work and when we're starting a business, we can all face these challenges. So, we just need to learn from humans, stay calm, and work out how to check what information the traitors are passing on to their opponents without them knowing. Then we can work out ways to deal with the enemy! If you use the traitor pawn well, you'll be in a great position to beat the enemy!

So, that's a quick summary of the first part of The Three-Body Problem, The Past of the Earth. That's a wrap! We've chatted about three thought experiments so far.

Let's dive into the first thought experiment together! In this modern age of information, it's a fascinating question: just how much damage can an ordinary individual really do to the system? The lovely answer given in the novel is that the system can be destroyed. It's so important to handle critical information with care. And now, let's dive into the second thought experiment together! Have you ever wondered where you should hit a civilisation to kill it? The answer given in the novel is to hit theoretical physics – which is a pretty good idea! If we meet physicists in our daily lives, we should be really respectful of them. The third thought experiment is a tricky one! It's about what you should do first when you discover a traitor in the system. The answer is to get a look at the chat history between the traitor and the opponent. It's so interesting how the key point that the opponent wants to seize is also the key point that you want to seize!

And that's a wrap on the first part of the Three-Body trilogy, The Earthly Past! Let's take a moment to look at the situation together. The mighty Three-Body fleet has already set sail, and in roughly 450 years, our descendants will face these alien invaders. Their technology is superior to ours, they have sealed off our technology with the Thought Child, and they are eavesdropping on our information and reading our data every second of the day. It's a tough situation, isn't it? But we'll get through it together! Stay tuned for the second part of the Three-Body trilogy, The Dark Forest.