Does anyone believe in aliens? Has anybody seen an alien?

Li chengyuan, a researcher at the purple mountain observatory, told us that there is an important scientific theorem in astronomy called the Copernican theorem, which tells us that in addition to earthmen, there must be aliens. Why?

• Copernicus is known to all, before him, it was thought that the earth is the center of the universe, but then he put forward the heliocentric theory, and then people found that in fact the sun is not the center of the universe, it is just a normal star the Milky Way, even the Milky Way is not the center of the universe, because there are billions of galaxies in the universe. So astronomers have come up with a Copernican theorem, which means that since the time of Copernicus, human beings are no longer special, and if we find ourselves special in our studies, we should be careful, because this “special” may well be some kind of prejudice.
• For example, we used to think that the earth was special, that it was not too close to the sun, not too far away, just hot enough for water to exist as a liquid. But according to Copernicus, we are not special. There should be thousands of planets like earth, and there must be creatures like us. This led scientists to the idea of looking for aliens.
• By the same token, is our universe unique? That’s not necessarily true. There are thousands of other universes out there, and we’re just one of them.
• So the Copernican principle tells us that if you ever find yourself very special, you have to be careful, it’s probably just some bias in your mind.

Science writer cao tianyuan recently made a wonderful speech in a lecture, he raised a question: in the universe and the earth is very similar to the planet, the Milky Way alone, there are 1 million to 10 million planets may have intelligent life, but there is a very strange thing, why we have not yet found aliens?

• We’ve made a lot of efforts to find aliens. We launched voyager a few decades ago, with pictures of humans on it, a golden record in every language, and all kinds of gifts for aliens. We also used a large radio telescope to send a telex into the sky, which has been commercialized for two years. You can send any message to outer space as long as you pay for it. Some people have sent advertisements, some people have sent science fiction movies and even sent tweets.
• Many people don’t agree with sending signals into space. Hawking said that humans had better not take the initiative to expose themselves, because aliens are good or bad you do not know. Science fiction there is a dark forest in the “three body” theory, said that the universe is like a dark forest, who also can’t see, you don’t know the darkness is a beast or a hunter, once you Shouting about, others in don’t know you is good or bad, the safest way is to position to play a gun at you, kill you first. Voyager was controversial when it was launched last century. There was a joke. After the NASA scientist came home, his daughter said, “dad, I took a nude photo of myself today, recorded a song, and inscribed my home address on a CD, then threw it on the street.” His father said there was something wrong with you. ! His daughter said, you know this is looking for death, then you throw our human information into space, this is not the same looking for death?
• But many people don’t think it makes sense to send a signal or not, because since the invention of radio, we’ve been sending messages out into space. Our television transmissions, our cell phones, our radars, all these signals travel out into space, they travel out at the speed of light, and you can’t catch them. If alien technology is advanced enough, he can receive the signal from our TV station 40 light years away. So, in fact, we have exposed the earth’s position to outer space. But the strange thing is, our message has been spread to outer space for a hundred years, so far, we have not found any alien response to us, which is really very strange to scientists.
• So, there’s a saying in science about the great silence of the universe, which means that the whole universe is as silent as death. One of the great scientists, Fermi, asked the question: if the universe is so big and there are so many earth-like planets that could have developed alien life, why haven’t we found aliens yet? This is the Fermi paradox.
• Some people say that the Milky Way is too big for aliens to fly over. In fact, the Milky Way is not very big. But don’t forget, our galaxy is 13.6 billion years old. All it has to do is keep sending ships to new planets, and then build more ships there, and then fly to the next station, and in this viral way, it doesn’t take much time for a civilization to take over the entire galaxy. For example, if a bacterium enters a room, it won’t be long before the whole room is full of bacteria, but the strange thing is that 13.6 billion years later, the whole galaxy is still empty, just like an empty house without any bacteria. What’s the reason?

Scientists offer three explanations.

• The first is that humans may be the only life in the universe.
• The second explanation is that there is a civilization that rules the universe. It has developed something in the universe that looks like a nature reserve, and our earth is probably a protected, observed object, so no alien civilization has come into contact with us.
• The third explanation is that there may be many alien civilizations and intelligent creatures in the universe, but there is a general rule in the universe that all civilizations destroy themselves at a certain stage. This is a very popular theory in science called the big filter. The “big filter” theory holds that the development of all civilizations will come to a threshold that cannot be crossed. This threshold is actually a filter that everyone has been filtered out. This could explain why we haven’t found aliens yet, and why the universe we see is empty. What’s more frightening is that if this is a universal law of the development of the universe, do we humans have the same fate? ‘if this is the law of the universe, then earth civilization can’t be an exception,’ cao said. ‘and we can use probability to calculate when humans will reach the threshold of the big filter.’
• Cao tianyuan’s calculation is very complicated, I will try to explain it. Let’s say you have a box with a hundred numbered balls in it, and you touch it, and the probability of finding the top ten is 10 percent, right? So the scientists could go back and say, well, if you pick a random ball and it’s number 10, there’s a 90 percent chance that there won’t be more than 100 balls in the box. Hear here, estimation majority person also did not understand, but we also do not understand, calculate according to this truth. There have been 60 billion people born on the planet since ancient times, and those 60 billion are the number of balls we picked up, and we can do the reverse, and there’s a 95 percent chance that the total number of humans will not exceed 1.2 trillion. How many more years will it take before the next 1.2 trillion people are born? Ten thousand years is enough, so human civilization has ten thousand years left.
• You see, there are a lot of things, including the universe, including alien civilization, a lot of people do not care about it, think it and we have what ah, but since we are a member of the universe, our development law and the law of the universe must be closely related. For aliens, what happens to them, what fate they will encounter, in essence, also determines our own future, our own destiny.