About face-to-face communication between humans and alien civilizations?

For 200 million years, the Earth was an empty house to live in if you moved in.

Our galaxy is about 13 billion years old, and every star and planet in it didn't form at the same point in time, so it makes sense that alien civilizations evolved hundreds of millions of years apart.

Let's say 200 million years, 200 million years is not a long time for the planet Earth, except for 65 million years ago when it hit a large meteorite, the Earth's environment has not changed significantly for 200 million years, and it has been a habitable environment for carbon-based life.

Two hundred million years ago (called the Triassic Triassic) ancient geology, atmospheric oxygen levels of 15%, is about 2500 meters above sea level modern levels of plateau area (East Africa Ethiopia's average of about 3000 meters above sea level).

The average temperature of the North and South Pole is 8 ~ 10 ℃, and the low latitude tropical area is 25 ~ 30 ℃.

Gold, silver, copper, iron and tin deposits in the Earth's crust are not different from modern deposits.

On land, there are ferns, ginkgo biloba, pine, fir, cypress and other large plants, primitive mammals and early dinosaurs began to appear.

If you and I were sent to the earth 200 million years ago, you and I could fish, hunt, farm, livestock, and survive without any problems.

So the question is, if you're a high-tech alien carbon-based life civilization, sightseeing? Immigration? Mining? Expand your territory? Is 200 million years enough time for you? Did you have to wait until now to visit Earth? Or take over the planet?

If it's a selenobased civilization, then maybe two billion years ago, Earth would have been a habitable environment for selenobased life.

The answer should be obvious: even alien civilizations 200 million years ahead of us could not travel across the universe to visit Earth. In 1950 Enrico Fermi, who won the 1938 Nobel Prize in physics (and who built the world's first controlled nuclear reactor), proposed the famous Fermi Paradox: If alien civilizations exist, then we must find evidence for them.

Scientists and science fiction writers have some ideas, but I don't think they make any logical sense.

Trisolaran proposes the Dark Forest Law, which argues that alien civilizations are hiding for security reasons.

When we test this theory, the first question is: is it safe to be "silent"? I'm afraid not. A large and complete detection scheme is possible. I personally made a simple calculation: assuming a speed of 1/10 of the speed of light and an effective detection radius of 50 light years, a single mission of 8,000 detectors would take 2.5 million years to see all over the galaxy."Three body" about the destruction of human because jack replied to an alien civilization, the main information, so be exposed to the coordinates of the earth, this set is a little wronged Ye Wenjie, with the increase in the precision of astronomical instruments, new observation method supplemented by artificial intelligence analysis, from 1992 to 2022, human has found more than five thousand extrasolar planets, The number of planet discoveries could increase dramatically in the future. The Chandra X-ray Observatory, an X-ray telescope launched in 1999, discovered an exoplanet (M51-ULS-1B) 30 million light-years away in September 2020, With modern human technology already able to detect planets this far away, high-tech alien civilizations would probably be able to map the entire galaxy of stars and planets

(1). For hundreds of millions of years, the blue sun reflection reveals that there is a lot of water on the Earth's surface. Now we let the earth disappear from sight, and give the Earth a transparent optical camouflage like the "Ghost in the shell" of the Kusanagi Suko. In fact, even without the old maps, according to the Titius-Bode Law, a formula developed by the German astronomer Johann Elert Bode, the distances of planets from the sun can be easily calculated. There should be a planet in this orbit. Why is it missing? Gravitational waves cannot be hidden, and the perfectly transparent Earth can be found using astronomy's gravitational lensing method. Putting all eight planets in optical camouflage would be even more suspicious because the solar system has become too "clean".

(2) Wearing planetary camouflage, camouflage is a second-order strategy compared with full transparency, the Earth is completely covered with metal mesh of about 15 kilometers, so as to form a Gaussian sphere, which can shield all external radio waves, and polarize the surface of photovoltaic panels under the metal mesh. From a distance, The Earth would be a desolate desert planet or a rocky planet, but if you calculate the amount of solar radiation the Earth receives, and if you analyze the reflection spectra of the surface and the outer atmosphere, you know that the Earth has a habitable temperature and a high proportion of oxygen and water molecules, possibly liquid water, and you're not a fool. It is absolutely clear that when looking specifically at planets in the third or fourth orbits of G-type yellow dwarfs like the Sun in the prime of life, camouflage should not be able to fool the detection of all kinds of scientific instruments and methods.

(3) Finally, consider the envelope at the level of the solar system, the three-body is called the black domain, Douglas Adams wrote in 1979 "Hitchhiker's Guide to the Galaxy", which is intuitively called "bull step envelope", and proposed to cover the whole solar system with black holes at low speed of light. This scheme has shortcomings, the first reason is that gravitational waves can not be hidden. Instead, there is no silver here. The second reason is that the small black hole (large curvature mass) can be used as a drill bit to Pierce the black field. If it is drilled at a tricky Angle, it can even be made into a zigzag snake channel, which must be passed unless there is a road map. The dark domain can be completely invisible and undetectable back door, if I am a very paranoid alien civilization, can not know the dark domain is a small countryside or rebel base, then of course, let it go first...

(4). Follow the bees can find the honeycomb, all spacecraft, space base is a huge risk, if since the abolition of all outer space communication and activities, seems to be from the Great Wall all the way back to the Forbidden City, when found the enemy, has stood in front of you...

The Sniping Theory of the Law of the Dark Forest

The Law of the Dark Forest calls for "snibbing" civilizations that reveal their movements, which may seem shocking at first, but if you think about it, the risks are high.

(1). The first strike is not a winning factor in the war. What if the enemy is another super powerful galaxy sent to our galactic outpost? Or the other side is particularly good at "escape", you hit the time, the other side has long run, perhaps after a while, the other side with a brother and ally back to you revenge for justice?

(2). "Cleaning up" is very likely (definitely) not clean up, such as the case of "Genghis Khan" revolt: "Zarein" poisoned Genghis Khan's father, and the tables turned 25 years later, Genghis Khan killed "Zarein Buhe".

(3) If they fail to deal with their own internal affairs, such as the case of "Luke Skywalker", the opposition is very likely to leak the killer high-tech intelligence to the enemy. In the history of mankind, all the regimes will have heavyweight opposition, not only with words, but with concrete actions to actively fight. Skywalker may be a "Star Wars" fictional character, but I think he is the best example of anyone who opposes authoritarianism. He even killed his father.

(4). Perhaps because of the "Honeypot" strategy, soon after computer viruses became popular in the 1980s, someone came up with the "Honeypot" strategy. They deliberately placed a computer with many vulnerabilities in the network to lure viruses or hackers, and then performed reverse analysis: Find out the source of the attack, the way, the method and so on, and finally carry out the corresponding countermeasures, one honey pot is not enough, more than a few, the big BOSS want to hide is impossible.

(5). Multiple risks may exist at the same time, and their degree of risk is multiplied, [Genghis Khan strike back] X [Luke Skywalker Nest Strike back] X [Honey pot reverse analysis]. At this time, it should not be called a risk but a rollover, and the collapse of the regime is already certain.