What will be the last question of human civilization?

This question has been mentioned in many science fiction novels. When human beings know that they are about to become extinct (for example, the sun is about to die but they are unable to become interstellar immigrants), the last question is how to build a "tombstone" for civilization. It is to record everything created in human history for a long time (tens of millions of years) in some way, so that future visiting aliens can know that such a civilization once existed in the history of the universe. This is a technical problem that is not easy to solve.

The following is a passage from the Earth Museum mentioned in "Three-body". The idea of the museum should come from Clark's star.

"At first, it was a big research project to study how to keep information in the geological calendar. The original standard was one billion years. Ha, a billion years. At first, those idiots thought it was easy. After all, they can build a bunker world. What is this? But soon they found that the modern quantum memory, that is, that branch, the size of a grain of rice can hold the contents of a large library, and the information in it can only be kept for about two thousand years at most, and it can't be read after two thousand years because of internal decay. In fact, this still refers to those memories with the best quality. According to research, two-thirds of the existing ordinary quantum memories will be broken in 500 years. This is very interesting. Originally, what we were doing was a very detached thing that leisure people did, and suddenly it became a real problem. For 500 years, it has been somewhat realistic. Aren't we all people more than 400 years ago? The government immediately ordered the museum to stop its research and study how to back up important modern data so that it can be read at least five centuries later. Hehe ... Later, a research institution was separated from me, so let us continue to study museums or tombstones. " Scientists have found that no matter how long the information is kept, our memory is better at that time. They found some U-disks and hard disks in the century AD, some of which can even be read. According to experiments, if these memories are of good quality, they can keep information for about 5 thousand years; Especially our CD-ROM at that time, if made of special metal materials, can reliably store information100000 years. But these are not as good as printed matter. Good quality printed matter, with special synthetic paper and ink, can still be read after 200,000 years. But this is the end, that is to say, the means we usually use to store information can only reliably save information for 200 thousand years at most. They want to live for a billion years! "But it is also an extremely difficult thing. Scholars began to look for information that had been preserved for a long time. The patterns on prehistoric ancient pottery have been preserved for about 10 thousand years; The murals found in European caves have a history of about 40 thousand years; The nicks carved on the stone by the ancestors of human apes for making tools, if counted as information, first appeared in the middle Pliocene, about 2.5 million years ago. But don't say, you really found the information left more than 100 million years ago, of course, not human, but dinosaur footprints. " The research is still going on, but there is no progress. Scientists have obviously reached some conclusions, but they may be embarrassed in front of me. I said to them, nothing, no matter how bizarre and outrageous your result is, there is no other result, and we have to accept it. I assure them that nothing is more bizarre and outrageous than my experience, and I will not laugh at them. So they told me that based on the most advanced theory and technology of modern science in various disciplines, according to the results of a large number of theoretical studies and experiments, and through the comprehensive analysis and comparison of a large number of programs, they came up with a method to save information for about 100 million years. They stressed that this is the only feasible method known at present, and it is-"Luo Ji held his crutch high above his head, with white hair and beard, dancing like a Moses who separated the Red Sea, and solemnly shouted," Carve the words on it.