How will future generations survive when the earth becomes uninhabitable?

Going to other planets

A long time ago, some people thought that Mars and Venus might be good choices, but now we know that except for the Earth, other planets orbiting the sun may not be very good. Suitable for human survival. Obviously, we have another star system to consider.

With today’s scientific level, we still cannot know the specific number of habitable planets among the more than 200 billion stars in the entire Milky Way, or whether these habitable planets already have indigenous people (foreigners) Starman). Frank Drake, an American astronomer and founder of the Search for Extraterrestrial Intelligence (SETI) organization, proposed the "Cosmic Civilization Equation" in 1961, also known as the Drake Equation. The Drake equation mainly includes 7 factors, such as the grade of stars born in the Milky Way, how many planets the star has, and whether the planets can adapt to the survival of life forms, etc. He used the equation to calculate the odds of finding aliens. The results show that there may be about 10,000 detectable civilizations in the Milky Way, and the nearest civilized world may be about 1,000 light-years away from us. Current research indicates that there may be many habitable planets in the Milky Way, and some people estimate that the number even reaches tens of billions.

In any case, this implies that if humans colonize other parts of the solar system, it will be difficult for the human species to be "eradicated." Because even if the human branch of one of the planets is killed, humans on other planets will still exist and can learn from the tragic experiences of their ancestors, develop and try new technologies, continue to explore, understand life elsewhere, and promote Humanity develops to a higher level.

How to reach a habitable planet?

Due to the great distance between the Earth and other stars, assuming that humans begin to colonize the galaxy, the initial expansion rate should be slow. Because even if we go to the three-body star system closest to the earth, Alpha Centauri, assuming we travel at 10% of the speed of light (about 30,000 kilometers/second), it will take about 40 years to reach it.

Why was 10% the speed of light chosen? First of all, we must consider the life span of human beings. The current average life span of human beings is about seventy or eighty years old. 10% of the speed of light can at least allow humans to reach the nearest star within a short life span. Secondly, compared to the speed limit - the speed of light, 10% of the speed of light is actually not very fast, and it can also minimize the chance of collisions between the traveling spacecraft and interstellar gas and dust.

So, how do we get the spacecraft to get 10% of the speed of light?

Maybe it will rely on a huge sail, or in other words, entering other star systems will be a "light sail" project (or solar sail). Since light also has energy, it can also produce light pressure when it shines on an object. This principle is just like the wind blowing on a sail and causing the sail to exert force. A light sail is like a solar panel that receives light. It is driven by a high-energy laser or microwave station near the sun. It uses photons in the beam to obtain power. After a long enough time, it will reach a considerable proportion of the speed of light.

In the recent "Breakthrough Star Photography" project launched by physicist Stephen Hawking, he proposed to develop a small light sail aircraft called "Star Slice". It is planned to reach Alpha Centauri at 20% of the speed of light, after a voyage of more than 20 years, and transmit information about the star system back to the earth. Although for now, this aircraft can only carry cameras, navigation systems and small items, and its success or failure is difficult to predict, it still points a way for human beings to travel in space in the future.

In addition to light sails, there are of course other possible methods of interstellar propulsion, ranging from antimatter fusion, interstellar ramjets, to "hyperdrives." It is said that American scientists are secretly studying a "hyperspace engine". Once the "hyperspace engine" is proven to be feasible, it will only take 3 hours to travel from the earth to Mars, and 80 days to travel from the earth to a planet 11 light years away. Some scientists also predict that the time when a suitable spaceship can actually be built and set off to the destination planet will be in the 26th century.

After arriving at the destination, how to slow down and land smoothly is also a huge problem. The most logical approach is to develop so-called "magnetic sails". A "magnetic sail" usually refers to wrapping a spacecraft with a magnetic field of opposite polarity to the solar wind (solar wind is a flow of charged particles with its own magnetic field), and flying out of the solar system through the repulsion between magnetic fields. Here, what we want to use is not the solar wind, but the diamagnetism of the particle stream emitted by the target star to decelerate and brake in the final stage of reaching the destination.