The speed of light is about 300,000 km/s, and one light-year flight per second is 31.5 million times faster than the speed of light, and it only takes 1 second to reach the edge of the solar system, and it can fly to the Andromeda Galaxy in 29 days, and it can fly out of the local galaxy group in 3.8 months, it can reach the edge of the Virgo supercluster in about 3 years, and it can fly out of the Laniakea supercluster in 17 years, which is the upper class of the Milky Way and is one of the components of the largest structure known in the universe, with 100,000 galaxies and a range of 520 million light-years.
Larger than the Laniakea Supercluster is the Pisces Cetus Supercluster complex, which is 1 billion light-years long and 150 million light-years wide, and the larger is the Great Wall of Hercules-Corona Constellation, which extends for more than 10 billion light-years, and even if humans fly 1 light-year in 1 second, it will take 317 years to fly out of this place.
The Great Wall of Warriors-Corona is the largest known structure in the observable universe, accounting for 10.75% of the diameter of the observable universe, so it can be calculated that it would take humans 1,470 years to reach the edge of the observable universe at a speed of 1 light-year/second.
It can be seen that the universe is so big that interstellar travel, even if it reaches tens of millions of times the speed of light, is too slow. Crossing galaxies is measured in years at every turn, and the efficiency is too low. Speaking of which, many people may fall into a misunderstanding, that is, according to the theory of relativity, calculated at the speed of light, the speed of time is equal to that of the spaceship pilot, and theoretically it is the state of immortality, and moving at the speed of light will easily reach any corner of the universe.
However, the theory of relativity says that if a beam of light is 300,000 kilometers per second, and a spacecraft is 150,000 kilometers per second, the spacecraft and the light are always separated by 150,000 kilometers for others, and the spacecraft always sees the picture half a second faster than others, and does not say that they can live forever if they see the light earlier than others, otherwise the earthlings will live longer than the Jupiters if they are close to the sun and see the sun's rays faster.
And don't forget, the year 1470 calculated above is only the time it takes to theoretically fly to the edge of the observable universe, not the real edge of the universe. It could be a galaxy that repeats itself, or it could be the legs of four turtles, but what's the point, it's a world that can never be understood, a world that doesn't exist for us.
Within the cone of light is fate, and theoretically, for the Andromeda galaxy now, there are people on the earth, and this has not happened. The rules that cannot be broken by the huge scale and the speed of light have made the universe fragmented.
And as the universe expands faster and faster, we will not be able to observe many places in the universe in the future. The reason why we can't detect extraterrestrial civilizations or extraterrestrial civilizations can't see us is because the span of time and space is too large.
Human cognition of the universe is like a baby's cognition of the world, even if we think that we are highly technologically advanced today, but this is the case. The universe is boundless, beyond the imagination of the human brain, and perhaps human beings will never reach the edge of the universe.
At present, although human technology is accelerating, human beings are still desperate to fly out of the solar system. In terms of the fastest spacecraft (both manned and unmanned) built by human beings, even if it was launched from the time of Hemudu and flew to Proxima Centauri, the closest star to the Earth, it has not been possible until now. It is also the closest star to the solar system, and it is also in the Milky Way. And the thought of other extragalactic galaxies is desperate.
It is impossible to orient the universe with the flesh and blood of carbon-based creatures like humans. Perhaps when the current human body is replaced by a mechanical body, the human-machine combination will invent intelligent objects with more advanced materials, so that after n generations of substitution, the last intelligent body may resist radiation, other hazards and longevity problems in the universe.
As for the technology of space travel, it needs to at least have the ability to obtain sufficient energy in a stable manner, which cannot be supported by simple heavy water nuclear fusion, either controlled nuclear fusion, or a breakthrough in antimatter research to obtain energy through the annihilation of positive and antimatter, or a new, unknown way to obtain energy in the universe.
At this stage, there is a promising controllable nuclear fusion, which can only be heavy water, hydrogen. To say that the nuclear fusion of burning stones can only be achieved at the end of supermassive stars in the universe, which is more than an order of magnitude more difficult. If you really want to sail outside the galaxy, it feels like you have to jump in space, like the ghostly telepathic effect of quantum entanglement.
For now, it's still concerned about whether we can know what a planet on Proxima Centauri looks like before humanity perishes, and these light-years distance may be a fate that humans can't cross after all.