At that time, people also began to be curious about the starry sky, and various conjectures were born, and due to lack of in-depth understanding, many ideas also appeared absurdly wrong, such as the theory that the sky is round and the place is round, and the European theory that the earth is the center of the solar system and the sun revolves around the earth.

With the progress of society and the continuous development of science and technology, those erroneous conjectures have begun to be overturned.

The ancients never thought that people could actually fly in the sky, but airplanes appeared. In the age of steam, the industrial revolution, and the age of electricity, with the advent of automobiles, the iron shell ran faster than the horse. Aircraft have achieved supersonic flight, twice or even triple the speed of sound. In ancient times, it took several months to walk or ride a horse to enter Beijing, but now it may only take three to five hours to reach the same destination at the same place, saving time dozens of times or hundreds of times.

In the 20th century, and even in the 21st century, with the launch of manned spacecraft, human beings are no longer limited to flying in the sky, but breaking through the atmosphere, entering outer space, flying around the earth, and even landing on the moon.

Science and technology are constantly developing, human beings are constantly progressing, 100 years, 1,000 years, 5,000 years, who know that in that distant future, it is impossible for human beings on the earth to break through the shackles of the solar system and enter the broader starry sky of the Milky Way.

The diameter of the Milky Way alone is 100,000 light-years, and the speed of light is 300,000 kilometers per second. As for the cosmic regions outside the Milky Way, the boundless starry sky, planets, stars, comets, neutron stars, white dwarfs, hundreds of millions, billions, tens of billions, or even hundreds of billions of planets, Ye Xing does not believe that the Earth alone is a living planet.

Among these trillions of countless planets, there is no only planet on Earth that is suitable for life. There must be other planets of life in other exotic starry skies in the universe, which may or may not be inhabited by people, and are other extreme life forms.

The Earth is not the center of the universe, and the universe does not revolve around the Earth. The Earth is nothing but a planet in the solar system, which revolves around the sun.

In fact, after the Big Bang, the earth was also a dead star earlier, and later with the change of the starry sky environment, planets, comets, meteors collided, the earth's crust moved, and reintegrated together, more water, oxygen, and life was born, that is, dinosaurs, Tyrannosaurus rex, saberodontosaurs and other large carnivores.

It was only later that the dinosaurs became extinct again, and the earth was home to new life forms, single-cell evolution, and various evolutions. Humans are the higher animals that evolved from apes.

Human beings in the primitive period had low productivity and lived a life of drinking blood, and many human beings at that time could only live to be in their teens or twenties. Until he entered the feudal society, his life expectancy was extended a lot, but he was only forty or fifty years old. The ancients called themselves old men in their thirties, and they knew the destiny of heaven in their fifties. Being able to live to the age of 50 was already considered a group of people with a high life in ancient times, so the custom of celebrating and celebrating birthday was born. This custom has also been passed down to this day, and when modern people reach the age of 50, they also have relatives and friends to send congratulatory gifts to celebrate their birthdays, such as the longevity of the East China Sea than Nanshan and so on.

Of course, with the improvement of medical standards, modern people can generally live to be seventy or eighty years old, and even some elderly people have lived to be more than 100 years old.

In terms of medicine, biology, etc., human research is becoming more and more in-depth. It is possible to clone an identical human or animal from a single cell or even a single hair, which is an incredible thing in ancient times. As for how far science will develop in the future, God knows.

Of course, in addition to these inferences, there is another important reason why Ye Xing believes that there are aliens. That is the person who himself has left the earth, and he should be regarded as the first person to leave and reach the Martial Arts Continent of the other world.

The martial arts continent is a martial arts world, and the earth is taking a diametrically opposite path, martial arts pursues its own breakthrough from the inside out, and cultivates the single energy to the extreme, while the earth takes the scientific and technological route, and the scientific and technological route is more with the help of external forces, such as pistols, tanks, fighter jets and other mecha foreign objects to improve themselves. For example, compared with the martial artists of the Houtian Realm, the person with the pistol is really not necessarily who has done whom. It is possible that the earthling with the pistol was killed by the Houtian realm warrior before he could shoot, or it is possible that the Houtian realm warrior was destroyed by the earthling's pistol. It depends on the tactics and environment, each with its own advantages and disadvantages.

In short, martial arts civilization and technological civilization have their own characteristics, and they can be regarded as two unique civilizations. Maybe there are more than these two civilizations in the vast starry sky, who knows.

Regarding the spatial location of the Martial Arts Continent, although Ye Xing had a purple light cluster portal, he still had no way to find out. It may be in some distant unknown star field, or it may not be in this starry sky at all.

Ye Xing is currently most worried about the alien problem, from Aunt Xu's photo, and various inferences, it can be judged that the alien flying saucer has indeed come to the earth. It's just that I don't know why I left later, but since I came once, I don't know if I will come again next time, after all, the other party has already found out the coordinates of the earth's starry sky.

"Instructor Ye, if there are really aliens invading the earth, you ...... Will you help?" Aunt Xu suddenly asked.

"Definitely!" Ye Xing nodded, and then said with a wry smile: "It's just that it depends on whether I have the ability to help!"

Earth is the home of Ye Xing, this beautiful aqua blue planet. Ye Xing naturally couldn't bear to let it be destroyed by the flames of war. If there is really an alien invasion, Ye Xing will definitely help. It's just that this kind of thing can only be said to be done within one's ability, after all, there is too little understanding of aliens, and those mysterious aliens have terrible black technology, the devil knows.

"Instructor Ye, you are too modest. Feng Qi, a short-haired girl, said: "You were so perverted in Japan last time, you can't even hurt a single hair of a missile, you are a superhuman existence yourself, I guess aliens can't beat you!"

"It's different, missiles are missiles, and they are not the strongest weapons. Ye Xing rolled his eyes and said, "If I am hit by a nuclear bomb, I will have to die!"

"Hehe, it turns out that there are things in this world that you are afraid of!" Feng Qi, a short-haired girl, smiled, her eyes rolled, and she couldn't help but be curious: "Instructor Ye, you said that if there are aliens, what will those aliens look like?"

"I don't know. It could be red skin!" Ye Xing said blindly: "It may also be green skin, and he will be green all his life." ”

"Flutter, you really dare to think that if you have green skin, how ugly it is!"

"Hey, don't believe me. Due to the influence of climate and environmental factors, Africa is basically black, Asia is yellow, and Europe and the United States are mostly white. How do you know that aliens are not green people, maybe other people's alien environment is more special. ”

Ye Xing was also aroused by this little girl for a while, "Think about it, our earthlings evolved from apes, so aliens may also evolve from tigers, or even elephants, with such long noses......"

(Yes, the author is ready to break through the atmosphere and take everyone to the cosmic starry sky, black holes, white holes, auroras, singularities, nebulae and other cosmic wonders, and the interstellar era will be opened in the near future, hum, our goal is the sea of stars!)