Is it because the universe is too big for human beings to contact with alien civilizations?

"Whether aliens exist" and "How to find aliens" have always been a topic of great concern. Scientists also try to prove the former through various methods and try to realize the latter. However, before the discovery of aliens, it is inappropriate for us to conclude that "aliens exist" or "aliens do not exist".

Then why do many scientists think that aliens may exist? Secondly, if aliens exist, why haven't we got in touch with them?

Today we will briefly talk about these two issues.

Are the rules of the universe consistent?

As we all know, science originated from the natural philosophy of ancient Greece. In ancient Greece, natural philosophers always thought that one set of rules applied to the earth and the other set of rules applied to the universe. More precisely, the lower part of the moon is a collection, and the upper part of the moon is a collection. Specifically, the smallest constituent unit under the moon is fire, water, earth and air, and the smallest constituent unit above the moon is ether. All celestial bodies follow a perfect circular motion.

This academic recognition lasted until Newton's time. In fact, physicists especially like unification. Newton completed the unification. He unified the physics of "heaven" and "earth". To put it bluntly, he successfully proved that the above and below the moon actually apply to the same set of rules.

With the progress of observation instruments, scientists have found that not only Newton's law of gravity is applicable to the whole universe, but also various laws of physics are generally applicable. With the development of astronomy, scientists put forward cosmological principles on the basis of existing knowledge. I won't go into details about the detailed cosmological principles here. We just need to know the general idea of cosmology principle is:

On a large scale, the universe is the same everywhere. For observers at all locations in the universe, the observed physical quantities and physical laws are exactly the same, and no one is special. Does the cosmological principle make sense?

1995, Hubble telescope is the most precious detector resource in the eyes of astronomers all over the world, but it was temporarily requisitioned to observe the darkest sky area in the universe, which is the area in the box below.

Astronomers at that time were basically angry and joking. As a result, the Hubble telescope was exposed in this position for ten days, which shocked the entire astronomical community. In such a small area, more than 3000 galaxies were observed in 10 day. (Each bright spot in the picture below is a galaxy similar to the Milky Way. )

The observation of Hubble telescope tells us that any direction you look at the universe from the earth is the same, and there are countless galaxies. The Milky Way alone has1500 ~ 400 billion stars and countless planets. In other words, there must be many situations similar to the solar system or even the earth. That is to say, even if the probability of the birth of life is lower, according to the principle of cosmology, there will definitely be life in the universe, and even complex intelligent creatures like the earth have evolved. Similarly, according to the principle of cosmology, that is, we should not be treated specially, then human beings will not be the most civilized among these intelligent creatures, but the probability is at a medium level.

So the question is, in that case, why haven't we contacted aliens yet?

Is space an obstacle?

We are all familiar with the model of the sun, and many times we are deceived by this model.

Compared with the size of celestial bodies, the distance between celestial bodies is really too big. Take the earth and the moon for example. The radius of the earth is only over 6,000 kilometers, but the average distance between the earth and the moon is 380,000 kilometers. (The picture below was taken by a detector 5 million kilometers away. You can feel it. )

The same is true of the distance between the sun and the earth. The radius of the sun is 6.955 * 10.5 km, but the average distance from the sun to the earth reaches 1.5 * 10.8 km, which is two orders of magnitude less. This is only in the solar system. The nearest star system is that of proxima centauri, which is more than 4 light years away.

If the sun is regarded as a coin, then proxima centauri is probably a smaller coin 700 kilometers away. Such a terrible distance makes it take tens of thousands of years for us to fly to proxima centauri, even with the most advanced spacecraft, regardless of supplies and other aspects. According to scientists' estimation, the average distance between star systems in the Milky Way is about 3 light years. In this case, it may take hundreds of thousands of years to cross several star systems. So the reason why we can't contact aliens is probably related to distance.

Probably because of the long distance between star systems, planetary civilizations are separated and cannot communicate with each other.