This is the question that has made scientists around the world try to find the answer for decades, that if there are aliens living in the universe, why have they not visited Earth?

Dr Michael Wong, from the Carnegi Institute of Science and Dr Stuart Bartlett, from the California Institute of Technology, theorize that alien civilizations have evolved to what is known as a “crisis point” and have since disappeared. chance to visit other worlds.

In 1950, Italian physicist Enrico Fermi once stated the Fermi Paradox that bears his name. He estimates that in the universe there are 200-400 billion stars and at least 100 billion planets in the galaxy, meaning that life cannot be created solely on Earth.

In new research published in the journal Royal Society Open Science, Dr Wong and Dr Bartlett seek answers to the Fermi Paradox.

The two scientists assessed the development of a civilization accompanied by population explosion and increasing energy consumption. To a certain extent, these two problems exceed the capacity of society to innovate, causing the whole system to collapse.

On Earth, scientists cite a few examples such as the depletion of the ozone layer, the explosion of weapons of mass destruction, and over-hunting, which leads to habitat depletion, if left unchecked. remedy.

The two scientists think that alien civilizations also experience the same exhaustion. “Civilizations go through many stages of development, reaching a level of brilliance and then becoming exhausted. A crisis sooner or later occurs, although not to the point of destruction, but makes civilization towards more balanced development and cannot expand space exploration,” said Dr Wong and Dr Bartlett, stressing. emphasized that it is difficult to detect such civilizations from a distance, due to the limited human technology.

The two scientists concede that alien civilizations can predict when a “crisis point” will be reached to create change and prevent this event from happening. But controlling the use of resources makes civilization less developed and harder to detect.

When a civilization approaches a crisis point, this may be when humans are most likely to spot it. “Changes on the planetary scale can form signals that are easy to detect from a distance,” the two scientists said.

The two scientists emphasized that their study is just a hypothesis and needs further studies to prove it.

Recently, researchers from Beijing Normal University made a prediction about the time it takes for humans to contact aliens.

Researchers predict that it will take 2,000 years at the earliest, and if more realistic assessment is made, it may take another 400,000 years before humans can communicate with aliens.