Shulou(Shulou.com)11/24 Report--

This article comes from the official account of Wechat: SF Chinese (ID:kexuejiaodian), author: SF

(photo Source: Bruce Murray Space Image Library) tens of thousands of years ago, the ancestors of mankind looked up at the starry sky and sketched out the magical legends of constellations. We have been looking forward to the sky, imagining outside the sky-we now know that it is vast space, there will be all kinds of creatures and even fairies. A very important reason for human beings to explore space is to look for other civilizations in space, because many people always believe that we humans are not alone in space. However, our road to "finding neighbors" in space is not smooth.

(by Mei Lin / tr. by Robert Taylor)

We can imagine an astronomer sitting alone in the control room of a radio telescope when a strange signal comes from the loudspeaker. The astronomer inexplicably thought the signal came from an alien civilization. He tapped the keyboard several times and deciphered the signal. It turned out to be a letter from aliens to us. This is where the story begins.

Mysterious celestial bodies are the beacons of alien civilizations? You might say that this is a popular part of science fiction movies, and it's almost impossible to happen in the real world. But you may not imagine that this kind of thing is really going to happen in the near future. Recently, scientists from the International Center for Radio Astronomy (ICRAR) discovered a mysterious celestial body in the direction of Shield, whose performance and characteristics are completely inconsistent with the existing theories of astronomy and physics. This mysterious object, called GPM J1839-10, sends out powerful radio pulses in the direction of the Earth every 21 minutes, very regularly.

This is not the first time scientists have detected the signal of GPM J1839-10. Since it was first detected by scientists in 1988, periodic radio signals of GPM J1839-10 have been sent to us for 35 years. What scientists do not understand is that the cycle of these signals is as long as 21 minutes. Usually, pulsars periodically emit electromagnetic signals in the direction of the earth. According to the existing theory, the faster the pulsar rotates (then the shorter the period in which the earth receives the signal), the stronger the electromagnetic signal. The pulsar signal periods that scientists have detected so far are very short, while the period of the GPM J1839-10 signal is too long, according to the existing theory, its signal is not strong enough for scientists on Earth to detect. However, scientists have detected why this is so, and scientists are unable to explain at present.

GPM J1839-10 is so abnormal that it inevitably makes people think about it. Some scientists believe that the performance and characteristics of GPM J1839-10 are completely inconsistent with the existing theory, so it can not be a natural celestial body in the universe, it is very likely that it is a space lighthouse built by alien civilization, and we happen to find its signal.

In the attempt to find an alien civilization, some partners may feel that just from a series of unknown space signals, we can tell that this is sent by an alien civilization. However, around the world, there are many scientists who always believe that there must be alien civilizations in space, we are looking for them, and they are looking for us.

Since the American astronomer Frank Drake launched the SETI (Search for Extraterrestrial Intelligence) project in the 1960s, scientists have built many devices that can detect extraterrestrial signals, looking for evidence of the existence of other civilizations in space. But they still got nothing.

To say that they have found nothing does not mean that scientists have not detected a space signal. Scientists around the world have detected a lot of signals over the past 60 years, but how to judge whether these signals are signals of alien civilizations is a troublesome problem.

New technologies help identify alien civilization signals scientists may receive natural signals from space, such as the supernova Big Bang, or interference from Earth, such as the roar of car engines and cell phone signals. Apart from these, the remaining signals are likely to be signals from alien civilizations, and if we further study these signals, we may establish contact with our space neighbors in the future.

These are still beautiful imaginations. at present, it is difficult for scientists to identify possible alien civilization signals from so many interference signals. It is relatively easy to exclude natural signals from space because there is a significant difference in the distribution of frequency bands between natural signals from space and unnatural signals from a certain civilization (including ourselves)-natural signals are distributed in a wider frequency band. non-natural signals tend to be distributed in narrower bands.

Among these unnatural signals, interference from the earth should also be eliminated. Now, the common method for scientists is to extract signals with displacement characteristics, because most of the interference signals on Earth come from Earth's transmitters, which do not shift relative to the telescope. the signal source of an alien civilization shifts relative to the telescope at the speed of the earth's rotation. However, in practice, scientists have found that through this method, the identified signals of suspected alien civilizations are still mixed with some interference signals from Earth.

In order to identify alien civilization signals more accurately, scientists at the University of California, Berkeley have proposed a new method to identify alien civilization signals. Previous studies have found that low-temperature plasmas (mainly free electrons) in interstellar media can affect radio signals propagated in space-the amplitude changes over time, that is, flickering. The flicker occurs because radio waves refract when they propagate in an interstellar medium. This is like the light emitted by a star as it passes through the Earth's atmosphere. Due to the influence of the atmosphere, it seems to us that the star is also flashing.

Then, when signals from alien civilizations are transmitted to Earth through the cosmic medium and are detected by scientists, the signals detected by scientists will flicker. The interference signal from the earth does not propagate in the cosmic medium, and naturally there will be no flicker.

In astronomy, flicker refers to the phenomenon that the apparent brightness, color and position of a luminous object change when it is observed through a medium. (photo source: Pexels) now, scientists at the University of California, Berkeley have developed a computer algorithm that allows scientists to distinguish between possible alien civilization signals and interference signals from Earth.

However, some scientists have pointed out that this method is only applicable to places more than 10000 light-years from Earth, where alien civilization signals can be identified by this method, and for places closer to Earth, for example, signals from near Proxima, will not show this effect, and will not apply to this method, because the signal source is too close to Earth. In the process of signal propagation, there is not enough plasma to produce scintillation.

References:

A long-period radio transient active for three decades | Nature

Https://iopscience.iop.org/article/10.3847/1538-4357/acdee0

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