In the 1960s, people began to try to receive radio signals from the extraterrestrial civilization. The location was located at the National Radio Astronomical Observatory near Green Bank, West Virginia, USA. The work at that time was organized by Drake, an American radio astronomer, and was named Project Ozma. This is a plan to passively listen to the voice of extraterrestrial civilization. Oz is a place name in mythology. It is a very strange, very remote and inaccessible place, where a princess named Ozma lives . The meaning of Project Ozma is to search for distant extraterrestrial civilizations, with the purpose of searching for calls from aliens.
Receive external signals
The observatory uses a radio telescope with a diameter of 26 meters and a wavelength of 21 cm to receive external signals. Why make such a choice? We know that any radio wave emission can only use a certain wavelength. In fact, there are infinitely many wavelengths of radio signals. How do we know which wavelength is used by people in the universe? Scientists believe that the most element in the universe is hydrogen, so any intelligent creatures will thoroughly study hydrogen. The 21 cm wavelength is the wavelength of the microwaves emitted by hydrogen atoms. It may be the earliest recognized and used by all intelligent creatures in the universe.
Drake and others first aimed the radio antenna at the sun-like star Cetus, which is 11.9 light-years away from the earth, and they found nothing. Afterwards, they aimed their antenna at another target, the star Po Erio (10.7 light-years from the earth). At first, they received a strong radio signal of 8 pulses per second, and this signal appeared again 10 days later. But this is not the alien telegram signal that people expect. Ozma planned to monitor for 150 hours in three months, but unfortunately, he never found any valuable information.
In the Ozma Phase II program from 1972 to 1975, scientists observed more than 650 planets near the earth, hoping to listen to signals from aliens: You are not alone, please come and join the Galaxy Club. But the result is still nothing.
The first plan to find aliens in the history of human civilization
Project Ozma is the first purposeful and organized plan to search for aliens in space in the history of human civilization. Although no valuable results have been obtained so far, exploring the mysteries of nature has always been a relay race of generations of hard work, and it is impossible to expect success overnight.
The exploration of aliens also requires extensive international cooperation. The former Soviet Union set up a national committee to deal with this work. The radio telescope with 600 antennas was set up on the Caucasus Mountains to search for part of the time; the Algonquin Radio Astronomical Observatory in Ontario, Canada, also used the radio telescope near the earth. Some planets are searched and observed; the radio telescope with an antenna diameter of 305 meters at the Arecibo Observatory in the northeastern part of Puerto Rico has a receiving area 100 times larger than the antenna used by the Ozma program to search for space information for the first time. Six times faster, it can detect signals from celestial bodies hundreds of light-years to tens of thousands of light-years away.
The American astronomer Professor Drake is well aware of the difficulties of getting in touch with aliens. He pointed out that in this regard, we are like finding a needle in a haystack to explore the entire sky, even for a highly sensitive radio telescope like Arecibo. Must point to 20 million directions. Scientists have so far only listened to a few thousand planets, and most of them are planets near the earth, and the frequencies used are also very limited.
In 1985, under the leadership of Professor Paul Horowitz, an astrophysicist at Harvard University in the United States, a new project to explore extraterrestrials was started-the Space Multichannel Analysis Project (meta). Through more than 8 million different frequencies, use highly automated instruments to detect alien civilizations. As the band has increased tens of thousands of times, the corresponding workload has also greatly increased, and it takes 200 to 400 days for a census of space.
In addition to the United States, countries such as the former Soviet Union, Australia, Canada, Germany, France, and the Netherlands have successively participated in this exploration project.
Since the implementation of the Ozma plan, there have been many plans to search for intelligent life outside the world. The common understanding of scientists is: (1) Just like in the case of humans, life is likely to be produced in the extraterrestrial solar system. Therefore, the exploration target should be placed on a planet similar to the sun; (2) The radio telescope can hear the most The good frequency range is between 1000 and 10000 MHz. At this time, the natural radio noise of the universe is the lowest. Therefore, aliens who want to establish contact with the outside world may choose this band called the microwave window for interstellar dialogue; (3) ) If we want to establish contact with other planets, we should use electromagnetic waves (such as radio waves) because it travels at the speed of light. Regrettably, all the above-mentioned efforts have not been fruitful, and so far, no signal that can be confirmed as coming from aliens has been received.