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

Image source: Pixabay has two ways to find extraterrestrial life, and we have only focused on one of them.

When we ask whether human beings are lonely in the universe, what does loneliness mean?

The search for extraterrestrial life has always been one of the most important topics in astronomy. However, it may be difficult for people who are only occasionally interested in aliens to realize that this is far more complicated than they think. A core question is, what kind of life are we looking for? On Earth, life has a variety of forms and abilities, and if we look for extraterrestrial life in the universe, we can roughly divide them into two categories: "lower creatures" and "higher creatures". Lower organisms, such as microbes and plants, can thrive on the planet, but are not as self-aware and technological as humans. Smarter creatures, such as us, can build technology that covers the entire planet.

Under this rough classification, microbes, plants and even elephants are considered "inferior". Although I am deeply sorry for these creatures, this classification is really important because there are different ways to search for these two types of life in the universe. Because of the distance between galaxies, it is impossible to take images of alien surfaces, such as pine trees or anteaters, in the foreseeable future, even with the most advanced human observation tools.

Therefore, when investigating alien life on a planet, it is necessary to look for indirect evidence. The first is biological characteristics, such as the presence of both oxygen and methane in the atmosphere. When there is a biosphere on a planet, these two gases exist at the same time. The second is the technical characteristics. If a planet's atmosphere contains industrial emissions, or if there are reflections from large-scale solar panels on the surface of the planet, these can prove to astronomers that there is life on that distant planet with the same technology as we do.

Image source: the best way for Pixabay to maximize its chances of finding alien life is to look for both features on the same planet at the same time. However, because the universe is so large, the time and money that can be used to explore extraterrestrial life is limited. Some scientific research projects often take decades to reap results, so scientists need to be extra careful in choosing search targets. (the James Webb Space Telescope, the latest and most powerful observation equipment currently available to mankind, costs about $10 billion, which may give us some idea of the cost of research.)

So far, scientists have obtained significantly more information about "lower organisms" than "higher organisms" in the search for extraterrestrial life. With the full support of NASA, astronomers have made great progress in defining "what biological characteristics should be found on alien planets" over the past 20 years. Such an achievement is very encouraging, but it may also come at a price-so miss some signs of higher life.

The first human attempt to scientifically search for extraterrestrial life was the search for extraterrestrial civilizations, also known as SETI (Search for ExtraTerrestrial Intelligence). In 1960, astrophysicist Frank Drake launched the Ozma project, trying to use radio telescopes to find high-tech civilizations that like to send signals into space. At the time, no one could imagine any way to find trees, insects or microbes on planets in distant galaxies, or even to know whether such planets existed. Although SETI has been the only extraterrestrial search project for decades, it has received a lot of ridicule. SETI's funding chain has also been affected, and the project has been maintained with the help of all sectors of the community over the past 40 years.

Photo: Pixabay1995 year, a discovery revolutionized the search for extraterrestrial life. A planet orbiting a sun-like star has been discovered for the first time. Astronomers realized that the biological characteristics of extraterrestrial planets could be directly detected by observing the light passing through the atmosphere of extraterrestrial planets. The detection technology involved is also known as Atmospheric characterization (atmospheric characterization), and the research and development of this technology is also one of the important achievements of the NASA astrobiology project. In a recent 10-year survey in this field, astronomers agreed that a space-based extraterrestrial life exploration telescope should be a top priority. In fact, in the process of searching for life features, if we can find relevant technical features, it will usually be considered after biometrics.

This is because the search for extraterrestrial biometrics is more attractive. Many astronomers assumed from the beginning that the existence of life features would be more common than technical features in the universe. After all, if there is no life on a planet, let alone an alien civilization. At the same time, according to Earth's history, our only reference on the evolution of life, technology will not be possible until long after the emergence of basic life forms. As early as 3 billion years ago, the earth began to show biological characteristics to the entire universe, but it is only from the past few centuries that we have technological characteristics. This means that the time of existence of technical features on earth is less than 0.00001% of the time of existence of life features. From this point of view, the search for technical features can only be regarded as the icing on the cake in the observed alien life.

However, from the perspective of simple life evolution, it is difficult to deal with another dimension of this problem. A new study led by Jason Wright of the University of Pennsylvania suggests that astronomers may overlook the value of technical features. I also participated in this study as a member of the technical feature search team funded by NASA. The problem with focusing only on biometrics is that they are always tied to the planet and its biosphere. If all life on earth disappears tomorrow, so will the biological characteristics of the earth. For example, oxygen on earth is produced by the activities of life, and if life no longer exists, the oxygen will soon return to the rocks because of chemical reactions.

In other words, to detect biological characteristics, we need to have a biosphere still in motion on the planet we are exploring. However, we do not know how long the biosphere can usually exist. Our biosphere has been around for more than 3 billion years, which is obviously very lucky. Many events can lead to the demise of the biosphere, such as the solar wind blowing away the planet's atmosphere, or a massive asteroid impact. Once the biosphere disappears, the biological characteristics it produces will go with it.

By contrast, technical features do not have these limitations. In fact, the solar system is already full of technological features produced by Earth's civilization. On Mars alone, there are now more than 10 spacecraft in orbit or on the surface. And there are hundreds of spacecraft shuttling through the solar system. We even launched five spaceships into space outside the solar system. The existence of every aircraft we launch into the universe shows a technical feature in itself. More importantly, all operating aircraft are sending electromagnetic signals to the universe, and although these signals are very weak, it is conceivable that this technical feature may be detected by some intelligent life.

Unlike biometrics, various technical features can be moved and will persist. For example, without air or water erosion, the Apollo 11 lunar lander will be able to stand on the moon for millions of years. If we take a longer view, if we lay large-scale solar panels on the moon in the future, and human civilization is destroyed by some catastrophic events, even after we disappear for a long time, these solar panels may still be observed by alien civilizations.

At the same time, we can also imagine an interstellar civilization cargo ship shuttling between galaxies. Dust from the ship's engines, dense lasers used for communication and even waste disposal-or if aliens burn garbage, it's also a signal that can be detected from Earth. These technological features can spread far away from the planets produced by alien civilizations (we can call it the technological circle, technosphere). An alien civilization can even use uninhabitable planets in its star system to transform them into industrial or energy bases. Such a planet will only produce some technical features, not biological features.

Image source: Pixabay, meanwhile, the technical features may also be very rich. An alien civilization and its technological circle can produce millions or even hundreds of millions of items, and each item can produce detected technical features. Try to imagine an interstellar civilization that is millions of years longer than human history. It may not only often produce a large number of objects that can release technological features, but may also produce multiple technological circles. Unlike the biosphere, the technological circle can be expanded through planned interstellar migration. Based on these advanced technologies, we can imagine how creative inventions can be made by distant alien civilizations, and perhaps in their eyes, human beings are not even intelligent life.

There are also many controversial points. Critics might argue, for example, that the biosphere might be formed through the "embryo hypothesis" (panspermia), in which an asteroid impact causes a rock with microbes to enter the universe and land on other habitable planets. But the results show that even in the most ideal environment, the probability of such events is very low, while at the same time, as a civilization capable of interstellar travel can spread new technological circles to the entire galaxy, they can spread their technological circle to a more distant world.

Even so, all this is just speculation. We haven't found any extraterrestrial life so far, so we don't know what the proportion of higher and lower life in the universe is. Perhaps high-tech civilizations are so rare in the universe that they have a better chance of finding lower life. I don't want to bet between the two, but I want to stress again that there is still a lot to be discovered.

The research conducted by our team may give rise to a misunderstanding that priority should be given to the search for extraterrestrial life based on technical features. But in fact, our conclusion is not like this. After reviewing the biases in the past search and the possibilities in the future, we think that technical features and biometric features should be regarded as a continuous whole. So far, scientists have designed techniques to observe extraterrestrial life either for higher life or for lower life. However, with the development of exoplanet exploration technology, a telescope and its probe can now be used to explore these two life features at the same time. When observing an exoplanet, astronomers can look for biological and technical features at the same time in the same magnetic band.

Due to the limited resources, astronomers still need to make some difficult choices when searching for extraterrestrial life, but they should choose according to the specific search situation, rather than artificially antagonizing the search based on biometrics and technical features. We are at an unprecedented moment: the debate about extraterrestrial life in the universe has been going on for thousands of years, and now we have the ability to find the answer to that question. The discovery of any kind of life, whether it is higher or lower, will fundamentally reshape our understanding of our place in the universe. Let's find the answer to all this.

Original text link:

Https://www.theatlantic.com/science/archive/2022/09/search-for-extraterrestrial-life-aliens/671410/

This article comes from the official account of Wechat: global Science (ID:huanqiukexue), written by Adam Frank, translated by Zhang Yifei, revised by clefable

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.