The fascinating thing about being human in this day and age is that we can do more than be curious about other life and other civilizations. We can actually look for them, although our search has obvious limitations. But it's also fascinating that we are also skeptical that other people will be able to see us.
We assume that all civilizations that have already begun to explore their surroundings are interested in finding other civilizations, and that the question of who can detect whom will come down to a matter of technology. Finding the technological characteristics of other civilizations requires advanced technological tools. Moreover, most of them also require technology to produce. But what level of skill is needed on both sides of this equation?
The technology required to generate a technical signature is not complicated. We've had this technology for thousands of years. The Great Pyramid is proof of this. But what technology is needed to see them?How far is the distance?
In a new study published in the Journal of Astronautics, a SETI-related researcher asks the question: "Can advanced extraterrestrial civilizations see us?""His name is Zaza Osmanov (z.).Osmanov), he is the author and co-author of several studies and articles on SETI and related topics.
"The question we are thinking about is how our artificial structures can be seen by high-level aliens," Osmanov said. "Osmanov explained how the laws of the physics of the universe set limits for detection, and how more advanced civilizations solved this problem. According to Osmanov, the maximum distance detected is about 3000 light years, adding that "under certain conditions, advanced alien societies of type II may be able to solve this problem." ”
What technology is needed to receive our technical signatures?
The background of Osmanov's ** is the classification of civilizations known as the "Kardashev Scale", which is also familiar to many readers. This is a theory put forward by the Soviet astronomer Nikolai Kardashov, which describes three hypothetical civilizations:
Type I civilizations collect, use, and store all the energy on their planet.
Type II civilizations directly consume the energy of their stars with a Dyson sphere or something similar.
Type III civilizations can capture all available energy throughout the galaxy.
Note that in the Kardashov index, humans are about 075。)
In his research, Osmanov ignored Type III civilizations and focused instead on Type I and Type II civilizations. He asked a relatively straightforward question: "Can the product of our technological society be seen and detected by extraterrestrial telescopes?"”
Our technology products are things like large-scale engineering projects and satellites. If Type I or Type II civilizations could see these things, they would recognize them as technological artifacts. According to Osmanov, the best way for intelligent extraterrestrial beings to detect them is to use reflected light, which means using high-power optical telescopes with extremely high angular resolution.
Right now, we're busy building more powerful telescopes with higher angular resolution, and extraterrestrial intelligent beings may be working on it. Extraterrestrial civilizations that are more advanced than us are far ahead of us. "In this article, we analyze how much we can see advanced aliens, depending on their level of technology. ”
Osmanov said that extraterrestrial civilizations will use interferometry to detect us. Astronomical interferometry uses two or more vertical telescopes separated by a certain distance to observe the same object at the same time. The data from the detector is merged and processed. So, instead of observing things with the limited angular resolution of a single telescope, interferometry essentially builds a "virtual" telescope (an array of telescopes) that is much larger than any physical telescope.
Osmanov calculated that if an extraterrestrial civilization wanted to detect the Great Pyramid of Giza, the civilization would not be able to travel more than 3,000 light-years. Because in order to see the pyramids, the number of photons must be perceived, so the telescope must be very large. Only an interferometer can do that. "It is clear that the diameter of the telescope should be around several million kilometers," the author explains.
This precludes Type I civilizations. Osmanov wrote: "Such megastructures may only be built by Type II civilizations, not Type I alien societies. ”
But how do we know if a Type II or Type III extraterrestrial civilization is within 3000 light-years?Osmanov used the famous Drake equation to determine this number. The Drake equation is a probabilistic argument that thinkers can use to try to understand how many extraterrestrial civilizations there might be in the galaxy, but of course, there is no absolute way to verify its answer. It's a thought experiment tool that keeps everyone on the same page when thinking about alien problems.
In his calculations, the author determined the average distance between advanced civilizations. "As an order of magnitude, we assume that civilizations are evenly distributed in the galactic plane," writes Osmanov. There must be about 650 extraterrestrial intelligent beings in the galaxy for one close enough to be able to detect our massive engineering projects from the ancient world to the Middle Ages. This includes pyramids and other large structures.
This number is different when aliens detect our modern structures, as there is not enough time for the reflected light from these modern structures to travel into space. If we are to detect our modern structures, including satellites, there must be a lot more extraterrestrial intelligent life. Osmanov wrote: "Only when their total number in the MW is about 106, they will be able to detect our modern structures, which Sagan assumes." ”
Start planning my 2024 Of course, we have no way of knowing if there are other extraterrestrial intelligent beings, or if someone has already discovered our technological characteristics. But the study does provide context for this question and thought experiments.
Unless there is a first contact, we only have thought experiments.
If you like it, please pay attention to "Know the New"!