A little more than 80 years ago, mankind first began to broadcast radio and television signals, with sufficient force to leave the Earth’s atmosphere and moved into interstellar space. If someone living in a distant star system that vigilantly monitors these signals, it will not only be able to catch them, but immediately identificeret the sender as an intelligent species. In 1960, Frank Drake first proposed to look for such signals from other star systems, using large radiomarelli that led to the initiative of the SETI: search for extraterrestrial intelligence. But over the past half century we have developed much more effective means of communication for the entire globe than radio and television. Does this mean that finding aliens in the electromagnetic spectrum no longer makes sense?
This question, of course, extraordinary speculative, but gives us the opportunity to look at their own technical progress and to consider how it could take place elsewhere in the Universe. In the end, if someone from the society, which communicate with signals, drums, and fires, will be deep in the woods, he can come to the conclusion that intelligent life around does not exist. But give him a phone and he will be able to contact relatives. Our findings can be just as biased as the methods that we use.
The mechanism of electricity began to be understood only in the late 18th century, thanks to the work of Ben Franklin. Electricity power began to feed our wires and other devices only in the 19th century, and phenomena of classical electromagnetism began to understand only in the second half of this century. The first transmission of electromagnetic signals took place only in 1895, and the radio brought us into the interstellar medium only to 1930-m to years.
The speed of light is also very limited: if our radio signals flying through interstellar space in just 80 years, this means that only civilization within a radius of 80 light-years can catch these signals and only civilization within a radius of 40 light years can catch the signal and send back a response, which to this day would have came. If the Fermi paradox poses the question “where is everybody?”, the answer is “not in a radius of 40 light years from us.” But what does it say about intelligent life in the Universe? Nothing.
Although in our galaxy can be hundreds of billions of stars and about two trillion galaxies in the observable Universe, within 40 light years from Earth is less than 1000 stars.
In addition, electromagnetic signals, stretching from Earth into interstellar space, decrease, not increase. Television and radio signals often pass through cables, or transmitted via satellite and not towers broadcasting on the Ground. It will take another century, and, most likely, the signals that we sent throughout the 20th century, will cease to leave the Earth at all. Perhaps the alien civilisation will conclude that this blue water planet with life has reached a certain stage of development, and then was destroyed, and the signals ceased to go.
In other words, to draw conclusions about what is and what is not, on the specific form of the electromagnetic signal is completely the wrong strategy.
If we look at the Earth from close range in visible light, we undoubtedly would have decided that she inhabited: the glow of cities at night — is an unmistakable sign of activity. But this light pollution is a relatively new phenomenon. We are constantly learning and are investing money, effort and time to get rid of it. There is no reason to believe that by the end of the 21-22 century, the Earth will look the same as now and not as they looked billions of years before that: dark, sometimes illuminated by auroras, storms, or volcanoes.
But if the search is not electromagnetic signals, then what? Everything in the Universe is limited by the speed of light, and any signal created by another planet, must do something to show that we could detect it. These signals are divided into four categories:
- Electromagnetic signals, including any form of light at any wavelength, which could indicate the presence of intelligent life
- Gravitational-wave signals which in the case of belonging to the intelligent life — we will be able to detect sufficiently sensitive equipment from anywhere in the Universe
- Neutrino signals which, although exceedingly scattered at great distances — would be an unmistakable sign under certain conditions
- Finally, the macroscopic space probes, robotic, computerized, stand-alone or settlements that approach the Earth
Surprisingly, our fantastic imagination focused almost exclusively on the fourth possibility, which the least likely.
When you think about the huge distances between stars, how many stars have potentially habitable planets (or even moons), and how much resources need to physically send a space probe from one planet to another planet, another star, this method of communication seems completely insane. Much easier to build a detector that would explore different regions of the sky and find the signals that will indicate the existence of intelligent life.
From the point of view of the electromagnetic spectrum, we know how our living world reacts to the seasons. Winter and summer our planet “glows” differently. Along with the changing times and changing colors in different parts of our planet. With a large enough telescope (or array of telescopes), it would be possible to see some signs of our civilization: cities, satellites, aircraft and so on. But perhaps the best thing we could find is changes to the environment according to what would create only an intelligent civilization.
We didn’t do that, but perhaps large-scale modification of the planet — that’s what we should be looking for. Do not forget that the civilization that we find is unlikely to be technological baby as we are. If she survived, and survived all the catastrophes, it will be in the tens or hundreds of thousands of years older and more advanced than us. Just remember what we were like just 200 years ago.
Perhaps as our technology gravitational waves will be sufficiently developed to detect first signals from the Universe, we begin to access the more subtle signs of activity in space. We may be able to determine the planet with tens of thousands of satellites in orbit via its unique gravitational wave imprint. Now this area is very young, so it has a long way. But these signals do not disappear as do electromagnetic signals, and there is no way to hide them. Perhaps in a hundred years it will be our main tool for space exploration.
But there is another option. What energy source would be to use a sufficiently advanced civilization? Maybe nuclear. More likely it will be the energy of synthesis, a special type that is different from what occurs in the cores of stars, and emits a very specific neutrino signature as a by-product. And these neutrinos are right to point out that energy is not natural and anthropogenic process.
If we can predict what this signature is, to understand it and to build a detector for it and measure it, we can find civilization running on nuclear fusion, anywhere, and we don’t have to worry whether or not it is the radio or not. While it produces energy, we will be able to find her.