It's hard to say when a person first wondered if he was alone in the universe. But it is possible to determine the time when the search for an answer to this question moved from the pages of science fiction novels to science - the middle of the last century, the beginning of the space age. With the development of interplanetary space, more and more ideas about extraterrestrial civilizations began to appear. Intergalactic wars played out on the pages of science fiction, and astrophysicists and astronomers tried to understand whether life was possible in the vicinity of distant stars. If yes, how to find it? Among the latest ideas is the theory of Freeman Dyson. A sphere of enormous size, which allows accumulating the energy of a star, is what, in his opinion, it is worth looking for in the vast outer space in order to find aliens.
Freeman John Dyson
American scientist of English origin was born in 1923. Today, 92-year-old Dyson, whose area of interest covers quantum physics, astrophysics, and low-energy physics, is known as one of the founders of quantum electrodynamics. Perhaps more famous for him was the concept that the scientist borrowed from OlafStapledon, science fiction writer, author of The Star Maker. The theory, dubbed the "Dyson sphere", suggests that highly advanced civilizations can build a huge structure around a star in order to maximize its energy. By finding such a design, scientists will be able to detect extraterrestrial intelligence.
Concept
A highly developed civilization, hypothetically existing in outer space, sooner or later will face the depletion of energy resources - such is Dyson's assumption. A sphere with a radius of one astronomical unit with a star in the center can solve this problem. The impressive size of the structure allows you to fully use the energy of the star and, if necessary, becomes a home for its creators.
Parameters
The thickness of the sphere, according to Dyson's calculations, should be quite small. To build such a structure, you will need material that is close to Jupiter in mass. Today, such a project looks like a very bold fantasy. However, it is impossible to exclude the possibility that after hundreds or thousands of years, humanity will be able to translate it into reality, and now in the vast expanses of space, an extraterrestrial civilization that surpasses us in terms of development is engaged in the construction of such a structure.
A star with a Dyson sphere obeys the same physical laws as planetary systems. Therefore, the structure must rotate: the force of centrifugal rotation balances the force of attraction of the star and does not allow the object to collapse and fall on it.
Signs of a developedcivilizations
According to Dyson's idea, the sphere can become a kind of beacon, marking the presence of extraterrestrial intelligence. However, how to find it? According to theoretical calculations, such a design should constantly emit light. It is invisible to the human eye. The radiation should lie in the infrared part of the spectrum. Existing equipment is able to detect such sources, moreover, quite a few have already been found.
The hallmark of a Dyson sphere should be an atypical spectral distribution. The search for a design theoretically described by a physicist is carried out as part of the SETI program, aimed at detecting the presence of extraterrestrial intelligence in space. The main hopes for this difficult task are placed on the Spitzer telescope.
Arguments against
Since its inception, Dyson's theory has been repeatedly rethought and retested. As a result, a well-founded opinion appeared that such an object could not exist, no matter how advanced the civilization was and no matter what characteristics the star possessed. The Dyson sphere, revolving around the luminary, acquires its maximum speed in the equator region. At the same time, the structure remains motionless at the poles, which will inevitably lead to its collapse. This is the main argument against the American scientist's theory.
Researchers of the issue also note that the sphere spatially limits the development of civilization and gives rise to several significant socio-cultural problems that overshadow the benefits of its creation.
Alternative options
However, in the scientific worldDyson's theoretical development has not sunk into oblivion. Several variants of design modifications were described, in which the main criticisms were taken into account. The first of these is a ring of small width, as large in diameter as a sphere. You can meet such an object on the pages of the novel "The World-Ring" by Larry Niven.
The second option is a design resembling a top. The curved thickenings in the region of the poles are open. This version of the sphere is characterized by the same weight at any point on the inside.
Soviet physicist G. I. Pokrovsky. In his model, the design consists of many rings, forming something that looks like a shell. This version of the sphere was called the "Pokrovsky shell".
The Criswell structure is another modification of Dyson's proposed astro-construction. Its feature is a fractal surface, which allows to maximize the area that receives the star's radiation.
Searching for a hypothetical Dyson sphere
Theoretical development of the American physicist for more than fifty years. However, it was only in the 2000s that the development of technology made it possible to look into the remote corners of space to seriously think about the search for structures similar to a sphere. An analysis of information coming from telescopes showed that there are several hundred thousand objects suitable for the role of giant artificial structures. True, the characteristics of eachcandidates with varying degrees of probability are explained by more prosaic reasons, among which comet swarms, hydrogen clouds, and so on.
One of the last contenders for a star surrounded by a Dyson sphere was a star in the constellation Cygnus. In astronomical catalogs, it is designated as KIC 8462852.
Dyson sphere detected?
Last autumn, one could notice a headline on the pages of the media announcing the discovery of the location of an extraterrestrial civilization. The star, near which intelligent beings unknown to us live, was called KIC 8462852. The features of the star became known thanks to the Kepler telescope.
In the fall of 2015, the results of a study of its strange luminosity were published. Approximately once every 800 days, the star's radiation decreases by 15-20%. The recession lasts from several days to several months. Such behavior is not characteristic of known classes of luminaries and cannot be explained by the passage of the planet across the disk, since in this case the decrease in radiation would always be the same in time. Jason Wright, a scientist at the University of Pennsylvania, suggested that the reason for this anomaly is the Dyson sphere. KIC 8462852 has thus become a prime candidate for the search for extraterrestrial intelligence.
Other explanations
Wright has repeatedly noted that this is just one of the versions, and the most unlikely. However, thanks to the media, the news of the possible discovery of the Dyson sphere spread around the world. In the meantime, there are other explanations for the star's strange radiation. Researchers from Yale University, led by Tabeta Boyajian, suggest that the star is surrounded by a swarm of comets. Perhaps KIC 8462852 captured them a few thousand years ago when another star system passed by. Tabeta notes that this explanation is only slightly more likely than the Dyson sphere. The meeting of two star systems is a very rare event, and the volume of the captured swarm of comets must be huge. However, this theory has so far gained the largest number of supporters in the scientific world.
Take a closer look at white dwarfs
Scientists from Turkey also joined the search for the Dyson sphere. Recently, they published a study according to which it is necessary to look for such a structure in white dwarfs. Relatively small and cold objects of space represent the final stage in the evolution of luminaries like the Sun. In their vicinity, the construction of a sphere requires less effort and material than around more massive stars. According to the calculations of scientists, the thickness of the structure near the white dwarf would not exceed 1 meter. Its construction would require material roughly equal in mass to the moon.
Perhaps, after some time, scientists will come to the conclusion that the Dyson sphere is an unnecessary or too complicated structure. However, the search for a hypothetical design continues. It is safe to say that such ideas will arise in the future, as humanity will not stop trying to find brothers in mind in the vastness of space.
