|Fig. 1 An visualization of the Dyson swarm. A host of artificial satellites orbit a central star. (Source: Wikimedia Commons)|
In January 2016, a collective of scientists and citizen astronomers reported a strange optical phenomenon from the otherwise-unremarkable star KIC 8462852.  They found that its light, as seen from the Kepler Space Telescope, was growing dimmer by up to twenty percent of its maximum intensity before returning to full brightness over erratic and unpredictable periods of time. This could not be easily explained by known cosmic phenomena, and the leading hypothesis was that a dense host of foreign bodies passing through Earth's line-of-sight with the star was periodically obscuring it, making it occasionally appear less bright to distant observers. However, the abnormally high degree to which the star was dimmed, coupled with the fact that the dips in luminosity were irregular yet ceaseless, led scientists to hypothesize that the nature of these bodies could be artificial; a statement quickly picked up on and sensationalized by the press.
This article attempts to couch the rational existence of such objects in scientific reason, and motivates why a budding alien society might some day gaze at our Sun through their telescopes and be amazed when they observe the same phenomenon.
A Dyson sphere, as proposed by the physicist Freeman Dyson in 1960, describes an immense artificial construct - or a series thereof - orbiting a star, with the capability to capture its light and convert it to useful forms of energy.  Dyson originally envisioned a gargantuan spherical shell that would completely encapsulate the star and soak up all its light. This idea has been popularized within the scientific community, as well as being enthusiastically portrayed in the genre of science fiction, such as in the episode "Relics" in the television series Star Trek: The Next Generation. However, the physics of orbital mechanics and the veritable planet-sized mass of materials required preclude such an idea from being efficient.
The most realistic and feasible variant of the Dyson sphere is called the Dyson swarm. Such an installation is depicted in Fig. 1; a constellation of man-made satellites in orbit around a star. The basic dynamics of this orbital arrangement are similar to how the Earth and other planets revolve around the Sun, but at a much closer distance and with many more elements, conjuring up the image of a swarm of honey bees defending their hive. Each of these satellites would have solar panels to collect the Sun's radiation, both visible and invisible, and transmit this energy wirelessly back to Earth, where it would be intercepted and used. Such a setup would cause the Sun to be slightly eclipsed each time a satellite passes, causing fluctuations in light as is the case with KIC 8462852. Indeed, it is this line of justification that has led to renewed research and media speculation as to the possibility of alien megastructures, built by some advanced civilization in the past, that could be some variation of Dyson's initial postulate.
The idea of converting solar rays into energy to power our homes and fuel our industries is by no means novel, but the degree to which an advanced civilization might be able to use a star's energy has been a longstanding thought experiment among astronomers and searchers for extraterrestrial life. In 1964, the astrophysicist Nikolai Kardashev proposed that a civilization's level of technology is inevitably tied to its energy consumption, and hence civilizations could be classified by the sheer magnitude of energy they generated.  According to his metric, now christened the Kardashev scale, a Type I civilization would be able to fully utilize all the resources available on its home planet, while a Type III civilization would be capable of harnessing the energy of its host galaxy. The intermediary stage, a Type II civilization, is defined as being able to harvest the total energy output of its parent star, by means of a Dyson sphere of some form.
Humanity as we know it barely qualifies as a Type I civilization by the most lenient of criteria, and therefore it may seem that the discussion on harvesting any significant portion of the Sun's energy is only useful in writing new and exciting science fiction. However, as an end goal, there are distant but practical motivations for furthering such an endeavor. The solar activity of our Sun is estimated to remain stable for the next five billion years; compared to the finite - and rapidly diminishing - resources on Earth, the Sun would appear to be a limitless supply of energy that we have barely begun to tap into. Currently, most of solar radiation is blasted uselessly into space; of the total energy output by the Sun each second, less than a billionth of it reaches the face of the Earth. If we could harness but one part in a millionth of that energy, in one second we would have the energy equivalent of the total energy consumption of the modern world for an entire year.
|Fig. 2: Artist's impression of a mega-satellite orbiting the Earth, designed to collect and transmit solar energy." (Source: Wikimedia Commons)|
And the global demand for energy only increases, while the Earth's supply of non-renewable resources such as coal and oil can only dwindle.  Eventually, the nations of the world will need to seek serious alternatives to traditional primary energy sources, and solar energy is a foremost contender to be the most long-term, stable solution. A growing environmental drive towards sustainable energy sources, paired with the maturation of modern material technologies, has brought the possibilities of large-scale harvesting of solar energy into the spotlight. For instance, DESERTEC, an initiative founded in 2003 by an international network of scientists, politicians, and economists, explored the potential for a permanent series of installations, consisting of solar power plants and wind parks, in and around the North African deserts with the goal to achieve sustainable, long-term solutions to the energy needs of Africa and Europe.  However, the ambitions of the project have since been tempered by political disputes and regional instability, as well as a general loss of confidence by shareholders; an occurrence symptomatic of many such international green energy projects.
It would appear, then, a futile expenditure of research and goodwill to invest in far-flung futuristic energy solutions should the world not cooperate; if nations cannot come to a consensus on regional energy solutions, or if the capitalist economy is unwilling to support expensive ventures with uncertain return, then the utopian dream of unlimited space-based solar power may remain just that. However, even now, research is slowly advancing, in baby steps and in various countries, towards the towards the realization of space-based solar power of some description. Two of the world's leading space agencies, National Aeronautics and Space Administration (NASA) and Japan Aerospace Exploration Agency (JAXA), have laid down development plans for constructing mega-satellites, as showcased in Fig. 2, that will transmit a focused beam of reflected solar energy to a ground receiver via microwave-length radiation. [6,7] India has partnered with the American National Space Society (NSS) to launch the Kalam-NSS Energy Initiative; a forum with the purpose of strengthening the partnership between the two countries with regards to space-based solar power.  China has announced that it will pursue the generation of solar power in space after the launch of its third space station, Tiangong-3, in 2020.
Therefore, I am convinced that it is in space that the secrets of sustainable energy lie. Way up there, where the Earth shrinks to blue, there exists - in the absence of cloud cover, sunsets, and geopolitical toes to tread upon - a glimmer of hope for the future of human energy.
© Alastair Wee. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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 F. J. Dyson, "Search for Artificial Stellar Sources of Infrared Radiation," Science 131, 1667 (1960).
 N. S. Kardashev, "Transmission of Information by Extraterrestrial Civilizations," Sov. Astron. 41, 282 (1964).
 "Annual Energy Outlook 2013," U.S. Energy Information Administration, DOE/EIA-0383, April 2013.
 "Red Paper: An Overview of the Desertec Concept," Desertec Foundation, 2009.
 J. Mankins, "SPS-ALPHA: The First Practical Solar Power Satellite via Arbitrarily Large Phased Array," Artemis Innovation Management Solutions LLC, 15 Sep 12.
 S. Sasaki, "How Japan Plans to Build an Orbital Solar Farm," IEEE Spectrum, 24 Apr 14. [originally published under the title "It's Always Sunny in Space" in IEEE Spectrum (Volume: 51, Issue: 5, 2014), p. 46-51.]
 D. M. Flournoy, Solar Power Satellites (Springer, 2012), p. 50.