Are We Alone?

6. DYSON SPHERE

As the eons advanced, hundreds of thousands of worlds were constructed, all of this type, but gradually increasing in size and complexity. Many a star without natural planets came to be surrounded by concentric rings of artificial worlds. In some cases the inner rings contained scores, the outer rings thousands of globes adapted to life at some particular distance from the Sun..

— Olaf Stapledon, the British philosopher and author of several influential works of science fiction in his book “Star Maker”

In his 1960 article in the journal Science, entitled “Search for Artificial Stellar Sources of Infrared Radiation”, Freeman Dyson, the English-born theoretical physicist and mathematician famous for his work in quantum electrodynamics, solid-state physics, astronomy and nuclear engineering, argued that there may be another way to detect uncommunicative alien civilizations. The abstract read: “If extraterrestrial intelligent beings exist and have reached a high level of technical development, one by-product of their energy metabolism is likely to be the large-scale conversion of starlight into far-infrared radiation. It is proposed that a search for sources of infrared radiation should accompany the recently initiated search for interstellar radio communications.”

Figure 6-1
Figure 6-1: The Earth has 0.01% excess mid-infrared radiation because of human activity.
Dyson_Ring
Figure 6-2: A Dyson ring — the simplest form of the Dyson swarm — to scale. Orbit is 1 AU in radius, collectors are 1.0 × 107 km in diameter (~25× the Earth–Moon distance), spaced 3 degrees from center to center around the orbital circle. Image Credit: http://www.wikipedia.com.
640px-Dyson_Swarm
Figure 6-3: A relatively simple arrangement of multiple Dyson rings of the type pictured above, to form a more complex Dyson swarm. Rings’ orbital radii are spaced 1.5 × 107 km with regard to one another, but average orbital radius is still 1 AU. Rings are rotated 15 degrees relative to one another, around a common axis of rotation. Image Credit: http://www.wikipedia.com.

Dyson realized that advanced alien civilizations could be recognized by tracking their waste heat, detectable as infrared radiation (infrared excess). For example, see Figure 6 1, where the infrared excess for the Earth is shown as a result of human activity. Similarly, civilizations must, by the Second Law of Thermodynamics, emit waste heat even if they are uncommunicative and try to conceal their existence. Dyson further argued that really advanced civilizations would re-engineer their Solar Systems, perhaps dismantling planets to form a shell of satellites around their star to capture its energy. In Dyson’s own words “One should expect that, within a few thousand years of its entering the stage of industrial development, any intelligent species should be found occupying an artificial biosphere which completely surrounds its parent star.”

Dyson speculated that such an artificial biosphere would be the logical consequence of the long-term survival of our species. Not too far into the foreseeable future, all of Earth’s non-renewable sources, such as fossil and nuclear fuels, will be exhausted. Even the renewable sources will be unable to cope with growing demand. This is because the Earth receives about one billionth of the total radiant output of the Sun, according to the Berkeley astronomer Don Goldsmith, and that humans utilize about one millionth of that. To sustain the future growth, the human race will need to capture much more of the Sun’s light. It could do this with a Dyson Sphere, a gigantic artificial structure (which he referred to initially as a shell) for the purpose of intercepting vast amounts of solar energy. If this could be done with great efficiency, the total energy gain could easily be many trillion times larger than all of our current energy consumption on Earth.

The idea of artificial biosphere was inspired by the science fiction author Olaf Stapledon’s Star Maker and by J. D. Bernal.

Many variants of the design of the Dyson Sphere has been proposed, the design of some are not even practical. Today Dyson Spheres are envisioned more as a dense network of orbiting solar power satellites (orbiting collectors of solar energy) in the space around a star and capable of capturing most or all of the star’s energy output. Dyson suggested that this method of energy collection will be inevitable for advanced civilizations whose goal is to ensure a significant fraction of the star’s energy impinge on a receiving surface of the collectors that could be used to the civilization’s benefit. The simplest form of Dyson sphere—a ring of solar power collectors, at a distance from a star of, say, 100 million miles—is shown in Figure 6-2. The central dot represents a star. This configuration is called a Dyson ring. With time a civilization might continue to add more Dyson rings to the space around its star, creating an incredibly powerful Dyson sphere (Figure 6 3).

Detecting Dyson Spheres around other stars is challenging, and might not be possible with today’s technology. But that did not stop scientists from trying and the literature contains several attempts to find the expected waste energy in mid-infrared wavelengths that should be emanating from a Dyson sphere. Searches by Vyacheslav Slysh at the Space Research Institute in Moscow in 1985 and by Richard Carrigan at Fermilab in 2009, who used data from the Infrared Astronomical Satellite, produced no results. Jugaku, Noguchi, and Nishimura (1995) searched numerous stars with a 1.26 m infrared telescope in Japan and examined IRAS data looking for a 10-20 micron infrared excess. They did also not find any candidates. Null results were also reported by Jason Wright at Pennsylvania State University in University Park and Matt Povich at the California State Polytechnic University in Pomona. They used data from NASA’s Wide Field Infrared Survey Explorer (WISE) and the Spitzer space telescope, launched in 2009 and 2003 but found nothing so far.

With all of the false starts the question now is, how likely are we to ever find intelligent life, somewhere in our Galaxy, or in the Universe for that matter?

To answer that question one needs to be able to estimate the possible number of civilizations in our Galaxy first and identify the areas one must focus on in the search for alien life. That is done by an empirical equation called Drake equation.

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