Post by swamprat on Aug 30, 2018 15:56:13 GMT
What is a Dyson sphere?
By Deborah Byrd in HUMAN WORLD | SPACE | August 30, 2018
Dyson spheres are back in the news. In case you’ve never heard of them – or want to brush up – here’s a primer.
First step toward a Dyson sphere? Image via langalex.
Proponents of solar power know that only a tiny fraction of the sun’s total energy strikes the Earth. What if we, as a civilization, could collect all of the sun’s energy? If so, we would use some form of Dyson sphere, sometimes referred to as a Dyson shell or megastructure. Physicist and astronomer Freeman J. Dyson first explored this idea as a thought experiment in 1960. Dyson’s two-page paper in the journal Science was titled Search for Artificial Stellar Sources of Infrared Radiation because he was imagining a solar-system-sized solar power collection system not as a power source for us earthlings, but as a technology that other advanced civilizations in our galaxy would, inevitably, use. Dyson proposed that searching for evidence of the existence of such structures might lead to the discovery of advanced civilizations elsewhere in the galaxy.
In recent years, astronomers explored that possibility with a bizarre star, known to astronomers as KIC 8462852 – more popularly called Tabby’s Star for its discoverer Tabetha Boyajian. This star’s strange light was originally thought to indicate a possible Dyson sphere. That idea has been discarded, but, in 2018, other possibilities emerged, such as that of using the Gaia mission to search for Dyson spheres.
All of this is just to say that Dyson spheres – while in the realm of science fiction and scientific possibility during the 20th century – now seem real enough to astronomers that some are scrutinizing particular stars, looking for signs of them.
The central dot in this image represents a star. The simplest form of Dyson sphere might begin as a ring of solar power collectors, at a distance from a star of, say, 100 million miles. This configuration is sometimes called a Dyson ring. Image via Wikimedia Commons.
So what are these odd megastructures, these Dyson spheres? Originally, some envisioned a Dyson sphere as an artificial hollow sphere of matter around a star, and Dyson did originally use the word shell. But Dyson didn’t picture the energy-collectors in a solid shell. In an exchange of letters in Science with other scientists, following his 1960 Science article, Dyson wrote:
"A solid shell or ring surrounding a star is mechanically impossible. The form of ‘biosphere’ which I envisaged consists of a loose collection or swarm of objects traveling on independent orbits around the star."
As time passed, a civilization might continue to add Dyson rings to the space around its star, creating a relatively simple, but incredibly powerful, Dyson sphere. Image via Wikimedia Commons.
A Dyson sphere might be, say, the size of Earth’s orbit around the sun; we orbit at a distance of 93 million miles (about 150 million km). The website Sentient Developments describes the Dyson sphere this way:
"It would consist of a shell of solar collectors (or habitats) around the star. With this model, all (or at least a significant amount) of the energy would hit a receiving surface where it can be used. [Dyson] speculated that such structures would be the logical consequence of the long-term survival and escalating energy needs of a technological civilization."
And of course science fiction writers have had a field day writing about Dyson spheres. Dyson himself admitted he borrowed from science fiction before he began his technical exploration of the idea of a megastructure gathering energy from its star. Olaf Stapledon first mentioned this idea in his 1937 science fiction novel “Star Maker”, which Dyson apparently read and used as inspiration.
Eventually, as a civilization evolves – aided by the boundless energy gathered from its star – its surrounding Dyson sphere will surely evolve as well, in ways that are hard to predict. This artist’s concept of a Dyson sphere is via Sentient Developments.com.
What might astronomers look for, in the search for evidence of Dyson spheres in the space of our Milky Way galaxy? Even before the discovery of KIC 8462852 – feeling frustrated by decades of seeking radio signals from intelligent civilizations beyond Earth, and not finding any – a few astronomers in 2013 were contemplating new search strategy. Consider that if a system of solar power collectors – a megastructure – were put in place around a star, the star’s light, as seen from our perspective, would be altered. The solar collectors would absorb and reradiate energy from the star. Astronomers have spoken of seeking that reradiated energy.
Stephen Battersby at New Scientist wrote a great article about how astronomers search for Dyson spheres, using reradiated energy, released in April 2013. The article is available by subscription only, but if you search on the title (“Alien megaprojects: The hunt has begun”), you might find an alternative link.
In 2018, scientists began speaking of using the European Space Agency’s Gaia mission to seek Dyson spheres. You can read about Gaia's effort in the net post.
earthsky.org/space/what-is-a-dyson-sphere
By Deborah Byrd in HUMAN WORLD | SPACE | August 30, 2018
Dyson spheres are back in the news. In case you’ve never heard of them – or want to brush up – here’s a primer.
First step toward a Dyson sphere? Image via langalex.
Proponents of solar power know that only a tiny fraction of the sun’s total energy strikes the Earth. What if we, as a civilization, could collect all of the sun’s energy? If so, we would use some form of Dyson sphere, sometimes referred to as a Dyson shell or megastructure. Physicist and astronomer Freeman J. Dyson first explored this idea as a thought experiment in 1960. Dyson’s two-page paper in the journal Science was titled Search for Artificial Stellar Sources of Infrared Radiation because he was imagining a solar-system-sized solar power collection system not as a power source for us earthlings, but as a technology that other advanced civilizations in our galaxy would, inevitably, use. Dyson proposed that searching for evidence of the existence of such structures might lead to the discovery of advanced civilizations elsewhere in the galaxy.
In recent years, astronomers explored that possibility with a bizarre star, known to astronomers as KIC 8462852 – more popularly called Tabby’s Star for its discoverer Tabetha Boyajian. This star’s strange light was originally thought to indicate a possible Dyson sphere. That idea has been discarded, but, in 2018, other possibilities emerged, such as that of using the Gaia mission to search for Dyson spheres.
All of this is just to say that Dyson spheres – while in the realm of science fiction and scientific possibility during the 20th century – now seem real enough to astronomers that some are scrutinizing particular stars, looking for signs of them.
The central dot in this image represents a star. The simplest form of Dyson sphere might begin as a ring of solar power collectors, at a distance from a star of, say, 100 million miles. This configuration is sometimes called a Dyson ring. Image via Wikimedia Commons.
So what are these odd megastructures, these Dyson spheres? Originally, some envisioned a Dyson sphere as an artificial hollow sphere of matter around a star, and Dyson did originally use the word shell. But Dyson didn’t picture the energy-collectors in a solid shell. In an exchange of letters in Science with other scientists, following his 1960 Science article, Dyson wrote:
"A solid shell or ring surrounding a star is mechanically impossible. The form of ‘biosphere’ which I envisaged consists of a loose collection or swarm of objects traveling on independent orbits around the star."
As time passed, a civilization might continue to add Dyson rings to the space around its star, creating a relatively simple, but incredibly powerful, Dyson sphere. Image via Wikimedia Commons.
A Dyson sphere might be, say, the size of Earth’s orbit around the sun; we orbit at a distance of 93 million miles (about 150 million km). The website Sentient Developments describes the Dyson sphere this way:
"It would consist of a shell of solar collectors (or habitats) around the star. With this model, all (or at least a significant amount) of the energy would hit a receiving surface where it can be used. [Dyson] speculated that such structures would be the logical consequence of the long-term survival and escalating energy needs of a technological civilization."
And of course science fiction writers have had a field day writing about Dyson spheres. Dyson himself admitted he borrowed from science fiction before he began his technical exploration of the idea of a megastructure gathering energy from its star. Olaf Stapledon first mentioned this idea in his 1937 science fiction novel “Star Maker”, which Dyson apparently read and used as inspiration.
Eventually, as a civilization evolves – aided by the boundless energy gathered from its star – its surrounding Dyson sphere will surely evolve as well, in ways that are hard to predict. This artist’s concept of a Dyson sphere is via Sentient Developments.com.
What might astronomers look for, in the search for evidence of Dyson spheres in the space of our Milky Way galaxy? Even before the discovery of KIC 8462852 – feeling frustrated by decades of seeking radio signals from intelligent civilizations beyond Earth, and not finding any – a few astronomers in 2013 were contemplating new search strategy. Consider that if a system of solar power collectors – a megastructure – were put in place around a star, the star’s light, as seen from our perspective, would be altered. The solar collectors would absorb and reradiate energy from the star. Astronomers have spoken of seeking that reradiated energy.
Stephen Battersby at New Scientist wrote a great article about how astronomers search for Dyson spheres, using reradiated energy, released in April 2013. The article is available by subscription only, but if you search on the title (“Alien megaprojects: The hunt has begun”), you might find an alternative link.
In 2018, scientists began speaking of using the European Space Agency’s Gaia mission to seek Dyson spheres. You can read about Gaia's effort in the net post.
earthsky.org/space/what-is-a-dyson-sphere
