Dyson Sphere

One theoretical space construct that has always intrigued, amazed, perplexed — okay too many apropos adjectives here — me, is a Dyson's Sphere. What a concept ... and an imagination. It simply boggles my mind. And so many questions, and gedankens spring from contemplation.

Total use of a sun's energy. No waste. What effect would solar flares then play? Seems an incredible energy budget available. Star Trek featured an episode feauring an encountered Dyson Sphere. A ship was found crashed on the surface because it couldn't see the sphere. The sphere appeared as a space anomaly that blocked out a huge expanse of stars. The ship looked like a gnat had crashed into a moon.

Can anyone wrap their thoughts around it?


Dyson sphere

A Dyson sphere is a hypothetical megastructure that completely encompasses a star and hence captures most or all of its power output. It was first described by Freeman Dyson. Dyson speculated that such structures would be the logical consequence of the long-term survival and escalating energy needs of a technological civilization, and proposed that searching for evidence of the existence of such structures might lead to the detection of advanced intelligent extraterrestrial life. Different types of Dyson spheres correlate with information on the Kardashev scale.

Since then, other variant designs involving building an artificial structure or series of structures to encompass a star have been proposed in exploratory engineering or described in science fiction under the name "Dyson sphere". These later proposals have not been limited to solar-power stations. Many involve habitation or industrial elements. Most fictional depictions describe a solid shell of matter enclosing a star, which is considered the least plausible variant of the idea (see below). In May 2013, at the Starship Century Symposium in San Diego, Dyson repeated his comments that he wished the concept had not been named after him.[1]

The concept of the Dyson sphere was the result of a thought experiment by physicist and mathematician Freeman Dyson, when he theorized that all technological civilizations constantly increased their demand for energy. He reasoned that if human civilization expanded energy demands long enough, there would come a time when it demanded the total energy output of the Sun. He proposed a system of orbiting structures (which he referred to initially as a shell) designed to intercept and collect all energy produced by the Sun. Dyson's proposal did not detail how such a system would be constructed, but focused only on issues of energy collection. Dyson is credited with being the first to formalize the concept of the Dyson sphere in his 1960 paper "Search for Artificial Stellar Sources of Infra-Red Radiation", published in the journal Science.[2] However, Dyson was not the first to advance this idea. He was inspired by the mention of the concept in the 1937 science fiction novel Star Maker,[3] by Olaf Stapledon, and possibly by the works of J. D. Bernal, Raymond Z. Gallun, and Edgar Rice Burroughs who seem to have explored similar concepts in their work.[4]

Although such megastructures may be theoretically possible, all plans to build a fixed-in-place Dyson sphere are currently far beyond humanity's engineering capacity. However, parts of the technology, like orbiting satellites and solar sails, have already been developed. Deployment of spacecraft and satellites using photovoltaics might be seen as the first small steps towards building a Dyson swarm.[5] However, the number of craft required to obtain, transmit, and maintain a complete Dyson sphere far exceeds the present-day industrial capabilities.

Variants

[huge xircumxision]


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wiki site:
http://en.m.wikipedia.org/wiki/Dyson_sphere

Star Trek depiction
http://en.memory-alpha.org/wiki/Dyson_sphere

Star Trek: NextGen episode "Relics" snip
http://youtu.be/ECLvFLkvY7Y

I remember the Star Trek episode about one. But I've had discussions about these with other people when I was in college. It's a grand theory, but the reality is likely to be far from the truth. The amount of material needed to construct such a sphere is immense. I don't recall the calculations, but it was a massive amount of a star system's resources.

The Dyson Swarm and Dyson Bubble, as I understand matters, are the most feasible.

A sphere requires amazingly strong materials, plus energy systems to compensate for solar drift, solar pressures and gravitational forces. I can't recall all the arguments against the possibility of the sphere, but there were more then enough to make me believe that mere technological advances would justify such an accomplishment.

The classic idea of a Dyson Sphere (a solid enclosure around a star) isn't what Freeman Dyson actually described, but has become a sort of pop culture icon.

Strangely enough, it could be built out of the materials in the Solar System (you would have to turn all the planets, asteroids etc. into building material), and the end result would seem rather flimsy (an iron shell only a few cm thick), so that sort of Dyson Sphere is more of a thought experiment than anything else.

The lightest sort of "real" Dyson sphere would be a cloud of solar sails "hovering" over the star balancing the thrust of the light pressure against the gravitational pull of the star. If any civilization were to actually expand the way Dyson suggests, the star will be obscured by billions of habitations and solar collectors orbiting the star.

I do remember a book (but, unfortunately,not the Author) called 'Wall around a Star', about a Dyson Sphere that had been launched by a advanced race on the 'other' side of the universe as a lifeboat of sorts, etc.

The amusing thing was, it had been traveling so long it had accumulated enough material to establish a biosphere on the outside. Think about it: a sphere the size of a solar system, able to support life on it's exterior...

Another interesting thought I ran across some years back: perhaps we could find out if there were any Dyson constructs by taking a good look at red giants, as it was postulated that the emission spectrum for something that size would be in the dull red range I'm pretty sure the math didn't work for this one...

And as a side note, Niven described the Ringworld as being directly influenced by Dyson, sort of an intermediate structure. And then there was the Alderson Disc, a structure built in the same shape as a CD about the size of the solar system. Day and Night cycles were done by causing the star in the central hole to bob up and down.

Wouldn't the pole sections of a Dyson Sphere be pretty much useless? You'd have none of the benefit of gravity from the rotation of the Sphere.

Rod wrote:Wouldn't the pole sections of a Dyson Sphere be pretty much useless? You'd have none of the benefit of gravity from the rotation of the Sphere.

Nope, it'd give you a place for all the solar panels you need to generate electrical power. Given the approximate area involved, it would be the surface area equivalent of six hundred Earths at an absolute minimum.
Loadsapower!

Caliban wrote:I do remember a book (but, unfortunately,not the Author) called 'Wall around a Star', about a Dyson Sphere that had been launched by a advanced race on the 'other' side of the universe as a lifeboat of sorts, etc.

The amusing thing was, it had been traveling so long it had accumulated enough material to establish a biosphere on the outside. Think about it: a sphere the size of a solar system, able to support life on it's exterior...

Another interesting thought I ran across some years back: perhaps we could find out if there were any Dyson constructs by taking a good look at red giants, as it was postulated that the emission spectrum for something that size would be in the dull red range I'm pretty sure the math didn't work for this one...

What sort of biology would it be? Something that could exist in the cold dark airless wastes of space? Being outside the sphere, there would be no light, very little heat, no air (it would be all frozen gases anyways with no heat source), only ice for water. At the most I could see the material being used as material for repairing the hull of the sphere.

Dyson spheres are massively impractical. Per the wiki article:

There are several serious theoretical difficulties with the solid shell variant of the Dyson sphere:

Such a shell would have no net gravitational interaction with its englobed star (see shell theorem), and could drift in relation to the central star. If such movements went uncorrected, they could eventually result in a collision between the sphere and the star—most likely with disastrous results. Such structures would need either some form of propulsion to counteract any drift, or some way to repel the surface of the sphere away from the star.[9]

For the same reason, such a shell would have no net gravitational interaction with anything else inside it. The contents of any biosphere placed on the inner surface of a Dyson shell would not be attracted to the sphere's surface and would simply fall into the star. It has been proposed that a biosphere could be contained between two concentric spheres, placed on the interior of a rotating sphere (in which case, the force of artificial "gravity" is perpendicular to the axis of rotation, causing all matter placed on the interior of the sphere to pool around the equator, effectively rendering the sphere a Niven ring for purposes of habitation, but still fully effective as a radiant-energy collector) or placed on the outside of the sphere where it would be held in place by the star's gravity.[17][18] In such cases, some form of illumination would have to be devised, or the sphere made at least partly transparent, because the star's light would otherwise be completely hidden.[19]

If assuming a radius of one AU, then the compressive strength of the material forming the sphere would have to be immense to prevent implosion due to the star's gravity. Any arbitrarily selected point on the surface of the sphere can be viewed as being under the pressure of the base of a dome 1 AU in height under the Sun's gravity at that distance. Indeed it can be viewed as being at the base of an infinite number of arbitrarily selected domes, but because much of the force from any one arbitrary dome is counteracted by those of another, the net force on that point is immense, but finite. No known or theorized material is strong enough to withstand this pressure, and form a rigid, static sphere around a star.[20] It has been proposed by Paul Birch (in relation to smaller "Supra-Jupiter" constructions around a large planet rather than a star) that it may be possible to support a Dyson shell by dynamic means similar to those used in a space fountain.[21] Masses travelling in circular tracks on the inside of the sphere, at velocities significantly greater than orbital velocity, would press outwards on magnetic bearings due to centrifugal force. For a Dyson shell of 1-AU radius around a star with the same mass as the Sun, a mass travelling ten times the orbital velocity (297.9 km/s) would support 99 (a=v2/r) times its own mass in additional shell structure.

Also if assuming a radius of one AU, then there may not be sufficient building material in the Solar System to construct a Dyson shell. Anders Sandberg estimates that there is 1.82×1026 kg of easily usable building material in the Solar System, enough for a 1-AU shell with a mass of 600 kg/m²—about 8–20 cm thick on average, depending on the density of the material. This includes the hard-to-access cores of the gas giants; the inner planets alone provide only 11.79×1024 kg, enough for a 1-AU shell with a mass of just 42 kg/m².[10]

The shell would be vulnerable to impacts from interstellar bodies, such as comets, meteoroids, and material in interstellar space that is currently being deflected by the Sun's bow shock. The heliosphere, and any protection it theoretically provides, would cease to exist.

Whereas I agree that materials is one big question mark, let's assume that placement in the Universe will solve that one. That there are many places in the Universe where there are mass gatherings of super rock quarries err asteroid quarries that also feature the correct star configuration. In other words, let's at least donate the raw materials for this project. Or maybe there aren't many star systems where everything is available. Which means if such a sweet spot is found, then we must build. And they will come.

At any rate, with the available energy budget from that thing, system defense from comets and asteroids should be fundamental. In fact, comets and asteroids will simply be captured and used. It's like the Universe will be throwing building materials at the project. Certainly we have to assume certain technological capabilities/innovations of some race of beings that may attempt it.

If you can conceive of it. You can build it.

Um, wait ... do you think that's why alien ships have been visiting Earth. For raw materials? Someone has been digging in the Grand Canyon!

I'm a Civil Engineer. We often talk about black holes of a building project. Think this is one?

Depends where you built it. If it was around mercury distance it would be hot but the rest of the planets would freeze, except the big ones.

If you did it around the asteroid belt it would hide the rest of the stars. Around the ORT cloud well it would still hide the stars but its usefulness would be limited.

Earth level mars would suck unless a ray was opened for each desirable planet. Etc....

Materials used would be limited.

Would be a great way to hide your star or solar system from others.

They just wouldn't see us.