Dyson spheres and using energy to build them

T.Neo

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O-F Staff Note: This thread is for discussing [ame=http://en.wikipedia.org/wiki/Dyson_sphere]Dyson spheres[/ame] and building them by transformation of energy into matter.

Thread forked from "5 Earth sized planets in habitable zone found" discussion, and some quotes may refer the former thread.



I'd like to point out that in all probability, Dyson spheres won't resemble the solid-shell structures seen in science fiction. A civilisation could be extracting exawatts from a star and the structures by which they could do so would only occasionally occult the star as seen from Earth.
 
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Jarvitä

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I know it's a tad off-topic, but I'd like to point out that in all probability, Dyson spheres won't resemble the solid-shell structures seen in science fiction. A civilisation could be extracting exawatts from a star and the structures by which they could do so would only occasionally occult the star as seen from Earth.


Well than it wouldn't be a Dyson sphere, now would it? The only way to capture all of a star's energy output is to surround it entirely.
 

T.Neo

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Well than it wouldn't be a Dyson sphere, now would it? The only way to capture all of a star's energy output is to surround it entirely.

Who says they want to capture all of the star's energy by surrounding it with a physically implausible structure? Not even Dyson's original concept was defined by such a solid shell, he only seriously proposed satellite or statite swarms.

An exawatt is already the power worth of many Kardashev class I civilisations, and Sol outputs almost 400 million exawatts.

I have a feeling that class II civilisations would usually be spread out over many stars, each star housing it's own, smaller civilisation with more plausible power collection methods.
 

jinglesassy

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I really fail to see why ANY civilization would need that much power that they would need to cannibalize all the planets in the solar system in order to build a thing entirely around its star.
 

Scruce

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Given that Kepler is currently looking for transiting planets (planet passes between its star and us), not sure how they'd locate a Dyson sphere...if it passes between another star and us?

If the star emits no optical light but a strong infared source.
 

T.Neo

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If the star emits no optical light but a strong infared source.

We're still going by the Star Trek definition of Dyson Sphere, aren't we? :p

Less optical light and more infrared, yes, along with occasional potential occultation of the star, but I think we ought to be looking for scientifically credible concepts as opposed to stuff that would be more at home in Star Wars. :shifty:
 

iamwearingpants

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I really fail to see why ANY civilization would need that much power that they would need to cannibalize all the planets in the solar system in order to build a thing entirely around its star.

If I'm correct, it's possible to transform energy into matter.
So starting out with a fairly large power station orbiting the star, you could turn that energy into more and more and more power stations (With robots and stuff) until you have a dyson swarm. With that energy then you can do large scale constructions without ever touching a planet.

Or maybe you could ask the probe :hailprobe:
 

RisingFury

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If I'm correct, it's possible to transform energy into matter.
So starting out with a fairly large power station orbiting the star, you could turn that energy into more and more and more power stations (With robots and stuff) until you have a dyson swarm. With that energy then you can do large scale constructions without ever touching a planet.

Or maybe you could ask the probe :hailprobe:

Or you could beam that power to propell intestellar craft at high acceleration :)
 

T.Neo

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Transform energy into matter? Theoretically possible, maybe, but practically? I'm not entirely sure...

You can get almost 90 billion megajoules from a kilogram of matter, if you convert it into energy. That's great if you're somehow using matter as a form of energy storage, but not great if you want to construct something out of energy...
 

RisingFury

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Transform energy into matter? Theoretically possible, maybe, but practically? I'm not entirely sure...

You can get almost 90 billion megajoules from a kilogram of matter, if you convert it into energy. That's great if you're somehow using matter as a form of energy storage, but not great if you want to construct something out of energy...


Production of elements heavier then Iron will convert energy into mass, as will acceleration of particles. More then "theoretically possible", I guess.
 

T.Neo

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Good, all you need to do then is produce elements heavier than iron on an industrial scale... :shifty:
 

Scruce

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We're still going by the Star Trek definition of Dyson Sphere, aren't we? :p

Less optical light and more infrared, yes, along with occasional potential occultation of the star, but I think we ought to be looking for scientifically credible concepts as opposed to stuff that would be more at home in Star Wars. :shifty:

No it is absolutely true, i read about it in a space encyclopedia.
 

jedidia

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If I'm correct, it's possible to transform energy into matter.
So starting out with a fairly large power station orbiting the star, you could turn that energy into more and more and more power stations (With robots and stuff) until you have a dyson swarm. With that energy then you can do large scale constructions without ever touching a planet.

Just that, to get enough energy to convert into the stupendious amounts of mass we're talking about, you'll need a better energy source than a dyson sphere... But if you already have that, why even bother to build one? ;)

I think constructing a dyson sphere(TM) would presuppose a civilisation that can do matter transmutation on a humonguous scale, though, to transform materials from broken up planets to what they actually need, and matter-to-energy conversion to have enough power. By the way, how are you going to break the planets apart? RKVs? (which certainly would be possible if you had matter-to-energy conversion. But vice versa doesn't really make much sense for industrial use...)
 

T.Neo

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No it is absolutely true, i read about it in a space encyclopedia

A space encyclopedia, right...

If you look at even the scale of getting a single exawatt of power from a star, you'll soon realise that a solid dyson sphere is not only implausible, but also impractical...

Imagine covering the entire Earth in solar panels, for example- converting all of Earth's precious resources into such an array. Now, where is everyone going to live? Grow their food? Why do you need this power at all, if there are so few people to use it?
 

jedidia

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Well, the cool thing about a Dyson Sphere would of course be that you could dedicate a comparatively small fraction of the surface to living space. It'll still be as large as a few hundred planets...
 

T.Neo

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Nice idea, but gravity generation is a problem. You actually get a small acceleration pulling you towards the star. That doesn't help...

The structure would also have to be made of unobtanium to survive, of course. And it would be unstable...

Would be better to construct orbiting, rotating habitats (similar concept to an O'Neill cylinder, but potentially much larger), with their own orbiting power collection facilities.

EDIT:

the problem then is... where did you get a few hundred planets to use for construction mass?

More like: few thousand planets. If my math is correct, for a 1 km thick, 1 AU inside diameter sphere, with a density of water, you will need 47 000 Earth masses. For an aluminium shell, you will need 127 000 Earth masses. The first example is around 14% the mass of Sol itself, the second almost 38%!

I really don't know, where you're going to get all of that mass. :dry:
 
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