Dyson Sphere - The Ultimate in Navel Gazing?

[Asbo Zaprudder]

If you captured all or most of the power output of the star you would be burned to a cinder inside the Dyson sphere due to heat build up.The whole thing is very poorly thought out by the originator.

That wouldn't happen -- the Dyson sphere would reradiate the energy in a manner akin to a black body -- basic laws of thermodynamics and all that.

If you put a 100 watt incandescent bulb in a shoe box the temperature inside the shoe box will go quite high.The shoe box will of course radiate heat eventually, but the temperature will go very high inside the show box killing any insects inside.

As one would expect -- however, a shoe box is small in comparison with the light bulb -- it isn't 300 million km across. From the Stefan-Boltzmann law one can estimate that a body in orbit around the sun at 1AU should have an effective temperature of about 280K. The actual temperature will usually be a bit higher than this because of emissivity, albedo, internally generated heat, etc. For a Dyson sphere, I assume the incident radiation would be collected, energy extracted for whatever purpose is required to support the inhabitants, and waste heat radiated away from the outer surface.

 

[Ariadne]

If you captured all or most of the power output of the star you would be burned to a cinder inside the Dyson sphere due to heat build up.The whole thing is very poorly thought out by the originator.

That wouldn't happen -- the Dyson sphere would reradiate the energy in a manner akin to a black body -- basic laws of thermodynamics and all that.

If you put a 100 watt incandescent bulb in a shoe box the temperature inside the shoe box will go quite high.The shoe box will of course radiate heat eventually, but the temperature will go very high inside the show box killing any insects inside.

Unless you convert it into another form of energy - and, as discussed, you'll need a lot of power to rotate the sphere.

 

[noknowes]

That wouldn't happen -- the Dyson sphere would reradiate the energy in a manner akin to a black body -- basic laws of thermodynamics and all that.

If you put a 100 watt incandescent bulb in a shoe box the temperature inside the shoe box will go quite high.The shoe box will of course radiate heat eventually, but the temperature will go very high inside the show box killing any insects inside.

Unless you convert it into another form of energy - and, as discussed, you'll need a lot of power to rotate the sphere.

Dyson must have been drunk when he came up the idea as it is very poorly thought out.

Energy is still energy, regardless of conversion.

If the inside of the Dyson sphere was reflective then everyone would be cooked from the reflected radiation and even the star would would be effected.Just like a microwave oven enclosure.

If the inside was a dark color then they would still be cooked as the the "ground" would heat up to very high temperatures.Anyone ever inside a black or dark colored car on a sunny day with windows up and the fan off?


The Dyson concept is fundamentally flawed and I guarantee no civilization would ever go for it.

A 1000 Star systems would need to used to construct it ,including energy for transporting and processing.

It would be a huge act of genocidal vandalism and destruction of the surrounding star systems.Also any civilization trying it would have died out already as failure to expand is related to stagnation and a Dyson sphere would be the ultimate in navel gazing.

Furthermore there is no benefit at all.The energy requirements would have been met long before from artificial fusion,etc

 

[hyzmarca]

You wouldn't actually need that much mass, only about 2.17*10^20 kilograms. You can get that from a large asteroid or two.

 

[Asbo Zaprudder]

Yeah, whatever.

If you're really that interested, it would be a good idea to look at Dyson's original writings on the subject.

 

[Ariadne]

Unless you convert it into another form of energy - and, as discussed, you'll need a lot of power to rotate the sphere.

Dyson must have been drunk when he came up the idea as it is very poorly thought out.

Energy is still energy, regardless of conversion.

If the inside of the Dyson sphere was reflective then everyone would be cooked from the reflected radiation and even the star would would be effected.Just like a microwave oven enclosure.

If the inside was a dark color then they would still be cooked as the the "ground" would heat up to very high temperatures.Anyone ever inside a black or dark colored car on a sunny day with windows up and the fan off?

No, but if you convert it to electrical energy, (presumably using photovoltaics in the sky, but solar thermal on the ground would work as well), then you can use it to do whatever work needs doing (including spinning up the shell), and store the rest or emit it outside.

 

[FordSVT]

If you put a 100 watt incandescent bulb in a shoe box the temperature inside the shoe box will go quite high.The shoe box will of course radiate heat eventually, but the temperature will go very high inside the show box killing any insects inside.

Unless you convert it into another form of energy - and, as discussed, you'll need a lot of power to rotate the sphere.

Dyson must have been drunk when he came up the idea as it is very poorly thought out.

Energy is still energy, regardless of conversion.

If the inside of the Dyson sphere was reflective then everyone would be cooked from the reflected radiation and even the star would would be effected.Just like a microwave oven enclosure.

If the inside was a dark color then they would still be cooked as the the "ground" would heat up to very high temperatures.Anyone ever inside a black or dark colored car on a sunny day with windows up and the fan off?


The Dyson concept is fundamentally flawed and I guarantee no civilization would ever go for it.

A 1000 Star systems would need to used to construct it ,including energy for transporting and processing.

It would be a huge act of genocidal vandalism and destruction of the surrounding star systems. Also any civilization trying it would have died out already as failure to expand is related to stagnation and a Dyson sphere would be the ultimate in navel gazing.

Furthermore there is no benefit at all.The energy requirements would have been met long before from artificial fusion,etc

I'd appreciate it a lot if you wouldn't purposefully go out of your way to IGNORE things people have told you. That's what you're doing, you keep bringing up points that people have refuted already, like the mass requirements.

I'm also very interested in the sociological examination of a real life species that has had to deal with expanding beyond it's own solar system you keep referring to as fact.

And why would you assume that their energy needs would be met by nuclear fusion? What, exactly are their energy needs? Population size? Technological and manufacturing needs? You've already presumed to know the economic realities of a Type II or III civilization, now you're an expert on their energy needs?

I think you'll find little tolerance for two things in this forum:

1) grand pronouncements of fact on largely speculative matters,

2) totally ignoring facts presented to you by other posters and then continuing along the same lines of argument.

Both of these things render having a discussion with you pointless.

 

[noknowes]

I did not ignore you at all.You never understood what I said.To transport construction material requires energy.You ignored that.

"And why would you assume that their energy needs would be met by nuclear fusion?".

The sun is fusion I thought.Most of the energy is not required at all and the trend is towards lower usage machines.

You also ignored the fact most star systems are gas.Only a small fraction is solid matter.You ignored the poster above who raised this point.This is why you would need a 1000 star systems and you would need matter/energy conversion to move it.

I hope you are a happy bunny now.

 

[Neopeius]

I did not ignore you at all.You never understood what I said.To transport construction material requires energy.You ignored that.

"And why would you assume that their energy needs would be met by nuclear fusion?".

The sun is fusion I thought.Most of the energy is not required at all and the trend is towards lower usage machines.

You also ignored the fact most star systems are gas.Only a small fraction is solid matter.You ignored the poster above who raised this point.This is why you would need a 1000 star systems and you would need matter/energy conversion to move it.

This is incorrect.

Mass is mass. Sure, it would take energy to convert that mass into something denser, but you wouldn't need more mass. One Jupiter has enough mass to make 5 Dyson Spheres to your specifications.

As for where one gets the energy to do mass conversions, I haven't the foggiest.

 

[FordSVT]

I did not ignore you at all.You never understood what I said.To transport construction material requires energy.You ignored that.

"And why would you assume that their energy needs would be met by nuclear fusion?".

The sun is fusion I thought.Most of the energy is not required at all and the trend is towards lower usage machines.

You also ignored the fact most star systems are gas.Only a small fraction is solid matter.You ignored the poster above who raised this point.This is why you would need a 1000 star systems and you would need matter/energy conversion to move it.

I hope you are a happy bunny now.

Your name is certainly apt "no knows".

 

[hyzmarca]

The problem is that we want to keep the shell from crashing into the sun. The most efficient way to do this is with radiation pressure. This requires a solar sail with a mass/area ratio of 0.78 grams per square meter, which is absurdly light. The use of absurdly light solar sails pretty much negates most of the mass considerations.

We also want to avoid having the shell tear itself apart, which is pretty much guaranteed if the thing is solid. Which means that it can't be solid. Instead, it must be made up of a network of interconnected but free-floating modules. Since each module can move independently and supports only it's own mass, we don't have the absurd stresses that a full solid shell would be subject too.
Since the modules are free-floating, the thing can't spin. They'd ram into each-other. That's alright, though. You also can't walk on it's interior surface because it's so flimsy.
Instead, habitats are built on the outside of the solar sails, with each statite having it's own habitat. There are two ways to generate gravity in this case, have the statites placed close enough to the sun that it's gravitational attraction is equal to 1g, or simply have the habitats spin. Having the habitats spin is, by far, the easier feat.

The geat thing about using statites is that you don't have to build the entire shell at once. You don't even have to build the entire shell at all, as that would be counter-productive. Instead, you build statite habitats and power collectors one at a time, as needed. You launch them and place them outside the plane of orbit of the inhabitable planets, so that there are no resulting eclipses, Eventually, the result is two half-shells with a fairly large gap at the orbital plane.

 

[TerriO]

I did not ignore you at all.You never understood what I said.To transport construction material requires energy.You ignored that.

"And why would you assume that their energy needs would be met by nuclear fusion?".

The sun is fusion I thought.Most of the energy is not required at all and the trend is towards lower usage machines.

You also ignored the fact most star systems are gas.Only a small fraction is solid matter.You ignored the poster above who raised this point.This is why you would need a 1000 star systems and you would need matter/energy conversion to move it.

I hope you are a happy bunny now.

Your name is certainly apt "no knows".

Ford, just don't. Please.

I've seen this crop up more than once in the last few days. Let's step away from calling other posters variations on "ignorant", shall we? We're all ignorant of some subjects, and well-versed in others. It would do everyone some good to remember that.

 

[PurpleBuddha]

It would be a huge act of genocidal vandalism and destruction of the surrounding star systems.Also any civilization trying it would have died out already as failure to expand is related to stagnation and a Dyson sphere would be the ultimate in navel gazing.

Possibly, but why would you assume that if a civilization were able to develop such a thing, that it would lead to stagnation? Perhaps it would free them to continue to expand themselves in other directions.

And further, we have yet to significantly expand from our own planet for how many hundreds of thousands of years? It doesn't seem we have died off yet.

 

[Ariadne]

Mass is mass. Sure, it would take energy to convert that mass into something denser, but you wouldn't need more mass. One Jupiter has enough mass to make 5 Dyson Spheres to your specifications.

As for where one gets the energy to do mass conversions, I haven't the foggiest.

Actually, converting hydrogen to a heavier element? That's fusion, theoretically a source of energy. (Converting anything to iron generates energy.)

 

[Neopeius]

Mass is mass. Sure, it would take energy to convert that mass into something denser, but you wouldn't need more mass. One Jupiter has enough mass to make 5 Dyson Spheres to your specifications.

As for where one gets the energy to do mass conversions, I haven't the foggiest.

Actually, converting hydrogen to a heavier element? That's fusion, theoretically a source of energy. (Converting anything to iron generates energy.)

But where do you get the energy to start the fusion? Aside from teleporting monoliths in the center of your gas giant... hmm...

 

[hyzmarca]

http://en.wikipedia.org/wiki/Inertial_fusion_power_plant
http://en.wikipedia.org/wiki/ITER

 

[noknowes]

The problem is that we want to keep the shell from crashing into the sun. The most efficient way to do this is with radiation pressure. This requires a solar sail with a mass/area ratio of 0.78 grams per square meter, which is absurdly light. The use of absurdly light solar sails pretty much negates most of the mass considerations.

We also want to avoid having the shell tear itself apart, which is pretty much guaranteed if the thing is solid. Which means that it can't be solid. Instead, it must be made up of a network of interconnected but free-floating modules. Since each module can move independently and supports only it's own mass, we don't have the absurd stresses that a full solid shell would be subject too.
Since the modules are free-floating, the thing can't spin. They'd ram into each-other. That's alright, though. You also can't walk on it's interior surface because it's so flimsy.
Instead, habitats are built on the outside of the solar sails, with each statite having it's own habitat. There are two ways to generate gravity in this case, have the statites placed close enough to the sun that it's gravitational attraction is equal to 1g, or simply have the habitats spin. Having the habitats spin is, by far, the easier feat.

The geat thing about using statites is that you don't have to build the entire shell at once. You don't even have to build the entire shell at all, as that would be counter-productive. Instead, you build statite habitats and power collectors one at a time, as needed. You launch them and place them outside the plane of orbit of the inhabitable planets, so that there are no resulting eclipses, Eventually, the result is two half-shells with a fairly large gap at the orbital plane.

But then it is not a Dyson sphere is it,and by definition outside the scope of this discussion.

The mass quoted for the Dyson shell seems to be incorrect.

4 pi r *2 = area times 1000 kg /m3 density of water,etc times depth of 1 metre .

The previous poster thought the Dyson sphere would magically assemble itself without any expenditure of energy.How much enegy would be required to transport a jupiter per light year,to crush it,to reassemble it?

 

[Ariadne]

But then it is not a Dyson sphere is it,and by definition outside the scope of this discussion.

I thought you were disagreeing with the whole family of concepts, not just a Dyson shell in particular.

The mass quoted for the Dyson shell seems to be incorrect.

4 pi r *2 = area times 1000 kg /m3 density of water,etc times depth of 1 metre .

That gives you about 3 x 10^26 kg, even rounding up at every step, which is still significantly less than the mass of Jupiter. (If you want to use aluminum, you have to multiply it by about three, but it still fits).

And we'll lose some of the mass to energy, but there are still Saturn and Neptune, at over 10^26 kg each.

The previous poster thought the Dyson sphere would magically assemble itself without any expenditure of energy.How much enegy would be required to transport a jupiter per light year,to crush it,to reassemble it?

By that point we'll have fusion and it'll take care of itself.

 

[hyzmarca]

But then it is not a Dyson sphere is it,and by definition outside the scope of this discussion.

It is a Dyson sphere, for more true to Dyson's original concept than the solid shell of fiction.

Dyson's original concept was a swarm of orbiting power collectors and habitats, dense enough to capture the vast majority of the star's output. This is materially feasible, but has the disadvantage of risking catastrophic crashes because of how close the orbits will be to each other, and how precisely times they'll have to be. Because of this, there is a limit on how dense the swarm can be.

The shell model was never considered by Dyson, because it's just stupidly impossible. The stresses that such a shell would be under would cause it to collapse almost immediately. You just can't have a hollow body of that size. It is structurally impossible. The fact that it would eventually crash into the sun if not constantly corrected also makes it stupidly infeasible even if materials science was able to come up with something capable of holding together at that size.

The statite model is a compromise between the two, and probably the most feasable. Since statites are stationary relative to the sun and each-other, there is no chance of catastrophic orbital interactions. They can be placed very close together. Since statites are not absurdly huge, they can actually exist without being destroyed by their own mass. Interlocking statites would form a shell just as conplete as a solid shell would, with the advantage that it's easier to maintain, easier to build, and not stupidly impossible.

 

[Shawnster]

almost all of its power output would be captured. From the outside it would look like a 1AU-diameter object glowing in the IR with an effective black-body temperature aound 273K.

If you captured all or most of the power output of the star you would be burned to a cinder inside the Dyson sphere due to heat build up.The whole thing is very poorly thought out by the originator.

The originator being Olaf Stapledon in 1937.

Dyson is credited with being the first to formalize the concept of the Dyson sphere in his 1959 paper "Search for Artificial Stellar Sources of Infra-Red Radiation", published in the journal Science.[1] However, Dyson was inspired by the mention of the concept in the 1937 science fiction novel Star Maker, by Olaf Stapledon, and possibly by the works of J. D. Bernal and Raymond Z. Gallun who seem to have explored similar concepts in their work.[2]

Other interesting fun facts from Wiki:

A spherical shell Dyson sphere in our solar system with a radius of one astronomical unit, so that the interior surface would receive the same amount of sunlight as Earth does per solid angle, would have a surface area of at least 2.72x1017 km2, or around 550 million times the surface area of the Earth. This would intercept the full 4x1026 watts of the Sun's output; other variant designs would intercept less, but the shell variant represents the maximum possible energy captured for our solar system at this point of the Sun's evolution. To put this figure in perspective, it is approximately 3.3x1013 times the power consumption of humanity in 1998 which was 1.2x1013 W.

Such a shell would have no net gravitational interaction with its englobed sun (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.


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. In such cases, some form of illumination would have to be devised, or the sphere made at least partly transparent, as the star's light would otherwise be completely hidden.


Dyson Swarm: The variant closest to Dyson's original conception is the "Dyson swarm". It consists of a large number of independent constructs orbiting in a dense formation around the star. This approach to the construction of a Dyson sphere has several advantages: the components making it up could range widely in individual size and design, and such a sphere could be constructed incrementally over a long period of time.

Dyson Shell: The variant of the Dyson sphere most often depicted in fiction is the "Dyson shell": a uniform solid shell of matter around the star (see diagram at top of page).[6] Unlike the Dyson swarm, such a structure would completely alter the emissions of the central star, and would intercept 100% of the star's energy output. Such a structure would also provide an immense surface which many envision being used for habitation, if the surface could be made habitable.

Dyson Bubble: A third type of Dyson sphere is the "Dyson bubble". It would be similar to a Dyson swarm, composed of many independent constructs (usually solar power satellites and space habitats) and likewise could be constructed incrementally.

Dyson Net: A web of cables strung about the star which could have power or heat collection units strung between the cables. The Dyson net reduces to a special case of Dyson shell or bubble, however, depending on how the cables are supported against the sun's gravity.

Niven Ring: Larry Niven described it as "an intermediate step between Dyson Spheres and planets". The ringworld could perhaps be described as a slice of a Dyson Sphere (taken through its equator), spun for artificial gravity, and used mainly for habitation as opposed to energy collection. Like the Dyson Shell, the Niven ring is inherently unstable without active measures keeping it in position with regards to its central star.

Source: http://en.wikipedia.org/wiki/Dyson_sphere