jdreyer wrote on Jan 22, 2021, 14:11:
Yeah, I don't see advanced civilizations building entire spheres around stars. Sun-orbiting rings, maybe. Even a ring 1000 miles across orbiting the sun (thus 93 million miles long) would have the ability to support dozens of trillions of humans.

Wouldn't have to be that big, you don't have to go full "Ringworld" -- it would be much more practical to do something like what you see in the movie "Elysium" -- just scale it up as necessary. (the scaled up version is what you "see" in the Culture novels)

Kxmode wrote on Jan 22, 2021, 02:40:

Slick wrote on Jan 21, 2021, 15:50:

Kxmode wrote on Jan 21, 2021, 13:11:
A Dyson Sphere wraps itself around a star, so all the structures and people would be on the inside wall to benefit from the star's heat and energy.

I imagine it would be pretty inhospitable to humans on the inside, and the only machinery would be whatever equivalent of super solar cells we'd come up with to capture all that energy. I'd imagine that the outer side of the sphere would be home to all the more sensitive electronics (comparably) to regulate the flow of energy coming from the underside. Most importantly would be the battery system that would have to be devised. Being able to capture all the energy from a star continuously is great, but what do you do with it? It's like Lucy at the chocolate factory.

A Dyson Sphere is a massive enclosure for a reason. It has to be large enough so that its surface is at a reasonable distance to provide beneficial energy. The most practical thing for dissipating harmful radiation like gamma and infrared would be a glass-like surface shield that envelops the entire inner surface. The Dyson Sphere in the Star Trek: Next Generation episode "Relics" was a 200,000,000 km circumference. For the star's size, that was likely the right diameter.

Yeah, where a Dyson sphere makes the most sense would be around a low energy star like a brown dwarf. The energy output is low and stable enough to make containing it practical, and also allows you to build the sphere near enough to the star that it wouldn't require inordinate amounts of matter. Brown dwarfs also emit lower levels of radiation. I don't know that a glass shield is required, between ozone and some kind of EM field, that should be sufficient protection.

VaranDragon wrote on Jan 22, 2021, 02:27:
Dyson spheres are nice thought experiments, but they are not really practical even if you could theoretically build them. A civilization that has the technical knowhow to build a sphere should already have access to cheap and affordable energy sources. In any case it's safer and makes more sense to spread and colonize across the galaxy (even at sub-light speeds) since a single catastrophic event such as a wandering black hole, or a really bad solar flare wouldn't be able to kill off your entire civilization.

Yeah, I don't see advanced civilizations building entire spheres around stars. Sun-orbiting rings, maybe. Even a ring 1000 miles across orbiting the sun (thus 93 million miles long) would have the ability to support dozens of trillions of humans.

In the near term (over the next several thousand years), just building a habitable ring that orbits the Earth will be a major accomplishment.

jdreyer wrote on Jan 21, 2021, 14:03:

Kxmode wrote on Jan 21, 2021, 13:11:
A Dyson Sphere wraps itself around a star, so all the structures and people would be on the inside wall to benefit from the star's heat and energy.

True. But that sphere around the star is itself within a giant vacuum cleaner. Betcha didn't know that, didja? Didja??

I did not. You, sir, are an avalanche of useful information.

VaranDragon wrote on Jan 22, 2021, 02:27:
Dyson spheres are nice thought experiments, but they are not really practical even if you could theoretically build them. A civilization that has the technical knowhow to build a sphere should already have access to cheap and affordable energy sources. In any case it's safer and makes more sense to spread and colonize across the galaxy (even at sub-light speeds) since a single catastrophic event such as a wandering black hole, or a really bad solar flare wouldn't be able to kill off your entire civilization.

Larry Niven's Ringworld is another star-wrapper world. As far as I know, it is the largest "spaceship," clocking in at 300,000,000 km!

RedEye9 wrote on Jan 22, 2021, 02:48:

VaranDragon wrote on Jan 22, 2021, 02:27:
Dyson spheres are nice thought experiments, but they are not really practical even if you could theoretically build them. .

The human race will never build something similar to a dyson sphere but for a video game backdrop...

I'm sure someone in the past thought we'd never go to space too. That's smooth brain thinking.

VaranDragon wrote on Jan 22, 2021, 02:27:
Dyson spheres are nice thought experiments, but they are not really practical even if you could theoretically build them. .

The human race will never build something similar to a dyson sphere but for a video game backdrop...

Slick wrote on Jan 21, 2021, 15:50:

Kxmode wrote on Jan 21, 2021, 13:11:
A Dyson Sphere wraps itself around a star, so all the structures and people would be on the inside wall to benefit from the star's heat and energy.

I imagine it would be pretty inhospitable to humans on the inside, and the only machinery would be whatever equivalent of super solar cells we'd come up with to capture all that energy. I'd imagine that the outer side of the sphere would be home to all the more sensitive electronics (comparably) to regulate the flow of energy coming from the underside. Most importantly would be the battery system that would have to be devised. Being able to capture all the energy from a star continuously is great, but what do you do with it? It's like Lucy at the chocolate factory.

A Dyson Sphere is a massive enclosure for a reason. It has to be large enough so that its surface is at a reasonable distance to provide beneficial energy. The most practical thing for dissipating harmful radiation like gamma and infrared would be a glass-like surface shield that envelops the entire inner surface. The Dyson Sphere in the Star Trek: Next Generation episode "Relics" was a 200,000,000 km circumference. For the star's size, that was likely the right diameter.

Dyson spheres are nice thought experiments, but they are not really practical even if you could theoretically build them. A civilization that has the technical knowhow to build a sphere should already have access to cheap and affordable energy sources. In any case it's safer and makes more sense to spread and colonize across the galaxy (even at sub-light speeds) since a single catastrophic event such as a wandering black hole, or a really bad solar flare wouldn't be able to kill off your entire civilization.

Mr. Tact wrote on Jan 21, 2021, 15:37:
Yes, in a Dyson Sphere all the inhabited areas would be inside against inner surface. Although thinking about it, I don't know if Dyson addressed how gravity would be accomplished. Rotation wouldn't work for the entire area of the sphere even if the material could handle the stress of rotation. You'd have to have some kind of artificially generated gravity. I've always thought the "Obitials" of the Culture universe made a lot more sense.

I envision engineers creating gravity generators several hundred meters wide and dozens of meters tall that use large concentric spinners to produce artificial gravity. A team of specialist maintains each generator to ensure optimal performance. By placing them strategically on the outside surface, they would provide enough gravity for a given area on the inside. The generators would need to overlap their coverage to smooth out pockets of lesser or missing gravity, something I call a "Venn overlap." Unique engineered bridges and vehicles could address these small pockets of heavier gravity. People living on the Dyson Sphere's surface would know to use the cars to cross areas as it could cause health problems to be subjected to sudden heavier gravity shifts. From the outside, the generators would cover the entire sphere. So instead of a smooth surface, it would look bumpy.

Maintaining the generators is mission-critical. If too many stopped, the remaining could act as an engine by propelling the sphere and collide a section of the inner surface with the star, resulting in a potential supernova that would kill everything and likely tear the sphere to pieces. Think: a large grenade in space.

This comment was edited on Jan 22, 2021, 02:28.

yuastnav wrote on Jan 22, 2021, 01:36:
I don't think you would live on the inside of a Dyson sphere because
a) it's inhospitable and
b) that would actually hamper the ability to maximise the energy that you could capture from the sun.

It's not inhospitable though, part of the point of a dyson sphere is that you could live on the inner surface if the sphere is big enough. Indeed that would be the ONLY hospitable place in the solar system once the sphere is created anyways, since you'd be stealing most of the energy from nearby planets.

You probably don't want to capture ALL of the energy anyways all of them time either, so they would have ways of shedding excess energy.

I don't think you would live on the inside of a Dyson sphere because
a) it's inhospitable and
b) that would actually hamper the ability to maximise the energy that you could capture from the sun.

jdreyer wrote on Jan 21, 2021, 19:16:

RedEye9 wrote on Jan 21, 2021, 15:58:
If you have a free and endless stream of energy why would you need batteries to store it.
It's not like it will turn off at night (traditional solar) or stop producing power when the wind stops blowing.

Dude. You still need batteries at night. Duh. And I thought U were smart.

Night is irrelevant. They have essentially unlimited power. They could transport excess power to the other side of the planet, or they could light up the insides of the Dyson sphere, having day on both sides of any planet if they want to. And if they're advanced to make a Dyson sphere, I think it's safe to assume they have much better energy storage solutions as well.

Mr. Tact wrote on Jan 21, 2021, 15:37:
Yes, in a Dyson Sphere all the inhabited areas would be inside against inner surface. Although thinking about it, I don't know if Dyson addressed how gravity would be accomplished. Rotation wouldn't work for the entire area of the sphere even if the material could handle the stress of rotation. You'd have to have some kind of artificially generated gravity. I've always thought the "Obitials" of the Culture universe made a lot more sense.

You'd have to start building at the equator, and you'd have to orbit the structure around the sun. Not doing so would result in the structure falling into the sun due to gravity. So you'd have to worry about a lack of gravity up near the poles. If you manage to close the sphere, maybe that area can be used for energy collection.

RedEye9 wrote on Jan 21, 2021, 15:58:
If you have a free and endless stream of energy why would you need batteries to store it.
It's not like it will turn off at night (traditional solar) or stop producing power when the wind stops blowing.

Dude. You still need batteries at night. Duh. And I thought U were smart.

Kxmode wrote on Jan 21, 2021, 13:11:
A Dyson Sphere wraps itself around a star, so all the structures and people would be on the inside wall to benefit from the star's heat and energy.

And where would all the structures and people be for the hundreds or thousands of years it would take to build the Sphere? Oh yeah, on nearby planets.... Which is what the video's thumbnail depicts. The star is the orange glowy thing at the top, you can see the construction in progress around it. Though the "story" of the game dictates they only need the energy, for a massive megacomputer they're building on the homeworld.

Slick wrote on Jan 21, 2021, 16:20:
Sorry, my math was off...

Solar thermal systems covering 10 percent of the world’s deserts — about 1.5 percent of the planet’s total land area — could generate about 15 terawatts of energy, given a total efficiency of 2 percent. This amount is roughly equal to the projected growth in worldwide energy demand over the next half-century.

So yeah, at 2% efficiency, we'd only need 1.5% of the earth to capture the suns rays to fuel our civilization for the next 50 years of expansion, not 10% as I previously said. And sphere tech would be a lot more efficient than 2%... and probably more like trillions of times more energy than this civilization-fueling project described on our own planet.

I have no idea how good your math is but I can believe sufficient capture of solar energy striking our planet could theoretically produce enough energy to power the entire world. The modern power infrastructure has always been limited by loss during transmission and a lack of sufficiently efficient storage. Dyson's premise, " ...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." So, that directly addresses the need question...

Look at this way, if you had the ability to build a planet around a star I'm sure energy gathering would be the least of your concerns. And wouldn't the mass of the material used to create said sphere provide said gravity? How thick would the thing have to be? I suppose it all depends on what it was made of. Some ultra-light, ultra-strong hyper-alloy. And unless you could import or create a metric fuck ton of soil it would be a pretty barren world. So I don't really see the point of a Dyson Sphere.

Sorry, my math was off...

Solar thermal systems covering 10 percent of the world’s deserts — about 1.5 percent of the planet’s total land area — could generate about 15 terawatts of energy, given a total efficiency of 2 percent. This amount is roughly equal to the projected growth in worldwide energy demand over the next half-century.

So yeah, at 2% efficiency, we'd only need 1.5% of the earth to capture the suns rays to fuel our civilization for the next 50 years of expansion, not 10% as I previously said. And sphere tech would be a lot more efficient than 2%... and probably more like trillions of times more energy than this civilization-fueling project described on our own planet.

RedEye9 wrote on Jan 21, 2021, 15:58:

Slick wrote on Jan 21, 2021, 15:50:
Most importantly would be the battery system that would have to be devised. Being able to capture all the energy from a star continuously is great, but what do you do with it?

If you have a free and endless stream of energy why would you need batteries to store it.
It's not like it will turn off at night (traditional solar) or stop producing power when the wind stops blowing.

The purpose of a sphere is to harness an amount of energy logarithmically more massive than any amount a civilization would require for advanced sustenance. I mean think about how much of the sun's rays land on earth (well half of earth) at any given time? we're a fraction of a fraction of a degree billions of miles from the star, and it still provides us more energy than we'd ever need if we could capture 10% of it even.

A Dyson sphere is for doing shit that only a tier 4 civilization could do, like open Einstein-Rosen bridges and stuff like that, maybe build a warp engine. Thing that require energy on scales that we can't really conceive. And we'd need a way to contain and transport that energy, maybe a space laser network emanating to various planets in that system or beyond? Either way, we're talking billions of times more energy than we'd ever need, so there's a logistics problem with how to use it or store it.