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Thread: Dyson Spheres - Thoughts and Questions

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    Former Staff Senior Contributor Ironduke's Avatar
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    Dyson Spheres - Thoughts, Pros & Cons

    A brief primer from Wikipedia:
    https://en.wikipedia.org/wiki/Dyson_sphere

    A Dyson sphere is a hypothetical megastructure that completely encompasses a star and captures a large percentage of its power output. The concept is a thought experiment that attempts to explain how a spacefaring civilization would meet its energy requirements once those requirements exceed what can be generated from the home planet's resources alone. Only a fraction of a star's energy emissions reach the surface of any orbiting planet. Building structures encircling a star would enable a civilization to harvest far more energy.

    The first contemporary description of the structure was by Olaf Stapledon in his science fiction novel Star Maker (1937), in which he described "every solar system... surrounded by a gauze of light traps, which focused the escaping solar energy for intelligent use." The concept was later popularized by Freeman Dyson in his 1960 paper "Search for Artificial Stellar Sources of Infrared Radiation". Dyson speculated that such structures would be the logical consequence of the escalating energy needs of a technological civilization and would be a necessity for its long-term survival. He proposed that searching for such structures could lead to the detection of advanced, intelligent extraterrestrial life. Different types of Dyson spheres and their energy-harvesting ability would correspond to levels of technological advancement on the Kardashev scale.
    The person they're named for:
    https://en.wikipedia.org/wiki/Freeman_Dyson



    Fourteen questions/thoughts I had regarding this speculative technology, and some pros and cons.

    1. How practical are they?
    2. How soon could we possibly build them?
    3. What materials would be needed to build them?
    4. Is there enough matter in the solar system to build one?
    5. Are they a good idea?
    6. Stealth Dyson Spheres: what detection methods could a Dyson Sphere make itself invisible to, and what counter-measures could be used to penetrate the stealth?
    7. Freedom vs Confinement...
    8. Is it better to have free access to all the stars?, or:
    9. Would a Dyson Sphere retard the development and the ability for solar-wide civilization to adapt to unexpected challenges?
    10. Would a civilization go stir-crazy confined within a Dyson Sphere?
    11. Might confinement within a potentially undetectable Dyson Sphere one of the best defenses against other intelligent species, which may very well be hostile?, or:
    12. Would such confinement within a solar system be extremely risky - would a civilization, even within a Stealth Dyson Sphere, neglect interstellar travel and make themselves a sitting duck for an attack?
    13. A take on more money, more problems... more area to build on, more problems?
    14. Relativistic Kill Vehicles vs. Dyson Spheres - how would a Dyson Sphere defend itself against the ultimate planet-killing terror weapon?
    Last edited by Ironduke; 16 May 18, at 04:45.
    Appearances can be... deceptive. -Chad Feldheimer

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    Quote Originally Posted by Ironduke View Post
    4. Is there enough matter in the solar system to build one?
    There isn't. The matter of all planets in the solar system formed into a Dyson Ring at the average density of Earth and 1 km thickness would be about 4,000 km wide for scale.

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    Senior Contributor SteveDaPirate's Avatar
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    Main sequence stars fusing hydrogen should supply more power than any civilization could use without cooking whatever planet they inhabit without resorting to building any Dyson mega-structures. For example, large power stations could orbit the sun-earth L1 point and beam power back to earth or orbital structures that require it.

    The only time a Dyson Ring or Sphere would make any sense to me is if it were constructed around a White Dwarf. In that situation you have a star with the mass of the Sun but the size of the earth that is still radiating heat but no longer undergoing fusion. Building a ring or sphere around an earth sized object, even at some distance away is going to require drastically less material than a ring around the Sun and there would be more of a case for it since the power output of a white dwarf is lower than a star like the Sun.
    Last edited by SteveDaPirate; 16 May 18, at 21:36.

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    Resident Curmudgeon Military Professional Gun Grape's Avatar
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    Quote Originally Posted by SteveDaPirate View Post
    Main sequence stars fusing hydrogen should supply more power than any civilization could use without cooking whatever planet they inhabit without resorting to building any Dyson mega-structures. For example, large power stations could orbit the sun-earth L1 point and beam power back to earth or orbital structures that require it.
    Oh hell no. didn't you learn anything playing Sim City in disaster mode?
    Its called Tourist Season. So why can't we shoot them?

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    Senior Contributor DOR's Avatar
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    Ringworld?

    Bear in mind that we don’t have to create an entire sphere. We could just have a patchwork system that captures enough for whatever purpose there might be. Ringworld, for example: https://en.wikipedia.org/wiki/Ringworld

    Larry Niven's Ringworld is about one million miles (1,600,000 km) wide and approximately the diameter of Earth's orbit (which makes it about 600 million miles or 950 million km in circumference), encircling a sun-like star. It rotates to provide artificial gravity 99.2% as strong as Earth's The Ringworld has a habitable, flat inner surface (equivalent in area to approximately three million Earths), a breathable atmosphere and a temperature optimal for humans. Night is provided by an inner ring of shadow squares which are connected to each other by thin, ultra-strong wire.

    Back to the original post:

    Practical? Given another century of improvements in technology similar to what happened in the last century, it might be possible. “Practical” is an entirely different matter. Practical includes things like what else might we do instead, and how would the cost affect our economy.


    When? Just as soon as the technology and financing are available. Say, 100-500 years?

    Materials? Probably things we haven’t even thought of. The kind of stuff you build space elevators out of, as per Arthur C. Clarke (https://en.wikipedia.org/wiki/The_Fountains_of_Paradise). As for material supply, the asteroid belt is an obvious source for whatever minerals might be needed, but a breakthrough in anti-gravity would be nice, too.

    (Side note: we can block heat, cold, air, water, magnetism, light and a bunch of other stuff. Someday maybe we can block gravity.)



    Just because we can do it, should we?
    When was that ever a serious question?
    Trust me?
    I'm an economist!

  6. #6
    Former Staff Senior Contributor Ironduke's Avatar
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    Quote Originally Posted by kato View Post
    There isn't. The matter of all planets in the solar system formed into a Dyson Ring at the average density of Earth and 1 km thickness would be about 4,000 km wide for scale.
    Do you know if there are any estimates for the total mass of the objects in the Kuiper Belt, including asteroids, dwarf planets (of which there may be thousands), and as of yet, possible undiscovered worlds lying as much as a substantial fraction of a light-year beyond the limit of our solar system?

    Proxima Centauri, for example, is approximately 0.125 lights years from the main star in the Alpha Centauri trinary star system. There certainly aren't any stars within that distance of our Sun, perhaps not even so much as a brown dwarf (though this could yet be a possibility, however unlikely). There could thus be orbiting bodies in our solar system/"neighborhood" with a sum total mass that is quite substantial.

    I believe there may yet be a very substantial amount of bodies orbiting anywhere out to 0.5 light-years from the Solar System, of which perhaps we have possibly only detected a fraction of 1% of, thus far.

    We had mapped the surface of Venus with orbiting satellites, before we even knew what the topography of our oceans were. Likewise, while we've been using Kepler to detect the dimming and brightening of stars to arrive at conclusions of the planets orbiting them, their distance from their parent star, and their mass, much as with the example of the mapping of Venus and our oceans, we may be far, far behind in mapping out and detecting all of the total objects in our very own solar system.

    With Kepler, we had an outsider's perspective and a reference point (another star) to use in detecting extrasolar planets. We are thus on the outside looking in when it comes to extrasolar planet detection. We cannot do the same in our own solar system, as we're on the inside looking out, and don't have a convenient reference point to use in detecting such orbiting bodies.

    Obvious exceptions to this are the Moon, Venus, and Mercury, which often lie in front of our orbit and transit in front of us relative to our Sun. Making observations of these three bodies is thus not too different than the methods used in detecting extrasolar planets. Everything else in the Solar System is beyond Earth's orbit, and requires entirely different observational techniques. It may be the case that extrasolar planet detection is far, far easier than detecting Kuiper-and-beyond objects that lie within 0.5 light-years of our own Sun.
    Last edited by Ironduke; 18 May 18, at 21:45.
    Appearances can be... deceptive. -Chad Feldheimer

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    Quote Originally Posted by Ironduke View Post
    Do you know if there are any estimates for the total mass of the objects in the Kuiper Belt, including asteroids, dwarf planets (of which there may be thousands), and as of yet, possible undiscovered worlds lying as much as a substantial fraction of a light-year beyond the limit of our solar system?
    Current models of solar system formation assume that the collective mass of all objects nowadays beyond Neptune was up to 30 times the mass of Earth, including any object pushed further out during planetary migration. That's the required mass if the Kuiper Belt formed in place instead of just being scattered objects from further in and thus never exceeding its current mass. The modern Kuiper Belt including the Scattered Disc is estimated at about 0.1-0.2 Earth masses as most; Pluto is 1% of that. If it had 30 Earth Masses most of that was grinded down and then blown into interstellar space by solar radiation.

    For objects further out, the entire Oort Cloud, our hypothetical garbage yard out to the extent of the Sun's Hill Sphere, i.e. up to 3 light years depending on direction, is estimated at having around 5 times the mass of Earth.

    For scale though: The eight planets together run around 446.6 times as much as Earth, with 92.5% of that in the two gas giants. And the Sun itself dwarfs that at around 250,000 Earth Masses.

    Quote Originally Posted by Ironduke View Post
    With Kepler, we had an outsider's perspective and a reference point (another star) to use in detecting extrasolar planets. We are thus on the outside looking in when it comes to extrasolar planet detection. We cannot do the same in our own solar system, as we're on the inside looking out, and don't have a convenient reference point to use in detecting such orbiting bodies.
    Actually we do the same photometry as Kepler does with other systems with our own system using hundreds of telescopes and satellites. Some more, some less capable. Gaia has traced 17,000 individual objects in the Solar System that way, by them passing in front of other stars by our line of sight - and that's just the "bycatch" while looking at the Milkyway as a whole methodically mapping every single star in it.

    Detection inward of Earth's orbit - looking at the sun - is a pretty complicated topic btw. We know far less about the asteroid population inwards of us than outwards of us for example. Mostly because of that pesky Sun down there.
    Last edited by kato; 18 May 18, at 22:32.

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    Former Staff Senior Contributor Ironduke's Avatar
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    Here I'd thought I had made a perfectly intelligent post about matters concerning these things... in my defense, based on what little I do know.

    kato - you just made me feel like these guys. :-)

    https://www.youtube.com/watch?v=NFTaiWInZ44

    Quote Originally Posted by kato View Post
    For scale though: The eight planets together run around 446.6 times as much as Earth, with 92.5% of that in the two gas giants. And the Sun itself dwarfs that at around 250,000 Earth Masses.
    Do you think it would be possible to build what DOR had mentioned? Perhaps not a million miles wide. Let's say, for the sake of argument, perhaps a ring with a width equivalent to the diameter of the Earth (12,742km), with a circumference of 940 million km, forming a ring that covers the entirety the Earth's 150 million km orbit around the Sun.

    Would there be enough matter in the Solar System to build such a "ringworld"? Or would we come up short using all matter available to us?

    Quote Originally Posted by DOR View Post
    Bear in mind that we don’t have to create an entire sphere. We could just have a patchwork system that captures enough for whatever purpose there might be. Ringworld, for example: https://en.wikipedia.org/wiki/Ringworld


    Larry Niven's Ringworld is about one million miles (1,600,000 km) wide and approximately the diameter of Earth's orbit (which makes it about 600 million miles or 950 million km in circumference), encircling a sun-like star. It rotates to provide artificial gravity 99.2% as strong as Earth's The Ringworld has a habitable, flat inner surface (equivalent in area to approximately three million Earths), a breathable atmosphere and a temperature optimal for humans. Night is provided by an inner ring of shadow squares which are connected to each other by thin, ultra-strong wire.
    Appearances can be... deceptive. -Chad Feldheimer

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    "Ringworld" in the dimensions presented would take up about 5 million times the matter in the Solar System.
    For Earth width we could build something rather flimsy at only about 300m thickness.

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