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posted by martyb on Friday June 22 2018, @02:25AM   Printer-friendly
from the star-wars:-where-combatants-toss-stars-at-each-other dept.

How an Advanced Civilization Could Stop Dark Energy From Preventing Their Future Exploration

For the sake of his study, which recently appeared online under the title "Life Versus Dark Energy: How An Advanced Civilization Could Resist the Accelerating Expansion of the Universe", Dr. Dan Hooper considered how civilizations might be able to reverse the process of cosmic expansion. In addition, he suggests ways in which humanity might looks[sic] for signs of such a civilization.

[...] This harvesting, according to Dr. Hooper, would consist of building unconventional Dyson Spheres that would use the energy they collected from stars to propel them towards the center of the species' civilization. High-mass stars are likely to evolve beyond the main sequence before reaching the destination of the central civilization and low-mass stars would not generate enough energy (and therefore acceleration) to avoid falling beyond the horizon.

For these reasons, Dr. Hooper concludes that stars with masses of between 0.2 and 1 Solar Masses will be the most attractive targets for harvesting. In other words, stars that are like our Sun (G-type, or yellow dwarf), orange dwarfs (K-type), and some M-type (red dwarf) stars would all be suitable for a Type III civilization's purposes.

[...] Based on the assumption that such a civilization could travel at 1 – 10% the speed of light, Dr. Hooper estimates that they would be able to harvest stars out to a co-moving radius of approximately 20 to 50 Megaparsecs (about 65.2 million to 163 million light-years). Depending on their age, 1 to 5 billion years, they would be able to harvest stars within a range of 1 to 4 Megaparsecs (3.3 million to 13 million light-years) or up to several tens of Megaparsecs.

In addition to providing a framework for how a sufficiently-advanced civilization could survive cosmic acceleration, Dr. Hooper's paper also provides new possibilities in the search for extra-terrestrial intelligence (SETI). While his study primarily addresses the possibility that such a mega-civilization will emerge in the future (perhaps it will even be our own), he also acknowledges the possibility that one could already exist.

Kardashev scale. One parsec is equivalent to a distance of approximately 3.26156 light years. Corrections made above.


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  • (Score: 2) by Aiwendil on Friday June 22 2018, @07:32AM (7 children)

    by Aiwendil (531) on Friday June 22 2018, @07:32AM (#696622) Journal

    Warfare - I'm kinda curious about how to defend against a dwarf star that is being hurled towards your solar-system at 0.1c, especially when the star is "cloaked" (shrouded by the dyson sphere, you only need to cover the target-side) :)
    (Hey, if the civilisation is old enough for it to consider moving stars then the long game should be par for the course)

    But a bit less tounge in cheek - to save on fuel, yeah it seems kinda silly at this scale but at the same timescales it probably would matter, and since the star is burning all that energy anyways just placing it closer really should cut down on trips to the gas station (star).

    And then we have the possibility of optimizing slingshot maneouvers for more fuel-saving (if you line the dyson spheres up properly you should be able to put up a fairly decent conveyer "belt" between them, even when you start to measure the round trip in whole parsecs)

    Another thing to consider would probably be dying or dead stars, if they have a nearby spare living star they they should have enough energy to be able to chip away at the heavier elements from dead or dying stars.
    (To put this into context - the reason why we have so much iron around is that our solarsystem is a few (3 iirc) generations of stars in the running, also worth pointing out is that our star is too small to be assumed to create non-trivial (at this scale) amounts of the really heavy elements (such as uranium) when it dies; so heavy elements might be in (relative) shortage even for an insanely advanced civilisation unless they mine stars)

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  • (Score: 2) by maxwell demon on Friday June 22 2018, @02:55PM (6 children)

    by maxwell demon (1608) on Friday June 22 2018, @02:55PM (#696764) Journal

    also worth pointing out is that our star is too small to be assumed to create non-trivial (at this scale) amounts of the really heavy elements (such as uranium) when it dies; so heavy elements might be in (relative) shortage even for an insanely advanced civilisation unless they mine stars

    Star mining won't help them with those really heavy elements, as even the biggest stars don't produce those during their life time. It's only the supernova explosion at the end which produces them. And blasts them out into space.

    --
    The Tao of math: The numbers you can count are not the real numbers.
    • (Score: 2) by Immerman on Friday June 22 2018, @05:26PM

      by Immerman (3985) on Friday June 22 2018, @05:26PM (#696850)

      True, but mining an immensely diffused gas spread across millions of cubic parsecs is probably not worth the energy invested, but pretty much everything in space ends up concentrated back into new stars eventually.

    • (Score: 2) by Aiwendil on Friday June 22 2018, @06:18PM

      by Aiwendil (531) on Friday June 22 2018, @06:18PM (#696870) Journal

      Which will make dead stars the best place to gather the uranium, since it basically is a gigantic dust-magnet for a few billion years, and in that time it can catch a lot of uranium. Kinda like a stellar version of a nodule.

      Dying stars will have the advantage of still providing enough energy to actually move the star.

      (I was unclear on that I mainly included the tidbit out our sun for the sake of illustrating the insane power requirements to create the really heavy elements)

    • (Score: 2) by legont on Friday June 22 2018, @09:03PM (3 children)

      by legont (4179) on Friday June 22 2018, @09:03PM (#696964)

      Actually even supernova is not powerful enough to produce the interesting species such as gold and uranium. They think neutron stars collision is the source.

      --
      "Wealth is the relentless enemy of understanding" - John Kenneth Galbraith.
      • (Score: 1) by khallow on Saturday June 23 2018, @02:21AM (2 children)

        by khallow (3766) Subscriber Badge on Saturday June 23 2018, @02:21AM (#697082) Journal

        Actually even supernova is not powerful enough to produce the interesting species such as gold and uranium.

        There's no question that supernova are more than powerful enough. And the process by which they would create such heavy nuclei is known to exist (repeated particle capture by nuclei).

        • (Score: 3, Interesting) by legont on Saturday June 23 2018, @02:12PM (1 child)

          by legont (4179) on Saturday June 23 2018, @02:12PM (#697197)

          There's no question that supernova are more than powerful enough. And the process by which they would create such heavy nuclei is known to exist (repeated particle capture by nuclei).

          http://news.berkeley.edu/2017/10/16/astronomers-strike-cosmic-gold/ [berkeley.edu]

          Initially, astrophysicists thought ordinary supernovae might account for the heavy elements, but there have always been problems with that theory, said co-author Enrico Ramirez-Ruiz, a professor of astronomy and astrophysics at UC Santa Cruz. According to Ramirez-Ruiz, the new observations support the theory that neutron star mergers can account for all the gold in the universe, as well as about half of all the other elements heavier than iron.

          The reality just changed on you, man; probably by liberals :)

          --
          "Wealth is the relentless enemy of understanding" - John Kenneth Galbraith.
          • (Score: 1) by khallow on Sunday June 24 2018, @01:14AM

            by khallow (3766) Subscriber Badge on Sunday June 24 2018, @01:14AM (#697416) Journal
            I think I'll wait for evidence first rather than unfounded speculation.