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← Could we harness the power of a black hole? - Fabio Pacucci

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Showing Revision 3 created 10/16/2020 by lauren mcalpine .

  1. Imagine a distant future when humans
    reach beyond our pale blue dot,
  2. forge cities on planets
    thousands of light-years away,
  3. and maintain a galactic web
    of trade and transport.
  4. What would it take for our civilization
    to make that leap?
  5. There are many things to consider—
    how would we communicate?
  6. What might a galactic government
    look like?
  7. And one of the most fundamental
    of all:
  8. where would we get enough energy
    to power that civilization—
  9. its industry, its terraforming operations,
    and its starships?
  10. An astronomer named Nikolai Kardashev
    proposed a scale

  11. to quantify an evolving civilization’s
    increasing energy needs.
  12. In the first evolutionary stage,
    which we’re currently in,
  13. planet-based fuel sources
    like fossil fuels,
  14. solar panels and nuclear power plants
  15. are probably enough to settle other
    planets inside our own solar system,
  16. but not much beyond that.
  17. For a civilization on the third
    and final stage,
  18. expansion on a galactic scale
    would require about 100 billion times
  19. more energy than the full 385 yotta joules
    our sun releases every second.
  20. Barring a breakthrough in exotic physics,
  21. there’s only one energy source
    that could suffice:
  22. a supermassive black hole.
  23. It’s counterintuitive to think
    of black holes as energy sources,

  24. but that’s exactly what they are,
    thanks to their accretion disks:
  25. circular, flat structures formed
    by matter falling into the event horizon.
  26. Because of conservation
    of angular momentum,

  27. particles there don’t just plummet
    straight into the black hole.
  28. Instead, they slowly spiral.
  29. Due to the intense gravitational field
    of the black hole,
  30. these particles convert their potential
    energy to kinetic energy
  31. as they inch closer to the event horizon.
  32. Particle interactions allow
    for this kinetic energy
  33. to be radiated out into space
  34. at an astonishing matter-to-energy
    efficiency:
  35. 6% for non-rotating black holes,
    and up to 32% for rotating ones.
  36. This drastically outshines
    nuclear fission,
  37. currently the most efficient
    widely available mechanism
  38. to extract energy from mass.
  39. Fission converts just 0.08%
    of a Uranium atom into energy.
  40. The key to harnessing this power
    may lie in a structure

  41. devised by physicist Freeman Dyson,
    known as the Dyson sphere.
  42. In the 1960s, Dyson proposed
    that an advanced planetary civilization
  43. could engineer an artificial sphere
    around their main star,
  44. capturing all of its radiated energy
    to satisfy their needs.
  45. A similar, though vastly
    more complicated design
  46. could theoretically be applied
    to black holes.
  47. In order to produce energy,
    black holes need to be continuously fed—
  48. so we wouldn’t want to fully cover
    it with a sphere.
  49. Even if we did, the plasma jets
    that shoot from the poles
  50. of many supermassive black holes
  51. would blow any structure
    in their way to smithereens.
  52. So instead, we might design
    a sort of Dyson ring,

  53. made of massive,
    remotely controlled collectors.
  54. They’d swarm in an orbit
    around a black hole,
  55. perhaps on the plane
    of its accretion disk, but farther out.
  56. These devices could use
    mirror-like panels
  57. to transmit the collected energy
    to a powerplant,
  58. or a battery for storage.
  59. We’d need to ensure that these collectors
    are built at just the right radius:
  60. too close and they’d melt
    from the radiated energy.
  61. Too far, and they’d only collect
    a tiny fraction of the available energy
  62. and might be disrupted by stars orbiting
    the black hole.
  63. We would likely need several Earths
    worth of highly reflective material
  64. like hematite to construct
    the full system—
  65. plus a few more dismantled planets
    to make a legion of construction robots.
  66. Once built, the Dyson ring
    would be a technological masterpiece,
  67. powering a civilization spread
    across every arm of a galaxy.
  68. This all may seem like wild speculation.

  69. But even now,
    in our current energy crisis,
  70. we’re confronted
    by the limited resources of our planet.
  71. New ways of sustainable energy
    production will always be needed,
  72. especially as humanity works
    towards the survival
  73. and technological progress of our species.
  74. Perhaps there’s already a civilization
    out there
  75. that has conquered
    these astronomical giants.
  76. We may even be able to tell
  77. by seeing the light
    from their black hole periodically dim
  78. as pieces of the Dyson ring pass
    between us and them.
  79. Or maybe these superstructures are fated
    to remain in the realm of theory.
  80. Only time— and our scientific ingenuity—
    will tell.