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← Can you solve the multiverse rescue mission riddle? - Dan Finkel

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Showing Revision 4 created 08/26/2019 by lauren mcalpine .

  1. It was a normal Tuesday
    at the superconductor,
  2. until a bug in the system created
    a small situation.
  3. Now your team is trapped in eleven
    separate pocket dimensions.
  4. Luckily for you, there’s a half-finished
    experimental teleportation robot
  5. that may be able to get you all home,
  6. if you can figure out how to work through
    the quirks of its design.
  7. Over interdimensional radio,

  8. your engineers explain
  9. that the robot can teleport into the
    alternate universes you’re trapped in,
  10. but it’ll do so completely at random.
  11. The robot has two levers
    and one big button.
  12. When it appears,
  13. you just switch the position of one
    of the levers from A to B or vice versa,
  14. and then the robot will note your
    dimensional position
  15. and teleport to another of the eleven
    dimensions at random.
  16. If it shows up again, you’ll have to pull
    a lever before it’ll teleport away.
  17. When anyone presses the button,
  18. the robot will bring everyone who pulled
    a lever back home.
  19. Anyone who didn’t will be lost
    in the multi-verse forever.
  20. The challenge is to make sure everyone
    has pulled a lever

  21. before anyone hits the button.
  22. While you can talk to each other now
    over the interdimensional radio
  23. and agree on a plan,
  24. the robot’s teleportation technology
  25. will interfere with all attempts
    at communication once it arrives.
  26. You won’t be able to attach messages
    to the robot
  27. or scratch notes into its superstrong
    alloy body.
  28. Your only way to communicate information
  29. is to change the position of exactly
    one lever or hit the button.
  30. What plan will make sure
    everyone gets home?

  31. Pause the video now if you want to
    figure it out for yourself.

  32. Answer in 3

  33. Answer in 2

  34. Answer in 1

  35. It would be nice if you could set
    different combinations of the levers

  36. to indicate who’s already
    been visited by the robot.
  37. But it has only two levers.
  38. That gives four combinations—
  39. far too few to communicate
    about 11 people,
  40. especially when you’re forced to flip
    one to send the robot onward.
  41. There must be another way.
  42. The critical insight is that not
    everyone has to know

  43. when every pocket dimension
    has been visited.
  44. If one person accepts responsibility
    ahead of time for hitting the button,
  45. then only they need to know who the robot
    has visited.
  46. In fact, they don’t even need to know
    exactly who’s been visited…
  47. just how many people have been.
  48. You volunteer to be the person in charge
    of pressing the button

  49. when the moment is right,
  50. and give the following directions
    to everyone else.
  51. Your plan is simple:
  52. you’ll use the left lever to count visits,
  53. and the right lever will have no meaning,
  54. so there’s no harm in
    moving it up or down.
  55. Each of the others will pull the left
  56. from position A to position
    B exactly once.
  57. If the robot appears with the left lever
    already pulled down,
  58. or if an individual has previously pulled
    the left lever down
  59. at any point in the past,
  60. then they should move the right lever.
  61. You, meanwhile, will be the only one who
    ever resets the left lever from position B
  62. to position A.
  63. This gives you a way to count how many
    people have been visited by the robot.
  64. Everyone needs to pull the left lever
    down exactly once,
  65. and you’re the only one
    to pull it back up.
  66. So you know that the tenth time
    the robot visits you
  67. with its left lever in the down position,
  68. it must have visited
    all ten of the others.
  69. And that means you’re safe to press the
    button and teleport everyone home.
  70. It may take a while–
  71. most likely the robot will need to
    teleport around 355 times;
  72. but better that than leave anyone behind.
  73. Your teammates phase back into your home
    dimension one at a time.
  74. The mission proves a great success.
  75. Well...mostly.