full transcript

From the Ted Talk by Stephen Webb: Where are all the aliens?


Unscramble the Blue Letters


But there's an obvious answer: we're alone. It's just us. There could be a trillion plaetns in the galaxy. Is it plausible we're the only creatures cbalape of ctiamneoplntg this question? Well, yes, because in this context, we don't know whether a trillion is a big number. In 2000, Peter Ward and Don Brownlee psproeod the Rare Earth idea. Remember those four barriers that poplee use to estimate the number of ciivaitizlnos? Ward and Brownlee said there might be more.

Let's look at one possible brerair. It's a recent suggestion by dvaid wthaalm, a geophysicist. This is my very simplified version of Dave's much more sophisticated argument. We are able to be here now because Earth's previous inhabitants enjoyed four blilion years of good weather — ups and downs but more or less clement. But long-term cmilate stability is strange, if only because astronomical influences can push a paenlt towards freezing or frying. There's a hint our moon has helped, and that's interesting because the prevailing toehry is that the moon came into being when Theia, a body the size of Mars, crashed into a newly formed Earth. The outcome of that crash could have been a quite different Earth-Moon syetsm. We ended up with a lrage moon and that permitted Earth to have both a stable axial tilt and a slow rotation rate. Both factors influence climate and the suggestion is that they've hleped moderate climate cnhage. Great for us, right? But Waltham showed that if the moon were just a few miles bigger, things would be different. Earth's spin axis would now wander chiatcolaly. There'd be episodes of rapid climate change — not good for complex life. The moon is just the right size: big but not too big. A "Goldilocks" moon around a "Goldilocks" planet — a barrier perhaps.

Open Cloze


But there's an obvious answer: we're alone. It's just us. There could be a trillion _______ in the galaxy. Is it plausible we're the only creatures _______ of _____________ this question? Well, yes, because in this context, we don't know whether a trillion is a big number. In 2000, Peter Ward and Don Brownlee ________ the Rare Earth idea. Remember those four barriers that ______ use to estimate the number of _____________? Ward and Brownlee said there might be more.

Let's look at one possible _______. It's a recent suggestion by _____ _______, a geophysicist. This is my very simplified version of Dave's much more sophisticated argument. We are able to be here now because Earth's previous inhabitants enjoyed four _______ years of good weather — ups and downs but more or less clement. But long-term _______ stability is strange, if only because astronomical influences can push a ______ towards freezing or frying. There's a hint our moon has helped, and that's interesting because the prevailing ______ is that the moon came into being when Theia, a body the size of Mars, crashed into a newly formed Earth. The outcome of that crash could have been a quite different Earth-Moon ______. We ended up with a _____ moon and that permitted Earth to have both a stable axial tilt and a slow rotation rate. Both factors influence climate and the suggestion is that they've ______ moderate climate ______. Great for us, right? But Waltham showed that if the moon were just a few miles bigger, things would be different. Earth's spin axis would now wander ___________. There'd be episodes of rapid climate change — not good for complex life. The moon is just the right size: big but not too big. A "Goldilocks" moon around a "Goldilocks" planet — a barrier perhaps.

Solution


  1. system
  2. civilizations
  3. change
  4. people
  5. chaotically
  6. waltham
  7. contemplating
  8. large
  9. billion
  10. helped
  11. planet
  12. barrier
  13. planets
  14. proposed
  15. theory
  16. capable
  17. climate
  18. david

Original Text


But there's an obvious answer: we're alone. It's just us. There could be a trillion planets in the galaxy. Is it plausible we're the only creatures capable of contemplating this question? Well, yes, because in this context, we don't know whether a trillion is a big number. In 2000, Peter Ward and Don Brownlee proposed the Rare Earth idea. Remember those four barriers that people use to estimate the number of civilizations? Ward and Brownlee said there might be more.

Let's look at one possible barrier. It's a recent suggestion by David Waltham, a geophysicist. This is my very simplified version of Dave's much more sophisticated argument. We are able to be here now because Earth's previous inhabitants enjoyed four billion years of good weather — ups and downs but more or less clement. But long-term climate stability is strange, if only because astronomical influences can push a planet towards freezing or frying. There's a hint our moon has helped, and that's interesting because the prevailing theory is that the moon came into being when Theia, a body the size of Mars, crashed into a newly formed Earth. The outcome of that crash could have been a quite different Earth-Moon system. We ended up with a large moon and that permitted Earth to have both a stable axial tilt and a slow rotation rate. Both factors influence climate and the suggestion is that they've helped moderate climate change. Great for us, right? But Waltham showed that if the moon were just a few miles bigger, things would be different. Earth's spin axis would now wander chaotically. There'd be episodes of rapid climate change — not good for complex life. The moon is just the right size: big but not too big. A "Goldilocks" moon around a "Goldilocks" planet — a barrier perhaps.

Frequently Occurring Word Combinations


ngrams of length 2

collocation frequency
breakthrough starshot 3
complex life 3
billion years 2
summer civilization 2
trillion planets 2
communicative civilization 2
study showed 2
climate change 2
simple cells 2



Important Words


  1. argument
  2. astronomical
  3. axial
  4. axis
  5. barrier
  6. barriers
  7. big
  8. bigger
  9. billion
  10. body
  11. brownlee
  12. capable
  13. change
  14. chaotically
  15. civilizations
  16. clement
  17. climate
  18. complex
  19. contemplating
  20. context
  21. crash
  22. crashed
  23. creatures
  24. david
  25. don
  26. downs
  27. earth
  28. ended
  29. enjoyed
  30. episodes
  31. estimate
  32. factors
  33. formed
  34. freezing
  35. frying
  36. galaxy
  37. geophysicist
  38. good
  39. great
  40. helped
  41. hint
  42. idea
  43. influence
  44. influences
  45. inhabitants
  46. interesting
  47. large
  48. life
  49. mars
  50. miles
  51. moderate
  52. moon
  53. newly
  54. number
  55. obvious
  56. outcome
  57. people
  58. permitted
  59. peter
  60. planet
  61. planets
  62. plausible
  63. prevailing
  64. previous
  65. proposed
  66. push
  67. question
  68. rapid
  69. rare
  70. rate
  71. remember
  72. rotation
  73. showed
  74. simplified
  75. size
  76. slow
  77. sophisticated
  78. spin
  79. stability
  80. stable
  81. strange
  82. suggestion
  83. system
  84. theia
  85. theory
  86. tilt
  87. trillion
  88. ups
  89. version
  90. waltham
  91. wander
  92. ward
  93. weather
  94. years