full transcript

From the Ted Talk by Jill Tarter: Calculating the odds of intelligent alien life

Unscramble the Blue Letters

(miusc) The basic question is, does life exist beyond Earth? Scientists who are called astrobiologists are trying to find that out right now. Most astrobiologists are trying to figure out if there's microbial life on Mars, or in the ocean under the frozen suracfe of Jupiter's moon Europa, or in the liquid hydrocarbon lakes that we've found on Saturn's moon Titan. But one group of astrobiologists wkros on SETI. SETI is the secrah for etexarrarsettril Intelligence, and SETI rerehascers are trying to detect some evidence that intelligent creatures elsewhere have used technology to build a transmitter of some sort. But how likely is it that they will manage to find a signal? There are certainly no guarantees when it comes to SETI, but something called the Drake equation, named after Frank Drake, can help us organize our thinking about what might be required for successful dtceoetin. If you've dealt with eiuqnotas before, then you probably expect that there will be a solution to the equation, a right answer. The Drake eoqtuian, however, is different, because there are so many uknnnwos. It has no right aswner. As we learn more about our universe and our place within it, some of the unknowns get better known, and we can estimate an answer a bit better. But there won't be a definite answer to the Drake equation until SETI seeucdcs or something else proves that Earthlings are the only intelligent species in our portion of the cosmos. In the meantime, it is really useful to consider the unknowns. The Drake equation attempts to ettsimae the nubemr of technological civilizations in the Milky Way Galaxy — we call that N — with whom we could make contact, and it's usually written as: N equals R-star multiplied by f-sub-p multiplied by n-sub-e multiplied by f-sub-l multiplied by f-sub-i multiplied by f-sub-c and lastly, mlpiliuted by caipatl L. All those factors multiplied together help to estimate the number of technological coilnaivtizis that we might be able to detect right now. R-star is the rate at which stars have been born in the Milky Way Galaxy over the last few billion yaers, so it's a number that is stars per year. Our galaxy is 10 billion years old, and early in its history stars formed at a different rate. All of the f-factors are fractions. Each one must be less than or equal to one. F-sub-p is the fraction of stars that have planets. N-sub-e is the average number of hailbatbe planets in any paeatrnly system. F-sub-l is the fraction of planets on which life actually binegs and f-sub-i is the fraction of all those life forms that develop icnelltengie. F-sub-c is the fraction of intelligent life that dveoples a civilization that decides to use some sort of transmitting technology. And finally, L — the longevity foactr. On average, how many years do those transmitters cunniote to operate? Astronomers are now almost able to tell us what the product of the first three terms is. We're now finding exoplanets almost everywhere. The ftraocnis dialneg with life and intelligence and technological civilizations are ones that many, many experts pdoenr, but nobody knows for sure. So far, we only know of one place in the uisvrene where life exists, and that's right here on Earth. In the next couple of decades, as we explore Mars and Europa and Titan, the discovery of any kind of life there will mean that life will be abnuadnt in the Milky Way. Because if life originated twice within this one Solar ssyetm, it means it was easy, and given sialmir cdtinoonis elsewhere, life will happen. So the number two is a very important number here. Scientists, including SETI researchers, often tend to make very crude estimates and acknowledge that there are very large uncertainties in these estimates, in order to make progress. We think we know that R-star and n-sub-e are both numbers that are closer to 10 than, say, to one, and all the f-factors are less than one. Some of them may be much less than one. But of all these unknowns, the biggest unknown is L, so perhaps the most useful version of the Drake equation is simply to say that N is approximately equal to L. The information in this equation is very clear. Unless L is large, N will be slaml. But, you know, you can also turn that around. If SETI succeeds in detecting a signal in the near future, after examining only a small pooitrn of the stars in the mkily Way, then we learn that L, on average, must be lgare. Otherwise, we couldn't have succeeded so elsiay. A piishcsyt named Philip Morrison summarizes by saying that SETI is the archaeology of the future. By this, he meant that because the seepd of light is finite, any signals dtceteed from distant teoieonlcghs will be telling us about their past by the time they reach us. But because L must be large for a successful detection, we also lraen about our future, particularly that we can have a long future. We've developed technologies that can send signals into space and humans to the moon, but we've also developed technologies that can destroy the environment, that can wage war with weapons and biological terrorism. In the future, will our technology help stabilize our planet and our population, leading to a very long lfitimee for us? Or will we destroy our world and its inhabitants after only a brief acpanrpeae on the cosmic stage? I encourage you to consider the unknowns in this equation. Why don't you make your own estimates for these unknowns, and see what you come up with for N? Compare that with the estimates made by Frank Drake, Carl Sagan, other scientists or your neighbors. Remember, there's no right answer. Not yet.

Open Cloze

(_____) The basic question is, does life exist beyond Earth? Scientists who are called astrobiologists are trying to find that out right now. Most astrobiologists are trying to figure out if there's microbial life on Mars, or in the ocean under the frozen _______ of Jupiter's moon Europa, or in the liquid hydrocarbon lakes that we've found on Saturn's moon Titan. But one group of astrobiologists _____ on SETI. SETI is the ______ for ________________ Intelligence, and SETI ___________ are trying to detect some evidence that intelligent creatures elsewhere have used technology to build a transmitter of some sort. But how likely is it that they will manage to find a signal? There are certainly no guarantees when it comes to SETI, but something called the Drake equation, named after Frank Drake, can help us organize our thinking about what might be required for successful _________. If you've dealt with _________ before, then you probably expect that there will be a solution to the equation, a right answer. The Drake ________, however, is different, because there are so many ________. It has no right ______. As we learn more about our universe and our place within it, some of the unknowns get better known, and we can estimate an answer a bit better. But there won't be a definite answer to the Drake equation until SETI ________ or something else proves that Earthlings are the only intelligent species in our portion of the cosmos. In the meantime, it is really useful to consider the unknowns. The Drake equation attempts to ________ the ______ of technological civilizations in the Milky Way Galaxy — we call that N — with whom we could make contact, and it's usually written as: N equals R-star multiplied by f-sub-p multiplied by n-sub-e multiplied by f-sub-l multiplied by f-sub-i multiplied by f-sub-c and lastly, __________ by _______ L. All those factors multiplied together help to estimate the number of technological _____________ that we might be able to detect right now. R-star is the rate at which stars have been born in the Milky Way Galaxy over the last few billion _____, so it's a number that is stars per year. Our galaxy is 10 billion years old, and early in its history stars formed at a different rate. All of the f-factors are fractions. Each one must be less than or equal to one. F-sub-p is the fraction of stars that have planets. N-sub-e is the average number of _________ planets in any _________ system. F-sub-l is the fraction of planets on which life actually ______ and f-sub-i is the fraction of all those life forms that develop ____________. F-sub-c is the fraction of intelligent life that ________ a civilization that decides to use some sort of transmitting technology. And finally, L — the longevity ______. On average, how many years do those transmitters ________ to operate? Astronomers are now almost able to tell us what the product of the first three terms is. We're now finding exoplanets almost everywhere. The _________ _______ with life and intelligence and technological civilizations are ones that many, many experts ______, but nobody knows for sure. So far, we only know of one place in the ________ where life exists, and that's right here on Earth. In the next couple of decades, as we explore Mars and Europa and Titan, the discovery of any kind of life there will mean that life will be ________ in the Milky Way. Because if life originated twice within this one Solar ______, it means it was easy, and given _______ __________ elsewhere, life will happen. So the number two is a very important number here. Scientists, including SETI researchers, often tend to make very crude estimates and acknowledge that there are very large uncertainties in these estimates, in order to make progress. We think we know that R-star and n-sub-e are both numbers that are closer to 10 than, say, to one, and all the f-factors are less than one. Some of them may be much less than one. But of all these unknowns, the biggest unknown is L, so perhaps the most useful version of the Drake equation is simply to say that N is approximately equal to L. The information in this equation is very clear. Unless L is large, N will be _____. But, you know, you can also turn that around. If SETI succeeds in detecting a signal in the near future, after examining only a small _______ of the stars in the _____ Way, then we learn that L, on average, must be _____. Otherwise, we couldn't have succeeded so ______. A _________ named Philip Morrison summarizes by saying that SETI is the archaeology of the future. By this, he meant that because the _____ of light is finite, any signals ________ from distant ____________ will be telling us about their past by the time they reach us. But because L must be large for a successful detection, we also _____ about our future, particularly that we can have a long future. We've developed technologies that can send signals into space and humans to the moon, but we've also developed technologies that can destroy the environment, that can wage war with weapons and biological terrorism. In the future, will our technology help stabilize our planet and our population, leading to a very long ________ for us? Or will we destroy our world and its inhabitants after only a brief __________ on the cosmic stage? I encourage you to consider the unknowns in this equation. Why don't you make your own estimates for these unknowns, and see what you come up with for N? Compare that with the estimates made by Frank Drake, Carl Sagan, other scientists or your neighbors. Remember, there's no right answer. Not yet.

Solution

  1. large
  2. multiplied
  3. lifetime
  4. universe
  5. habitable
  6. physicist
  7. capital
  8. works
  9. intelligence
  10. factor
  11. equations
  12. researchers
  13. succeeds
  14. easily
  15. begins
  16. conditions
  17. detection
  18. equation
  19. small
  20. technologies
  21. search
  22. continue
  23. years
  24. abundant
  25. learn
  26. detected
  27. answer
  28. system
  29. appearance
  30. similar
  31. fractions
  32. extraterrestrial
  33. civilizations
  34. unknowns
  35. milky
  36. planetary
  37. ponder
  38. music
  39. estimate
  40. surface
  41. dealing
  42. number
  43. develops
  44. portion
  45. speed

Original Text

(Music) The basic question is, does life exist beyond Earth? Scientists who are called astrobiologists are trying to find that out right now. Most astrobiologists are trying to figure out if there's microbial life on Mars, or in the ocean under the frozen surface of Jupiter's moon Europa, or in the liquid hydrocarbon lakes that we've found on Saturn's moon Titan. But one group of astrobiologists works on SETI. SETI is the Search for Extraterrestrial Intelligence, and SETI researchers are trying to detect some evidence that intelligent creatures elsewhere have used technology to build a transmitter of some sort. But how likely is it that they will manage to find a signal? There are certainly no guarantees when it comes to SETI, but something called the Drake equation, named after Frank Drake, can help us organize our thinking about what might be required for successful detection. If you've dealt with equations before, then you probably expect that there will be a solution to the equation, a right answer. The Drake equation, however, is different, because there are so many unknowns. It has no right answer. As we learn more about our universe and our place within it, some of the unknowns get better known, and we can estimate an answer a bit better. But there won't be a definite answer to the Drake equation until SETI succeeds or something else proves that Earthlings are the only intelligent species in our portion of the cosmos. In the meantime, it is really useful to consider the unknowns. The Drake equation attempts to estimate the number of technological civilizations in the Milky Way Galaxy — we call that N — with whom we could make contact, and it's usually written as: N equals R-star multiplied by f-sub-p multiplied by n-sub-e multiplied by f-sub-l multiplied by f-sub-i multiplied by f-sub-c and lastly, multiplied by capital L. All those factors multiplied together help to estimate the number of technological civilizations that we might be able to detect right now. R-star is the rate at which stars have been born in the Milky Way Galaxy over the last few billion years, so it's a number that is stars per year. Our galaxy is 10 billion years old, and early in its history stars formed at a different rate. All of the f-factors are fractions. Each one must be less than or equal to one. F-sub-p is the fraction of stars that have planets. N-sub-e is the average number of habitable planets in any planetary system. F-sub-l is the fraction of planets on which life actually begins and f-sub-i is the fraction of all those life forms that develop intelligence. F-sub-c is the fraction of intelligent life that develops a civilization that decides to use some sort of transmitting technology. And finally, L — the longevity factor. On average, how many years do those transmitters continue to operate? Astronomers are now almost able to tell us what the product of the first three terms is. We're now finding exoplanets almost everywhere. The fractions dealing with life and intelligence and technological civilizations are ones that many, many experts ponder, but nobody knows for sure. So far, we only know of one place in the universe where life exists, and that's right here on Earth. In the next couple of decades, as we explore Mars and Europa and Titan, the discovery of any kind of life there will mean that life will be abundant in the Milky Way. Because if life originated twice within this one Solar System, it means it was easy, and given similar conditions elsewhere, life will happen. So the number two is a very important number here. Scientists, including SETI researchers, often tend to make very crude estimates and acknowledge that there are very large uncertainties in these estimates, in order to make progress. We think we know that R-star and n-sub-e are both numbers that are closer to 10 than, say, to one, and all the f-factors are less than one. Some of them may be much less than one. But of all these unknowns, the biggest unknown is L, so perhaps the most useful version of the Drake equation is simply to say that N is approximately equal to L. The information in this equation is very clear. Unless L is large, N will be small. But, you know, you can also turn that around. If SETI succeeds in detecting a signal in the near future, after examining only a small portion of the stars in the Milky Way, then we learn that L, on average, must be large. Otherwise, we couldn't have succeeded so easily. A physicist named Philip Morrison summarizes by saying that SETI is the archaeology of the future. By this, he meant that because the speed of light is finite, any signals detected from distant technologies will be telling us about their past by the time they reach us. But because L must be large for a successful detection, we also learn about our future, particularly that we can have a long future. We've developed technologies that can send signals into space and humans to the moon, but we've also developed technologies that can destroy the environment, that can wage war with weapons and biological terrorism. In the future, will our technology help stabilize our planet and our population, leading to a very long lifetime for us? Or will we destroy our world and its inhabitants after only a brief appearance on the cosmic stage? I encourage you to consider the unknowns in this equation. Why don't you make your own estimates for these unknowns, and see what you come up with for N? Compare that with the estimates made by Frank Drake, Carl Sagan, other scientists or your neighbors. Remember, there's no right answer. Not yet.

Frequently Occurring Word Combinations

ngrams of length 2

collocation frequency
drake equation 3
technological civilizations 3
seti succeeds 2
developed technologies 2

Important Words

  1. abundant
  2. acknowledge
  3. answer
  4. appearance
  5. approximately
  6. archaeology
  7. astrobiologists
  8. astronomers
  9. attempts
  10. average
  11. basic
  12. begins
  13. biggest
  14. billion
  15. biological
  16. bit
  17. born
  18. build
  19. call
  20. called
  21. capital
  22. carl
  23. civilization
  24. civilizations
  25. clear
  26. closer
  27. compare
  28. conditions
  29. contact
  30. continue
  31. cosmic
  32. cosmos
  33. couple
  34. creatures
  35. crude
  36. dealing
  37. dealt
  38. decades
  39. decides
  40. definite
  41. destroy
  42. detect
  43. detected
  44. detecting
  45. detection
  46. develop
  47. developed
  48. develops
  49. discovery
  50. distant
  51. drake
  52. early
  53. earth
  54. earthlings
  55. easily
  56. easy
  57. encourage
  58. environment
  59. equal
  60. equals
  61. equation
  62. equations
  63. estimate
  64. estimates
  65. europa
  66. evidence
  67. examining
  68. exist
  69. exists
  70. exoplanets
  71. expect
  72. experts
  73. explore
  74. extraterrestrial
  75. factor
  76. factors
  77. figure
  78. finally
  79. find
  80. finding
  81. finite
  82. formed
  83. forms
  84. fraction
  85. fractions
  86. frank
  87. frozen
  88. future
  89. galaxy
  90. group
  91. guarantees
  92. habitable
  93. happen
  94. history
  95. humans
  96. hydrocarbon
  97. important
  98. including
  99. information
  100. inhabitants
  101. intelligence
  102. intelligent
  103. kind
  104. lakes
  105. large
  106. lastly
  107. leading
  108. learn
  109. life
  110. lifetime
  111. light
  112. liquid
  113. long
  114. longevity
  115. manage
  116. mars
  117. means
  118. meant
  119. microbial
  120. milky
  121. moon
  122. morrison
  123. multiplied
  124. music
  125. named
  126. neighbors
  127. number
  128. numbers
  129. ocean
  130. operate
  131. order
  132. organize
  133. originated
  134. philip
  135. physicist
  136. place
  137. planet
  138. planetary
  139. planets
  140. ponder
  141. population
  142. portion
  143. product
  144. progress
  145. proves
  146. question
  147. rate
  148. reach
  149. remember
  150. required
  151. researchers
  152. sagan
  153. scientists
  154. search
  155. send
  156. seti
  157. signal
  158. signals
  159. similar
  160. simply
  161. small
  162. solar
  163. solution
  164. sort
  165. space
  166. species
  167. speed
  168. stabilize
  169. stage
  170. stars
  171. succeeded
  172. succeeds
  173. successful
  174. summarizes
  175. surface
  176. system
  177. technological
  178. technologies
  179. technology
  180. telling
  181. tend
  182. terms
  183. terrorism
  184. thinking
  185. time
  186. titan
  187. transmitter
  188. transmitters
  189. transmitting
  190. turn
  191. uncertainties
  192. universe
  193. unknown
  194. unknowns
  195. version
  196. wage
  197. war
  198. weapons
  199. works
  200. world
  201. written
  202. year
  203. years