full transcript

From the Ted Talk by Ariel Anbar: A needle in countless haystacks Finding habitable worlds

Unscramble the Blue Letters

The universe contains about 100 billion galaxies. Each of those galaxies contains about 100 bliilon stars. Many of those stars have planets orbiting them. So how do we look for life in all that immensity? It's like searching for a needle in trillions of haystacks. We might want to focus our search on ptlnaes that we know can sproupt life as we know it — what we call habtilabe worlds. What do such planets look like? To answer that question, we don't look out there. Instead, we look at ourselves. At Earth. Because this is the one planet in the universe that we know for certain is habitable. When we look at Earth from space, we see a blue, watery world. It's no coincidence that three quarters of the surface is covered by oceans. Because of its unuqie chemical and physical properties, water is absolutely eantsesil for all life as we know it. And so we get especially ecxited about other wodlrs on which water is aadnbnut. Fortunately, water is very common in the universe. But life needs water in the form of liquid, not ice, and not vapor, and that's a little bit less common. For a planet to have liquid water at its surface, three things are important. First, the planet needs to be lgrae enough that the force of gravity keeps the water mecloelus from flying off into space. For example, Mars is smaller than Earth, and so has less gravity, and that's one important reason that Mars has a very thin atmosphere, and no oceans at its surface. Second, the planet needs to have an atmosphere. Why? Because without an atmosphere, the planet is in a vacuum, and liquid water isn't stable in a vcuuam. For example, our moon has no atmosphere, and so if you splil some water on the moon, it will either boil away as vapor, or freeze solid to make ice. Without the prsesrue of an atmosphere, luqiid water can't survive. Third, the planet needs to be at the right distance from its star. Too close, and the surface temperature will eeecxd the biionlg point of water, and oceans will turn to vpaor. Too far, and the surface temperature will fall below the freezing point of water, causing the oceans to turn to ice. Fire or ice. For life as we know it, neither will suffice. You can imagine that the perfect zone where water stays liquid looks kind of like a belt around a star. We call that belt the habitable zone. So when we search for habitable worlds, we definitely want to look for planets in the habitable zenos around their stars. Those regions are the best bets to find planets like Earth. But while habitable zones are a prttey good place to begin the search for planets with life, there are a couple of cmlatinpcioos. First, a planet isn't necessarily habitable just because it's in the habitable zone. Consider the planet Venus in our solar system. If you were an alien astronomer, you'd think Venus is a pretty good bet for life. It's the right size, it has an atmosphere, and it's in the habitable zone of our sun. An alien astronomer might see it as Earth's twin. But Venus is not habitable, at least not at its surface. Not by life as we know it. It's too hot. That's because Venus' atmosphere is full of carbon dioxide, an iporntmat greenhouse gas. In fact, its arpsmohtee is almost entirely carbon doixide, and is almost 100 teims thicker than our own. As a result, the temperature on Venus is hot enough to melt lead, and the planet is dry as a bone. So finding planets of the right size and disnatce from their stars is only a beginning. We also want to know about the makeup of their atmospheres. The second complication egreems when we look a little more deeply at planet etrah. In the last 30 years, we've discovered mrieocbs living in all srtos of extreme environments. We find them in fissures of rock miles beneath our feet, in boiling waters of the ocean floor, in acidic waters of thermal springs, and in cloud droplets meils above our haeds. These so-called extremophiles aren't rare. Some scientists eittsame that the mass of microbes living deep underground equals the mass of all the life at Earth's surface. These subterranean microbes don't need oceans or sunshine. These discoveries suggest that Earth-like planets may be only the tip of the astrobiological iceberg. It's possible that life might persist in aquifers beneath the surface of Mars. Microbes may thrive on Jupiter's moon Europa, where liquid water ocean probably lies beneath the icy crust. Another ocean btneaeh the sfcraue of Saturn's moon Enceladus is the source of gresyes eturnpig into space. Could these geysers be raining microbes? Could we fly through them to find out? And what about life as we don't know it, using a liquid other than wtear? Maybe we are the crazy creatures living in an unusual and extreme environment. Maybe the real habitable zone is so large that there are bllniois of needles in those trillions of haystacks. Maybe in the big scheme of things, Earth is only one of many different kinds of habitable worlds. The only way to find out is to go out and exporle.

Open Cloze

The universe contains about 100 billion galaxies. Each of those galaxies contains about 100 _______ stars. Many of those stars have planets orbiting them. So how do we look for life in all that immensity? It's like searching for a needle in trillions of haystacks. We might want to focus our search on _______ that we know can _______ life as we know it — what we call _________ worlds. What do such planets look like? To answer that question, we don't look out there. Instead, we look at ourselves. At Earth. Because this is the one planet in the universe that we know for certain is habitable. When we look at Earth from space, we see a blue, watery world. It's no coincidence that three quarters of the surface is covered by oceans. Because of its ______ chemical and physical properties, water is absolutely _________ for all life as we know it. And so we get especially _______ about other ______ on which water is ________. Fortunately, water is very common in the universe. But life needs water in the form of liquid, not ice, and not vapor, and that's a little bit less common. For a planet to have liquid water at its surface, three things are important. First, the planet needs to be _____ enough that the force of gravity keeps the water _________ from flying off into space. For example, Mars is smaller than Earth, and so has less gravity, and that's one important reason that Mars has a very thin atmosphere, and no oceans at its surface. Second, the planet needs to have an atmosphere. Why? Because without an atmosphere, the planet is in a vacuum, and liquid water isn't stable in a ______. For example, our moon has no atmosphere, and so if you _____ some water on the moon, it will either boil away as vapor, or freeze solid to make ice. Without the ________ of an atmosphere, ______ water can't survive. Third, the planet needs to be at the right distance from its star. Too close, and the surface temperature will ______ the _______ point of water, and oceans will turn to _____. Too far, and the surface temperature will fall below the freezing point of water, causing the oceans to turn to ice. Fire or ice. For life as we know it, neither will suffice. You can imagine that the perfect zone where water stays liquid looks kind of like a belt around a star. We call that belt the habitable zone. So when we search for habitable worlds, we definitely want to look for planets in the habitable _____ around their stars. Those regions are the best bets to find planets like Earth. But while habitable zones are a ______ good place to begin the search for planets with life, there are a couple of _____________. First, a planet isn't necessarily habitable just because it's in the habitable zone. Consider the planet Venus in our solar system. If you were an alien astronomer, you'd think Venus is a pretty good bet for life. It's the right size, it has an atmosphere, and it's in the habitable zone of our sun. An alien astronomer might see it as Earth's twin. But Venus is not habitable, at least not at its surface. Not by life as we know it. It's too hot. That's because Venus' atmosphere is full of carbon dioxide, an _________ greenhouse gas. In fact, its __________ is almost entirely carbon _______, and is almost 100 _____ thicker than our own. As a result, the temperature on Venus is hot enough to melt lead, and the planet is dry as a bone. So finding planets of the right size and ________ from their stars is only a beginning. We also want to know about the makeup of their atmospheres. The second complication _______ when we look a little more deeply at planet _____. In the last 30 years, we've discovered ________ living in all _____ of extreme environments. We find them in fissures of rock miles beneath our feet, in boiling waters of the ocean floor, in acidic waters of thermal springs, and in cloud droplets _____ above our _____. These so-called extremophiles aren't rare. Some scientists ________ that the mass of microbes living deep underground equals the mass of all the life at Earth's surface. These subterranean microbes don't need oceans or sunshine. These discoveries suggest that Earth-like planets may be only the tip of the astrobiological iceberg. It's possible that life might persist in aquifers beneath the surface of Mars. Microbes may thrive on Jupiter's moon Europa, where liquid water ocean probably lies beneath the icy crust. Another ocean _______ the _______ of Saturn's moon Enceladus is the source of _______ ________ into space. Could these geysers be raining microbes? Could we fly through them to find out? And what about life as we don't know it, using a liquid other than _____? Maybe we are the crazy creatures living in an unusual and extreme environment. Maybe the real habitable zone is so large that there are ________ of needles in those trillions of haystacks. Maybe in the big scheme of things, Earth is only one of many different kinds of habitable worlds. The only way to find out is to go out and _______.

Solution

  1. large
  2. beneath
  3. sorts
  4. water
  5. habitable
  6. pressure
  7. unique
  8. explore
  9. planets
  10. microbes
  11. times
  12. earth
  13. vacuum
  14. emerges
  15. excited
  16. miles
  17. zones
  18. dioxide
  19. atmosphere
  20. worlds
  21. complications
  22. geysers
  23. abundant
  24. spill
  25. heads
  26. erupting
  27. support
  28. exceed
  29. billion
  30. billions
  31. molecules
  32. distance
  33. important
  34. liquid
  35. estimate
  36. surface
  37. essential
  38. boiling
  39. vapor
  40. pretty

Original Text

The universe contains about 100 billion galaxies. Each of those galaxies contains about 100 billion stars. Many of those stars have planets orbiting them. So how do we look for life in all that immensity? It's like searching for a needle in trillions of haystacks. We might want to focus our search on planets that we know can support life as we know it — what we call habitable worlds. What do such planets look like? To answer that question, we don't look out there. Instead, we look at ourselves. At Earth. Because this is the one planet in the universe that we know for certain is habitable. When we look at Earth from space, we see a blue, watery world. It's no coincidence that three quarters of the surface is covered by oceans. Because of its unique chemical and physical properties, water is absolutely essential for all life as we know it. And so we get especially excited about other worlds on which water is abundant. Fortunately, water is very common in the universe. But life needs water in the form of liquid, not ice, and not vapor, and that's a little bit less common. For a planet to have liquid water at its surface, three things are important. First, the planet needs to be large enough that the force of gravity keeps the water molecules from flying off into space. For example, Mars is smaller than Earth, and so has less gravity, and that's one important reason that Mars has a very thin atmosphere, and no oceans at its surface. Second, the planet needs to have an atmosphere. Why? Because without an atmosphere, the planet is in a vacuum, and liquid water isn't stable in a vacuum. For example, our moon has no atmosphere, and so if you spill some water on the moon, it will either boil away as vapor, or freeze solid to make ice. Without the pressure of an atmosphere, liquid water can't survive. Third, the planet needs to be at the right distance from its star. Too close, and the surface temperature will exceed the boiling point of water, and oceans will turn to vapor. Too far, and the surface temperature will fall below the freezing point of water, causing the oceans to turn to ice. Fire or ice. For life as we know it, neither will suffice. You can imagine that the perfect zone where water stays liquid looks kind of like a belt around a star. We call that belt the habitable zone. So when we search for habitable worlds, we definitely want to look for planets in the habitable zones around their stars. Those regions are the best bets to find planets like Earth. But while habitable zones are a pretty good place to begin the search for planets with life, there are a couple of complications. First, a planet isn't necessarily habitable just because it's in the habitable zone. Consider the planet Venus in our solar system. If you were an alien astronomer, you'd think Venus is a pretty good bet for life. It's the right size, it has an atmosphere, and it's in the habitable zone of our sun. An alien astronomer might see it as Earth's twin. But Venus is not habitable, at least not at its surface. Not by life as we know it. It's too hot. That's because Venus' atmosphere is full of carbon dioxide, an important greenhouse gas. In fact, its atmosphere is almost entirely carbon dioxide, and is almost 100 times thicker than our own. As a result, the temperature on Venus is hot enough to melt lead, and the planet is dry as a bone. So finding planets of the right size and distance from their stars is only a beginning. We also want to know about the makeup of their atmospheres. The second complication emerges when we look a little more deeply at planet Earth. In the last 30 years, we've discovered microbes living in all sorts of extreme environments. We find them in fissures of rock miles beneath our feet, in boiling waters of the ocean floor, in acidic waters of thermal springs, and in cloud droplets miles above our heads. These so-called extremophiles aren't rare. Some scientists estimate that the mass of microbes living deep underground equals the mass of all the life at Earth's surface. These subterranean microbes don't need oceans or sunshine. These discoveries suggest that Earth-like planets may be only the tip of the astrobiological iceberg. It's possible that life might persist in aquifers beneath the surface of Mars. Microbes may thrive on Jupiter's moon Europa, where liquid water ocean probably lies beneath the icy crust. Another ocean beneath the surface of Saturn's moon Enceladus is the source of geysers erupting into space. Could these geysers be raining microbes? Could we fly through them to find out? And what about life as we don't know it, using a liquid other than water? Maybe we are the crazy creatures living in an unusual and extreme environment. Maybe the real habitable zone is so large that there are billions of needles in those trillions of haystacks. Maybe in the big scheme of things, Earth is only one of many different kinds of habitable worlds. The only way to find out is to go out and explore.

Frequently Occurring Word Combinations

ngrams of length 2

collocation frequency
liquid water 4
habitable zone 4
habitable worlds 2
surface temperature 2
habitable zones 2
pretty good 2
microbes living 2

Important Words

  1. absolutely
  2. abundant
  3. acidic
  4. alien
  5. answer
  6. aquifers
  7. astrobiological
  8. astronomer
  9. atmosphere
  10. atmospheres
  11. beginning
  12. belt
  13. beneath
  14. bet
  15. bets
  16. big
  17. billion
  18. billions
  19. bit
  20. blue
  21. boil
  22. boiling
  23. bone
  24. call
  25. carbon
  26. causing
  27. chemical
  28. close
  29. cloud
  30. coincidence
  31. common
  32. complication
  33. complications
  34. couple
  35. covered
  36. crazy
  37. creatures
  38. crust
  39. deep
  40. deeply
  41. dioxide
  42. discovered
  43. discoveries
  44. distance
  45. droplets
  46. dry
  47. earth
  48. emerges
  49. enceladus
  50. environment
  51. environments
  52. equals
  53. erupting
  54. essential
  55. estimate
  56. europa
  57. exceed
  58. excited
  59. explore
  60. extreme
  61. extremophiles
  62. fact
  63. fall
  64. feet
  65. find
  66. finding
  67. fire
  68. fissures
  69. floor
  70. fly
  71. flying
  72. focus
  73. force
  74. form
  75. fortunately
  76. freeze
  77. freezing
  78. full
  79. galaxies
  80. gas
  81. geysers
  82. good
  83. gravity
  84. greenhouse
  85. habitable
  86. haystacks
  87. heads
  88. hot
  89. ice
  90. iceberg
  91. icy
  92. imagine
  93. immensity
  94. important
  95. kind
  96. kinds
  97. large
  98. lead
  99. lies
  100. life
  101. liquid
  102. living
  103. makeup
  104. mars
  105. mass
  106. melt
  107. microbes
  108. miles
  109. molecules
  110. moon
  111. necessarily
  112. needle
  113. needles
  114. ocean
  115. oceans
  116. orbiting
  117. perfect
  118. persist
  119. physical
  120. place
  121. planet
  122. planets
  123. point
  124. pressure
  125. pretty
  126. properties
  127. quarters
  128. question
  129. raining
  130. rare
  131. real
  132. reason
  133. regions
  134. result
  135. rock
  136. scheme
  137. scientists
  138. search
  139. searching
  140. size
  141. smaller
  142. solar
  143. solid
  144. sorts
  145. source
  146. space
  147. spill
  148. springs
  149. stable
  150. star
  151. stars
  152. stays
  153. subterranean
  154. suffice
  155. suggest
  156. sun
  157. sunshine
  158. support
  159. surface
  160. survive
  161. system
  162. temperature
  163. thermal
  164. thicker
  165. thin
  166. thrive
  167. times
  168. tip
  169. trillions
  170. turn
  171. twin
  172. underground
  173. unique
  174. universe
  175. unusual
  176. vacuum
  177. vapor
  178. venus
  179. water
  180. waters
  181. watery
  182. world
  183. worlds
  184. years
  185. zone
  186. zones