full transcript

From the Ted Talk by Aatish Bhatia: The physics of human sperm vs. the physics of the sperm whale

Unscramble the Blue Letters

In 1977, the physicist Edward Purcell calculated that if you push a bacteria and then let go, it will stop in about a millionth of a second. In that time, it will have traveled less than the width of a single atom. The same holds true for a sperm and many other microbes. It all has to do with being really samll. mocicrpoisc creatures iihabnt a world alien to us, where making it through an inch of water is an incredible eenvodar. But why does size matter so much for a swimmer? What makes the wlrod of a sperm so fundamentally different from that of a sperm whale? To find out, we need to dive into the physics of fuilds. Here's a way to think about it. Imagine you are swimming in a pool. It's you and a whole bunch of water molecules. Water molecules outnumber you a thousand trillion trillion to one. So, pushing past them with your gigantic body is easy, but if you were really small, say you were about the size of a water molecule, all of a sudden, it's like you're smwmiing in a pool of people. Rather than splimy swishing by all the teeny, tiny mloeulecs, now every single water molecule is like another person you have to push past to get anywhere. In 1883, the physicist Osborne Reynolds figured out that there is one simple number that can predict how a fulid will behave. It's called the Reynolds nmeubr, and it depends on simple properties like the size of the swimmer, its seepd, the density of the fluid, and the stickiness, or the viscosity, of the fluid. What this means is that creatures of very different szies inhabit vastly different worlds. For example, because of its huge size, a sperm whale inhabits the large rdoneyls number world. If it flaps its tail once, it can coast ahead for an incredible distance. Meanwhile, sperm live in a low Reynolds number world. If a sperm were to stop flapping its tail, it wouldn't even coast past a slngie atom. To imagine what it would feel like to be a sperm, you need to bring yourself down to its Reynolds number. Picture yourself in a tub of mslosaes with your arms moving about as slow as the minute hand of a clock, and you'd have a pretty good idea of what a sperm is up against. So, how do meoircbs manage to get anywhere? Well, many don't bohetr swimming at all. They just let the food drift to them. This is somewhat like a lazy cow that waits for the grass under its mouth to grow back. But many microbes do swim, and this is where those ibrelcinde adaptations come in. One trick they can use is to dfreom the shape of their paddle. By cleverly flexing their paddle to create more drag on the power stroke than on the recovery stroke, single-celled organisms like paramecia manage to inch their way through the crowd of water molecules. But there's an even more inoinuegs solution arrived at by bacteria and sperm. Instead of wagging their pedadls back and forth, they wind them like a cork screw. Just as a cork screw on a wine btolte converts winding motion into forward mtoion, these tiny creatures spin their hacelil tails to push themselves forward in a world where water feels as thick as cork. Other strategies are even stranger. Some bacteria take Batman's aapropch. They use grappling hooks to pull themselves along. They can even use this grappling hook like a sling shot and fling themselves forward. Others use cmecihal engineering. H. pylori lvies only in the slimy, aidicc mucus inside our stomachs. It releases a chemical that tnihs out the surrounding mucus, allowing it to glide through slime. Maybe it's no surprise that these guys are also responsible for stomach ulcers. So, when you look really closely at our bdieos and the world around us, you can see all sorts of tiny creatures fdinnig clever ways to get around in a sticky situation. Without these aatoitanpds, bacteria would never find their hosts, and sperms would never make it to their eggs, which means you would never get stomach ulcers, but you would also never be born in the first place. (Pop)

Open Cloze

In 1977, the physicist Edward Purcell calculated that if you push a bacteria and then let go, it will stop in about a millionth of a second. In that time, it will have traveled less than the width of a single atom. The same holds true for a sperm and many other microbes. It all has to do with being really _____. ___________ creatures _______ a world alien to us, where making it through an inch of water is an incredible ________. But why does size matter so much for a swimmer? What makes the _____ of a sperm so fundamentally different from that of a sperm whale? To find out, we need to dive into the physics of ______. Here's a way to think about it. Imagine you are swimming in a pool. It's you and a whole bunch of water molecules. Water molecules outnumber you a thousand trillion trillion to one. So, pushing past them with your gigantic body is easy, but if you were really small, say you were about the size of a water molecule, all of a sudden, it's like you're ________ in a pool of people. Rather than ______ swishing by all the teeny, tiny _________, now every single water molecule is like another person you have to push past to get anywhere. In 1883, the physicist Osborne Reynolds figured out that there is one simple number that can predict how a _____ will behave. It's called the Reynolds ______, and it depends on simple properties like the size of the swimmer, its _____, the density of the fluid, and the stickiness, or the viscosity, of the fluid. What this means is that creatures of very different _____ inhabit vastly different worlds. For example, because of its huge size, a sperm whale inhabits the large ________ number world. If it flaps its tail once, it can coast ahead for an incredible distance. Meanwhile, sperm live in a low Reynolds number world. If a sperm were to stop flapping its tail, it wouldn't even coast past a ______ atom. To imagine what it would feel like to be a sperm, you need to bring yourself down to its Reynolds number. Picture yourself in a tub of ________ with your arms moving about as slow as the minute hand of a clock, and you'd have a pretty good idea of what a sperm is up against. So, how do ________ manage to get anywhere? Well, many don't ______ swimming at all. They just let the food drift to them. This is somewhat like a lazy cow that waits for the grass under its mouth to grow back. But many microbes do swim, and this is where those __________ adaptations come in. One trick they can use is to ______ the shape of their paddle. By cleverly flexing their paddle to create more drag on the power stroke than on the recovery stroke, single-celled organisms like paramecia manage to inch their way through the crowd of water molecules. But there's an even more _________ solution arrived at by bacteria and sperm. Instead of wagging their _______ back and forth, they wind them like a cork screw. Just as a cork screw on a wine ______ converts winding motion into forward ______, these tiny creatures spin their _______ tails to push themselves forward in a world where water feels as thick as cork. Other strategies are even stranger. Some bacteria take Batman's ________. They use grappling hooks to pull themselves along. They can even use this grappling hook like a sling shot and fling themselves forward. Others use ________ engineering. H. pylori _____ only in the slimy, ______ mucus inside our stomachs. It releases a chemical that _____ out the surrounding mucus, allowing it to glide through slime. Maybe it's no surprise that these guys are also responsible for stomach ulcers. So, when you look really closely at our ______ and the world around us, you can see all sorts of tiny creatures _______ clever ways to get around in a sticky situation. Without these ___________, bacteria would never find their hosts, and sperms would never make it to their eggs, which means you would never get stomach ulcers, but you would also never be born in the first place. (Pop)

Solution

  1. approach
  2. bother
  3. chemical
  4. lives
  5. adaptations
  6. paddles
  7. swimming
  8. reynolds
  9. single
  10. deform
  11. simply
  12. motion
  13. acidic
  14. fluids
  15. molasses
  16. bodies
  17. inhabit
  18. bottle
  19. microscopic
  20. incredible
  21. fluid
  22. number
  23. microbes
  24. ingenious
  25. endeavor
  26. helical
  27. small
  28. sizes
  29. speed
  30. world
  31. molecules
  32. finding
  33. thins

Original Text

In 1977, the physicist Edward Purcell calculated that if you push a bacteria and then let go, it will stop in about a millionth of a second. In that time, it will have traveled less than the width of a single atom. The same holds true for a sperm and many other microbes. It all has to do with being really small. Microscopic creatures inhabit a world alien to us, where making it through an inch of water is an incredible endeavor. But why does size matter so much for a swimmer? What makes the world of a sperm so fundamentally different from that of a sperm whale? To find out, we need to dive into the physics of fluids. Here's a way to think about it. Imagine you are swimming in a pool. It's you and a whole bunch of water molecules. Water molecules outnumber you a thousand trillion trillion to one. So, pushing past them with your gigantic body is easy, but if you were really small, say you were about the size of a water molecule, all of a sudden, it's like you're swimming in a pool of people. Rather than simply swishing by all the teeny, tiny molecules, now every single water molecule is like another person you have to push past to get anywhere. In 1883, the physicist Osborne Reynolds figured out that there is one simple number that can predict how a fluid will behave. It's called the Reynolds number, and it depends on simple properties like the size of the swimmer, its speed, the density of the fluid, and the stickiness, or the viscosity, of the fluid. What this means is that creatures of very different sizes inhabit vastly different worlds. For example, because of its huge size, a sperm whale inhabits the large Reynolds number world. If it flaps its tail once, it can coast ahead for an incredible distance. Meanwhile, sperm live in a low Reynolds number world. If a sperm were to stop flapping its tail, it wouldn't even coast past a single atom. To imagine what it would feel like to be a sperm, you need to bring yourself down to its Reynolds number. Picture yourself in a tub of molasses with your arms moving about as slow as the minute hand of a clock, and you'd have a pretty good idea of what a sperm is up against. So, how do microbes manage to get anywhere? Well, many don't bother swimming at all. They just let the food drift to them. This is somewhat like a lazy cow that waits for the grass under its mouth to grow back. But many microbes do swim, and this is where those incredible adaptations come in. One trick they can use is to deform the shape of their paddle. By cleverly flexing their paddle to create more drag on the power stroke than on the recovery stroke, single-celled organisms like paramecia manage to inch their way through the crowd of water molecules. But there's an even more ingenious solution arrived at by bacteria and sperm. Instead of wagging their paddles back and forth, they wind them like a cork screw. Just as a cork screw on a wine bottle converts winding motion into forward motion, these tiny creatures spin their helical tails to push themselves forward in a world where water feels as thick as cork. Other strategies are even stranger. Some bacteria take Batman's approach. They use grappling hooks to pull themselves along. They can even use this grappling hook like a sling shot and fling themselves forward. Others use chemical engineering. H. pylori lives only in the slimy, acidic mucus inside our stomachs. It releases a chemical that thins out the surrounding mucus, allowing it to glide through slime. Maybe it's no surprise that these guys are also responsible for stomach ulcers. So, when you look really closely at our bodies and the world around us, you can see all sorts of tiny creatures finding clever ways to get around in a sticky situation. Without these adaptations, bacteria would never find their hosts, and sperms would never make it to their eggs, which means you would never get stomach ulcers, but you would also never be born in the first place. (Pop)

Frequently Occurring Word Combinations

ngrams of length 2

collocation frequency
water molecules 3
reynolds number 3
single atom 2
number world 2
cork screw 2
tiny creatures 2

ngrams of length 3

collocation frequency
reynolds number world 2

Important Words

  1. acidic
  2. adaptations
  3. alien
  4. allowing
  5. approach
  6. arms
  7. arrived
  8. atom
  9. bacteria
  10. behave
  11. bodies
  12. body
  13. born
  14. bother
  15. bottle
  16. bring
  17. bunch
  18. calculated
  19. called
  20. chemical
  21. clever
  22. cleverly
  23. clock
  24. closely
  25. coast
  26. converts
  27. cork
  28. cow
  29. create
  30. creatures
  31. crowd
  32. deform
  33. density
  34. depends
  35. distance
  36. dive
  37. drag
  38. drift
  39. easy
  40. edward
  41. eggs
  42. endeavor
  43. engineering
  44. feel
  45. feels
  46. figured
  47. find
  48. finding
  49. flapping
  50. flaps
  51. flexing
  52. fling
  53. fluid
  54. fluids
  55. food
  56. fundamentally
  57. gigantic
  58. glide
  59. good
  60. grappling
  61. grass
  62. grow
  63. guys
  64. hand
  65. helical
  66. holds
  67. hook
  68. hooks
  69. hosts
  70. huge
  71. idea
  72. imagine
  73. inch
  74. incredible
  75. ingenious
  76. inhabit
  77. inhabits
  78. large
  79. lazy
  80. live
  81. lives
  82. making
  83. manage
  84. matter
  85. means
  86. microbes
  87. microscopic
  88. millionth
  89. minute
  90. molasses
  91. molecule
  92. molecules
  93. motion
  94. mouth
  95. moving
  96. mucus
  97. number
  98. organisms
  99. osborne
  100. outnumber
  101. paddle
  102. paddles
  103. paramecia
  104. people
  105. person
  106. physicist
  107. physics
  108. picture
  109. place
  110. pool
  111. pop
  112. power
  113. predict
  114. pretty
  115. properties
  116. pull
  117. purcell
  118. push
  119. pushing
  120. pylori
  121. recovery
  122. releases
  123. responsible
  124. reynolds
  125. screw
  126. shape
  127. shot
  128. simple
  129. simply
  130. single
  131. situation
  132. size
  133. sizes
  134. slime
  135. slimy
  136. sling
  137. slow
  138. small
  139. solution
  140. sorts
  141. speed
  142. sperm
  143. sperms
  144. spin
  145. stickiness
  146. sticky
  147. stomach
  148. stomachs
  149. stop
  150. stranger
  151. strategies
  152. stroke
  153. sudden
  154. surprise
  155. surrounding
  156. swim
  157. swimmer
  158. swimming
  159. swishing
  160. tail
  161. tails
  162. teeny
  163. thick
  164. thins
  165. thousand
  166. time
  167. tiny
  168. traveled
  169. trick
  170. trillion
  171. true
  172. tub
  173. ulcers
  174. vastly
  175. viscosity
  176. wagging
  177. waits
  178. water
  179. ways
  180. whale
  181. width
  182. wind
  183. winding
  184. wine
  185. world
  186. worlds