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The physics of human sperm vs. the physics of the sperm whale

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Traveling is extremely arduous for microscopic sperm -- think of a human trying to swim in a pool made of...other humans. We can compare the journey of a sperm to that of a sperm whale by calculating the Reynolds number, a prediction of how fluid will behave, often fluctuating due to size of the swimmer. Aatish Bhatia explores the great (albeit tiny) sperm’s journey.

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  • Educator Aatish Bhatia
  • Animator Brad Purnell
  • Narrator Addison Anderson

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Additional Resources for you to Explore
For more on the strange world of sperm, bacteria, and other tiny creatures, or to learn how to swim in corn syrup, check out my blog post on the subject, also featured in The Best Science Writing Online 2012.
Have you heard of the Great Molasses Flood? In 1919, an industrial accident created a wave of molasses that swept through streets of Boston at 35 miles per hour, killing 21 people in its wake. Over at Scientific American, Ferris Jabr deftly explains why the Reynolds number of molasses made this disaster all the more lethal, and how microbes are faced with an even more sticky situation on a daily basis. (This tragedy also happened recently in Hawaii.)
The low Reynolds number world can be a very counterintuitive place. Here's a neat video that shows the odd behavior of three drops of colored dye in a vat of glycerine. I guarantee you'll be surprised by how it ends.
Because corn syrup is more viscous than water, a swimmer submerged in corn syrup has a low Reynolds number. This has some surprising consequences. This series of videos shows that a corkscrew works better than a paddle in the Low Reynolds number world. This is why sperm and bacteria use corkscrew shaped flagella instead of a paddle.
http://www.youtube.com/watch?v=4h079P7qRSw
http://www.youtube.com/watch?v=2kkfHj3LHeE
http://www.youtube.com/watch?v=s_5ygWhcxKk

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TED-Ed Animation lessons feature the words and ideas of educators brought to life by professional animators. Are you an educator or animator interested in creating a TED-Ed Animation? Nominate yourself here »

Meet The Creators

  • Educator Aatish Bhatia
  • Animator Brad Purnell
  • Narrator Addison Anderson

Share

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