2012-10-30

[public] 3.63M views, 157K likes, 1.32K dislikes audio only

Veritasium

Hope this was worth the wait! So many people helped with this video: Prof John Sperry, Hank Green, Henry Reich, CGP Grey, Prof Poliakoff, my mum filmed for me in beautiful Stanley Park and Jen S helped with the fourth version of the script.

Prof John Sperry http://biologylabs.utah.edu/sperry/john.html

Hank Green (SciShow) http://www.youtube.com/user/scishow

Henry Reich (minutephysics) http://www.youtube.com/user/minutephysics

CGP Grey http://www.youtube.com/user/cgpgrey

Prof Poliakoff (Periodic Videos) http://www.youtube.com/user/periodicvideos

Also thanks to the Palais de la Decouverte - they helped me with the whole vacuum pump setup in Paris. No, I could not actually suck water up 10m - I did about 4m, but the vacuum pump was easily able to do it and I saw spontaneous boiling on all of our various trials. Footage from this may end up on 2Veritasium.

Trees create immense negative pressures of 10's of atmospheres by evaporating water from nanoscale pores, sucking water up 100m in a state where it should be boiling but can't because the perfect xylem tubes contain no air bubbles, just so that most of it can evaporate in the process of absorbing a couple molecules of carbon dioxide. Now I didn't mention the cohesion of water (that it sticks to itself well) but this is implicit in the description of negative pressure, strong surface tension etc.