#NoDesign🙄 (2022-12-03) #

0:00:01 I love doing the no design posts the subject is virtually inexhaustible and infinite
0:00:14 God's design in creation is everywhere we look from the Apparently simple flower to complex DNA 0:00:22 we see evidence of design in the universe it's not just the irreducibly complex molecular machines or 0:00:31 how the laws of physics unexpectedly conspire in an extraordinary way to make the universe 0:00:38 habitable for life thanks to science we can now see design in unappreciated living things all 0:00:47 around us I want to share with you a fascinating video explaining how trees do the impossible 0:00:57 it features the physicist Dr Derek Muller who is a specialist in explaining science to the 0:01:03 General Public after watching this I promise you will never look at trees the same way again enjoy 0:01:14 sometimes the simplest questions have the most amazing answers like how can trees be so tall 0:01:20 it's a question that doesn't even seem like it needs an answer trees just are tall some of them 0:01:26 are over 100 meters why should there be a height limit I'll tell you why trees need to transport 0:01:32 water from their Roots up until their topmost branches in order to survive and that is no 0:01:36 trivial task there is a limit to the height that water can be sucked up a tube it's 10 meters if 0:01:42 you suck on a long vertical straw the water will go no higher than 10 meters at this point there 0:01:48 will be a perfect vacuum at the top of the straw and the water will start to boil spontaneously 0:01:53 for a tree to raise water 100 meters it would have to create a pressure difference of 10 0:01:57 atmospheres how would trees do that when I posed this conundrum a lot of people said the answer is 0:02:04 transpiration and that's when water evaporates from the leaf pulling up the water molecules 0:02:09 behind it now that's clearly a mechanism a tree can use to create suction but it doesn't help 0:02:14 us overcome this 10 meter limit the lowest the pressure can go is the pure vacuum which I imagine 0:02:18 is not happening inside of tree leaves right right Hank so you might suspect that a tree does 0:02:25 not contain continuous straw-like tubes the tree effectively has valves in it so you don't have a 0:02:32 column of water this big tube which you're saying needs to be filled with water is actually made up 0:02:37 of cells although these are good speculations they don't turn out to be correct scientists who study 0:02:42 trees find that the xylem tubes that transport water do contain a continuous water column so 0:02:48 how else could the tree transport water from the roots to the leaves they don't suck they don't use 0:02:52 a vacuum oh okay so how do they do it pleasing like a cow like you're squeezing the cowlitter 0:02:57 all the way up there's little tree muscles in there yeah besides being a giant waste of energy 0:03:02 all of the cells that make up the xylem tubes are dead what about osmotic pressure If there is more 0:03:08 solute in The Roots than in the surrounding soil water would be pushed up the tree but some trees 0:03:13 live in mangroves where the water is so salty that osmotic pressure actually acts in the other 0:03:18 direction so the tree needs additional pressure to suck water into the tree then it must be capillary 0:03:23 action the thinner the tube the higher the water can climb but the tubes in a tree are too wide at 0:03:30 20 to 200 micrometers in diameter water should rise less than a meter so how do trees do it 0:03:36 well one of the assumptions we made is wrong the lowest the pressure can go is the pure vacuum pure 0:03:42 vacuum your vacuum in a gas this is true when you eliminate all of the gas molecules the pressure is 0:03:47 zero and you have a perfect vacuum but in a liquid you can go lower than zero pressure and actually 0:03:54 get Negative pressures in a solid we would think of this as tension this means that the molecules 0:03:59 are pulling on each other and their surroundings as the water evaporates from the pores of the cell 0:04:05 wall they create immense negative pressures of -15 atmospheres in an average tree think about 0:04:12 the air water interface at the pore there is one atmosphere of pressure pushing in and negative 15 0:04:18 atmospheres of suction on the other side so why doesn't the meniscus break because the pores are 0:04:24 tiny only two to five nanometers in diameter at this scale water's high surface tension 0:04:30 ensures the air water boundary can withstand huge pressures without caving As you move down the tree 0:04:37 the pressure increases up to atmospheric at the roots so you can have a large pressure difference 0:04:42 between the top and the bottom of the tree because the pressure at the top is so negative but hang 0:04:47 on if the pressure at the top is negative 15 atmospheres shouldn't the water be boiling 0:04:52 yes yes it should but changing phase from liquid to gas requires activation energy and that can 0:05:00 come in the form of a nucleation site like a tiny air bubble that's why it's so important that the 0:05:04 xylem tubes contain no air bubbles and they can do this because unlike a straw they've been water 0:05:10 filled from the start this way water remains in the metastable liquid state when it really 0:05:15 should be boiling it's just like supercooled water remains liquid even though it should be 0:05:20 ice so you could say that the water in a tree is super sucked because it remains liquid at 0:05:25 such negative pressures and why are trees moving all this water up the tree I want you to make a 0:05:31 guess say it out loud for photosynthesis actually no less than one percent of the water is used in 0:05:37 photosynthetic reactions any other ideas okay what about growth well five percent of the water is 0:05:43 used to make new cells well so what happens to the other 95 percent of the water it just evaporates 0:05:50 for each molecule of carbon dioxide a tree takes in it loses hundreds of molecules of water whoa 0:05:56 can you believe how amazing this is trees create huge negative pressures of tens of atmospheres by 0:06:03 evaporating water through nanoscale pores sucking water up 100 meters in a state where it should 0:06:08 be boiling but can't because the perfect xylem tubes contain no air bubbles just so 0:06:12 that most of it can evaporate in the process of absorbing a couple molecules of carbon dioxide 0:06:19 I will never look at trees the same way again