9 ms·
Where does a tree get its mass?
- shasta 16y agoAdam: Who invented the cotton gin? Bob: That's easy, Eli Whitney Adam: What's a cotton gin? Bob: Shrug
- waivej 16y agoThis reminds me of a snippet from Buckminster Fuller's "Critical Path". He's talking about specialists and generalists and how we rarely see the big picture of what's important. "Nobody is born a specialist. Every child is born with comprehensive interests, asking the most comprehensively logical and relevant questions. Pointing to the logs burning in the fireplace, one child asked me, "What is fire?" I answered, "Fire is the Sun unwinding from the tree's log. The Earth revolves and the trees revolve as the radiation from the Sun's flame reaches the revolving planet Earth. By photosynthesis the green buds and leaves of the tree convert that Sun radiation into hydrocarbon molecules, which form into the bio-cells of the green, outer, cambium layer of the tree." http://www.maebrussell.com/Critical%20Path/Critical%20Path%20excerpts%201.html http://www.maebrussell.com/Critical%20Path/Critical%20Path%2...
- sliverstorm 16y agoThe example is not all that potent. before the link even loaded, the following flashes through my head: 'well of course carbon from the air. ... oh, and water. They have a lot of water.' He tries to use something pretty clear cut, like mass and trees (mass is mass, and trees are pretty typically also trees) as an analogue to something inherently vague- psychiatry in this case. Whether someone is bipolar is way more up to interpretation than whether something that weights 100kg has a mass of 100kg or not.
- Retric 16y agoThis forget's about all the H as a tree get's most of it's hydrogen from water. EX:"Glucose" (C6H12O6) is from 6 * H20 + 6 * C02 => C6H12O6 + 6 * O2. So a reasonable ansewer would be mostly air and water with some minirals from the soil.
- ErrantX 16y agoUh, the second "section" on the page basically says about the same thing :)
- Retric 16y agoSome trees are more than 50% water by mass This is true, but missing my point. A lot of a trees weight is water but the H in it's DNA is from watter but not still water.
- sliverstorm 16y agoYes, and the question was where does the tree get it's mass from. I suppose you could look at it in the twisted sense of 'what in the tree contributes so much to it's mass', but that's a rather tortured use of English.
- Retric 16y agoIf the meant "50% of the mass of some trees is from water" that then he should have said so. Some trees are more than 50% water by mass is a true statement, but it means something else. The author saying something related to the truth, but I think he has a poor understanding of what is going on. Reading that I felt like a teacher who wants to give some created for a student using the correct words while realizing they don't quite get it. As to precision it's more accurate to say 3 +/- 0.5 times 101 +/- 0.5 = 256.25 to 355.25 or 305.75 +/- 49.5 than to just say 300. For an extreme example (1 +/- .1) ^ 1,000 can be any ware from ~2.47e41 to ~1.748e-46. PS: "Dead stars" is a reasonable if incomplete answer to the same question, but context matters so it's not acceptable on a botany or chemistry exam. In the same way that Air + Soil + Water would be missing the point on an astronomy exam.
- ErrantX 16y ago> As to precision it's more accurate to say 3 +/- 0.5 times 101 +/- 0.5 = 256.25 to 355.25 or 305.75 +/- 49.5 than to just say 300. Ah, problem is you've changed the question now. Which is a reasonable thing to do when face with 3 + 101.5 = ?, but not the point the author was making (or, actually, it is the exact point the author is making) :)
- ErrantX 16y agoExcellent. After the first line I deliberately closed my eyes and tried to re-reason it (and got it right, thankfully). It was quite refreshing to have a blog post make you actually stop and really think for a second. The point was good as well. ;)
- radu_floricica 16y agoIt's the whole blog, not just the post :) Really worth bookmarking.
- ErrantX 16y agoDamn straight. I just finished reading one of his latest entries; acidic, critical and brilliant IMO. http://thelastpsychiatrist.com/2010/06/are_certain_behaviors--_and_jo.html http://thelastpsychiatrist.com/2010/06/are_certain_behaviors... EDIT: money quote: The science error of our generation is this: If A is strongly associated with B, and B is strongly associated with C, then A is strongly associated to C.
- superkarn 16y agoThe analogy at the end (section IV) made the whole article easier to "get". ...an answer cannot be more precise than its data. Or its question.
- JabavuAdams 16y agoExcept the example he gave was also wrong. 3 + 4.2 is 7.2, using exact arithmetic, which should be the default assumption. If you're measuring values under uncertainty, then his explanation makes some sense. But that's a property of measurement and uncertainty, not of numbers or arithmetic.
- djacobs 16y agoHear, hear. A voice of reason. This blog entry is the perfect example of where knowing a little information is dangerous.
- samatman 16y agoDefault assumption for whom? For a scientist, or someone working with real world data, this should never be the default assumption. Besides, in the paragraph with the arithmetic he explicitly talks about significant figures. In context, the answer is unambiguously 7 .
- djacobs 16y agoIt's 7.2. Without context (and he gives none for the expression) everyone (including me as a scientist) must assume abstract numbers. What's more, we know he's not using measurements because there are no units...
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- WilliamLP 16y agoDid anyone else think this was going to be about the Higgs boson?
- chaosmachine 16y agoFeynman knows: http://www.youtube.com/watch?v=N1pIYI5JQLE http://www.youtube.com/watch?v=N1pIYI5JQLE
- ckuehne 16y agoCan't upvote you enough for this. By the way, Feynman also knows the difference "between knowing the name of something and knowing something": http://www.youtube.com/watch?v=05WS0WN7zMQ http://www.youtube.com/watch?v=05WS0WN7zMQ
- jules 16y agoThis. He really articulates clearly the difference between two ways of thinking. Thinking by really understanding then translating the thoughts into words and thinking by manipulating words.
- scrod 16y agoWhile we're talking about Feynman, I think most people here could relate to his perspective on uninterrupted time, and the avoidance of administrative work: http://www.youtube.com/watch?v=Y08g3OXAA14&NR=1 http://www.youtube.com/watch?v=Y08g3OXAA14&NR=1
- ostso 16y agoMore Feynman on the same topic ("Energy makes it go"): http://physics.gu.se/~f3aamp/teaching/wakalix.html http://physics.gu.se/~f3aamp/teaching/wakalix.html
- joubert 16y agoThe difference between knowing the name for something and knowing something, is probably most clearly elucidated when you ask someone who believes in a deity, what it is. The answer is invariably contains contradictory, unreconcilable aspects.
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- dtf 16y ago
- JshWright 16y agoAn interesting topic, but I couldn't get more than a few paragraphs in. It's really poorly written. EDIT "couldn't" (I suppose if I'm going to gripe about grammar, I should at least proof read...)
- drats 16y agoI stopped reading at "Whatever you just said, it's wrong" as it was evident from there that it was the usual HN hyperbole article. Not to say HN is dominated by such articles, but their number has been steadily growing and one is already too much.
- wrs 16y agoThe concept of uncertainty is hard to grasp. In my high school (1979) we were required to use slide rules for the first year of science class, despite the availability of inexpensive calculators. The reason was to impress upon us the importance of significant figures, and also to develop our intuition for orders of magnitude. Unless your slide rule is really expensive, you just can't get more than 3 significant figures from it, which is a good match to the accuracy of just about every measurement in high school. It also tells you the figures without the magnitude--you have to determine in your head whether you just calculated microns or kilometers.
- djacobs 16y agoAs far as I know, most of the CO2 in plants goes to respiration for energy production. Not saying it doesn't go to mass, as well, but it's the energy side of things that people learn in elementary school. We're not stupid, and this man needs to think about his accusations before he blogs about them...
- ErrantX 16y agoIn defence I don't read his points as being "you're stupid" but more about the fact that we don't think about what we are talking about. The Ask question... wrong! thing strikes me as simply a device to make this point.
- djacobs 16y agoI don't think his premise is true. He says we were all taught photosynthesis in elementary and high schools and now all we know is a phrase that has no meaning for us. In fact, no one teaches the whole story of anything in biology before college, and not everyone takes college bio. Those of us that did knew the answer. It's a question of how far into biology you've studied...
- InclinedPlane 16y agoAre you aware that cellulose is just interlinked glucose molecules? A tree is basically a giant hunk of hydrated sugar byproducts with some minor mineral and other components.
- djacobs 16y agoYes, very. I could tell you all about the glycosidic linkages. Some observations: Polysaccharides are not sugars. Mono- and di-saccharides made of carbohydrates are. Glucose has other uses than becoming cellulose or starch or glycogen. The life cycle of a plant is not linear or simplistic. CO2 is not only used as a substrate in anabolism.
- ars 16y agoAnd what does a tree do with this energy? It's not a light bulb. It uses the energy to split the oxygen off of the CO2, splits the oxygen of off water, and makes hydrocarbons from the C in CO2 and the H in water. The oxygen is released as waste (a small amount is used). So all the energy used in a tree is devoted to making its mass.
- jules 16y agoI asked this question to my brother who is in high school and he got it right without me steering: CO2, water and a little bit from the ground. Education works :)
- DarrenMills 16y agoI agree with the ultimate point in this article, but the way he got there seemed to be rather jumpy. I also had a hard time following his train of thought. I will say that the way the article ended was excellent.
- Tichy 16y agostupid mode Opens up more questions than it answers. It seems when trees die, they become earth or even oil. How come they don't completely dissolve into air again? And if they don't completely dissolve into air, how come all the CO2 is not bound in the earth yet (trees pluck it out of the air, then die and bind it to the ground)? There would have to be bacteria or something that converts soil into air (CO2), but then, why don't they dissolve everything?
- gxti 16y agoTrees do dissolve. Forest fires are the most elegant way -- the reaction liberates much of the carbon and all of the oxygen into gasses including CO2, and the cycle is complete. Bacteria that break down the rotting remains of a dead tree also consume the energy stored in the cellulose and release gasses like carbon dioxide and methane. At some point the remains don't contain bonds with easily freed energy and you have regular old dirt. If they had a way to break down the dirt further they would, but the cost is too high.
- todayiamme 16y agoAn interesting thing here is that this article assumes that the way science is taught is wrong. I do not intend to make any conclusions about this, but I just graduated from high school and I just realized why people don't learn science as opposed to a bunch of meaningless phrases. Although a lot of it is a broken system, but the truth is that they aren't expected to. What is expected of them is to get good grades, and since that is possible through rote almost all of my peers take that route. If you ask them in a moment of honesty they say; "why should I do it? I'll just get the grades get into a good college a good job... Why should I waste my time learning this?". I used to gripe about the system whenever I heard that reply and why they just didn't get it, but now I realize that they are simply reflecting society in general. Most parents quite frankly don't care that they know science or anything as long as they get good grades. Most teachers hardly give a damn about teaching and they aren't even remotely interested in science. Most employers upon employment cannot check and do not look at how much the individual understands anything. They just ask for a degree from a reputable institute. I admit that it is harder to change the mindset of a population, but this is something that has to be done. Changing the school system and bringing out new books will have limiting impact unless the foundations of this problem (societies attitude toward learning) aren't addressed.
- splat 16y agoAnd here in the animal kingdom, when you exercise and lose thirty pounds, much of that weight is breathed out.
- cellis 16y agoI got the water part without even thinking, and photosynthesis danced in my head as an answer, but carbon didn't even cross my mind.
- electromagnetic 16y agoThe article started by pointing out a logical incongruency that most people have. I know better than to think the tree is made of the ground, however I know many people are not. However he's talking mass and reneges on his statement that trees are made from the air by stating that many trees are over 50% water. Well IMO when talking about mass the majority-share counts as the subjects mass origins. The plant breaks down CO2 into C + O2 via photosynthesis. The C makes up the plant. This is the simplified version he starts with, which was an ample metaphor. However then he states that the tree can be predominantly water. Meaning the plant is made up of say 60% water and 40% carbon. However the plant is made up of predominantly of water trapped within cellulose membranes. If we talk dry weight, we're still talking 6 carbon atoms (72), 10 hydrogen atoms (10) and 5 oxygen atoms (80). This means roughly 66% of the trees mass comes directly from water from the ground sequestered in its cellulose. This means roughly only 20% of the tree actually comes directly from carbon sequestered from the air. So really, where does the plant get its mass? The ground. If you're asking where the plant gets its dry weight, still the ground by ~6%. By tackling a logical fallacy with scientific thinking he opened the window to be completely corrected by it himself. Trees grow because they take the carbon out of the air. However you talk about mass and we're talking about molecular weights. Now if he'd have been as smart of Feynman he would have dismissed the water quite logically again. The rain falls from the sky. Save for a few very large trees that actually reach into the water table, trees well inland rely solely on the rain for their supply of water. That means the 50% of its mass that is water still technically comes from the air from moisture being condensed in cold air and forming water droplets.
- pbhjpbhj 16y ago>The rain falls from the sky. Save for a few very large trees that actually reach into the water table, trees well inland rely solely on the rain for their supply of water. But they draw up that rain from the local soil using transpiration as I was explaining to my 4yo yesterday, I'm pretty sure he'll have forgotten it by now, I digress. What I'm not sure about is rainwater capture - do shrubs capture (internally) water higher up the plant (eg in at limb connections) or are leaves simply directing the water to fall close to the "trunk" to maximise root take-up. It's a good catch though as I'm sure I'd fall to the leap from knowing that "trees grow by taking in CO2 and that is where they get their mass of carbon from" to the false assumption that "tree mass comes primarily from the air" without really thinking about it. Thanks for your analysis.
- millettjon 16y agoI had this same though recently after thinking about how much shrub/tree/grass growth I have pruned out of my yard over the last 4 years ;-). Keeping a compost pile of all trimmings keeps this in perspective. Conversely, the amount of mass left after you burn wood is quite minimal. There was a nice scene about that topic in the move "Smoke". Screenplay dialog here: http://www.script-o-rama.com/movie_scripts/s/smoke-script-transcript-paul-auster.html http://www.script-o-rama.com/movie_scripts/s/smoke-script-tr...
- frankus 16y agoThree vaguely related observations: 1. When we lose weight due to eating right and/or exercising (excluding water weight), it's because the air that we breathe out is slightly heavier than the air that we breathe in. 2. When we're burning wood in a fireplace, the heat it gives off is essentially the sunlight that the tree has collected over its lifetime -- i.e. the heat difference between full sun and the shade of the tree. 3. A solar cell producing peak power is slightly colder than one that is either open- or short-circuited.
- pbhjpbhj 16y agoYou'll have to give me some citations for 1. A priori it seems sensible ...
- a-priori 16y agoRe #1: You're ignoring metabolic byproducts that are excreted in urine or feces or sweat. Are there any byproducts that are released in the breath?
- frankus 16y agoI should have qualified that by saying it's true to roughly the same degree as the claim that a tree's mass comes from the air. I.e. if you wave your hands and ignore a lot of potentially-important second-order effects, it more or less holds water :).
- TheLastPsych 16y agoAs the author of the article, I thought I'd add my observation about the comments here. The point of my post was twofold. First, an observation about what we think we know. When you say, "tiananmen square massacre" to people, most have a basic understanding of what happened, EXCEPT that the single image they have associated with it is the one of the student in front of the tank. That incident happened, of course, but it was the image selected to "teach" you about that incident, and that's what stuck. 1) This allows you to think you know something (one image), thought you don't know really anything (what was the point of the whole thing?) 2) you know only what someone else decided to tell you. If they had chosen to show you a pic of a student dropping a hand grenade in a tank, well, there you go. Second, the most pointed criticisms on this board come from scientists (e.g. electromagnetic). This is because you're not relying on words, you're actually trying to understand the process. Some will do it better than others, fine; but my point was that most people are not taught that that process is important, they are taught only to "know" things. In college I knew a guy who could identify a lot (30?) dinosaurs. By name. Is he an expert? Everyone thought he was. Point: when I asked him what the modern descendant of the triceratops was, he said it was a rhino. And no one disagreed with him, even after I pointed out that triceratops laid eggs and rhinos don't. He didn't know that, but even once he knew it it did not change his thinking; he was taught to think in terms of names and appearances, and he applied himself accordingly. (I write that story up, in case anyone cares.) That he thought he was an expert is fine; that he didn't know dinos laid eggs is also fine, but it is of importance to understand the divergence between egg layers and mammals. That's where most people fail, and that's entirely the fault of the way we learn: the news. It's not school-- we barely remember much. But watch a segment on the news, and you think you're informed, and then you extrapolate from that "information" entirely on the force of prejudices you've acquired from watching other news... Who thinks China is mean to students? Ask around. Then ask them why they think that. I hope it obvious that had the desire of the news media been to tell you that the Chines govt. was nice to them... I'm probably preaching to the choir here, but let me spin it around. While I'm guessing most of you are technically oriented, how many would bristle if, after a catastrophe, the government refused to send in crisis counselors and mental health support people to the site? It's not been shown to be effective, and could be counterproductive. But your intuition might suggest to you that it should be done, and so the govt. is left defending itself. Or perhaps you have a strong opinion on what Paulson should have done with AIG. Or whatever-- there is some field out of your expertise where you abandon your logical and scientific mind, in favor of prejudice and presumption in the form of empty words. And you don't know it. The criticism that I am a poor writer is a common one. I know, I know. I hope I made my point here (and perhaps enticed some readers?) without offending anyone, which is something I try very hard not to do. Cheers.
- ashutoshm 16y agoreminds me of Minds of Our Own http://www.learner.org/resources/series26.html http://www.learner.org/resources/series26.html