Comments on: They do it because they can.

They do it because they can.

klausman — Wed, 31 Oct 2012 12:08:44 -0800

Trees are Freaking Awesome! (SLYT)

By: mannequito

mannequito — Wed, 31 Oct 2012 12:17:07 -0800

15 Negative Atmospheres!?

By: Sys Rq

Sys Rq — Wed, 31 Oct 2012 12:19:15 -0800

Amazingly inefficient.

By: echo target

echo target — Wed, 31 Oct 2012 12:25:16 -0800

"Efficient" doesn't mean anything by itself. You can't say how efficient something is until you say what output you're trying to get and what input you're trying to minimize. The system here isn't efficient in its use of input water for the output of getting water to the upper branches, but it's extremely efficient in its use of the tree's energy, which is much more important for the tree to conserve.

By: blue_beetle

blue_beetle — Wed, 31 Oct 2012 12:29:19 -0800

"If trees could scream, would we be so cavalier about cutting them down? We might, if they screamed all the time, for no good reason." (via)

By: feral_goldfish

feral_goldfish — Wed, 31 Oct 2012 12:35:57 -0800

Also awesome: puzzles, hypotheses, and natural facts that run contrary to my previously held common sense. Thank you, klausman & MetaFilter!

By: Ad hominem

Ad hominem — Wed, 31 Oct 2012 12:39:02 -0800

But really, it isn't like trees decided to to this cuz they wanted to be tall. This was simply a physical property of liquids that allowed trees to grow over 10 meters. Those trees got more sunlight and overshadowed the short trees, killing them. If it was impossible, or too inefficient those trees that somehow were the first to grow over 10 meters would have died.

By: netbros

netbros — Wed, 31 Oct 2012 12:46:09 -0800

Also from the cool folks a Veritasium: Where Do Trees Come From?

By: Philosopher Dirtbike

Philosopher Dirtbike — Wed, 31 Oct 2012 12:55:36 -0800

Fun fact: Because the earth is round, trees aren't really *tall*, they're long. Consider this: There are trees on the other side of the earth, going the OTHER DIRECTION! That's like, negative height! Get it RIGHT, science people!

By: weapons-grade pandemonium

weapons-grade pandemonium — Wed, 31 Oct 2012 13:02:31 -0800

And planes don't really *fly*, they sashay.

By: jamjam

jamjam — Wed, 31 Oct 2012 13:12:46 -0800

Fun fact: Because the earth is round, trees aren't really *tall*, they're long. Didn't Sally teach you anything?

By: klausman

klausman — Wed, 31 Oct 2012 13:15:35 -0800

Thank you, klausman & MetaFilter! It's what we do.

By: bicyclefish

bicyclefish — Wed, 31 Oct 2012 13:46:40 -0800

With negative pressures like that, I'm amazed that lumberjacks aren't blown away by implosions.

By: klausman

klausman — Wed, 31 Oct 2012 13:56:48 -0800

Giraffes use a rete mirabile to regulate the blood pressure in their heads when they put their heads down to drink. I was expecting something along those lines, but I forgot that trees don't have to do that.

By: Foam Pants

Foam Pants — Wed, 31 Oct 2012 14:00:08 -0800

Leave it to a Canadian to make his thank you portion almost as long as the actual video. The sequel to this video contains 10 minutes of apologies.

By: Benny Andajetz

Benny Andajetz — Wed, 31 Oct 2012 14:13:22 -0800

Does efficiency really matter if there's no other way to do it?

By: Popular Ethics

Popular Ethics — Wed, 31 Oct 2012 15:34:07 -0800

Does efficiency really matter if there's no other way to do it? There is. Same way we do it - using muscular vessels and peristalsis. Compared to that, this evaporating thing is way more efficient. In fact, I wonder how much power the moving column of water is generating... :)

By: benito.strauss

benito.strauss — Wed, 31 Oct 2012 15:52:45 -0800

My take away is that I do not understand what pressure means when it's not referring to a gas. Time for some Wikipedia.

By: hal9k

hal9k — Wed, 31 Oct 2012 16:30:15 -0800

Dude splains to you what sucks. And well.

By: Benny Andajetz

Benny Andajetz — Wed, 31 Oct 2012 16:32:35 -0800

There is. Same way we do it - using muscular vessels and peristalsis. But trees can't do that.

By: Popular Ethics

Popular Ethics — Wed, 31 Oct 2012 17:14:14 -0800

But trees can't do that. That's begging the question. Trees draw water by transpiration because that's what trees do. In an alternate universe where the mechanism didn't work as well as it does here, trees might have evolved muscles. They might not have grown very tall though, as muscles take a comparatively huge amount of energy.

By: LEGO Damashii

LEGO Damashii — Wed, 31 Oct 2012 17:58:31 -0800

The Veritasium video about where trees come from is cool, but feels long. Richard Feyneman also explained where trees come from, or rather where the matter comes from. I like his version better, but YMMV. ( tl;dw: They're made of air ! ) Also on the Feyneman video, where the energy from burning wood comes from. Wow. And now I also learn that trees defeat the 10m rule through a crazy physics loophole? Mind = Blown.

By: Malor

Malor — Wed, 31 Oct 2012 18:33:20 -0800

I kinda figured it out on my own, from real-life experience: our water well, when I was a kid. I don't know how he did it, but somehow, my father managed to lose the prime in the well. IIRC, it was 90 feet deep. This meant that the motor could spin until it broke, but there wasn't going to be any water coming up. So he ended up using a bucket, and making trip after trip after trip from the hot water heater (in the garage) to the well (out in the, um, I guess you could call it the front yard; it was somewhat rural.) It took him a long time, many many trips. I should have offered to help, but I was really young, and it didn't occur to me. With no water in the pipe, the well wouldn't work, but fill the pipe up completely, and it would pull up all the water you wanted. Trees are like that; they simply start filled, and then never lose 'priming', so they can drag water up to great heights, just like our well could pull water 90 feet straight up. If air bubbles were somehow to ever get into their 'pipes', they would stop working, and the tree would die. Interesting, though, that the actual energy to pull the water up that far comes from the transpiration into the air. That, I did not know. I'd never really thought about it -- that's a huge amount of energy. There's no way a tree would have enough chemical energy to do that much work; even highly efficient mammals intensely dislike using their muscles to haul water up thirty flights of stairs. And we live on highly concentrated energy sources. Living on just sunlight and CO2, I don't think that would even be possible. So, ultimately, this means that trees are more or less passive; they grow around their own piping, and only a small amount of the water that piping carries is directly beneficial to them. 95% of the water flow exists to carry the remaining 5%. Yes, it's 'wasteful' of water, but trees are part of an ecosystem, and the water returns as rain, so it's only a problem from the standpoint of humans, which are highly dependent on fresh water, and running out of new supplies.

By: Mei's lost sandal

Mei's lost sandal — Wed, 31 Oct 2012 20:17:03 -0800

You know, there are people, most people in fact, who will have lived their entire lives without the joy of hearing Richard Feynman speak. How is this state of things possible? Why am I so lucky?

By: five fresh fish

five fresh fish — Wed, 31 Oct 2012 20:25:50 -0800

So, ultimately, this means that trees are more or less passive; they grow around their own piping ...which leads me to odd thoughts about my gut tract.

By: JackFlash

JackFlash — Wed, 31 Oct 2012 21:04:56 -0800

Malor, that isn't the way a water well works. A suction well pump can only draw water from a maximum of 30 feet. I suspect that you misremember the depth of the well since you were young. In that case, it really is air pressure that is pushing the water up the pipe. You have to prime the pump to remove the air from the pipe so that the pump can work. The well has a foot valve at the bottom to keep the pump from losing its prime when the pump is off, but the valve can leak requiring re-priming. But it is impossible to "pull" water up from 90 feet in a well. For a well deeper than 30 feet you need a pump at the bottom of the well that can push water up and out. This can be either a submersible pump or a jet pump at the bottom of the well.

By: Malor

Malor — Thu, 01 Nov 2012 07:25:46 -0800

Well, all I can do is repeat what my father told me. He said that it was 90 feet, much deeper than the 30 feet that most folks had in the area. He said that was why we still had water when they were running out. (the local aquifer was being depleted, I guess.) But he never mentioned a subterranean pump. It's pretty clear from this post alone that you do not need a motor, even at the bottom of a 300 foot well, if you can exert enough pressure on a solid column of water.

By: JackFlash

JackFlash — Thu, 01 Nov 2012 09:06:12 -0800

If it was deeper than 30 feet and the motor was at the top, you may have had a jet pump. This type of well has a double pipe. The motor and pump pushes high pressure water down the well through one pipe to the jet at the bottom. The jet at the bottom has a venturi that entrains and pushes water back up the low pressure pipe. In this case you are pushing water up from the bottom using the jet, not sucking it from the top. This is not like the tree case which pulls from the top. The advantage is that the pump can be at the surface. However, jet pumps for deep wells are pretty inefficient. The pump needs to circulate about 5 times the water to the jet as you get out for use. And the system needs to be primed with water because it is the high pressure water pushed down the pipe that pushes well water up the other pipe. Today most deep wells use reliable submersible pumps at the bottom that don't require priming.

By: Malor

Malor — Fri, 02 Nov 2012 02:27:45 -0800

Well, you gotta realize it's been more than twenty-five years since I last saw it, but I _think_ that pump did have two pipes on it, one big one, and one little one. And it did manage to lose its priming, and my father had to refill the pipe for it to work again, and that took bloody forever. If I remember the sizes correctly, the big pipe was about 2, or maybe 2.5 inches in diameter. At 90 feet deep, that's a lot of water to fill it up again. So maybe it was a push-pump, instead of a pull, and perhaps I misunderstood why priming it worked. But it did work.

By: Malor

Malor — Fri, 02 Nov 2012 02:29:09 -0800

(And the original well was, I believe, dug sometime in the early 70s.)