PILOT SPIN
Pilot Zone => Pilot Zone => Topic started by: Jaybird180 on March 05, 2016, 08:54:13 PM
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As water evaporates from the surface, it becomes part of the atmosphere and makes weather, the stuff we fly in.
What is the theoretical altitude limit of evaporation and why? Why doesn't water continue into space, escaping our planet?
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This is all about the water phase diagram:
(http://www.phy.duke.edu/~hsg/363/table-images/water-phase-diagram.gif)
You see that liquid water cannot really exist much below 1kPa, and below that critical pressure, water will go from ice to vapour directly without passing through a liquid state.
Clouds result from condensation of water into liquid form...or some are ice as well, but most "weather" type clouds are liquid water, and once the atmospheric pressure drops below the point where liquid water can exist, no more weather clouds.
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I have found the worst haze layers broke around 8000 feet.
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Why first water continue into space, escaping our planet?
That's a bit more complex question.
You will find that the amount of H2 or He in the atmosphere is incredibly low. That's due, in large part, to thermodynamics. As temperature increases, so does the velocity of gas molecules. Very light items (like H2 or He) have sufficient velocity to reach escape velocity, so they'll bump around the lower atmosphere for a bit, but once they get into the thinner reaches with fewer collisions, they will simply escape, just like anything else accelerated to escape velocity.
Water vapour, on the other hand, is too heavy to reach those velocities, so it remains confined around the earth.
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Sorry for the bad auto incorrect late lastnight. Thanks for the chart Jeff. Help me understand it please.
It doesn't provide a max as I understand per se. I understand that liquid water cannot remain liquid above a certain pressure but gaseous state H2O? What about a few particles (atoms) escaping our spheres? You're saying they're still too heavy? At what altitude does this occur?
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Sorry for the bad auto incorrect late lastnight. Thanks for the chart Jeff. Help me understand it please.
It doesn't provide a max as I understand per se. I understand that liquid water cannot remain liquid above a certain pressure but gaseous state H2O? What about a few particles (atoms) escaping our spheres? You're saying they're still too heavy? At what altitude does this occur?
It's actually that water cannot remain liquid BELOW a certain pressure. If you put room temp water in a vacuum chamber, you can make it boil at room temperature pretty easily.
In terms of escape, water doesn't really escape. The velocity of molecules in a gas are dependent upon their mass and the temperature. At "Earth" temperatures, water molecules are too heavy to achieve escape velocity, so they will remain bound to Earth's gravity.
My rough math at 0*C (273 K), gives the following:
O2 = 461.3 m/s
N2 = 493 m/s
H2 = 1,845 m/s
He = 1,304 m/s
H2O = 615 m/s
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It's actually that water cannot remain liquid BELOW a certain pressure. If you put room temp water in a vacuum chamber, you can make it boil at room temperature pretty easily.
Which is why water boils at a lower temp in Denver than it does in Death Valley.
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Which is why water boils at a lower temp in Denver than it does in Death Valley.
So those folks in Denver get their pasta a bit quicker than us flatlanders. I would seem my altitude envy has no end....
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So those folks in Denver get their pasta a bit quicker than us flatlanders. I would seem my altitude envy has no end....
It's a double-edged sword.
Yes, the water boils faster at higher altitude, but there is less overall thermodynamic energy contained in the boiling water. That's why steam engines and such always keep the water under pressure. The higher the temperature, the more energy it contains. Boiling at a lower temperature is not useful.
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So those folks in Denver get their pasta a bit quicker than us flatlanders. I would seem my altitude envy has no end....
Well, no. Food is "done" based on temperature and time. If the boiling water is at a lower temperature, it will take more time for the same level of doneness. Try it will hard-boiled eggs.
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Well, no. Food is "done" based on temperature and time. If the boiling water is at a lower temperature, it will take more time for the same level of doneness. Try it will hard-boiled eggs.
aaahhhh... if water takes longer to boil because it boils at a lower temp at altitude, wouldn't that mean the pasta would be placed in the "boiling" water at a earlier time, which means it would be earlier when "done"? People generally don't place pasta in water at a temperature, they start the cooking process at the time water boils. What am I missing?
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aaahhhh... if water takes longer to boil because it boils at a lower temp at altitude, wouldn't that mean the pasta would be placed in the "boiling" water at a earlier time, which means it would be earlier when "done"? People generally don't place pasta in water at a temperature, they start the cooking process at the time water boils. What am I missing?
Given the same amount of heat (burner level), the water doesn't take a longer time to boil. It boils faster, because it boils at a lower temperature. The food takes a longer time to cook to the same level because the temperature is lower.
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aaahhhh... if water takes longer to boil because it boils at a lower temp at altitude, wouldn't that mean the pasta would be placed in the "boiling" water at a earlier time, which means it would be earlier when "done"? People generally don't place pasta in water at a temperature, they start the cooking process at the time water boils. What am I missing?
Actually, placing pasta in the water when boiling IS placing it in at a temperature.
Boiling water will not heat further. All of the energy being pumped into the system is dissipated by the act of boiling.
A sea level with standard atmosphere for example, boiling water is 212 degrees, whether it just started boiling or has been boiling for 5 minutes. Similarly, ice water (ie water that still contains ice) will stabilize at 32 degrees and remain there until either the ice melts and the temperature can rise, or the water freezes completely and the ice can get colder.
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Given the same amount of heat (burner level), the water doesn't take a longer time to boil. It boils faster, because it boils at a lower temperature. The food takes a longer time to cook to the same level because the temperature is lower.
I stand corrected and take back my quip.
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Jeff- what does the rough math represent?
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So, what's the highest altitude above the earth water molecules can go?
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Jeff- what does the rough math represent?
Particles in a gas move at an average velocity that is dependent upon the temperature of the gas and inversely related to the mass of the molecules.
Here's the formula:
(https://upload.wikimedia.org/math/e/3/8/e3824335b373aba9ea8b4cb7c9ebf9fc.png)
v is the average velocity of the molecules in the gas
T is the thermodynamic tempurature (ie measured from absolute zero, either Kelvin or Rankin)
m is the molar mass of the molecules...so O2 is ~ 32g/mol while water is ~18g/mol (16 for the O, 1 each for the H)
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So, what's the highest altitude above the earth water molecules can go?
That's the objective of the OP. I think we got sidetracked with learning how to fish.
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That's a bit more complex question.
You will find that the amount of H2 or He in the atmosphere is incredibly low. That's due, in large part, to thermodynamics. As temperature increases, so does the velocity of gas molecules. Very light items (like H2 or He) have sufficient velocity to reach escape velocity, so they'll bump around the lower atmosphere for a bit, but once they get into the thinner reaches with fewer collisions, they will simply escape, just like anything else accelerated to escape velocity.
Water vapour, on the other hand, is too heavy to reach those velocities, so it remains confined around the earth.
Say what? What force accelerates H or HE molecules to 25000 mph?
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Say what? What force accelerates H or HE molecules to 25000 mph?
Heat.
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Heat.
Sorry, not buying it.
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Sorry, not buying it.
This is basic thermodynamics.
http://ocw.mit.edu/courses/chemistry/5-60-thermodynamics-kinetics-spring-2008/
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Heat.
don't forget collision in the upper atmosphere (between water molecules and solar wind)
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Well, no. Food is "done" based on temperature and time. If the boiling water is at a lower temperature, it will take more time for the same level of doneness. Try it will hard-boiled eggs.
Actually, time has nothing to do with food being "done". It is based on temperature alone. I've heard my chef wife explain this for many semesters in a culinary class she teaches at the local JUCO.
Carry on...
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Actually, time has nothing to do with food being "done". It is based on temperature alone. I've heard my chef wife explain this for many semesters in a culinary class she teaches at the local JUCO.
Carry on...
That may quite well be true, but it takes more time for an egg to be done in boiling water that is 200 degrees than it does when the boiling water is 212.
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That may quite well be true, but it takes more time for an egg to be done in boiling water that is 200 degrees than it does when the boiling water is 212.
And that loops us back to Thermodynamics yet again and the properties of heat transfer!
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Actually, time has nothing to do with food being "done". It is based on temperature alone. I've heard my chef wife explain this for many semesters in a culinary class she teaches at the local JUCO.
Carry on...
Instant done is called charbroiled.
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It's actually that water cannot remain liquid BELOW a certain pressure. If you put room temp water in a vacuum chamber, you can make it boil at room temperature pretty easily.
In terms of escape, water doesn't really escape. The velocity of molecules in a gas are dependent upon their mass and the temperature. At "Earth" temperatures, water molecules are too heavy to achieve escape velocity, so they will remain bound to Earth's gravity.
My rough math at 0*C (273 K), gives the following:
O2 = 461.3 m/s
N2 = 493 m/s
H2 = 1,845 m/s
He = 1,304 m/s
H2O = 615 m/s
Okay, so the water moving at 22,140kph doesn't reach the required escape velocity (https://en.wikipedia.org/wiki/Escape_velocity)of 40,270kph to leave. So I guess it just bumps around until it gets heavy enough to return. to the surface. So that answers the question as to why it doesn't leave the Earth but doesn't give us the maximum altitude it can reach. Certainly we know that water can get colder than 0C.
(http://www.wou.edu/las/physci/poston/everest/CameraandFilm_files/image011.jpg)
Since it looks like H2O can exist at extremely low pressures, there is no theoretical floor (max altitude), which brings me back to the question of how high can it go: 5 miles, 6 miles, 7 miles up?
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If you don't care about the state (ie liquid, solid or gaseous), there is no maximum altitude. The ISS probably bumps into a few water molecules from time to time.
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If you don't care about the state (ie liquid, solid or gaseous), there is no maximum altitude. The ISS probably bumps into a few water molecules from time to time.
I can accept this answer considering when parts of a comet in space breaks off the ice (solid water) sublimates into gaseous form.
So we have all this water traveling around the universe. Perhaps it will coalesce into a space cloud ;)
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One theory of where the Earth got it's water is from bombardment by comets.
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I can accept this answer considering when parts of a comet in space breaks off the ice (solid water) sublimates into gaseous form.
So we have all this water traveling around the universe. Perhaps it will coalesce into a space cloud ;)
You can detect H2O spectra from many nebulae
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One theory of where the Earth got it's water is from bombardment by comets.
Where did the comets get their water?
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Why doesn't water continue into space, escaping our planet?
Because gravity.
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Because gravity.
Yes, but the answer is more involved. Gravity is M1*M1/D^2, so if gravity were the simple answer it would never leave the surface and we wouldn't have clouds and no IMC and no weather.
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Which brings me this question:
Where does the lifting force come from that allows us to have clouds at altitude? Why don't we just have ground fog?
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Where did the comets get their water?
From the combination of Hydrogen and Oxygen.
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If you don't care about the state (ie liquid, solid or gaseous), there is no maximum altitude. The ISS probably bumps into a few water molecules from time to time.
Hold a second! If the water cannot reach esscape velocity there is a point of equilibrium where it will remain in low Earth orbit (?) or at some point in the troposphere. Again bringing us back to the original question: what is the maximum altitude of the evaporated water?
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Which brings me this question:
Where does the lifting force come from that allows us to have clouds at altitude? Why don't we just have ground fog?
What happens when warm air encounters cold air?
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What happens when warm air encounters cold air?
A heat transfer will occur and they will eventually reach thermodynamic equilibrium.
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A heat transfer will occur and they will eventually reach thermodynamic equilibrium.
nothing else happens?
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Which brings me this question:
Where does the lifting force come from that allows us to have clouds at altitude?
From the sun, either directly or indirectly.
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From the sun, either directly or indirectly.
Okay, thanks for helping me flesh that out. Heat causes things to move.
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I still don't know the maximum altitude of water. Are we at the end of the road on this?
I tried to see if the orbital distance would be, but I ran into a problem with one too many unknowns to plug into the formula.
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I still don't know the maximum altitude of water. Are we at the end of the road on this?
I tried to see if the orbital distance would be, but I ran into a problem with one too many unknowns to plug into the formula.
one way to look at it: Do you think there is any limit to how fast a molecule of H20 can go? More specifically, why would you think a water molecule can't go faster than ~25,000 mph relative to the earth? (let's ignore relativistic speeds)
Of course, there is also the question of how long a water molecule would remain intact in the near vacuum of space - something will eventually hit and break apart the molecule.
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one way to look at it: Do you think there is any limit to how fast a molecule of H20 can go? More specifically, why would you think a water molecule can't go faster than ~25,000 mph relative to the earth? (let's ignore relativistic speeds)
Of course, there is also the question of how long a water molecule would remain intact in the near vacuum of space - something will eventually hit and break apart the molecule.
Well, we can see on the face of it this can't be true otherwise we'd lose all the water on the planet.
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Well, we can see on the face of it this can't be true otherwise we'd lose all the water on the planet.
ah, you are assuming that if water molecules can get into space means they must.
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ah, you are assuming that if water molecules can get into space means they must.
The planet is slowing down on its axial rotation, the Sun's hydrogen fuel is depleting; I get it. But certainly if water can escape it would have done so by now. Are you disputing that water can reach escape velocity as cited a few pages back?
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What natural phenomena can accelerate H2O to 25000 MPH?
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The planet is slowing down on its axial rotation, the Sun's hydrogen fuel is depleting; I get it. But certainly if water can escape it would have done so by now. Are you disputing that water can reach escape velocity as cited a few pages back?
nope. not disputing it.
But you seem to be forgetting to consider net rates of loss/absorbtion. With a low enough net loss rate, the earth's water could last until the sun goes nova
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What natural phenomena can accelerate H2O to 25000 MPH?
Eating ice cream when you're lactose intolerant?
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nope. not disputing it.
But you seem to be forgetting to consider net rates of loss/absorbtion. With a low enough net loss rate, the earth's water could last until the sun goes nova
(http://static.safehaven.com/authors/hook/11397_a.png)
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In my quest for an answer, I reached out to Scott Dennstaedt and we spoke about this for a few minutes. He says that the answer would involve a specialty that he doesn't get much into but did provide a few nuggets for me to chew on and investigate.
He said that most of the moisture is contained in the troposphere (check) and that about 99% of it remains below 40,000 feet. He says that convective activity can take water upwards of 65-70,000feet where the moisture in the form of ice crystals can linger for weeks or months until it settles, reaching for hydrostatic balance.
And I learned that Helium is finite on the earth :o
I'm still digging
(http://cache3.asset-cache.net/gc/165807854-digging-hole-gettyimages.jpg?v=1&c=IWSAsset&k=2&d=wBwFnzbpO%2FbCx5fCJUMjaPqOZwLpTFUd8WvTELNM2ghXZYTs0OKIpgZV%2BwsoBEFl)