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Nick Thompson

atmospherics

So, somebody asked me, in my role as a weather nerd, how come the nitrogen in the atmosphere doesn’t all fall to the bottom on still nights and suffocate us all. I asked the question of stupid-answers-to-stupid-questions-asked-by-stupid-people.com and THEY said, well, there’s just too much going on. N molecules and the O molecules are just too busy, what with convection and windcurrents, and all, to separate, even on still nights. Now, that business doesn’t prevent cold molecules of Nitrogen and Oxygen to separate from warm ones, or wet ones (not sure what that means) to separate from dry ones. I was hoping that somebody on FRIAM could give some sort of a clue what kind of a mixture AIR is? It is suddenly seeming kinda special.

Nicholas S. Thompson

Emeritus Professor of Psychology and Biology

Clark University

http://home.earthlink.net/~nickthompson/naturaldesigns/

http://www.cusf.org

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

Pamela McCorduck

Re: atmospherics

<base href="x-msg://38/">Let's call it interesting questions it never occurred to me to ask, Nick.

Pamela

On Jun 12, 2012, at 10:44 AM, Nicholas Thompson wrote:

So, somebody asked me, in my role as a weather nerd, how come the nitrogen in the atmosphere doesn’t all fall to the bottom on still nights and suffocate us all. I asked the question of stupid-answers-to-stupid-questions-asked-by-stupid-people.com and THEY said, well, there’s just too much going on. N molecules and the O molecules are just too busy, what with convection and windcurrents, and all, to separate, even on still nights. Now, that business doesn’t prevent cold molecules of Nitrogen and Oxygen to separate from warm ones, or wet ones (not sure what that means) to separate from dry ones. I was hoping that somebody on FRIAM could give some sort of a clue what kind of a mixture AIR is? It is suddenly seeming kinda special.

Nicholas S. Thompson
Emeritus Professor of Psychology and Biology
Clark University
http://home.earthlink.net/~nickthompson/naturaldesigns/
http://www.cusf.org

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

"Summer afternoon - Summer afternoon... the two most beautiful words in the English language."

Henry James

Robert J. Cordingley

Re: atmospherics

In reply to this post by Nick Thompson

For a start the density of oxygen is higher than nitrogen. Secondly gravity is not strong enough to overcome the zipping around of the molecules of gas that naturally mix together due to thermal energy (temperature). It takes a lot of effort and processing to separate atmospheric gasses (see the price of liquid oxgen).

The top 5 components of dry air are nitrogen (78%), oxygen (21%), argon (0.9%), carbon dioxide (0.04%) and neon (0.002%). With tiny amounts of methane, krypton, hydrogen and nitrous oxide. Moist air has varying amounts of water vapor depending on the humidity (the same thing really).

Robert C

On 6/12/12 10:44 AM, Nicholas Thompson wrote:

So, somebody asked me, in my role as a weather nerd, how come the nitrogen in the atmosphere doesn’t all fall to the bottom on still nights and suffocate us all. I asked the question of stupid-answers-to-stupid-questions-asked-by-stupid-people.com and THEY said, well, there’s just too much going on. N molecules and the O molecules are just too busy, what with convection and windcurrents, and all, to separate, even on still nights. Now, that business doesn’t prevent cold molecules of Nitrogen and Oxygen to separate from warm ones, or wet ones (not sure what that means) to separate from dry ones. I was hoping that somebody on FRIAM could give some sort of a clue what kind of a mixture AIR is? It is suddenly seeming kinda special.

Nicholas S. Thompson

Emeritus Professor of Psychology and Biology

Clark University

http://home.earthlink.net/~nickthompson/naturaldesigns/

http://www.cusf.org
============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

Roger Critchlow-2

Re: atmospherics

In reply to this post by Nick Thompson

Nick --

N2 weighs 28 gm/mole, O2 weighs 32 gm/mole, Ar weighs 40 gm/mole, CO2 weighs 44 gm/mole, and H2O weighs 18 gm/mole.

Why would anyone expect the lighter components of a mixture to fall down more than the heavier ones? If anything, you'd expect the heavier ones to concentrate toward the bottom.

And why would anyone expect a mixture to spontaneously separate into pure components? That happens in real life like where?

As it happens, CO2 is the heaviest normal component and it does pool in confined spaces often enough that CO2 alarms are available in hardware stores. Propane, C3H8, weighs 44 gm/mole and is notorious for pooling in confined spaces and then exploding, often in the bilge of a boat and spectacularly.

-- rec --

On Tue, Jun 12, 2012 at 10:44 AM, Nicholas Thompson <[hidden email]> wrote:

So, somebody asked me, in my role as a weather nerd, how come the nitrogen in the atmosphere doesn’t all fall to the bottom on still nights and suffocate us all. I asked the question of stupid-answers-to-stupid-questions-asked-by-stupid-people.com and THEY said, well, there’s just too much going on. N molecules and the O molecules are just too busy, what with convection and windcurrents, and all, to separate, even on still nights. Now, that business doesn’t prevent cold molecules of Nitrogen and Oxygen to separate from warm ones, or wet ones (not sure what that means) to separate from dry ones. I was hoping that somebody on FRIAM could give some sort of a clue what kind of a mixture AIR is? It is suddenly seeming kinda special.

Nicholas S. Thompson
Emeritus Professor of Psychology and Biology

Clark University
http://home.earthlink.net/~nickthompson/naturaldesigns/

http://www.cusf.org

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

Douglas Roberts-2

Re: atmospherics

Let's not ignore temperature: my farts are a good 20 degrees F above ambient (at present), and tend to rise before mixing into the unfortunate nearby environs. And, just in case you were wondering what the composition of a fart was:

The major components of the flatus, which are odorless, by percentage are:^[4]

Nitrogen: 20–90%
Hydrogen: 0–50%
Carbon dioxide: 10–30%
Oxygen: 0–10%
Methane: 0–10%

4. ^ "Human Digestive System". Encyclopædia Britannica. Retrieved 2007-08-22.

--Doug

On Tue, Jun 12, 2012 at 12:33 PM, Roger Critchlow <[hidden email]> wrote:

Nick --

N2 weighs 28 gm/mole, O2 weighs 32 gm/mole, Ar weighs 40 gm/mole, CO2 weighs 44 gm/mole, and H2O weighs 18 gm/mole.

Why would anyone expect the lighter components of a mixture to fall down more than the heavier ones? If anything, you'd expect the heavier ones to concentrate toward the bottom.

And why would anyone expect a mixture to spontaneously separate into pure components? That happens in real life like where?

As it happens, CO2 is the heaviest normal component and it does pool in confined spaces often enough that CO2 alarms are available in hardware stores. Propane, C3H8, weighs 44 gm/mole and is notorious for pooling in confined spaces and then exploding, often in the bilge of a boat and spectacularly.

-- rec --

On Tue, Jun 12, 2012 at 10:44 AM, Nicholas Thompson <[hidden email]> wrote:

So, somebody asked me, in my role as a weather nerd, how come the nitrogen in the atmosphere doesn’t all fall to the bottom on still nights and suffocate us all. I asked the question of stupid-answers-to-stupid-questions-asked-by-stupid-people.com and THEY said, well, there’s just too much going on. N molecules and the O molecules are just too busy, what with convection and windcurrents, and all, to separate, even on still nights. Now, that business doesn’t prevent cold molecules of Nitrogen and Oxygen to separate from warm ones, or wet ones (not sure what that means) to separate from dry ones. I was hoping that somebody on FRIAM could give some sort of a clue what kind of a mixture AIR is? It is suddenly seeming kinda special.

Nicholas S. Thompson
Emeritus Professor of Psychology and Biology

Clark University
http://home.earthlink.net/~nickthompson/naturaldesigns/

http://www.cusf.org

Steve Smith

Re: atmospherics

ahh Doug... I *knew* we could count on you!

Let's not ignore temperature: my farts are a good 20 degrees F above ambient (at present), and tend to rise before mixing into the unfortunate nearby environs. And, just in case you were wondering what the composition of a fart was:

The major components of the flatus, which are odorless, by percentage are:^[4]

Nitrogen: 20–90%

Hydrogen: 0–50%

Carbon dioxide: 10–30%

Oxygen: 0–10%

Methane: 0–10%

4. ^ "Human Digestive System". Encyclopædia Britannica. Retrieved 2007-08-22.

While I still refuse to believe the myths about igniting one's own petard (by which extra lift is gained beyond the mere ejection at high velocity?) I'd never researched it this far but anecdotally assumed it was the "methane" presumed to be flammable, but if this "recipe for a petard" is accurate, it seems more likely to be the Hydrogen that one would get their "lift" from.

Your recent silence online lead me to believe you were already "putt-putting" your way toward Alaska on your yearly loop! Or are you posting from the road?

The only factoid in the Flatulence FAQ that really caught my eye was that NZ's GDP is so highly based in agriculture that they have a "Flat"ulence Tax to offset the Greenhouse gas emissions. And complementary to this, it was interesting to note that the majority of Bovine Methane emissions are NOT flatulence but rather exhalations and gastric belching (how many stomachs do they have again?)...

On the other hand, I do believe that methane production from cellulose by anaerobic bacteria is a big deal, and I'm a little surprised that the Bovine intestinal tract is not an obvious place for this to occur already?

I'm presuming that Hydrogen production is a byproduct of the very same bacterium? Or perhaps it is a different one. I suppose it is also possible that "biogas" production en vitro suffers from the difficulty of *containing* hydrogen and perhaps that direct, immediate use of "biogas" benefits from high H concentrations with the methane?

Too much to ponder on such a hot day!

Pull your own damned finger!
- Steve

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

Douglas Roberts-2

Re: atmospherics

Thanks, Steve, I just got back a couple of weeks ago: http://mc-california-trip-2012.blogspot.com/

Yes, I had a gas...

--Doug

On Tue, Jun 12, 2012 at 1:09 PM, Steve Smith <[hidden email]> wrote:

ahh Doug... I *knew* we could count on you!

Let's not ignore temperature: my farts are a good 20 degrees F above ambient (at present), and tend to rise before mixing into the unfortunate nearby environs. And, just in case you were wondering what the composition of a fart was:

The major components of the flatus, which are odorless, by percentage are:^[4]

Nitrogen: 20–90%

Hydrogen: 0–50%

Carbon dioxide: 10–30%

Oxygen: 0–10%

Methane: 0–10%

4. ^ "Human Digestive System". Encyclopædia Britannica. Retrieved 2007-08-22.

While I still refuse to believe the myths about igniting one's own petard (by which extra lift is gained beyond the mere ejection at high velocity?) I'd never researched it this far but anecdotally assumed it was the "methane" presumed to be flammable, but if this "recipe for a petard" is accurate, it seems more likely to be the Hydrogen that one would get their "lift" from.

Your recent silence online lead me to believe you were already "putt-putting" your way toward Alaska on your yearly loop! Or are you posting from the road?

The only factoid in the Flatulence FAQ that really caught my eye was that NZ's GDP is so highly based in agriculture that they have a "Flat"ulence Tax to offset the Greenhouse gas emissions. And complementary to this, it was interesting to note that the majority of Bovine Methane emissions are NOT flatulence but rather exhalations and gastric belching (how many stomachs do they have again?)...

On the other hand, I do believe that methane production from cellulose by anaerobic bacteria is a big deal, and I'm a little surprised that the Bovine intestinal tract is not an obvious place for this to occur already?

I'm presuming that Hydrogen production is a byproduct of the very same bacterium? Or perhaps it is a different one. I suppose it is also possible that "biogas" production en vitro suffers from the difficulty of *containing* hydrogen and perhaps that direct, immediate use of "biogas" benefits from high H concentrations with the methane?

Too much to ponder on such a hot day!

Pull your own damned finger!
- Steve

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

Bruce Sherwood

Re: atmospherics

In reply to this post by Roger Critchlow-2

A really spectacular (and somewhat dangerous) demo involves what I
would guess is the densest gas of all, uranium hexafloride, with a
mass of 352 gm/mole. Remember that at equal temperature and pressure a
mole of any gas whatsoever occupies a volume of 22.4 liters, so the
grams/mole is proportional to the grams/liter.

The demonstrator breathes in the UF6 and then talks with a very deep
voice, the opposite effect to breathing in helium and talking with a
very high voice. The explanation is that the vocal cavity dimensions
don't change, so resonant wavelengths don't change. The speed of sound
in a gas is similar to the average speed of molecules in the air,
which is v = sqrt(3kT/m), where m is the mass of one molecule, k is
Boltzmann's constant, and T is the absolute temperature. Therefore the
speed of sound is much higher in helium than in air, and much lower in
UF6 than in air. Since the speed of sound = wavelength/period =
wavelength*frequency, the frequency of a resonance in the voice cavity
is high in helium and low in UF6.

In the helium case, it's easy to get rid of the helium and replace it
with air because the helium has lower density than air. But to get rid
of the UF6 the demonstrator has to lean over or stand upside down to
spill the heavy gas out of the lungs. (Note: the radioactivity of
ordinary uranium, which is 99.3% U238, or of "depleted" uranium from
which the U235 has been removed, is quite low. U238 has a very long
half-life of 4.4 billion years, so the number of decays per second in
the UF6 is low. The danger in breathing in UF6 is from lack of oxygen,
not from radioactivity.)

In an atmosphere with approximately constant absolute temperature and
no convection, the density of a particular gas is proportional to e
raised to the power (-mgy/kT), where m is the mass of one molecule in
kilograms, g is 9.8 N/kg (gravitational field strength), y is the
height above the ground in meters, k is Boltzmann's constant in
joules/kelvin, and T is the absolute temperature in kelvins. For
oxygen, at a height y = 7920 meters (roughly the height of Mt.
Everest), (-mgy/kT) = 1, so the density is down by a factor of e to
the -1, which is 0.37. In other words, in this simplified model the
density of oxygen at the top of Everest is about one-third what it is
at sea level. (Note that some climbers have made it to the top
breathing only what air was available there.)

The corresponding "mean heights" for various gases in this model:

oxygen 7920 m
nitrogen 9050 m
CO2 5500 m
helium 63400 m (way above almost all of our atmosphere)
UF6 720 m

Note that the mean heights for oxygen and nitrogen aren't very
different, so one can expect mixing to destroy any significant
separation. On the other hand, one can expect helium to escape from
the Earth, and it does, and one can expect some significant pooling of
UF6 when you pour it out onto the floor.

Bruce

On Tue, Jun 12, 2012 at 12:33 PM, Roger Critchlow <[hidden email]> wrote:

> Nick --
>
> N2 weighs 28 gm/mole, O2 weighs 32 gm/mole, Ar weighs 40 gm/mole, CO2 weighs
> 44 gm/mole, and H2O weighs 18 gm/mole.
>
> Why would anyone expect the lighter components of a mixture to fall down
> more than the heavier ones? If anything, you'd expect the heavier ones to
> concentrate toward the bottom.
>
> And why would anyone expect a mixture to spontaneously separate into pure
> components? That happens in real life like where?
>
> As it happens, CO2 is the heaviest normal component and it does pool in
> confined spaces often enough that CO2 alarms are available in hardware
> stores. Propane, C3H8, weighs 44 gm/mole and is notorious for pooling in
> confined spaces and then exploding, often in the bilge of a boat and
> spectacularly.
>
> -- rec --
>
> On Tue, Jun 12, 2012 at 10:44 AM, Nicholas Thompson
> <[hidden email]> wrote:
>>
>> So, somebody asked me, in my role as a weather nerd, how come the nitrogen
>> in the atmosphere doesn’t all fall to the bottom on still nights and
>> suffocate us all. I asked the question of
>> stupid-answers-to-stupid-questions-asked-by-stupid-people.com and THEY said,
>> well, there’s just too much going on. N molecules and the O molecules are
>> just too busy, what with convection and windcurrents, and all, to separate,
>> even on still nights. Now, that business doesn’t prevent cold molecules of
>> Nitrogen and Oxygen to separate from warm ones, or wet ones (not sure what
>> that means) to separate from dry ones. I was hoping that somebody on FRIAM
>> could give some sort of a clue what kind of a mixture AIR is? It is
>> suddenly seeming kinda special.
>>
>>
>>
>>
>>
>>
>>
>> Nicholas S. Thompson
>>
>> Emeritus Professor of Psychology and Biology
>>
>> Clark University
>>
>> http://home.earthlink.net/~nickthompson/naturaldesigns/
>>
>> http://www.cusf.org
>>
>>
>>
>>
>>
>>
>> ============================================================
>> FRIAM Applied Complexity Group listserv
>> Meets Fridays 9a-11:30 at cafe at St. John's College
>> lectures, archives, unsubscribe, maps at http://www.friam.org
>
>
>
> ============================================================
> FRIAM Applied Complexity Group listserv
> Meets Fridays 9a-11:30 at cafe at St. John's College
> lectures, archives, unsubscribe, maps at http://www.friam.org

Steve Smith

Methanobrevibacter smithii was:Athmospherics

In reply to this post by Douglas Roberts-2

I hate following references to any encyclopaedia... even (especially?!) Wikipedia...

The rabbit hole to be found there is an infinite labyrinth (maze?) with bits of cheese to keep me going at every turn!

I learn something new everytime... Who knew Archaea? Really? I was still in school in 1977 when this distinction was made (apparently). I forgive myself for still thinking of "Kingdoms" rather than "Domains" but how did I miss this one? My daughter is a PhD in BioMedicine and we talk all the time! But she *is* a virologist and "her" viruses (HPV, West Nile, Dingue) prey on Eu not Pro Caryota!

And then there is the thing about converting both Hydrogen *and* CO2 to methane? I haven't tracked down (and really shouldn't I have other projects!) where the H2 and CO2 come from in digestion for Meth Smithii to refactor... and then *what* does the body do with methane in the gut (besides expel it one end or the other?)

Ok... back down the rabbit hole!

I'm presuming that Hydrogen production is a byproduct of the very same bacterium? Or perhaps it is a different one. I suppose it is also possible that "biogas" production en vitro suffers from the difficulty of *containing* hydrogen and perhaps that direct, immediate use of "biogas" benefits from high H concentrations with the methane?

Nick Thompson

Re: atmospherics

In reply to this post by Douglas Roberts-2

Sorry. Mixed up the weight of N and O. So my question should have been, Why don’t we wake up in a layer of oxygen on still nights?

Which brings us to your question about what would make me expect that a mixture would separate out into its lighter and heavier components. You tell me! Other things being equal, don’t heavier things tend to sink when mixed with lighter ones?

From: [hidden email] [mailto:[hidden email]] On Behalf Of Douglas Roberts
Sent: Tuesday, June 12, 2012 2:43 PM
To: The Friday Morning Applied Complexity Coffee Group
Subject: Re: [FRIAM] atmospherics

The major components of the flatus, which are odorless, by percentage are:^[4]

§ Nitrogen: 20–90%

§ Hydrogen: 0–50%

§ Carbon dioxide: 10–30%

§ Oxygen: 0–10%

§ Methane: 0–10%

4. ^ "Human Digestive System". Encyclopædia Britannica. Retrieved 2007-08-22.

--Doug

On Tue, Jun 12, 2012 at 12:33 PM, Roger Critchlow <[hidden email]> wrote:

Nick --

N2 weighs 28 gm/mole, O2 weighs 32 gm/mole, Ar weighs 40 gm/mole, CO2 weighs 44 gm/mole, and H2O weighs 18 gm/mole.

Why would anyone expect the lighter components of a mixture to fall down more than the heavier ones? If anything, you'd expect the heavier ones to concentrate toward the bottom.

And why would anyone expect a mixture to spontaneously separate into pure components? That happens in real life like where?

-- rec --

On Tue, Jun 12, 2012 at 10:44 AM, Nicholas Thompson <[hidden email]> wrote:

So, somebody asked me, in my role as a weather nerd, how come the nitrogen in the atmosphere doesn’t all fall to the bottom on still nights and suffocate us all. I asked the question of stupid-answers-to-stupid-questions-asked-by-stupid-people.com and THEY said, well, there’s just too much going on. N molecules and the O molecules are just too busy, what with convection and windcurrents, and all, to separate, even on still nights. Now, that business doesn’t prevent cold molecules of Nitrogen and Oxygen to separate from warm ones, or wet ones (not sure what that means) to separate from dry ones. I was hoping that somebody on FRIAM could give some sort of a clue what kind of a mixture AIR is? It is suddenly seeming kinda special.

Nicholas S. Thompson
Emeritus Professor of Psychology and Biology
Clark University
http://home.earthlink.net/~nickthompson/naturaldesigns/
http://www.cusf.org

Steve Smith

Re: atmospherics

Nick -

I think Bruce just gave a good calibration on this with his great description not only of why or why not to breathe Uranium Hexaflouride (cuz you will have to stand on your head to empty it from your lungs!) but also the relative density of the gasses in question.

Try the analogy of mixed drinks. Every good bartender knows that you put the alcohol into the glass first so that when you add the water-based stuff (tonic, seltzer, juice, etc.) the two mix naturally. If you pour the alcohol *over* the watery things, you risk the alcohol "floating" rather than mixing. We could go into the implications of low and high "proof" alcohol, etc.

But are you surprised that your bottle of wine, beer, or hard liquor hasn't seperated before you even get to pour it?

AS I think Doug mentioned, thermal energy alone is a good mixer... even without the constant stirring of wind and convection...

- Steve

Sorry. Mixed up the weight of N and O. So my question should have been, Why don’t we wake up in a layer of oxygen on still nights?

Which brings us to your question about what would make me expect that a mixture would separate out into its lighter and heavier components. You tell me! Other things being equal, don’t heavier things tend to sink when mixed with lighter ones?

N

From: [hidden email] [[hidden email]] On Behalf Of Douglas Roberts
Sent: Tuesday, June 12, 2012 2:43 PM
To: The Friday Morning Applied Complexity Coffee Group
Subject: Re: [FRIAM] atmospherics

Let's not ignore temperature: my farts are a good 20 degrees F above ambient (at present), and tend to rise before mixing into the unfortunate nearby environs. And, just in case you were wondering what the composition of a fart was:

The major components of the flatus, which are odorless, by percentage are:^[4]

§ Nitrogen: 20–90%

§ Hydrogen: 0–50%

§ Carbon dioxide: 10–30%

§ Oxygen: 0–10%

§ Methane: 0–10%

4. ^ "Human Digestive System". Encyclopædia Britannica. Retrieved 2007-08-22.

--Doug

On Tue, Jun 12, 2012 at 12:33 PM, Roger Critchlow <[hidden email]> wrote:

Nick --

N2 weighs 28 gm/mole, O2 weighs 32 gm/mole, Ar weighs 40 gm/mole, CO2 weighs 44 gm/mole, and H2O weighs 18 gm/mole.

Why would anyone expect the lighter components of a mixture to fall down more than the heavier ones? If anything, you'd expect the heavier ones to concentrate toward the bottom.

And why would anyone expect a mixture to spontaneously separate into pure components? That happens in real life like where?

As it happens, CO2 is the heaviest normal component and it does pool in confined spaces often enough that CO2 alarms are available in hardware stores. Propane, C3H8, weighs 44 gm/mole and is notorious for pooling in confined spaces and then exploding, often in the bilge of a boat and spectacularly.

-- rec --

On Tue, Jun 12, 2012 at 10:44 AM, Nicholas Thompson <[hidden email]> wrote:

So, somebody asked me, in my role as a weather nerd, how come the nitrogen in the atmosphere doesn’t all fall to the bottom on still nights and suffocate us all. I asked the question of stupid-answers-to-stupid-questions-asked-by-stupid-people.com and THEY said, well, there’s just too much going on. N molecules and the O molecules are just too busy, what with convection and windcurrents, and all, to separate, even on still nights. Now, that business doesn’t prevent cold molecules of Nitrogen and Oxygen to separate from warm ones, or wet ones (not sure what that means) to separate from dry ones. I was hoping that somebody on FRIAM could give some sort of a clue what kind of a mixture AIR is? It is suddenly seeming kinda special.

Nicholas S. Thompson

Emeritus Professor of Psychology and Biology

Clark University

http://home.earthlink.net/~nickthompson/naturaldesigns/

http://www.cusf.org
============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

Douglas Roberts-2

Re: atmospherics

I'm (patiently) waiting for this discussion to morph into "the philosophy of mixing".

Which reminds me: I haven't had a good Manhattan in a while.

--Doug

On Tue, Jun 12, 2012 at 1:44 PM, Steve Smith <[hidden email]> wrote:

Nick -

I think Bruce just gave a good calibration on this with his great description not only of why or why not to breathe Uranium Hexaflouride (cuz you will have to stand on your head to empty it from your lungs!) but also the relative density of the gasses in question.

Try the analogy of mixed drinks. Every good bartender knows that you put the alcohol into the glass first so that when you add the water-based stuff (tonic, seltzer, juice, etc.) the two mix naturally. If you pour the alcohol *over* the watery things, you risk the alcohol "floating" rather than mixing. We could go into the implications of low and high "proof" alcohol, etc.

But are you surprised that your bottle of wine, beer, or hard liquor hasn't seperated before you even get to pour it?

AS I think Doug mentioned, thermal energy alone is a good mixer... even without the constant stirring of wind and convection...

- Steve
Sorry. Mixed up the weight of N and O. So my question should have been, Why don’t we wake up in a layer of oxygen on still nights?

Which brings us to your question about what would make me expect that a mixture would separate out into its lighter and heavier components. You tell me! Other things being equal, don’t heavier things tend to sink when mixed with lighter ones?

N

From: [hidden email] [[hidden email]] On Behalf Of Douglas Roberts
Sent: Tuesday, June 12, 2012 2:43 PM
To: The Friday Morning Applied Complexity Coffee Group
Subject: Re: [FRIAM] atmospherics

Let's not ignore temperature: my farts are a good 20 degrees F above ambient (at present), and tend to rise before mixing into the unfortunate nearby environs. And, just in case you were wondering what the composition of a fart was:

The major components of the flatus, which are odorless, by percentage are:^[4]

§ Nitrogen: 20–90%

§ Hydrogen: 0–50%

§ Carbon dioxide: 10–30%

§ Oxygen: 0–10%

§ Methane: 0–10%

4. ^ "Human Digestive System". Encyclopædia Britannica. Retrieved 2007-08-22.

--Doug

On Tue, Jun 12, 2012 at 12:33 PM, Roger Critchlow <[hidden email]> wrote:

Nick --

N2 weighs 28 gm/mole, O2 weighs 32 gm/mole, Ar weighs 40 gm/mole, CO2 weighs 44 gm/mole, and H2O weighs 18 gm/mole.

Why would anyone expect the lighter components of a mixture to fall down more than the heavier ones? If anything, you'd expect the heavier ones to concentrate toward the bottom.

And why would anyone expect a mixture to spontaneously separate into pure components? That happens in real life like where?

As it happens, CO2 is the heaviest normal component and it does pool in confined spaces often enough that CO2 alarms are available in hardware stores. Propane, C3H8, weighs 44 gm/mole and is notorious for pooling in confined spaces and then exploding, often in the bilge of a boat and spectacularly.

-- rec --

On Tue, Jun 12, 2012 at 10:44 AM, Nicholas Thompson <[hidden email]> wrote:

So, somebody asked me, in my role as a weather nerd, how come the nitrogen in the atmosphere doesn’t all fall to the bottom on still nights and suffocate us all. I asked the question of stupid-answers-to-stupid-questions-asked-by-stupid-people.com and THEY said, well, there’s just too much going on. N molecules and the O molecules are just too busy, what with convection and windcurrents, and all, to separate, even on still nights. Now, that business doesn’t prevent cold molecules of Nitrogen and Oxygen to separate from warm ones, or wet ones (not sure what that means) to separate from dry ones. I was hoping that somebody on FRIAM could give some sort of a clue what kind of a mixture AIR is? It is suddenly seeming kinda special.

Nicholas S. Thompson

Emeritus Professor of Psychology and Biology

Clark University

http://home.earthlink.net/~nickthompson/naturaldesigns/

http://www.cusf.org
============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org
============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

--
Doug Roberts
[hidden email]
[hidden email]

http://parrot-farm.net/Second-Cousins

505-455-7333 - Office
505-670-8195 - Cell

Steve Smith

Re: atmospherics

In reply to this post by Bruce Sherwood

BasherWo the Science Ninja does it again!

Bruce, that was a killer "lecture", especially about the He/UF6 thing...

I always wondered if there were *another* example of the "speed of sound
in gas" thing to complement the helium experiment virtually everyone has
tried (or at least observed). Breathing UF6 seems just so wrong at so
many levels, but I suppose it stands to reason that the lung physiology
might not "couple" at all with such a heavy and odd element. I suppose
the whole Alveola thing is about Oxygen one direction or the other
(absorb O2, release CO2?) with Nitrogen being pretty benign and CO
wicked. And all the hydrocarbons playing in there somewhere too I
suppose...

I'm feeling an itch to open the encyclopaedia again! Dammit!

> A really spectacular (and somewhat dangerous) demo involves what I
> would guess is the densest gas of all, uranium hexafloride, with a
> mass of 352 gm/mole. Remember that at equal temperature and pressure a
> mole of any gas whatsoever occupies a volume of 22.4 liters, so the
> grams/mole is proportional to the grams/liter.
>
> The demonstrator breathes in the UF6 and then talks with a very deep
> voice, the opposite effect to breathing in helium and talking with a
> very high voice. The explanation is that the vocal cavity dimensions
> don't change, so resonant wavelengths don't change. The speed of sound
> in a gas is similar to the average speed of molecules in the air,
> which is v = sqrt(3kT/m), where m is the mass of one molecule, k is
> Boltzmann's constant, and T is the absolute temperature. Therefore the
> speed of sound is much higher in helium than in air, and much lower in
> UF6 than in air. Since the speed of sound = wavelength/period =
> wavelength*frequency, the frequency of a resonance in the voice cavity
> is high in helium and low in UF6.
>
> In the helium case, it's easy to get rid of the helium and replace it
> with air because the helium has lower density than air. But to get rid
> of the UF6 the demonstrator has to lean over or stand upside down to
> spill the heavy gas out of the lungs. (Note: the radioactivity of
> ordinary uranium, which is 99.3% U238, or of "depleted" uranium from
> which the U235 has been removed, is quite low. U238 has a very long
> half-life of 4.4 billion years, so the number of decays per second in
> the UF6 is low. The danger in breathing in UF6 is from lack of oxygen,
> not from radioactivity.)
>
> In an atmosphere with approximately constant absolute temperature and
> no convection, the density of a particular gas is proportional to e
> raised to the power (-mgy/kT), where m is the mass of one molecule in
> kilograms, g is 9.8 N/kg (gravitational field strength), y is the
> height above the ground in meters, k is Boltzmann's constant in
> joules/kelvin, and T is the absolute temperature in kelvins. For
> oxygen, at a height y = 7920 meters (roughly the height of Mt.
> Everest), (-mgy/kT) = 1, so the density is down by a factor of e to
> the -1, which is 0.37. In other words, in this simplified model the
> density of oxygen at the top of Everest is about one-third what it is
> at sea level. (Note that some climbers have made it to the top
> breathing only what air was available there.)
>
> The corresponding "mean heights" for various gases in this model:
>
> oxygen 7920 m
> nitrogen 9050 m
> CO2 5500 m
> helium 63400 m (way above almost all of our atmosphere)
> UF6 720 m
>
> Note that the mean heights for oxygen and nitrogen aren't very
> different, so one can expect mixing to destroy any significant
> separation. On the other hand, one can expect helium to escape from
> the Earth, and it does, and one can expect some significant pooling of
> UF6 when you pour it out onto the floor.
>
> Bruce
>
> On Tue, Jun 12, 2012 at 12:33 PM, Roger Critchlow<[hidden email]> wrote:
>> Nick --
>>
>> N2 weighs 28 gm/mole, O2 weighs 32 gm/mole, Ar weighs 40 gm/mole, CO2 weighs
>> 44 gm/mole, and H2O weighs 18 gm/mole.
>>
>> Why would anyone expect the lighter components of a mixture to fall down
>> more than the heavier ones? If anything, you'd expect the heavier ones to
>> concentrate toward the bottom.
>>
>> And why would anyone expect a mixture to spontaneously separate into pure
>> components? That happens in real life like where?
>>
>> As it happens, CO2 is the heaviest normal component and it does pool in
>> confined spaces often enough that CO2 alarms are available in hardware
>> stores. Propane, C3H8, weighs 44 gm/mole and is notorious for pooling in
>> confined spaces and then exploding, often in the bilge of a boat and
>> spectacularly.
>>
>> -- rec --
>>
>> On Tue, Jun 12, 2012 at 10:44 AM, Nicholas Thompson
>> <[hidden email]> wrote:
>>> So, somebody asked me, in my role as a weather nerd, how come the nitrogen
>>> in the atmosphere doesn’t all fall to the bottom on still nights and
>>> suffocate us all. I asked the question of
>>> stupid-answers-to-stupid-questions-asked-by-stupid-people.com and THEY said,
>>> well, there’s just too much going on. N molecules and the O molecules are
>>> just too busy, what with convection and windcurrents, and all, to separate,
>>> even on still nights. Now, that business doesn’t prevent cold molecules of
>>> Nitrogen and Oxygen to separate from warm ones, or wet ones (not sure what
>>> that means) to separate from dry ones. I was hoping that somebody on FRIAM
>>> could give some sort of a clue what kind of a mixture AIR is? It is
>>> suddenly seeming kinda special.
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> Nicholas S. Thompson
>>>
>>> Emeritus Professor of Psychology and Biology
>>>
>>> Clark University
>>>
>>> http://home.earthlink.net/~nickthompson/naturaldesigns/
>>>
>>> http://www.cusf.org
>>>
>>>
>>>
>>>
>>>
>>>
>>> ============================================================
>>> FRIAM Applied Complexity Group listserv
>>> Meets Fridays 9a-11:30 at cafe at St. John's College
>>> lectures, archives, unsubscribe, maps at http://www.friam.org
>>
>>
>> ============================================================
>> FRIAM Applied Complexity Group listserv
>> Meets Fridays 9a-11:30 at cafe at St. John's College
>> lectures, archives, unsubscribe, maps at http://www.friam.org
> ============================================================
> FRIAM Applied Complexity Group listserv
> Meets Fridays 9a-11:30 at cafe at St. John's College
> lectures, archives, unsubscribe, maps at http://www.friam.org
>

Steve Smith

Re: atmospherics

In reply to this post by Douglas Roberts-2

Doug -

I'm (patiently) waiting for this discussion to morph into "the philosophy of mixing".

Not really patiently... I can hear your riding booted foot tapping all the way from Nambe!

And don't tempt me... this does call for a riff on "the mixing of Philosophies" and analogies of He and UF6 in one's lungs with various Philosophies.

As a weak throwaway on the topic, I think there could be an analogy drawn where realism in it's strongest form is like UF6 and idealism in *it's strongest form* is like Helium.

In both cases, breathing nothing but pure He nor UF6 is a good idea, as one will not get the O2 needed for life, but one is much more entertaining and easier to expunge...

I have an image of some of the hardcore "realists" here having to stand on their head to empty their lungs enough to avoid suffocating in the heaviness of it all while the rest of us huff helium and laugh at eachother's voices!

Now, where does N2O and the recently mentioned cocktails known as farts come in? Ok... I'll stop now...

And maybe order a Manhattan at dinner tonight.

- Steve

Which reminds me: I haven't had a good Manhattan in a while.
--Doug
On Tue, Jun 12, 2012 at 1:44 PM, Steve Smith <[hidden email]> wrote:
Nick -

I think Bruce just gave a good calibration on this with his great description not only of why or why not to breathe Uranium Hexaflouride (cuz you will have to stand on your head to empty it from your lungs!) but also the relative density of the gasses in question.

Try the analogy of mixed drinks. Every good bartender knows that you put the alcohol into the glass first so that when you add the water-based stuff (tonic, seltzer, juice, etc.) the two mix naturally. If you pour the alcohol *over* the watery things, you risk the alcohol "floating" rather than mixing. We could go into the implications of low and high "proof" alcohol, etc.

But are you surprised that your bottle of wine, beer, or hard liquor hasn't seperated before you even get to pour it?

AS I think Doug mentioned, thermal energy alone is a good mixer... even without the constant stirring of wind and convection...

- Steve
Sorry. Mixed up the weight of N and O. So my question should have been, Why don’t we wake up in a layer of oxygen on still nights?

Which brings us to your question about what would make me expect that a mixture would separate out into its lighter and heavier components. You tell me! Other things being equal, don’t heavier things tend to sink when mixed with lighter ones?

N

From: [hidden email] [[hidden email]] On Behalf Of Douglas Roberts
Sent: Tuesday, June 12, 2012 2:43 PM
To: The Friday Morning Applied Complexity Coffee Group
Subject: Re: [FRIAM] atmospherics

Let's not ignore temperature: my farts are a good 20 degrees F above ambient (at present), and tend to rise before mixing into the unfortunate nearby environs. And, just in case you were wondering what the composition of a fart was:

The major components of the flatus, which are odorless, by percentage are:^[4]

§ Nitrogen: 20–90%

§ Hydrogen: 0–50%

§ Carbon dioxide: 10–30%

§ Oxygen: 0–10%

§ Methane: 0–10%

4. ^ "Human Digestive System". Encyclopædia Britannica. Retrieved 2007-08-22.

--Doug

On Tue, Jun 12, 2012 at 12:33 PM, Roger Critchlow <[hidden email]> wrote:

Nick --

N2 weighs 28 gm/mole, O2 weighs 32 gm/mole, Ar weighs 40 gm/mole, CO2 weighs 44 gm/mole, and H2O weighs 18 gm/mole.

Why would anyone expect the lighter components of a mixture to fall down more than the heavier ones? If anything, you'd expect the heavier ones to concentrate toward the bottom.

And why would anyone expect a mixture to spontaneously separate into pure components? That happens in real life like where?

As it happens, CO2 is the heaviest normal component and it does pool in confined spaces often enough that CO2 alarms are available in hardware stores. Propane, C3H8, weighs 44 gm/mole and is notorious for pooling in confined spaces and then exploding, often in the bilge of a boat and spectacularly.

-- rec --

On Tue, Jun 12, 2012 at 10:44 AM, Nicholas Thompson <[hidden email]> wrote:

So, somebody asked me, in my role as a weather nerd, how come the nitrogen in the atmosphere doesn’t all fall to the bottom on still nights and suffocate us all. I asked the question of stupid-answers-to-stupid-questions-asked-by-stupid-people.com and THEY said, well, there’s just too much going on. N molecules and the O molecules are just too busy, what with convection and windcurrents, and all, to separate, even on still nights. Now, that business doesn’t prevent cold molecules of Nitrogen and Oxygen to separate from warm ones, or wet ones (not sure what that means) to separate from dry ones. I was hoping that somebody on FRIAM could give some sort of a clue what kind of a mixture AIR is? It is suddenly seeming kinda special.

Nicholas S. Thompson

Emeritus Professor of Psychology and Biology

Clark University

http://home.earthlink.net/~nickthompson/naturaldesigns/

http://www.cusf.org
============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org
============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org
--
Doug Roberts
[hidden email]
[hidden email]
http://parrot-farm.net/Second-Cousins

505-455-7333 - Office
505-670-8195 - Cell
============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

Steve Smith

Long Rides, Was: atmospherics

In reply to this post by Douglas Roberts-2

On 6/12/12 1:13 PM, Douglas Roberts wrote:
> Thanks, Steve, I just got back a couple of weeks ago:
> http://mc-california-trip-2012.blogspot.com/
>
> Yes, I had a gas...

Looks like a great trip... I haven't done a long ride in decades...
round trip to ABQ still qualifies. If I had your bike I'd probably
forget to come home... one of the (many) reasons I don't indulge in
such awesome toys. I have much less self-restraint than you
(apparently) do. I didn't see a single picture with beer at breakfast
for example! Or skinny dipping in any of those lakes! Or maybe you
are just better at self-editing than I am.

All that sitting upright and pub-food, however... surely *that* gave you
gas. Not tempted to route some of that "methane/H2" mixture into the
carbs (oh... probably fuel injected... so into the air intake?) when you
thought you were not going to make the one-gas-station town of Caliente UT?

Me, I always drive *faster* when I think I might run out of gas...
welll, maybe not any more, but I *did* do that once... not out of
ignorance of aerodynamics and fuel economy, but some kind of willful
frustration with myself and the universe... the last 20 miles *were*
downhill and it only took 2 hours to push/coast into the only gas
station open on a Thanksgiving morning 1976! I could have been there
1:45 earlier *without* pushing if I'd just ridden very carefully...
maybe a little deliberate hypermile coasting, etc. But noooo!

Anecdotally yours!
- Steve

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
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Bruce Sherwood

Re: atmospherics

In reply to this post by Nick Thompson

I realize that I didn't address one of the questions (or one of the
possible questions): "Why don't all the air molecules just fall to the
ground and stay there"? In case anyone was wondering about that
question, the answer is that the air molecules DO fall toward the
ground, but they continually run into other air molecules (or
molecules in the ground if they get that far down), all of which share
a nonzero absolute temperature and therefore are in random motion, and
in collisions sometimes a molecule will be knocked upward. When you
work out the statistical mechanics of all this, you get an exponential
falloff of density (in the approximation of a constant-temperature
non-convective atmosphere). This falloff is a bit faster for the
lower-mass nitrogen molecules than for the oxygen molecules, but as I
explained in a previous note, both of these molecular species have
mean heights of around 8000 meters, so you shouldn't expect much
difference in oxygen vs nitrogen between your cellar and your attic.

A picturesque way of looking at this is the following. Imagine there
is no atmosphere, and you're sitting at a table out in the open (in
your spacesuit). Place a cup on the table. The atoms in the bottom of
the cup are in contact with atoms in the top of the table, and all of
these atoms are moving with random thermal motion related to the
absolute temperature. At any given moment, there is a finite (but
exquisitely small) probability that all of the atoms in the table
underneath the cup happen to all be heading upward. In that case the
cup will leap up off the table, knocked upward by the upward-moving
atoms in the table. This would not violate conservation of energy or
conservation of momentum (the Earth would recoil), but it would
violate the Second Law of Thermodynamics, because given the gigantic
number of atoms lying underneath the cup, the probability of all those
atoms simultaneously heading upward is vanishingly small. You might
have to wait for billions of billions of billions of years to observe
the leap.

Suppose instead of placing a cup on the table you place a single
molecule of oxygen. Now it's not so improbable that an atom in the
table might impart a significant upward speed to this single molecule
of oxygen. Statistical mechanics provides the tools for calculating
quantitatively the probabilities of various upward speeds. What you
find is that the average speed imparted to an oxygen molecule by an
atom in a table at room temperature is a speed sufficient for the
oxygen molecule to go up 7920 meters before falling back down!

In other words, statistical mechanics gives the answer (the same
answer) to two different questions:

1) What is the average height attained by one oxygen molecule in
contact with a table at room temperature? (Ans. 7920 m)

2) What is the average height of all the oxygen molecules in a
constant-temperature atmosphere? (Ans. 7920 m)

(I'm deliberately playing rather loose with the word "average" here,
but the basic idea is correct.)

There's yet another source of amusement in this statistical picture.
Suppose you have a box whose sides have an accurately known mass.
Suppose you weigh the box in an airless room (to avoid buoyancy
effects) with and without the box being filled with
atmospheric-density air. You're not astonished that the extra mass
with the air is equal to the mass of the air added to the box. But
maybe you should be astonished, because at any given instant almost
none of the air molecules are touching the inside of the box! The
reason why the scale measures an increase is because of the e to the
(-mgy/kT) density gradient. The air density and pressure are just a
tiny bit higher at the bottom of the air (in contact with the bottom
of the box) than at the top of the air (in contact with the top of the
box). Momentum transfer per second from the bottom of the air to the
bottom of the box is very slightly greater than the momentum transfer
per second from the top of the air to the top of the box. When you
work out the details, you find that this difference provides the
conspiracy that let's you think you're measuring the mass of the air.
The difference is small, but so is the mass of the air.

Sometimes one describes air pressure at sea level as "the weight per
area of the column of air above that area". But almost none of those
air molecules are in contact with your measuring device! However, the
number of molecules per cubic meter, and their average y component of
velocity, is such (conspiratorially) as to hit your area with the same
force as though an object with the mass of the total column of air sat
on this area.

Related amusement: Consider a steel ball bearing dropped from a height
h onto a scale, and rebounding to nearly the same height every time.
If the scale can respond very quickly, you will see sudden sharp
spikes when the ball bearing hits, and zero at other times. Now
suppose that the scale is sluggish, and/or h is small enough that the
ball bearing hits the scale at a high rate (though small speed). What
you can calculate is that the average reading of the scale is exactly
the same as if you simply place the ball bearing at rest on the scale!

Bruce

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

Bruce Sherwood

Re: atmospherics

In reply to this post by Steve Smith

I hadn't thought of the physiological issue you raise, but I would
expect a molecule of UF6 to be far too large to pass from the lungs
into the blood stream. Good point, though.

Bruce

On Tue, Jun 12, 2012 at 1:49 PM, Steve Smith <[hidden email]> wrote:

> BasherWo the Science Ninja does it again!
>
> Bruce, that was a killer "lecture", especially about the He/UF6 thing...
>
> I always wondered if there were *another* example of the "speed of sound in
> gas" thing to complement the helium experiment virtually everyone has tried
> (or at least observed). Breathing UF6 seems just so wrong at so many
> levels, but I suppose it stands to reason that the lung physiology might not
> "couple" at all with such a heavy and odd element. I suppose the whole
> Alveola thing is about Oxygen one direction or the other (absorb O2, release
> CO2?) with Nitrogen being pretty benign and CO wicked. And all the
> hydrocarbons playing in there somewhere too I suppose...
>
> I'm feeling an itch to open the encyclopaedia again! Dammit!

Steve Smith

Re: atmospherics

In reply to this post by Bruce Sherwood

Again... amazing detail here Bruce... thanks...

I forgot to mention to Nick that planetary atmospheres *do* vary over
altitude and even stratify. So your intuition is not wrong in
quality... just in quantity. Here's to your intuition! (Raising a
poorly mixed Manhattan)

My senior project for my BS in physics involved elaborating/modifying a
huge wad of Fortran IV code that did those calculations for real and
imagined planets. Put in the presumed (or known) mix of gasses, the
solar irradiance/spectrum, surface reflectance, rate of planetary
rotation (and a bunch of other stuff) and "viola" you get out an
idealized profile of the atmosphere by altitude. I don't remember the
code actually including any chemistry, just statistics and mechanics of
mixing gasses in the context of a rotating (think coriolis and shear)
body irradiated by a spectrum of (solar) radiation.

I spent a lot of time procrastinating on my *real* project by trying to
conjure suns, planets and atmospheres with interesting
characteristics.... I don't remember any worth mentioning... I mostly
just remember the time-wasting nature of it.

The ozone layer and damage to it by CFCs and NO (not N2O?) and ... are
all storied evidence of such things. Or something...

> I realize that I didn't address one of the questions (or one of the
> possible questions): "Why don't all the air molecules just fall to the
> ground and stay there"? In case anyone was wondering about that
> question, the answer is that the air molecules DO fall toward the
> ground, but they continually run into other air molecules (or
> molecules in the ground if they get that far down), all of which share
> a nonzero absolute temperature and therefore are in random motion, and
> in collisions sometimes a molecule will be knocked upward. When you
> work out the statistical mechanics of all this, you get an exponential
> falloff of density (in the approximation of a constant-temperature
> non-convective atmosphere). This falloff is a bit faster for the
> lower-mass nitrogen molecules than for the oxygen molecules, but as I
> explained in a previous note, both of these molecular species have
> mean heights of around 8000 meters, so you shouldn't expect much
> difference in oxygen vs nitrogen between your cellar and your attic.
>
> A picturesque way of looking at this is the following. Imagine there
> is no atmosphere, and you're sitting at a table out in the open (in
> your spacesuit). Place a cup on the table. The atoms in the bottom of
> the cup are in contact with atoms in the top of the table, and all of
> these atoms are moving with random thermal motion related to the
> absolute temperature. At any given moment, there is a finite (but
> exquisitely small) probability that all of the atoms in the table
> underneath the cup happen to all be heading upward. In that case the
> cup will leap up off the table, knocked upward by the upward-moving
> atoms in the table. This would not violate conservation of energy or
> conservation of momentum (the Earth would recoil), but it would
> violate the Second Law of Thermodynamics, because given the gigantic
> number of atoms lying underneath the cup, the probability of all those
> atoms simultaneously heading upward is vanishingly small. You might
> have to wait for billions of billions of billions of years to observe
> the leap.
>
> Suppose instead of placing a cup on the table you place a single
> molecule of oxygen. Now it's not so improbable that an atom in the
> table might impart a significant upward speed to this single molecule
> of oxygen. Statistical mechanics provides the tools for calculating
> quantitatively the probabilities of various upward speeds. What you
> find is that the average speed imparted to an oxygen molecule by an
> atom in a table at room temperature is a speed sufficient for the
> oxygen molecule to go up 7920 meters before falling back down!
>
> In other words, statistical mechanics gives the answer (the same
> answer) to two different questions:
>
> 1) What is the average height attained by one oxygen molecule in
> contact with a table at room temperature? (Ans. 7920 m)
>
> 2) What is the average height of all the oxygen molecules in a
> constant-temperature atmosphere? (Ans. 7920 m)
>
> (I'm deliberately playing rather loose with the word "average" here,
> but the basic idea is correct.)
>
> There's yet another source of amusement in this statistical picture.
> Suppose you have a box whose sides have an accurately known mass.
> Suppose you weigh the box in an airless room (to avoid buoyancy
> effects) with and without the box being filled with
> atmospheric-density air. You're not astonished that the extra mass
> with the air is equal to the mass of the air added to the box. But
> maybe you should be astonished, because at any given instant almost
> none of the air molecules are touching the inside of the box! The
> reason why the scale measures an increase is because of the e to the
> (-mgy/kT) density gradient. The air density and pressure are just a
> tiny bit higher at the bottom of the air (in contact with the bottom
> of the box) than at the top of the air (in contact with the top of the
> box). Momentum transfer per second from the bottom of the air to the
> bottom of the box is very slightly greater than the momentum transfer
> per second from the top of the air to the top of the box. When you
> work out the details, you find that this difference provides the
> conspiracy that let's you think you're measuring the mass of the air.
> The difference is small, but so is the mass of the air.
>
> Sometimes one describes air pressure at sea level as "the weight per
> area of the column of air above that area". But almost none of those
> air molecules are in contact with your measuring device! However, the
> number of molecules per cubic meter, and their average y component of
> velocity, is such (conspiratorially) as to hit your area with the same
> force as though an object with the mass of the total column of air sat
> on this area.
>
> Related amusement: Consider a steel ball bearing dropped from a height
> h onto a scale, and rebounding to nearly the same height every time.
> If the scale can respond very quickly, you will see sudden sharp
> spikes when the ball bearing hits, and zero at other times. Now
> suppose that the scale is sluggish, and/or h is small enough that the
> ball bearing hits the scale at a high rate (though small speed). What
> you can calculate is that the average reading of the scale is exactly
> the same as if you simply place the ball bearing at rest on the scale!
>
> Bruce
>
> ============================================================
> FRIAM Applied Complexity Group listserv
> Meets Fridays 9a-11:30 at cafe at St. John's College
> lectures, archives, unsubscribe, maps at http://www.friam.org

Douglas Roberts-2

Re: Long Rides, Was: atmospherics

In reply to this post by Steve Smith

Re: slower vs faster when low on gas, I also have the urge to speed up. But on this bike I've got the computer that tells me my current MPG, and expected (moving average) range on remaining gas, so it was fairly easy to find the most economical speed that would get me there.

The upright/pub food thing helped me gain 5 pounds, dammit.

We need to get together again to eat too much, and drink too much thereby getting the wives mad at us again.

--Doug

On Tue, Jun 12, 2012 at 2:09 PM, Steve Smith <[hidden email]> wrote:

On 6/12/12 1:13 PM, Douglas Roberts wrote:

Thanks, Steve, I just got back a couple of weeks ago: http://mc-california-trip-2012.blogspot.com/

Yes, I had a gas...

Looks like a great trip... I haven't done a long ride in decades... round trip to ABQ still qualifies. If I had your bike I'd probably forget to come home... one of the (many) reasons I don't indulge in such awesome toys. I have much less self-restraint than you (apparently) do. I didn't see a single picture with beer at breakfast for example! Or skinny dipping in any of those lakes! Or maybe you are just better at self-editing than I am.

All that sitting upright and pub-food, however... surely *that* gave you gas. Not tempted to route some of that "methane/H2" mixture into the carbs (oh... probably fuel injected... so into the air intake?) when you thought you were not going to make the one-gas-station town of Caliente UT?

Me, I always drive *faster* when I think I might run out of gas... welll, maybe not any more, but I *did* do that once... not out of ignorance of aerodynamics and fuel economy, but some kind of willful frustration with myself and the universe... the last 20 miles *were* downhill and it only took 2 hours to push/coast into the only gas station open on a Thanksgiving morning 1976! I could have been there 1:45 earlier *without* pushing if I'd just ridden very carefully... maybe a little deliberate hypermile coasting, etc. But noooo!

Anecdotally yours!
- Steve

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Doug Roberts
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Douglas Roberts-2

Re: atmospherics

In reply to this post by Steve Smith

Sort of adds a new spin to "Brownian motion", doesn't it...

On Tue, Jun 12, 2012 at 1:09 PM, Steve Smith <[hidden email]> wrote:

ahh Doug... I *knew* we could count on you!

Let's not ignore temperature: my farts are a good 20 degrees F above ambient (at present), and tend to rise before mixing into the unfortunate nearby environs. And, just in case you were wondering what the composition of a fart was:

The major components of the flatus, which are odorless, by percentage are:^[4]

Nitrogen: 20–90%

Hydrogen: 0–50%

Carbon dioxide: 10–30%

Oxygen: 0–10%

Methane: 0–10%

4. ^ "Human Digestive System". Encyclopædia Britannica. Retrieved 2007-08-22.

While I still refuse to believe the myths about igniting one's own petard (by which extra lift is gained beyond the mere ejection at high velocity?) I'd never researched it this far but anecdotally assumed it was the "methane" presumed to be flammable, but if this "recipe for a petard" is accurate, it seems more likely to be the Hydrogen that one would get their "lift" from.

Your recent silence online lead me to believe you were already "putt-putting" your way toward Alaska on your yearly loop! Or are you posting from the road?

The only factoid in the Flatulence FAQ that really caught my eye was that NZ's GDP is so highly based in agriculture that they have a "Flat"ulence Tax to offset the Greenhouse gas emissions. And complementary to this, it was interesting to note that the majority of Bovine Methane emissions are NOT flatulence but rather exhalations and gastric belching (how many stomachs do they have again?)...

On the other hand, I do believe that methane production from cellulose by anaerobic bacteria is a big deal, and I'm a little surprised that the Bovine intestinal tract is not an obvious place for this to occur already?

I'm presuming that Hydrogen production is a byproduct of the very same bacterium? Or perhaps it is a different one. I suppose it is also possible that "biogas" production en vitro suffers from the difficulty of *containing* hydrogen and perhaps that direct, immediate use of "biogas" benefits from high H concentrations with the methane?

Too much to ponder on such a hot day!

Pull your own damned finger!
- Steve

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

--
Doug Roberts
[hidden email]
[hidden email]

http://parrot-farm.net/Second-Cousins

505-455-7333 - Office
505-670-8195 - Cell