# Air getting thinner and thicker - what's the Straight Dope? **URL:** \ **Category:** Factual Questions\ **Created:** [December 9, 2016, 8:47pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303 "2016-12-09T20:47:00Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [December 10, 2016, 3:30pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303/21 "2016-12-10T15:30:57Z")
> [@Leo\_Bloom](#): > > Yes you understood the query–and the source of it–correctly. I just wanted to correct the initial over emphasis on radiation _from_ the ground material by radioactive decay, independent of current solar irradiation, in this thread about temperatures/heat --although interesting in its own right. You may be using the term “radiation” incorrectly - radiation is a transmission of energy, like electromagnetic radiation (including visible light, X-rays, radio, gamma rays, etc). It’s not a _source_ of energy, it’s how energy is transmitted. I think what you meant is _radioactive decay_. Various types of radiation are usually produced by radioactive decay, but it’s not the same thing. ---
**Author:** ![Morgenstern](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@Morgenstern](https://boards.straightdope.com/u/Morgenstern)\ **Post date:** [December 10, 2016, 3:32pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303/22 "2016-12-10T15:32:02Z")
> [@doreet](#): > > uh…I just read that because of all the OIL IN THE ATMOSPHERE, which we are all breathing, world intelligence is going DOWN.ALL over the world. yeah, we’re gassing ourselves into the film “Idiocracy.” they have it figured out, this will keep going, our IQs will be way down in 20 yrs. pretty far. guess what happens to a big planet of too many STUPID PEOPLE? GUESS!!! > > ITS CALLED “SAVAGERY.”(SPELLING? I live next to a 5-lane highway, mine is going fast) we will also have MORE PEOPLE, less food and water. go ahead, guess!! RIGHT!! ENDLESS WAR!!! you’ll even get so dumb, frustrated, unable to work, do stuff we can do now, we’ll be close to dementia–or retardation. And with that many angry helpless people, i do not wanta be around. I am 70 now, next summer. i do not regret never having had kids now. I am (was) one of the very smart. i guess dumb people are happier, they can’t see all the s— going on. Wow. I think a brown font would have been better to describe a dying race and orange or red for hopelessness. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [December 10, 2016, 8:23pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303/23 "2016-12-10T20:23:58Z")
> [@LSLGuy](#): > > The reason it’s hotter at the bottom of a deep hole or mine IS that it’s closer to the very hot center of the Earth. You’re omitting the “more atmosphere above you, raising the pressure” factor here. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [December 10, 2016, 8:26pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303/24 "2016-12-10T20:26:31Z")
No, a black font would be fine. There’s nothing but Blackness and Bleakness. Sob. Blackness and Bleakness. Black is the mood, black is the soul, and black is the Mind. Or whatever’s left of it. 😃 ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [December 10, 2016, 8:37pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303/25 "2016-12-10T20:37:23Z")
> [@LSLGuy](#): > > … > > Which two thermoclines do you think you’re talking about? > > If you mean residual heating conducting up from below versus solar heating conducting down from above the two lines cross a few feet below the surface. That’s where weather stops having an effect and you get below the frost line. I may have spoken too soon in this last sentence. I retract it pending further research. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [December 10, 2016, 9:08pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303/26 "2016-12-10T21:08:06Z")
> [@watchwolf49](#): > > Actually, all this radioactive stuff all came from the supernova dust our solar system condensed out of … a fairly sizable chunk of it has already decayed … however it takes time for the energy to work it’s way to the surface and radiate away from the Earth … no need to worry about the Earth dynamo freezing up before our Sun expands and boils us off into interplanetary space … you’re still okay buying unripe bananas … Wiki says otherwise. In the [Timeline of the Far Future](https://en.wikipedia.org/wiki/Timeline_of_the_far_future), we only have 2.3 billion years before the outer core freezes. This will shut down the magnetic field. It will be 7 billion years before the Sun expands sufficiently to consume the Earth. Not that it will really matter because the Earth can only support us for 600-800 million years or so due to the gradual brightening of the sun. > [@](#): > > The Sun’s increasing luminosity begins to disrupt the carbonate–silicate cycle; higher luminosity increases weathering of surface rocks, which traps carbon dioxide in the ground as carbonate. As water evaporates from the Earth’s surface, rocks harden, causing plate tectonics to slow and eventually stop. Without volcanoes to recycle carbon into the Earth’s atmosphere, carbon dioxide levels begin to fall.[52] By this time, carbon dioxide levels will fall to the point at which C3 photosynthesis is no longer possible. All plants that utilize C3 photosynthesis (~99 percent of present-day species) will die.[53] ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [December 10, 2016, 9:26pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303/27 "2016-12-10T21:26:20Z")
Yeah, but that’s a quibble. Wiki still supports **watchwolf49** ’s conclusion that it’s OK for **Leo** to buy unripe bananas. He’ll have plenty of time to eat them before anything too bad happens. 🙂 ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [December 10, 2016, 9:36pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303/28 "2016-12-10T21:36:12Z")
Right, 600-800 million years to be boiled off … 2.3 billion before the magnetic field weakens … less than 7 billion years before the planet is consumed by the surface of the sun … assuming the universe doesn’t wink out of existence before then … I think it’s safe to plant banana trees right now … ---
**Author:** ![Blue\_Blistering\_Barnacle](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/blue_blistering_barnacle/32/3386_2.png) [@Blue\_Blistering\_Barnacle](https://boards.straightdope.com/u/Blue_Blistering_Barnacle)\ **Post date:** [December 10, 2016, 11:08pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303/29 "2016-12-10T23:08:05Z")
> [@scr4](#): > > “Don’t buy unripe bananas” is a droll way of saying you’re going to die soon (i.e. before the bananas ripen). > [@scr4](#): > > You may be using the term “radiation” incorrectly - radiation is a transmission of energy, like electromagnetic radiation (including visible light, X-rays, radio, gamma rays, etc). It’s not a _source_ of energy, it’s how energy is transmitted. > > I think what you meant is _radioactive decay_. Various types of radiation are usually produced by radioactive decay, but it’s not the same thing. minor nitpick: I am not a comedian or a poet (IANACOAP), but the phrase should really be “green bananas”, as in “Don’t buy any green bananas!”. “Green bananas” is funnier, and “unripe bananas” is just clunky. I’ll also point out that if Leo does survive to the time when the core cools and the magnetosphere fails, he’ll surely have “one foot in the grave and the other on a banana peel”. What a droll fruit! Given the lack of genetic diversity of bananas and the state of politics lately, I fear humor will die out long before we lose our oil-laden brain-rotting bottom-heated atmosphere to the solar wind. ---
**Author:** ![Blue\_Blistering\_Barnacle](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/blue_blistering_barnacle/32/3386_2.png) [@Blue\_Blistering\_Barnacle](https://boards.straightdope.com/u/Blue_Blistering_Barnacle)\ **Post date:** [December 10, 2016, 11:29pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303/30 "2016-12-10T23:29:10Z")
Boy- now I have to critique myself! That would’ve been funnier (I think!) if I’d quoted the right posts! ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [December 11, 2016, 2:34pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303/31 "2016-12-11T14:34:34Z")
> [@LSLGuy](#): > > The reason it’s hotter at the bottom of a deep hole or mine IS that it’s closer to the very hot center of the Earth. Some Googling suggests that this is a secondary effect - the principal one is the increase in air pressure with depth. Here’s the Wiki article on the [TauTona gold mine](https://en.wikipedia.org/wiki/TauTona_Mine) west of Johannesburg. It’s 3.5 km deep, at which depth the unconditioned air temperature is 55 C (131 F). The adiabatic lapse rate is 9.8 C per 1000 meters, which means the temperature at a depth of 3.5 km should be 34.3 C higher than at the surface. Thus, with a surface temperature of 20.7 C (70 F) we could account for the mine’s elevated temperature entirely by the increase in air pressure. It’s clear that this is not the only effect. The linked article says the rock face temperature is 60 C - 5 degrees higher than the air temperature. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [December 11, 2016, 3:27pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303/32 "2016-12-11T15:27:26Z")
An interesting suggestion … although the dry adiabatic lapse rate assumes there’s no thermodynamics going on … like dry air in the troposphere … However, when we put air in a 60ºC container, it won’t matter the pressure, the air will become 60ºC rather quickly, like in the bottom of a mine shaft … also, we’re still absorbing the infrared portion of the solar radiation in the stratosphere, so here dry air will be _increasing_ temperature with _decreasing_ pressure … Of course the dry adiabatic lapse rate has some effect … but I do believe the 60ºC walls have the far greater effect … plus I’m not sure about your 20ºC surface temperature that makes the math work out so nicely … I can’t say anything about the normal temps at 26ºS latitude in South Africa … but at 26ºN latitude in Mexico, 20ºC would be a chilly day indeed … ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [December 11, 2016, 6:36pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303/33 "2016-12-11T18:36:54Z")
> [@doreet](#): > > uh…I just read that because of all the OIL IN THE ATMOSPHERE, which we are all breathing, world intelligence is going DOWN.ALL over the world. yeah, we’re gassing ourselves into the film “Idiocracy.” they have it figured out, this will keep going, our IQs will be way down in 20 yrs. pretty far. guess what happens to a big planet of too many STUPID PEOPLE? GUESS!!! “They have it figured out”? Whomever “they” are you should probably reconsider listening to them. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [December 11, 2016, 7:26pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303/34 "2016-12-11T19:26:33Z")
“Oil in the atmosphere” … that’s a new one on me … hydrocarbons quickly oxidize in air … oxygen is nasty stuff … ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [December 11, 2016, 7:35pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303/35 "2016-12-11T19:35:21Z")
> [@scr4](#): > > You may be using the term “radiation” incorrectly - radiation is a transmission of energy, like electromagnetic radiation (including visible light, X-rays, radio, gamma rays, etc). It’s not a _source_ of energy, it’s how energy is transmitted. > > I think what you meant is _radioactive decay_. Various types of radiation are usually produced by radioactive decay, but it’s not the same thing. This I know, which I made clear (honest!) in the post you are responding to. But I still do not know the answer to more urgent question, even though a correct-within-given-definition-of-Leo-lifetime answer was given: What is the relative amount of potassium and its subsequent decay rate in ripe vs unripe bananas? ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [December 11, 2016, 9:30pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303/36 "2016-12-11T21:30:10Z")
> [@Leo\_Bloom](#): > > [snip] … What is the relative amount of potassium and its subsequent decay rate in ripe vs unripe bananas? Awww … yes … there’s a few species of radionuclides that form in the upper parts of the atmosphere … potassium, oxygen, carbon … however I’m not sure enough of these are being sequestered in the mantel or core areas, and then decaying releasing that energy into the Earth … my point here is that any energy we do find in the Earth due to radioactive decay would be from decay that has already happened … any decay that is yet to happen would have no effect on the current energy level … and that most of the species have a half life shorter than 5 or 6 billion years, most of the decay that could happen has already happened … I am glad I changed that to bananas at the last second … or I’d really be in trouble … ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [December 12, 2016, 2:11pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303/37 "2016-12-12T14:11:32Z")
> [@Xema](#): > > Some Googling suggests that this is a secondary effect - the principal one is the increase in air pressure with depth. > > Here’s the Wiki article on the [TauTona gold mine](https://en.wikipedia.org/wiki/TauTona_Mine) west of Johannesburg. It’s 3.5 km deep, at which depth the unconditioned air temperature is 55 C (131 F). > > The adiabatic lapse rate is 9.8 C per 1000 meters, which means the temperature at a depth of 3.5 km should be 34.3 C higher than at the surface. Thus, with a surface temperature of 20.7 C (70 F) we could account for the mine’s elevated temperature entirely by the increase in air pressure. The [adiabatic lapse rate](https://en.wikipedia.org/wiki/Lapse_rate) is relevant only when you have a parcel of air that is _changing_ altitude: it cools as it ascends because it is performing mechanical work on the rest of the atmosphere as it expands, or it warms as it descends because the atmosphere is performing mechanical work to compress it. If the air stagnates at the bottom of the mine, there is no mechanical work being done, so the only remaining temperature driver is the temperature of the rocks down there. It would be counterproductive to simply _ventilate_ the mine by forcing air from the surface down to the depths, since it would heat up on the way down. Instead, they employ air conditioning equipment to control temperature at the bottom of the mine. My guess is that there’s a refrigeration system on the surface that chills water/glycol that then gets pumped down to the depths for cooling. Liquids are pretty much incompressible, and so are not subject to the lapse rate in the same way that air is. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [December 12, 2016, 6:45pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303/38 "2016-12-12T18:45:54Z")
> [@LSLGuy](#): > > The atmosphere is heated by the Sun. But what really happens is the light and heat flow down through the atmosphere without heating it hardly at all. The light and heat from the sun then heat the land and the sea. Those things in turn heat the air. So like a pot on a stove, the atmosphere is heated from below, not from above. Which is why it’s hotter at sea level and colder on a mountain top. This is part of it, and would probably be all of it if the observer were on top of a tall, skinny tower poking up to high altitude without actually redirecting the ambient wind. But the thing about mountains and mountain ranges is that they force air parcels to climb to go up over them, inducing adiabatic lapse - or vice versa, cold air that crosses a mountain range descends into a valley, warming as it descends simply because it’s being compressed. This is why the rim of the grand canyon can be balmy, while the bottom is sweltering, even on a day when both areas are receiving the same insolation. A similar situation exists when one drives from Boulder, CO (elevation 5400’) just a few miles west to Nederland (elevation 8200’). Nederland doesn’t sit on a mountain top piercing the sky, either; it’s in the Rockies, sure, but the sky-piercing peaks are all around it. And yet it’s generally a good bit cooler than Boulder. [In this time lapse video,](https://www.youtube.com/watch?v=xDxNFRxqC1g) you can see from the motion of the wisps of cloud that the air is moving down off of the mountain. But the cloud itself stays glued to the mountain top: as its leading edge moves downslope, the adiabatic temperature increase causes the condensed water droplets to evaporate, making the cloud disappear. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [December 12, 2016, 8:07pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303/39 "2016-12-12T20:07:51Z")
> [@Machine\_Elf](#): > > …But the thing about mountains and mountain ranges is that they force air parcels to climb to go up over them, inducing adiabatic lapse - or vice versa, cold air that crosses a mountain range descends into a valley, warming as it descends simply because it’s being compressed. This is why the rim of the grand canyon can be balmy, while the bottom is sweltering, even on a day when both areas are receiving the same insolation. A similar situation exists when one drives from Boulder, CO (elevation 5400’) just a few miles west to Nederland (elevation 8200’). Nederland doesn’t sit on a mountain top piercing the sky, either; it’s in the Rockies, sure, but the sky-piercing peaks are all around it. And yet it’s generally a good bit cooler than Boulder… The principal “background” variation in temperature with altitude/elevation is not due to adiabatic processes. Although as you say mountainous terrain does cause parcels of air to rise and fall adiabatically and to change in temperature accordingly, the “background” variation in temperature with altitude is called the Environmental Lapse Rate (ELR). The ELR in the [standard atmosphere](https://en.wikipedia.org/wiki/International_Standard_Atmosphere#ICAO_Standard_Atmosphere) (approximate average global conditions) is about -2°C (-3.5°F) per 1000 feet. As discussed above, the ELR is due to the fact that the atmosphere does not absorb much of the sun’s radiation, so most of the heat energy is added to the atmosphere from below. Based on the average ELR, you’d expect the bottom of the Grand Canyon at 5000’ lower to be 15-20°F warmer, which is just what you find. This fundamental background variation in temperature with altitude is not attributable to an adiabatic process of air rising or falling. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [December 12, 2016, 8:49pm UTC](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303/40 "2016-12-12T20:49:23Z")
> [@Riemann](#): > > As discussed above, the ELR is due to the fact that the atmosphere does not absorb much of the sun’s radiation, so most of the heat energy is added to the atmosphere from below. > > Based on the average ELR, you’d expect the bottom of the Grand Canyon at 5000’ lower to be 15-20°F warmer, which is just what you find. This fundamental background variation in temperature with altitude is not attributable to an adiabatic process of air rising or falling. I think we’re in agreement that both phenomena exist: [ul][li]solar heat is added to the atmosphere primarily at ground level, which is why the air gets colder as you move straight up through open air;[/li] [\*]adiabatic lapse explains why ground level at high elevations tends to be colder than ground level at low elevations.[/ul] In the case of the Grand Canyon, the rim is not simply 5000 feet straight up in open air; there is ground at the rim, collecting heat and locally warming the air at the same rate as the ground at the floor of the canyon. In the absence of any air movement (which would induce adiabatic lapse), shouldn’t we then expect approximately the same ground-level temperature at the rim as is observed at ground level on the canyon floor? [Previous page](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303.md?page=1) [Next page](https://boards.straightdope.com/t/air-getting-thinner-and-thicker-whats-the-straight-dope/774303.md?page=3)