Effects of a thicker atmosphere?

[Jimmy Magnusson]

I've had no trouble finding information on the effects of a thinner atmosphere. But what applies in the other direction, say if Earth's atmosphere was twice as thick (2 atm. at surface level)? Would you even notice the increased preassure, or would your body adjust to it? Would your breathing be slower, as there's more oxygen in each breath? Would you be able to increase your physical performance because of that increased oxygen level? Would the air "feel" thicker to breathe? How would it affect the development of plants and animals, would they develop in a certain way because of increased oxygen/co2 in the air?

And how much added preassue can you have and still live and breathe without a pressure suit? Two atmospheres? Six? Eight?

 

[Nik]

Check out saturation diving for utter limits, given evolutionary adaptation per deep-diving whales, seals etc, but 2 bar (atm) is only six feet or so depth...

One gotcha of two-bar surface would be that aircraft and balloons are *easy*, but air-friction keeps most slow. How about very big birds and bugs ? Or very-small winged with-respect-to body size ?Another is Everest routinely becomes climbable without oxygen.

I suspect the weather may be much more extreme: Thicker Air holds more moisture, carries double momentum. Trees would have to sit low, or adopt c-nut palm tactics-- Thick stem, trailing fronds. More depth of atmosphere could lead to monster storms. Hypercanes are routine, immense dust-storms common, and sea-waves would be very scary. Think 'Roaring Forties' almost everywhere...

Building design would be lower, and only the brave would have big, glazed areas that lack shutters...

Okay, plants would have adapted, but think of wind-swept off-shore islands' wind-dwarfed shrubs. Farmers would have a lot of wind-breaks, sunken fields etc etc. I suspect a lot of people would live in earth-sheltered semi-caves. Think Hobbits & Tatooine, albeit for other reasons...

Of course, wind-power is a no-brainer...

 

[skeptical]

Think Venus, which has a much thicker atmosphere. Think greenhouse gases. Imagine, instead of frying an egg on the sidewalk, you melt lead ....

 

[jojajihisc]

Evaporation would be lower from increased atmospheric pressure so more water would be held in liquid form. (This is how nuclear reactors keep water from boiling off so rapidly.)

 

[Chinook]

Like a lot of complex questions, the answer isn't simple either. The answer is - It depends. Are you saying that the extra (doubled) atmosphere is held within the same thickness layer that we have now? If so, what would justify the extra density of the atmosphere? The current atmosphere is held by the Earth's gravitational field.

The gravity of a body is determined by it's mass, so either the Earth would have to be twice as large (in which case the atmosphere would probably stay the same density it is now, but go out further into space. - This would provide the increase in pressure, like stacking twice as many empty boxes on top of one another. The current air pressure at sea level is 101.3 kN/M squared (14.7 lb./in sqared) so you would then double these figures.)

The other option would be that the internal composition of the earth would be twice as dense, and this would most likely result in the same size layer of air on the surface with double the density. Remember that air is only 21% Oxygen, and is mostly made up of Nitrogen (N2) which is obviously harmless to us. There is roughly 1-4% water vapor contained in the Troposphere (the lowest portion that contains 80 % of the mass of the atmosphere and is thinnest at the equator - roughly 7 KM above sea level, and thickest at the poles - roughly 17 km above sea level.) So, we wouldn't just be getting twice as much Oxygen, we'd be getting twice as much of everything. Our lungs would need to be stronger, etc.

In either case the gravity would have to be double to hold twice the mass of atmosphere. I believe this would make plants, animals, and man shorter and thicker to handle the extra "weight". Also, temperature is related to pressure in this environment. It's possible the temperature would increase in either scenario (In the first because the thicker atmosphere's lensing effect, and the second because of the air density.) As for the extra storms, that all depends on a lot of variables That I don't have the time to research right now.

Was this an idea for a Science Fiction story?

 

[Karn Maeshalanadae]

Let me think....

There's all kinds of issues that would go along with this. One must realize that about 78% of Earth's atmosphere is nitrogen, with about 21% being oxygen. We breathe in that nitrogen along with our oxygen. Evolutionary standards.

Nature looks after her creatures. Evolution, however, is a slow process, so if such a thing were to happen fast enough, how would we adapt?

Then again, maybe my knee wouldn't pop so much.....

 

[skeptical]

Too many variables. It is impossible to give a good scientific answer.

There is no reason that the Earth could not hold an atmosphere twice as massy as we have. All that is needed is to add the air, say by cometary impact. Then we have an atmosphere twice as bulky.

This should not cause significant changes to the shape and size of life forms. However, there may be lots of changes on a more subtle level. Lung size may shrink. Stomata number may reduce.

Or, as I said before, the world may warm up to the point where life is impossible. Sterile Earth.

 

[Karn Maeshalanadae]

Or, skeptical, if the change was fast enough, then people might start suffering from an oxygen overdose.

Yes it IS possible. Google is awesome-in certain respects.

 

[Happy Joe]

It would definitely be noticeable I live at about 2,000 meters altitude and the air is noticeably thicker, with more oxygen when I get down to the flatlands around 300 meters above sea level.

Effects that I have noticed at reduced pressures: bread browns differently when baking, it takes longer to heat food by boiling (water boils at lower temperature) you can feel the effects more quickly when drinking less alcohol.

Enjoy!

 

[Nik]

"... the gravity would have to be double to hold twice the mass of atmosphere."
Sorry, no. Venus has very similar surface gravity to Earth. Agreed, the gas mix is different.

Also, IIRC, double density atmosphere should be able to hold a lot more moisture. And, yes, it is likely to have more greenhouse effect.

Uh, erosion is likely to be be faster, tall trees rare...

 

[Boneman]

By Happy Joe

you can feel the effects more quickly when drinking less alcohol.

But are the side-effects less, as well?

 

[jojajihisc]

Also, IIRC, double density atmosphere should be able to hold a lot more moisture. And, yes, it is likely to have more greenhouse effect.

The key to the air holding more moisture is temperature not density.

 

[Chinook]

Nik, and Skeptical: I am willing to believe that your assertions are true but; can you prove your assertions? How would you go about proving such a thing when you have no example that is a real model for it? The weights of the gasses on Venus are much greater. CO2 makes up 96.5% of the atmosphere on Venus. Another 3.5% is Nitrogen. 1 molecule of CO2 = 12 amu + 2(16 amu) = 44 amu. Whereas 78.5 % of our atmosphere is N2 = 28 amu, and 21.5 % is O2 which = 32 amu. This gives an average amu of 28.9 amu of mass in each molecule on earth. the average molecular mass on Venus is 43.44. There are at least tens of factors that are different about the two planets, and the two atmospheres. Venus has no magnetosphere whatsoever (only an "induced" magnetic magneto-tail created by solar wind.) Venus' mean sidereal day is equal to 243 earth days. The atmospheric pressure at the surface of Venus is about 92 times that of the Earth, similar to the pressure found 910 metres below the surface of the ocean. The atmosphere has a mass of 4.8 × 1020 kg, about 93 times the mass of the Earth's total atmosphere. This may explain why it can maintain the high pressure.

Venus' atmosphere is anywhere from 220 to 350 km thick at the outermost layer of it's exosphere, while Earth's atmosphere is extended out to 10,000 km. If we were reading an advert about it, it might say "Earth's atmosphere is lighter through and through".

The layers of Sulphuric acid and Chlorine in the cloud layers of Venus absorb light differently resulting in an Albedo that is roughly twice that of Earth (0.75 as compared to 0.39) Here is an interesting paper on the complexities of the Venutian atmosphere. www.terrapub.co.jp/journals/EPS/pdf/5203/52030197.pdf

So, I think the question remains - What would be the effect on humans if the atmosphere was twice as dense at the surface, yet contained exactly the same composition. Is that possible? Or do elements in the atmosphere follow the same laws that all elements in the Universe follow (as far as we know) given by Newton's famous equation: F = G * M1*M2/r2.

 

[Karn Maeshalanadae]

The key to the air holding more moisture is temperature not density.

Actually, it's rather a combination, to a point. More oxygen in the air would mean less hydrogen, therefore quite possibly less moisture, not more.

You would also have to consider what it would do with the Ozone layer as well. Wouldn't a thicker atmosphere mean thicker Ozone, therefore providing a more shielding cover from the sun's UV rays and therefore decreasing risk of skin cancers?


That's assuming we don't have an ozone layer so thick no heat would be able to get through at all, of course.

 

[jojajihisc]

Actually, it's rather a combination, to a point. More oxygen in the air would mean less hydrogen, therefore quite possibly less moisture, not more.

Which is exactly what this means.

Evaporation would be lower from increased atmospheric pressure so more water would be held in liquid form. (This is how nuclear reactors keep water from boiling off so rapidly.)

 

[Nik]

"The key to the air holding more moisture is temperature not density."

Yup. My bad.
PhysChem was NOT my forte...