Science Whoppers from Mormon Apologists

[_DrW]

Tarski,

No need to do the calculation. I agree with pretty much every point you have made. I simply point out that you are taking a highly theoretical approach that is of little practical use in evaluating thesometimesaint's statement.

The main variable that determines atmospheric pressure at the surface of the Earth is the vertical component of the motion of air. Low pressure areas develop in areas where (often warm moist) air is rising and higher pressure areas develop where (often cool dry) air is descending. When the air becomes saturated the moisture falls as precipitation. Since there is absolutely no mechanism, or nothing even close to a mechanism, for getting enough water into the atmosphere to create life crushing pressures, the statement just seems silly.

While it is theoretically possible (on some other planet) to load enough water into the atmosphere to increase the overall atmospheric pressure at the surface to "life crushing" , this would require exceedingly high temperatures and / or a very massive planet. Considering the atmosphere on Venus and given the molecular weight and boiling point of water relative to that of carbon dioxide, for example, I think you might be surprised at how hot it would have to be.

[_Tarski]

Tarski,

No need to do the calculation. I agree with pretty much every point you have made. I simply point out that you are taking a highly theoretical approach that is of little practical use in evaluating thesometimesaint's statement.

The main variable that determines atmospheric pressure at the surface of the Earth is the vertical component of the motion of air. Low pressure areas develop in areas where (often warm moist) air is rising and higher pressure areas develop where (often cool dry) air is descending. When the air becomes saturated the moisture falls as precipitation. Since there is absolutely no mechanism, or nothing even close to a mechanism, for getting enough water into the atmosphere to create life crushing pressures, the statement just seems silly.

While it is theoretically possible (on some other planet) to load enough water into the atmosphere to increase the overall atmospheric pressure at the surface to "life crushing" , this would require exceedingly high temperatures and / or a very massive planet. Considering the atmosphere on Venus and given the molecular weight and boiling point of water relative to that of carbon dioxide, for example, I think you might be surprised at how hot it would have to be.

Sounds like we have come to common ground. It was fun to think it through.

[_DrW]

Another aspect of the ridiculous assertion that a certain amount of water vapor in the air might crush all life:

Let us suppose a man develops gill-like structures in his lungs, thus gaining the ability to breath water. Take that man and dump him in the ocean, over the Mariana Trench, with a weight-belt. Supposing he doesn't sink too quickly, and he yawns and farts and belches all the way down, there is no physiological reason to conclude that he would be 'crushed'.

Animal life lives quite happily at the deepest sea bottom, where pressures are in the range of 1000x atmospheric pressure.

Unless it was a nearly instantaneous change, the idea that increased atmospheric pressure would kill life is just silly.

Actually, beefcalf, if the atmospheric pressure were to increase sufficiently, it would kill you. The atmospheric pressure on the surface of Venus (about 1300 psi) would kill you.

The scuba dive record is just over 1000 feet. The pressure at 1000 feet in water is about 450 psi. Humans can't go much deeper without protection from the external pressure, such as is provided by submersible. If humans were to go much deeper, their rib cage would be crushed and the lungs would collapse.

Organism that live or hunt in deep water have to be adapted to the high pressure or they would not survive. Air breathing humans would have little chance if exposed directly to 1300 psi. As for water breathing humans with gills, I couldn't say.

Air breathing sperm whales are adapted to dive to depths of 5000 feet or more. Their rib cages can fold up without permanent damage. The air in their lungs gets compressed to a small fraction of it original volume at these depths.

The Marianna Trench is something like 30,000 feet deep. The pressure at 30,000 feet is a bone crushing 13,350 psi.

[_DrW]

Tarski,

No need to do the calculation. I agree with pretty much every point you have made. I simply point out that you are taking a highly theoretical approach that is of little practical use in evaluating thesometimesaint's statement.

The main variable that determines atmospheric pressure at the surface of the Earth is the vertical component of the motion of air. Low pressure areas develop in areas where (often warm moist) air is rising and higher pressure areas develop where (often cool dry) air is descending. When the air becomes saturated the moisture falls as precipitation. Since there is absolutely no mechanism, or nothing even close to a mechanism, for getting enough water into the atmosphere to create life crushing pressures, the statement just seems silly.

While it is theoretically possible (on some other planet) to load enough water into the atmosphere to increase the overall atmospheric pressure at the surface to "life crushing" , this would require exceedingly high temperatures and / or a very massive planet. Considering the atmosphere on Venus and given the molecular weight and boiling point of water relative to that of carbon dioxide, for example, I think you might be surprised at how hot it would have to be.

Sounds like we have come to common ground. It was fun to think it through.

I agree and enjoyed it as well.

In deference to you and your efforts on behalf of thesometimesaint, I will edit my comments above regarding his statement.

Thanks.

[_beefcalf]

Actually, beefcalf, if the atmospheric pressure were to increase sufficiently, it would kill you. The atmospheric pressure on the surface of Venus (about 1300 psi) would kill you.

The scuba dive record is just over 1000 feet. The pressure at 1000 feet in water is about 450 psi. Humans can't go much deeper without protection from the external pressure, such as is provided by submersible. If humans were to go much deeper, their rib cage would be crushed and the lungs would collapse.

Organism that live or hunt in deep water have to be adapted to the high pressure or they would not survive. Air breathing humans would have little chance if exposed directly to 1300 psi. As for water breathing humans with gills, I couldn't say.

Air breathing sperm whales are adapted to dive to depths of 5000 feet or more. Their rib cages can fold up without permanent damage. The air in their lungs gets compressed to a small fraction of it original volume at these depths.

The Marianna Trench is something like 30,000 feet deep. The pressure at 30,000 feet is a bone crushing 13,350 psi.

With increased air pressure comes increased heat. Boyle's law If I recall correctly. If the air pressure was 1300 psi (vs ~14 on Earth at sea level), the x100 pressure would entail a lethal increase in temperature. But thesometimesaint was not talking about heat.

When a diver is deep underwater, he is breathing a compressible fluid, air or some other specialized mixture which does not include nitrogen. But, it is still compressible. The lethality of deep dives comes from the fact that the fluid on the inside of the lungs and various body cavities is a compressible gas. The deeper one descends, the more gas from his tanks he must pump into his lungs with each breath just to push against that pressure. One breath at a depth 300 meters might contain the same mass of air as ten breaths at the surface. Any diver can talk about bottom time, and the diving computers needed to calculate it.

My rather weird stipulation for breathing the water with gills, and for releasing all gasses from the body during the descent, is to fill all body cavities with incompressible water. Once that has happened, I think it is quite possible to live safely even at extreme pressures. There is no crushing force, because, when everything is filled with an incompressible fluid, nothing can be crushed. And I would wager that any bone dropped over the Mariana Trench which sank to the depths would not be crushed, hence the pressure would not be bone crushing. ;-)

The heat increase due to pressure would surely kill you. The changes in the propensity for blood to carry dissolved oxygen might kill you. But I don't think the pressure change itself is necessarily deadly.