DiscussMormonism.com

Visit the old MADBoard (now MDD) or even Mormon Discussions pretty much any day and you can find Mormon apologetic "science" on display.

Whether it is the recent report that faster than light neutrinos invalidate Einstein's E=mc2 (Zakuska on MDD) , the claim that the flood of Noah was a global event (too numerous to mention), or other demonstrations of ignorance, it makes for entertaining reading at times.

Here are three of my favorites from the last week or so:

1. String theory can be used to support the hypothesis that Kolob actually exists in another universe, which can be accessed by means of gateways for which the LDS Temples are analogs. (bcspace on MDB)

I kid you not.

2. Einstrin's E=mc2 is clearly invalid because a thermonuclear detnonation does not produce infinite energy. (Zakuska on MDD)

Yep.

3. Excess water vapor in the air at the time of Noah would have crushed all life on Earth. (thesometimesaint on MDD)

These are grown adults.

Forget about denial of evolution and belief in a global flood, some of these folks believe in science related claims that can be proven false by any good high school student. Worse yet, some of the apologists just seem to make this stuff up as they go along, or claim that they know about science because they "nearly went to Cal Tech" (DCP, and again, I kid you not).

(Gives new meaning to the term "MormonThink" TM )

What science whoppers have you heard from TBMs?

If they are as entertaining as the above, I would certainly love to hear them.

Here is an example of what I am talking about on this thread from a post I made this morning of the MADBoard quotes megathread.

In a discussion of the damage that would be caused by the Flood of Noah (an often discussed topic at MDD) thesometimesaint, who If I recall correctly has claimed a science background in the past, stated the following:

Plus add in the FACT that water vapor has weight. Suspending that much water in the air would crush all life.*

As anyone knows who flies a plane, or plays golf, or was paying attention in high school science class, the more moisture in the air less a cubic meter of it weighs. In other words, a given volume of moist air, at a give temperature and pressure, weighs less than dry air at the same temperature and pressure, not more.

The ideal gas law, PV=nRT, is taught in high school science classes (or at least it was when I was in high school). One consequence of this simple equation is that lower molecular weight gases serve to reduce the density of a gas mixture at a given temperature and pressure.

Nitrogen gas (N2) with a molecular weight of 28 makes up about 78% of the atmosphere.

Oxygen gas (O2) with a molecular weight of 32, makes up most of the rest (about 20%).

Water vapor (H2O) only has a molecular weight of 18, so as the amount of water vapor increases in the atmosphere, the less dense the air becomes at a given temperature and pressure.

Pilots who ignore the relative humidity when taking off fully loaded, especially on a hot day, could find themselves sitting at the far end of the runway with a badly damaged aircraft.
______________
P= Pressure in pascals
V= Volume in cubic meters

n = number of moles of gas
R= Universal Gas Constant (8.314 J/K mol)
T = Absolute Temperature in Kelvins
___________________________________
*ETA: Tarski understood this statement by thesometimesaint to be a huge what-if without the implication that it could ever happen. Had he taken the time to mention the temperatures involved, I would have understood it the same way.

DrW wrote:Here is an example of what I am talking about on this thread from a post I made this morning of the MADBoard quotes megathread.

In a discussion of the damage that would be caused by the Flood of Noah (an often discussed topic at MDD) thesometimesaint, who If I recall correctly has claimed a science background in the past, stated the following:

Plus add in the FACT that water vapor has weight. Suspending that much water in the air would crush all life.

This is a patently ridiculous statement. And I did not see that anyone caught this or challenged thesometimesaint about this later in the thread. If this statement reflects the level of understanding of basic scientific principles for folks in the Church who claim to have a scientific background, it is disappointing indeed.

As anyone knows who flies a plane, or plays golf, or was paying attention in high school science class, the more moisture in the air less a cubic meter of it weighs. In other words, a given volume of moist air, at a give temperature and pressure, weighs less than dry air at the same temperature and pressure, not more.

The ideal gas law, PV=nRT, is taught in high school science classes (or at least it was when I was in high school). One consequence of this simple equation is that lower molecular weight gases serve to reduce the density of a gas mixture at a given temperature and pressure.

Nitrogen gas (N2) with a molecular weight of 28 makes up about 78% of the atmosphere.

Oxygen gas (O2) with a molecular weight of 32, makes up most of the rest (about 20%).

Water vapor (H2O) only has a molecular weight of 18, so as the amount of water vapor increases in the atmosphere, the less dense the air becomes at a given temperature and pressure.

Pilots who ignore the relative humidity when taking off fully loaded, especially on a hot day, could find themselves sitting at the far end of the runway with a badly damaged aircraft.

Apologists who don't understand this simple principle should not be debating the fine points of atmospheric sciences with those who do.

Why do you get to suppose that the pressure would be the same? (See my last sentence below)

Well, more importantly, I think you may have approached this from the wrong angle.


The point was not about density, it was about weight.
To get that you will have to multiply by volume. The volume will have changed unless one can argue otherwise.

Let us approach this by making a couple simplifications to begin -the second one is the one we will have to backpeddle on in a moment.

First, lets talk about mass instead of weight since I don't want to assume that they will be proportional quite yet. This is because w=mg only holds precisely near the surface of the earth otherwise we nead to use Newton's full law F=GmM/R^2 and since I don't yet know the resulting volume of the atmosphere and I am about to pretend that none of it will escape into space I don't know how thick the atmosphere will be and so on).

Second, as mentioned above I am going to ignore the question of how much of the resulting vapor laden mixture will disapate into space.


Now, if we could get the volume we would take it and multiply by density which is less as you say (if temp and vol haven't changed as they might).

But the volume could be huge.

However, we don't need that at all. The fact is, the new mass will be a simple sum of the mass of the water added to the mass that was already in the atmosphere.
That means of course, the mass of the new atmosphere will be much higher even if the density is lower (which just proves the increase in volume would be dramatic and in fact, we could calculate it).
To the extent that mass is proportional to weight, we will have more weight (under my assumptions).


But, if the volume turns out to be too high, there is no immediately obvious reason to suppose that the earth can hold on to it. In fact, it seems unlikely so my assumption is very questionable. This latter issue also depends on temperature since whether molecules in the upper atmosphere have an average translational velocity higher than their escape velocity is a question of temperature. If the atmosphere is very very cold more can remain bound to the earth. Lots of factor could affect this.
But this is then one more reason your analysis has to be better.

As for pressure, that is not constant as a function of height. As for pressure at the surface, this is actually due to the weight of a column of air above a unit area. So, without a much better analysis I don't think we can get the answer to the question of whether the weight would be higher or lower.
Finally, if the weight isn't the same, the pressure won't be the same (the surface area of the earth will not have changed and from this it is easy to see that change in weight just gives change in pressure rather directly).

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.

DrW

lower molecular weight gases serve to reduce the density of a gas mixture at a given temperature and pressure.

This is true but is not relevant in the way you think. I will do the complete calculation for you assuming very little. A corollary will be that pressure does not stay constant.


As an intuition pump or warm up, please consider this little thought experiment:

Case 1
A very lax balloon is in space and it contains 10^18 kg of gaseous nitrogen and nothing else. What will its weight be when subjected to one g of acceleration or in an equivalent gravitational field?
OK, now release this gas mixture onto a planet with no previous atmosphere but such that it exerts 1 g of gravitation at the surface. Suppose the surface area of the planet is 510,000,0000 km^2. What is the total weight of the new atmosphere? What is the pressure at the surface?

Case 2
A very lax balloon is in space and it contains 10^18 kg of gaseous nitrogen and nothing else. Now inject into the balloon 10^18 kg of pure gaseous water. The mass is double. What will its weight be when subjected to one g of acceleration or in an equivalent gravitational field?
OK, now release this gas mixture onto a planet with no previous atmosphere but such that it exerts 1 g of gravitation at the surface. Suppose the surface area of the planet is 510,000,000 km^2 as before. What is the total weight of the new atmosphere? What is the atmospheric pressure at the surface?

Like I said, I will do the whole calculation for you later. I will identify also the subtle reason your way doesn't work if it is not already obvious by now.

See above, but you do realize that Sometimes_Saint is arguing against the Bible nuts don't you? He is not one of the anti-science nuts in that group.

Not that this has any bearing on who is right or how to think about the hypothetical water vapor problem.

Tarski,

Sorry, I edited the OP before I saw your response. The original OP can now be seen at viewtopic.php?f=1&t=20424

In any case, you are making this far too complicated. And if you did any calculations before you wrote your response you might want to re-check them if you think I am wrong.

In aviation, we have a parameter called "density altitude". This number is related to the lift that can be generated by a wing moving at a given speed through the air at a given angle of attack at a given temperature, barometric pressure, and relative humidity (dew point).

If one starts with PV=nRT, one can derive the equations for density altitude and from these calculate directly the mass of air in a cubic meter at a given pressure temperature and dew point. The math is a bit much for a message board but is laid out very clearly at:

http://wahiduddin.net/calc/density_altitude.htm

in case you are interested in how the derivation is done.

Here is an example of the mass of a cubic meter of air as a function of moisture content, with temperature and pressure held constant:

At an air temperature of 30 degrees C, and a pressure of 1015 mb:
The mass of a cubic meter of air with a dew point of 10 degrees C is 1.1611 kg
The mass of a cubic meter of air with a dew point of 25 degrees C is 1.1526 kg.

(All else being equal the higher the dew point, the more water vapor in the air and the less a cubic meter of this air weighs on Earth.)

This is why ATIS and the tower always report the relative humidity (along with temperature, barometric pressure and wind speed and direction) to aircraft about to use airport runways for take-offs and landings. It makes a difference in the airspeed that has to be maintained on approach and carried across the threshold at a give gross weight for landing aircraft, and the gross weight that a departing aircraft can safely carry for take-off.

Tarski,

Please look at my last post again. Then please back up and take another look at the claim of a water vapor laden atmosphere that would "crush all life" on Earth.

I showed that the mass (weight) of a cubic meter of moist air is less than that of a cubic meter of dry air.

And that fact of the matter is that the atmosphere takes up and releases billions of tons of water every day. In fact by volume the atmosphere holds approximately 3,000 cubic miles of water at any given time. When an area of the atmosphere is saturated with water, it simply falls back to earth as precipitation.

Given the size and mass of the Earth, its surface gravity, the temperatures found on its surface, and the composition of its atmosphere (not significantly different from the time of Noah), what mechanism can you possibly imagine wherein Earth's atmopshere could take up enough water to "crush all life on Earth" in the time of Noah?

You really need to think about this again, my friend. Here are some comparative data to consider:

The atmosphere of Venus is 98.6% carbon dioxide (molecular weight = 44 amu).

The atmosphere on Venus has a mass of 4.8 x 10 exp 20 kg.

The surface gravity on Venus in 8.87 m/s2.

The average surface Temperature of venus is 462 Degrees C

The average molecular weight of the Earths' atmosphere (78% N2 and 20% O2) without any water vapor, is something on the order of 29 amu.

The mass of Earth's atmosphere is 5.1 x 10 exp 18 kg

The surface gravity on earth is 9.78 m/s2.

The avreage surface temperature on the Earth is about 13 Degrees C

Now please consider:

The atmospheric pressure on the surface of Venus is 92 bar.

The atmospheric pressure on the surface of the Earth is barely 1 bar (1015 mb).

Do you still think it would be possible to build up a "life crushing" air pressure on Earth by adding 18 amu water to a 29 amu atmosphere with the surface temperatures found on Earth?

If this is possible under the atmospheric conditions that exist on Earth, given there is plenty of available water to transfer to the atmosphere (which contains far less than 1% of the water found on earth), why do we have no geological record of such life crushing pressures from a water laden atmosphere?
__________________

ETA: Average Surface Temperatures of Earth and Venus.

Tarski,

I have copied my posts over from the other thread and will stay on this one now for the discussion.

I do see your point about what would happen IF enough water vapor could be taken into the atmosphere, and IF no atmosphere were lost to space and IF the water didn't simply come down again as precipitation (which it does).

But the fact of the matter is, as I am sure you will agree, under the conditions that have existed or Earth for millions, if not billions, of years, it simply could not happen. In fact the conditions under which it could happen on Earth would be far outside the range (especially with regard to surface temperatures) in which life as we know it could exist.

In the meantime, I maintain that when it comes to figuring out many problems related to the atmosphere, the weather, aerodynamic lift involved in aviation and sailing, and the issue of a global flood on this planet, PV=nRT does just fine, and provides a reliable means by which to evaluate such statements such as those made by thesometimesaint.

I have enjoyed the discussion so far and have to leave for a few hours.

DrW wrote:Tarski,

Please look at my last post again. Then please back up and take another look at the claim of a water vapor laden atmosphere that would "crush all life" on Earth.

LOL, I didn't say anything would be crushed. I said that unless some atmosphere is lost to space (which it may be), the pressure will increase. That is, the weight of the column of air above a unit area at the surface will have increased. How much? I don't know yet but it will be increased despite the density having possibly lowered.

Your analysis missed the mark regardless of how ridiculous the crushing thing turns out to be.

I showed that the mass (weight) of a cubic meter of moist air is less than that of a cubic meter of dry air.

Yes of course, but that is not where the alleged "crushing" potential is. We have to ask about pressure (which is weight per area in this case).

Weight density is weight per volume, pressure is weight per area.
One may go down while the other goes up and this is what would happen if a massive amount of water were added to the atmosphere.

Granted, normal evaporation in the water cycle doesn't have a big enough effect and the local effects relating pressure, humidity and all that dominate. Not enough water is involved (though it sounds like a lot) to make the total mass of the atmosphere vary that much relatively speaking. But then we never see whole oceans evaporate. If they did, would the increase in pressure I am talking about be significant? I can't say unless I calculate it.

But, adding mass to the atmosphere increases average atmospheric pressure at the surface. That much is a one liner since roughly, the pressure is

mass of the atmosphere times g divided by surface area of the earth.