Accummulation of Gases in the Atmosphere

[Ptolemy]

I was reading that helium does not accummulate in the Earth's atmosphere due to the fact (a claim) that it is too light to be retained by gravity and diffuses out into space.

Does anyone know the physics that prevent the atmosphere seeking the vacuum at whooshing out into space.

Is there a molecular weight cut off that has been theoretically calculated whereby a gas will accummulate in the atmosphere or escape the gravitational pull and disperse?

 

[Andre]

That's interesting question indeed. I know that for the moist greenhouse gas theory for Venus, it was required that H2 would escape it's gravtitional field, to explain the water to disappear that would have triggered the heating initially.

Hypothesis can be falsified easily but anyway.

 

[Ptolemy]

.

So how do you falsify it?

As I understand the reason that we "know" helium does not accummulate is because we "know"
1) The Earth is x billion years old
2) The rate at which it is cooling
3) The fact in order to have the x billion we need an additional source of heat
4) That source of heat is radiation from the decay of Uranium
5) That decay produces Helium
6) But despite large amounts of helium in natural gas and oil there is very little in the Earth's atmosphere.

Ergo it must all escape into space. Or roughly.

The government of the United States set up the National Helium Reserve in 1925 at Amarillo, Texas with the goal of supplying military airships in time of war and commercial airships in peacetime. Helium use following World War II was depressed but the reserve was expanded in the 1950s to ensure a supply liquid helium as a coolant to create oxygen/hydrogen rocket fuel (among other uses) during the Space Race and Cold War. Helium use in the United States in 1965 was more than eight times the peak wartime consumption.

After the "Helium Acts Amendments of 1960" (Public Law 86-777), the U.S. Bureau of Mines arranged for five private plants to recover helium from natural gas. For this helium conservation program, the Bureau built a 425-mile pipeline from Bushton, Kansas to connect those plants with the government's Cliffside partially depleted gasfield, near Amarillo, Texas. This helium-nitrogen mixture was injected and stored in the Cliffside gasfield until needed, when it then was further purified.

By 1995 32 billion ft³ (1 billion m³) of the gas had been collected and the reserve was US$ 1.4 billion in debt, prompting the Congress of the United States to phase out the reserve starting the next year. The resulting "Helium Privatization Act of 1996" (P.L. 104-273) directed the United States Department of the Interior to start liquidating the reserve by 2005.
QUOTE]

Maybe we could let off the entire reserve at once and see what happens?

 

[Andre]

What I meant was falsifying the moist greenhouse theory for Venus of Kastings, Toon and Pollack concerning the diffusion of the H2. I agree on the Helium diffusion.

But that's off topic here.