The discussion revolves around calculating atmospheric pressure based on the composition of an atmosphere, the mass of the planet, and its dimensions. Participants explore the necessary parameters and equations for determining atmospheric pressure, addressing both theoretical and practical aspects of the calculation.
Participants generally agree on the need for specific parameters to calculate atmospheric pressure, but there are multiple competing views regarding the correct approach and units to use. The discussion remains unresolved regarding the exact calculations and results.
Participants express uncertainty about the correct values for the radius of the Earth and the implications of using different units in their calculations. There are also discussions about the significance of precision in the results based on the input data.
By composition, I meant quantity of each gas.DrStupid said:You need the mass of the atmosphere.
If you know the total mass of each gas separately then you know the total mass of all the gasses put together.The Exestentialist said:By composition, I meant quantity of each gas.
In what units? I tried this with Earth's atmosphere and I didn't get the right answer.Chestermiller said:To get the pressure at the surface, which is usually referred to as the atmospheric pressure, just divide the weight of the atmosphere mg by the total surface area of the planet.
What units did you use for the weight of the Earth's atmosphere and the surface area of the planet and what answer did you get?The Exestentialist said:In what units? I tried this with Earth's atmosphere and I didn't get the right answer.
I used 5.1x1018 kg for the atmosphere's weight and 4*π*12,742,0002 m2 for the surface area of the Earth. I got 2,499,684 kg/m2jbriggs444 said:What units did you use for the weight of the Earth's atmosphere and the surface area of the planet and what answer did you get?
Check your arithmetic and check your figure for the radius of the Earth in meters. I get around 11,000 kg/m2 on the back of an envelope.The Exestentialist said:I used 5.1x1018 kg for the atmosphere's weight and 4*π*12,742,0002 m2 for the surface area of the Earth. I got 2,499,684 kg/m2
PaThe Exestentialist said:In what units? I tried this with Earth's atmosphere and I didn't get the right answer.
Don't forget to multiply by g.jbriggs444 said:Check your arithmetic and check your figure for the radius of the Earth in meters. I get around 11,000 kg/m2 on the back of an envelope.
Edit: 7 significant figures of computed output on an input that is only stated to 2 digits reflects more precision than is justified.
I was assuming kilograms-force, but yes, I agree.Chestermiller said:Don't forget to multiply by g.