Understanding the effects of gravity on a gas

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Discussion Overview

The discussion centers on the effects of gravity on a gas contained in an insulated environment, specifically whether a temperature gradient exists within the gas due to gravitational influence. Participants explore concepts related to pressure differences and kinetic energy in the context of thermodynamics and the behavior of gases.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant suggests that there is less pressure at the top of an insulated container due to gravity and questions if this results in a colder temperature at the top.
  • Another participant asserts that the answer is no, referencing the second law of thermodynamics as a source, but does not elaborate on the reasoning behind this claim.
  • A request for further explanation is made regarding the initial 'no' response, indicating a desire for a more detailed discussion.
  • A participant describes the kinetic theory of gases, suggesting that the random motion of gas molecules leads to a uniform average kinetic energy throughout the container, but questions whether this results in a temperature gradient.
  • Contradicting the previous claims, another participant argues that a temperature gradient does exist, citing the concept of lapse rate and questioning the reliability of Wikipedia as a source.
  • A participant discusses the relationship between kinetic energy and gravitational potential energy, proposing that moving against gravity could affect the temperature of gas molecules.
  • Reference is made to a previous thread concerning the "altitude hypothesis," indicating ongoing exploration of related ideas and the complexities involved in understanding heat gradients in gases under gravitational influence.

Areas of Agreement / Disagreement

Participants express conflicting views regarding the existence of a temperature gradient in a gas under gravitational influence, with no consensus reached on the matter. Some argue against the gradient, while others support its existence.

Contextual Notes

Participants reference concepts such as the second law of thermodynamics, kinetic theory, and lapse rate, but the discussion remains unresolved regarding the implications of these theories on the temperature gradient within the gas.

striphe
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If a gas is enclosed in an insulated container on earth, I understand that at the top of the container there will be less pressure than at the bottom due to gravity.

What I want to know is if the top is colder due to the effects of gravity. If reliable sources could provided it would be appreciated (I can't seem to find any).
 
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Can you go into it any more than just simply 'no' curl, as to why?
 
The kinetic theory of gases describes the atoms or molecules of a confined gas as having a random distribution of the x,y and z components of velocity, and they move in straight lines until they collide with the container walls and bounce off. That description leads to a mixing that would have the population of molecules in any region of the container having the same average kinetic energy as the molecules in any other region of the container.

To produce the difference in pressure between the top and bottom due to gravity, change the reference to motion in straight lines into a reference to motion in parabolas that are very nearly straight lines. This makes the density and pressure slightly less at the top. Whether that causes a slight temperature gradient, I don't remember.
 
Curl said:
No. Here is a reliable source:

http://en.wikipedia.org/wiki/Second_law_of_thermodynamics
Wrong. The answer is yes. First off, Wikipedia is not a reliable source, and secondly that wiki article doesn't say anything about the question being asked.

Lots of people go to the mountains in the summer to escape the heat. Think about that for a second.

Google the phrase "lapse rate".
 
Mikelepore, My own consideration of what occurs within the gas regarding a possible heat difference; that heat is related to the kinetic energy of the molecules that make up the gas, with that kinetic energy being converted to gravitational potential energy if a molecule moves against the force of gravity.

D H, Curl may have read my other thread, "the altitude hypothesis" which brings about a particular dilemma based on this. The thread eventually came to a halt when I asked about lapse rate.

The hypothesis has two parts and what i was expecting was that the latter part to be the shortcoming. The users that posted opted for the first part as being the problem. That being a heat gradient does not emerge in contained body of gas under gravitational force.
 

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