Answer the Question: Is Completely Empty Room Possible?

  • Context: Graduate 
  • Thread starter Thread starter Firefox123
  • Start date Start date
  • Tags Tags
    Empty
Click For Summary

Discussion Overview

The discussion revolves around the question of whether a completely empty room, in the context of gas dynamics, is theoretically possible given an infinite amount of time. Participants explore the implications of molecular motion in a sealed container filled with gas and whether it is statistically likely for all gas molecules to occupy one half of the room, leaving the other half at zero pressure.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants suggest that given enough time, it is theoretically possible for all gas molecules to be found in one half of the room, resulting in zero pressure in the other half.
  • One participant expresses uncertainty about their initial answer, indicating a lack of expertise in fluid dynamics or statistical mechanics.
  • Another participant references "fluctuation theory" as a concept that could provide deeper insights into the phenomenon.
  • A different participant mentions the "Poincaré cycle" theorem, which they claim supports the possibility of such an event occurring.

Areas of Agreement / Disagreement

Participants generally agree that, theoretically, the state of having all gas molecules in one half of the room is possible given sufficient time, but there is uncertainty regarding the practical implications and the time scales involved. The discussion remains unresolved regarding the specifics of how likely or rare this occurrence would be.

Contextual Notes

Participants acknowledge limitations in their understanding of the underlying principles of gas dynamics and statistical mechanics, which may affect their interpretations of the question.

Firefox123
Messages
183
Reaction score
1
Someone asked me this question and I was wondering how you guys would answer it...


Consider a container with some gas in it. It can be a sealed living room filled with ordinary air at typical pressure.

The air molecules are in motion - colliding with each other and bouncing off the walls.

Question: If this random motion of molecules around the room is allowed to proceed long enough (say, a billion years raised to the billionth power), will it at some point happen that all of the gas molecules are in one half of the room, leaving the other half in zero pressure?

Is that situation forbidden by the principles of gas dynamnics, or are gas dynamics just statements about what is statistically likely to be the case at anyone time as gas molecules knock each other around? Will those principles be wildly violated on statistically rare occasions?
 
Physics news on Phys.org
steadele said:
(snip)Question: If this random motion of molecules around the room is allowed to proceed long enough (say, a billion years raised to the billionth power), will it at some point happen that all of the gas molecules are in one half of the room, leaving the other half in zero pressure?(snip)

Short answer: "Yes." You're a little short on the time scale necessary to be able to witness it, but, "sooner or later," the system passes through that state.
 
Bystander said:
Short answer: "Yes." You're a little short on the time scale necessary to be able to witness it, but, "sooner or later," the system passes through that state.


Cool...the person who originated the question was allowing for as much time as theoretically necessary for the event to occur.

My answer, with reservation, was that yes I did think such a state would occur given enough time.

But I am an electrical engineer who is not an expert in fluid dynamics or statistical mechanics so I wasnt sure if my intial answer waas correct or an oversimplification.

Do you know of any online resources that I could direct him to for a deeper explanation of why this could occur and how much time might be necessary?


Thanks.


Russ
 
You should also search for "Poincaré cycle"...

There's a theorem proved by Poincaré that allows this possibility.

Daniel.
 
dextercioby said:
You should also search for "Poincaré cycle"...

There's a theorem proved by Poincaré that allows this possibility.

Daniel.


Will do.

Thanks.
 

Similar threads

High School The 'all air in a room collecting on one side' adage
  • · Replies 22 ·
Replies
22
Views
4K
Undergrad Why do sound waves not bounce off of each other?
  • · Replies 20 ·
Replies
20
Views
6K
MHB What are some questions about thermodynamics and their potential answers?
  • · Replies 3 ·
Replies
3
Views
2K
Dalton's atomic theory, Avogadro, and caloric theory
  • · Replies 4 ·
Replies
4
Views
3K
High School Why gas clouds collapse if the forces are conservative?
  • · Replies 15 ·
Replies
15
Views
2K
Undergrad Kinetic theory of gases: rebound speed and force questions
  • · Replies 2 ·
Replies
2
Views
3K
Undergrad Is it possible to create a completely sealed room where a door can't be opened?
  • · Replies 11 ·
Replies
11
Views
4K
Graduate Answering Sound Wave Questions
  • · Replies 6 ·
Replies
6
Views
3K
Cooking (Thermodynamics) Problems
  • · Replies 14 ·
Replies
14
Views
5K
Undergrad What causes atmospheric pressure: gravity or molecular collisions?
  • · Replies 5 ·
Replies
5
Views
9K