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Author Topic: Does the air in a sealed room move?  (Read 6803 times)

Offline neilep

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Does the air in a sealed room move?
« on: 28/10/2006 04:45:25 »
Does air in a completely air tight room and shielded from vibration, move ?...

...If so...why ?
« Last Edit: 24/12/2006 09:11:24 by chris »


 

another_someone

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Re: Does the air in a sealed room move?
« Reply #1 on: 28/10/2006 04:52:46 »
Firstly, there is Brownian motion, where the molecules of air will themselves vibrate simply due to heat.

Then you will have convection currents (unless you can guarantee that the entire room is at an absolutely even temperature, with absolutely no warm or coll spots).
 

Offline neilep

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Re: Does the air in a sealed room move?
« Reply #2 on: 28/10/2006 05:08:56 »
THANK YOU GEORGE.

Ok, so even if we eliminate convection currents...brownian motion will still keep the air moving....but...really really slow yes ?

One  could hold a single hair or feather strand and it would not move ?
 

another_someone

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Re: Does the air in a sealed room move?
« Reply #3 on: 28/10/2006 05:25:06 »
You could not hold anything in the room because your own prescence in the room would be a source of heat, as well as a source of motion.
 

Offline neilep

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Re: Does the air in a sealed room move?
« Reply #4 on: 28/10/2006 06:30:58 »
Yes, I realise that. Thank You George,  It could be held by a clamp of sorts.

 

Offline lightarrow

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Re: Does the air in a sealed room move?
« Reply #5 on: 28/10/2006 07:59:33 »
You should also prevent any vibration from the walls, or it would transmit a (slight) movement to the air
 

Offline Gaia

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Re: Does the air in a sealed room move?
« Reply #6 on: 28/10/2006 13:04:23 »
It depends at what level you are measuring movement. I'll do a George and be pedantic. There are  electrons moving in their orbits etc. What about external sound causing vibrations? Also, have you filtered the air to remove micro-organisms etc? You will always have some type of movement, I suppose a temperature of zero kelvin might help.
 

another_someone

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Re: Does the air in a sealed room move?
« Reply #7 on: 28/10/2006 13:47:22 »
I'll do a George and be pedantic. There are  electrons moving in their orbits etc.

Doing a George is best left to George  :P

The Bohr model of the atom, with the notion of electrons orbiting around a nucleus, was a short lived model that is no longer considered the best model to use.

http://en.wikipedia.org/wiki/Atomic_orbital
Quote
Classically, the electrons were thought to orbit the atomic nucleus, much like the planets around the Sun (or more accurately, a moth orbiting very quickly around a lamp). However electrons cannot be described as solid particles (as a planet or a moth), so a more accurate comparison would be that of a (huge) atmosphere (the spatially distributed electron) around a (tiny) planet (the nucleus). Hence the term "orbit" had to be substituted with something else: orbital.

And, ofcourse, since air is mostly composed of molecules rather than isolated atoms, then the electrons are not necessarily bound to a single atom anyway.
« Last Edit: 28/10/2006 13:54:16 by another_someone »
 

Offline neilep

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Re: Does the air in a sealed room move?
« Reply #8 on: 28/10/2006 17:38:46 »
See Gaia ?..I knew that !..sheesh !!...you get these girlys who think they know it all !!...get back in the kitchen will ya ? ..and then la boudoir !! ;D :D ;) ;) ;)


Okayyyy !!....so...assuming we've eliminated all sources of vibration (of all types), and there are no convection currents and the temperature is an even , well, lets say 10 degrees C....if one was able to place a single air molecule that could be monitored , in the corner of a room which is , lets say 10 feet cubed...what would be the speed of movement of this molecule ?

Hope this is not asking too much ?...cos for me...just asking the question was taxing enough !! :)
 

Offline Gaia

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Re: Does the air in a sealed room move?
« Reply #9 on: 28/10/2006 17:44:57 »
Ok George, orbital rather than orbit, but there's still movement, even if only of energy.

From your fav, Wikipedia
In atoms with a single electron (essentially the hydrogen atom), the energy of an orbital (and, consequently, of any electrons in the orbital) is determined exclusively by n. The n = 1 orbital has the lowest possible energy in the atom. Each successively higher value of n has a higher level of energy, but the difference decreases as n increases. For high n, the level of energy becomes so high that the electron can easily escape from the atom.

In atoms with multiple electrons, the energy of an electron depends not only on the intrinsic properties of its orbital, but also on its interactions with the other electrons. These interactions depend on the detail of its spatial probability distribution, and so the energy levels of orbitals depend not only on n but also on \ell. Higher values of \ell are associated with higher values of energy; for instance, the 2p state is higher than the 2s state. When \ell = 3, the increase in energy of the orbital becomes so large as to push the energy of orbital above the energy of the s-orbital in the next higher shell; when \ell = 4 the energy is pushed into the shell two steps higher.
 

another_someone

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Re: Does the air in a sealed room move?
« Reply #10 on: 28/10/2006 19:49:59 »
lets say 10 degrees C....if one was able to place a single air molecule that could be monitored , in the corner of a room which is , lets say 10 feet cubed...what would be the speed of movement of this molecule ?

Hope this is not asking too much ?

It is asking far too much, so I found a web page that did it for me.

http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/kintem.html#c4

If you feed in the molecular weight of oxygen (32 atomic mass units) and an ambient temperature of 10 degrees Celsius, gives a mean speed of 968 miles per hour.

Nitrogen (molecular weight 28) gives a mean speed of 1035 mph.
« Last Edit: 28/10/2006 19:53:19 by another_someone »
 

Offline neilep

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Re: Does the air in a sealed room move?
« Reply #11 on: 28/10/2006 19:57:33 »
Oh MY Gawwwd !!

George !!...that is incredible that even such a page exists and more so that you found it !!..THANK YOU !

I am very suprised by the speeds !...way fatser than I imagined !!
 

another_someone

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Re: Does the air in a sealed room move?
« Reply #12 on: 28/10/2006 21:18:05 »
I am very suprised by the speeds !...way fatser than I imagined !!

If you think about it, the speed of molecules in the air must be faster than the speed of sound (which is over 700mph) in order that the molecules of air could transmit the sound waves.
 

Offline neilep

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Re: Does the air in a sealed room move?
« Reply #13 on: 28/10/2006 21:21:19 »
DOH !!...I luffs it when this man gives away so many ' penny dropping' moments !

Thank You George.

Well..I suppose that puts an end to this thread !
 

Offline moonfire

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Re: Does the air in a sealed room move?
« Reply #14 on: 06/11/2006 16:31:47 »
See Gaia ?..I knew that !..sheesh !!...you get these girlys who think they know it all !!...get back in the kitchen will ya ? ..and then la boudoir !! ;D :D ;) ;) ;)


Okayyyy !!....so...assuming we've eliminated all sources of vibration (of all types), and there are no convection currents and the temperature is an even , well, lets say 10 degrees C....if one was able to place a single air molecule that could be monitored , in the corner of a room which is , lets say 10 feet cubed...what would be the speed of movement of this molecule ?

Hope this is not asking too much ?...cos for me...just asking the question was taxing enough !! :)

too much vibration here Neilsy...
 

Offline neilep

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Re: Does the air in a sealed room move?
« Reply #15 on: 06/11/2006 19:55:07 »
See Gaia ?..I knew that !..sheesh !!...you get these girlys who think they know it all !!...get back in the kitchen will ya ? ..and then la boudoir !! ;D :D ;) ;) ;)


Okayyyy !!....so...assuming we've eliminated all sources of vibration (of all types), and there are no convection currents and the temperature is an even , well, lets say 10 degrees C....if one was able to place a single air molecule that could be monitored , in the corner of a room which is , lets say 10 feet cubed...what would be the speed of movement of this molecule ?

Hope this is not asking too much ?...cos for me...just asking the question was taxing enough !! :)

too much vibration here Neilsy...

Fresh batteries eh ? Mam ?  ;)..................................soooreeeeeeeyyy !!! ;)
 

Offline Karen W.

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Re: Does the air in a sealed room move?
« Reply #16 on: 09/11/2006 09:05:44 »
I cannot even begin to understand all that!
 

another_someone

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Re: Does the air in a sealed room move?
« Reply #17 on: 09/11/2006 12:51:42 »
I cannot even begin to understand all that!

OK, it got a teeny bit technical, but which bit do you want explained?
 

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Re: Does the air in a sealed room move?
« Reply #17 on: 09/11/2006 12:51:42 »

 

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