>> ...all of which is true. However, a simple experiment with a wavetank 
>> quickly demonstrates that, for some reason that I don't comprehend, 
>> large waves won't go through small gaps, and yet small waves will. 
>> This is the precise opposite of what you would expect, but the results 
>> are clear.
> 
> Hum... I hate to admit this, but it seems you're right: I just hacked 
> together a POV-Ray script to simulate a wavetank-kind-of-apparatus (very 
> idealized, but still...), initially to disprove your statement - only to 
> find that indeed small gaps will not let low-frequency waves pass. 
> Changes in gradient will pass through - but not oscillations.

Weird, isn't it?

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Tim Cook schrieb:
> clipka wrote:
>> Strictly speaking, there's no such thing as a "pulling" force in air.
> 
> Sure there is.  Ever heard the phrase "nature abhors a vacuum"?  That's 
> a pulling force.  Any decrease in pressure in an atmosphere will cause 
> molecules to be drawn to the source of the pressure difference.

"Natura abhoret vacui" is a very old misconception. At 0 degrees Kelvin, 
nature has no problems with vacuum.

What is commonly percieved as a pulling force of the vaccum is in 
reality a stronger pushing force (due to collisions of molecules) from 
the high-pressure region than from the low-pressure region. As a matter 
of fact, *both* exert a pushing force.

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On 08/11/09 03:51, Tim Cook wrote:
> clipka wrote:
>> Strictly speaking, there's no such thing as a "pulling" force in air.
>
> Sure there is. Ever heard the phrase "nature abhors a vacuum"? That's a
> pulling force. Any decrease in pressure in an atmosphere will cause
> molecules to be drawn to the source of the pressure difference.

	That's a push, not a pull.

	If you dip a straw into a glass of water, and "suck", all you're doing 
is forcing your diaphragm to go down a bit, causing your lungs to 
expand. This creates a region of low pressure in your lungs, and the 
atmospheric pressure *outside* is what will actually push the water into 
your mouth - it's a push by the atmosphere, not a pull by you.

-- 
Whose cruel idea was it for the word "Lisp" to have a "S" in it?

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Neeum Zawan wrote:
>     That's a push, not a pull.
>     If you dip a straw into a glass of water, and "suck", all you're 
> doing is forcing your diaphragm to go down a bit, causing your lungs to 
> expand. This creates a region of low pressure in your lungs, and the 
> atmospheric pressure *outside* is what will actually push the water into 
> your mouth - it's a push by the atmosphere, not a pull by you.

*thinks about it*  Seems to me like six of one, half-dozen of another, 
but then again, centrifugal force is a nonexistent force conjured up to 
describe motion in a particular frame of reference, too...from an 
outside point of view, the math is easier/makes more sense when you 
reduce everything to a single set of common elements with no overlap.

But having a word for 'suck' is handy for us lay-people--lets us 
describe life in a shorter phrase than "region of low density of 
pleasantness at self causes misfortune to be pushed onto me", as "life 
sucks".

;)

--
Tim Cook
http://empyrean.freesitespace.net

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On Tue, 11 Aug 2009 21:39:33 -0400, Tim Cook <z99### [at] gmailcom> wrote:

>"life sucks".

No! Death pushes ;)
-- 

Regards
     Stephen

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On 08/11/09 20:39, Tim Cook wrote:
> *thinks about it* Seems to me like six of one, half-dozen of another,
> but then again, centrifugal force is a nonexistent force conjured up to
> describe motion in a particular frame of reference, too...from an
> outside point of view, the math is easier/makes more sense when you
> reduce everything to a single set of common elements with no overlap.

	Oh sure. If your goal was just to have simple models, then your 
interpretation is fine (and even more accurate than centrifugal force).

	Note that I didn't say there _isn't_ a force on your part. Pulling down 
that diaphragm requires force - about the same amount of force that the 
atmospheric pressure applies to push the air in.

	Same as a vacuum cleaner. The mechanism requires a force/energy to 
*push* air out from the back. This causes a vacuum and atmospheric 
pressure then pushes the air into the tube from the other end - taking 
the mess along with it.

> But having a word for 'suck' is handy for us lay-people--lets us

	Well, I didn't imply you don't suck (no pun intended).

	Just think of the process of moving that diaphragm down as sucking 
(which it is).


-- 
If Wile E. Coyote had enough money to buy all those Acme goods, why 
didn't he just buy dinner?

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On 08/12/09 06:59, Stephen wrote:
> On Tue, 11 Aug 2009 21:39:33 -0400, Tim Cook<z99### [at] gmailcom>  wrote:
>
>> "life sucks".
>
> No! Death pushes ;)

Obligatory:

http://www.theatrecrafts.com/humour_darksuckers.html

-- 
If Wile E. Coyote had enough money to buy all those Acme goods, why 
didn't he just buy dinner?

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On Wed, 12 Aug 2009 09:38:55 -0500, Neeum Zawan <m.n### [at] ieeeorg> wrote:

>On 08/12/09 06:59, Stephen wrote:
>> On Tue, 11 Aug 2009 21:39:33 -0400, Tim Cook<z99### [at] gmailcom>  wrote:
>>
>>> "life sucks".
>>
>> No! Death pushes ;)
>
>Obligatory:
>
>http://www.theatrecrafts.com/humour_darksuckers.html

LOL
-- 

Regards
     Stephen

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A sound wave can be diffracted, this helps it to travel.

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clipka wrote:
> At 0 degrees Kelvin, 
> nature has no problems with vacuum.

Actually, it does. It like big vacuums better than small vacuums, tho.

http://en.wikipedia.org/wiki/Casimir_effect

-- 
   Darren New, San Diego CA, USA (PST)
   "We'd like you to back-port all the changes in 2.0
    back to version 1.0."
   "We've done that already. We call it 2.0."

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