<article>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#article09_06_27_1141242</id>
	<title>Researchers Discover That Sand Behaves Like Water</title>
	<author>Soulskill</author>
	<datestamp>1246109640000</datestamp>
	<htmltext><a href="mailto:slashdot@tracker.xeger.net" rel="nofollow">Xeger</a> writes <i>"University of Chicago researchers have found that <a href="http://www.wired.com/wiredscience/2009/06/sandgrains/">streams of sand can behave in a similar manner to liquids</a>, forming water-like droplets when poured from a funnel. To obtain these results, they dropped their expensive high-speed camera from a height of several meters and observed the sand forming into droplets &mdash; something that shouldn't happen without surface tension. These findings suggest that conventional engineering wisdom about sand, dirt and other grainy materials needs to be rethought, and that it might be possible to apply fluid dynamics to some solids problems."</i></htmltext>
<tokenext>Xeger writes " University of Chicago researchers have found that streams of sand can behave in a similar manner to liquids , forming water-like droplets when poured from a funnel .
To obtain these results , they dropped their expensive high-speed camera from a height of several meters and observed the sand forming into droplets    something that should n't happen without surface tension .
These findings suggest that conventional engineering wisdom about sand , dirt and other grainy materials needs to be rethought , and that it might be possible to apply fluid dynamics to some solids problems .
"</tokentext>
<sentencetext>Xeger writes "University of Chicago researchers have found that streams of sand can behave in a similar manner to liquids, forming water-like droplets when poured from a funnel.
To obtain these results, they dropped their expensive high-speed camera from a height of several meters and observed the sand forming into droplets — something that shouldn't happen without surface tension.
These findings suggest that conventional engineering wisdom about sand, dirt and other grainy materials needs to be rethought, and that it might be possible to apply fluid dynamics to some solids problems.
"</sentencetext>
</article>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494583</id>
	<title>I knew a prof that did that! (dropped a camera)</title>
	<author>StCredZero</author>
	<datestamp>1246116300000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext><p>He was a film prof, not physics, however.  He rigged up a pulley system, so you could film a Point Of View sequence for someone thrown down a stairwell.  The friction from the rope and pulley would slow down the acceleration and fall, but the camera could be run at a slower speed to compensate.  At the last moment, you could grab onto the rope (with thick gloves) and save the camera.  A bit of spin and/or off-center mounting of the camera would give you a more chaotic feel.</p><p>Effective and cheap.</p></htmltext>
<tokenext>He was a film prof , not physics , however .
He rigged up a pulley system , so you could film a Point Of View sequence for someone thrown down a stairwell .
The friction from the rope and pulley would slow down the acceleration and fall , but the camera could be run at a slower speed to compensate .
At the last moment , you could grab onto the rope ( with thick gloves ) and save the camera .
A bit of spin and/or off-center mounting of the camera would give you a more chaotic feel.Effective and cheap .</tokentext>
<sentencetext>He was a film prof, not physics, however.
He rigged up a pulley system, so you could film a Point Of View sequence for someone thrown down a stairwell.
The friction from the rope and pulley would slow down the acceleration and fall, but the camera could be run at a slower speed to compensate.
At the last moment, you could grab onto the rope (with thick gloves) and save the camera.
A bit of spin and/or off-center mounting of the camera would give you a more chaotic feel.Effective and cheap.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494297</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494305</id>
	<title>Mars</title>
	<author>Anonymous</author>
	<datestamp>1246113840000</datestamp>
	<modclass>Interestin</modclass>
	<modscore>5</modscore>
	<htmltext>Interesting.... I've always wondered how those Martian erosion patterns could definitively be ascribed to surface water, perhaps they will have to rethink that now?</htmltext>
<tokenext>Interesting.... I 've always wondered how those Martian erosion patterns could definitively be ascribed to surface water , perhaps they will have to rethink that now ?</tokentext>
<sentencetext>Interesting.... I've always wondered how those Martian erosion patterns could definitively be ascribed to surface water, perhaps they will have to rethink that now?</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494613</id>
	<title>Octave Engine</title>
	<author>LunarEffect</author>
	<datestamp>1246116540000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext>Hasn't this pretty much already been used in a physics engine? The <a href="http://www.youtube.com/watch?v=CyDcAyIPaXA" title="youtube.com" rel="nofollow">Octave Engine</a> [youtube.com], for instance, can simulate quite a few different small particle system with very similar results.</htmltext>
<tokenext>Has n't this pretty much already been used in a physics engine ?
The Octave Engine [ youtube.com ] , for instance , can simulate quite a few different small particle system with very similar results .</tokentext>
<sentencetext>Hasn't this pretty much already been used in a physics engine?
The Octave Engine [youtube.com], for instance, can simulate quite a few different small particle system with very similar results.</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494685</id>
	<title>!News</title>
	<author>Thelasko</author>
	<datestamp>1246117500000</datestamp>
	<modclass>Insightful</modclass>
	<modscore>3</modscore>
	<htmltext>Okay, maybe the sand forming droplets is news.  However, my old college roommate is a structural engineer.  On more than one occasion he told me that structural engineers consider soil to be a highly viscous fluid.<br> <br>
For example, most houses are built to "float" in the soil like a boat.  For structures that won't "float", like skyscrapers, they have to drive piles down to bedrock.</htmltext>
<tokenext>Okay , maybe the sand forming droplets is news .
However , my old college roommate is a structural engineer .
On more than one occasion he told me that structural engineers consider soil to be a highly viscous fluid .
For example , most houses are built to " float " in the soil like a boat .
For structures that wo n't " float " , like skyscrapers , they have to drive piles down to bedrock .</tokentext>
<sentencetext>Okay, maybe the sand forming droplets is news.
However, my old college roommate is a structural engineer.
On more than one occasion he told me that structural engineers consider soil to be a highly viscous fluid.
For example, most houses are built to "float" in the soil like a boat.
For structures that won't "float", like skyscrapers, they have to drive piles down to bedrock.</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28496591</id>
	<title>Re:hmm...</title>
	<author>Livius</author>
	<datestamp>1246133340000</datestamp>
	<modclass>Redundant</modclass>
	<modscore>0</modscore>
	<htmltext><p>Clearly some of the air will be accelerated and it's pressure will change.  They will have to try it in a vacuum.</p></htmltext>
<tokenext>Clearly some of the air will be accelerated and it 's pressure will change .
They will have to try it in a vacuum .</tokentext>
<sentencetext>Clearly some of the air will be accelerated and it's pressure will change.
They will have to try it in a vacuum.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494339</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494461</id>
	<title>Yawn</title>
	<author>Anonymous</author>
	<datestamp>1246115220000</datestamp>
	<modclass>Funny</modclass>
	<modscore>3</modscore>
	<htmltext>Call me when they can run linux on sand.

<br> <br>(Edit: Please note phone is off, due to slashdotting)</htmltext>
<tokenext>Call me when they can run linux on sand .
( Edit : Please note phone is off , due to slashdotting )</tokentext>
<sentencetext>Call me when they can run linux on sand.
(Edit: Please note phone is off, due to slashdotting)</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494739</id>
	<title>Sandworms</title>
	<author>killeena</author>
	<datestamp>1246117980000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext>Well, that makes things easier for sandworms.</htmltext>
<tokenext>Well , that makes things easier for sandworms .</tokentext>
<sentencetext>Well, that makes things easier for sandworms.</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28502951</id>
	<title>Re:They dropped their expensive camera?</title>
	<author>John Hasler</author>
	<datestamp>1246196580000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext><p>Strobe lights only work for periodic phemonena.</p></htmltext>
<tokenext>Strobe lights only work for periodic phemonena .</tokentext>
<sentencetext>Strobe lights only work for periodic phemonena.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494297</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494879</id>
	<title>Re:hmm...</title>
	<author>Anonymous</author>
	<datestamp>1246119240000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext><p>Gravity?</p></htmltext>
<tokenext>Gravity ?</tokentext>
<sentencetext>Gravity?</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494283</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494669</id>
	<title>Re:hmm...</title>
	<author>Anonymous</author>
	<datestamp>1246117260000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext>Aerodynamics, perhaps.  In the first video, we clearly see small "droplets" falling more slowly than larger blobs, indicating the sand is not falling in a vacuum.  The minimum energy state for a trail of non-spherical particles could easily be a series of ovoid blobs whose shape is carved out by turbulence in the airstream.</htmltext>
<tokenext>Aerodynamics , perhaps .
In the first video , we clearly see small " droplets " falling more slowly than larger blobs , indicating the sand is not falling in a vacuum .
The minimum energy state for a trail of non-spherical particles could easily be a series of ovoid blobs whose shape is carved out by turbulence in the airstream .</tokentext>
<sentencetext>Aerodynamics, perhaps.
In the first video, we clearly see small "droplets" falling more slowly than larger blobs, indicating the sand is not falling in a vacuum.
The minimum energy state for a trail of non-spherical particles could easily be a series of ovoid blobs whose shape is carved out by turbulence in the airstream.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494283</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28496503</id>
	<title>Who ya gonna call? A Geologist</title>
	<author>SpaceMika</author>
	<datestamp>1246132800000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext>The geotechnical/geological engineers have also been treating soils as fluids for years -- check out any papers by Oldrich Hungr or Stephen Evans on landslides. Neil Balmforth, a geologist/mathematician, has piles of papers on fluid dynamics of small grains (sands or glass beads).
<br> <br>
As a physicist working in earth science, yes, it is really nice to finally have some more solid reasons behind treating soft soils as fluids besides "because it works," but I disagree with the summary's claim that the discovery will lead to a whole new approach to soil sciences since it's already been treated as true for ages.</htmltext>
<tokenext>The geotechnical/geological engineers have also been treating soils as fluids for years -- check out any papers by Oldrich Hungr or Stephen Evans on landslides .
Neil Balmforth , a geologist/mathematician , has piles of papers on fluid dynamics of small grains ( sands or glass beads ) .
As a physicist working in earth science , yes , it is really nice to finally have some more solid reasons behind treating soft soils as fluids besides " because it works , " but I disagree with the summary 's claim that the discovery will lead to a whole new approach to soil sciences since it 's already been treated as true for ages .</tokentext>
<sentencetext>The geotechnical/geological engineers have also been treating soils as fluids for years -- check out any papers by Oldrich Hungr or Stephen Evans on landslides.
Neil Balmforth, a geologist/mathematician, has piles of papers on fluid dynamics of small grains (sands or glass beads).
As a physicist working in earth science, yes, it is really nice to finally have some more solid reasons behind treating soft soils as fluids besides "because it works," but I disagree with the summary's claim that the discovery will lead to a whole new approach to soil sciences since it's already been treated as true for ages.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494811</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494509</id>
	<title>Re:Water on Mars?</title>
	<author>Anonymous</author>
	<datestamp>1246115520000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext><p><div class="quote"><p>The finer the sand the more it acts like this, that's your "water on mars" right there.</p></div><p>A good example of that would have been observed by anyone changing the toner in one of the old high-end HP colour laser printers.  You could see the highly liquid nature of the fine grain toner through the translucent plastic cartridges.  That stuff <i>sloshes.</i></p></div>
	</htmltext>
<tokenext>The finer the sand the more it acts like this , that 's your " water on mars " right there.A good example of that would have been observed by anyone changing the toner in one of the old high-end HP colour laser printers .
You could see the highly liquid nature of the fine grain toner through the translucent plastic cartridges .
That stuff sloshes .</tokentext>
<sentencetext>The finer the sand the more it acts like this, that's your "water on mars" right there.A good example of that would have been observed by anyone changing the toner in one of the old high-end HP colour laser printers.
You could see the highly liquid nature of the fine grain toner through the translucent plastic cartridges.
That stuff sloshes.
	</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494321</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494327</id>
	<title>Meh...</title>
	<author>Bin\_jammin</author>
	<datestamp>1246114020000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext>It's probably just due to static electricity.</htmltext>
<tokenext>It 's probably just due to static electricity .</tokentext>
<sentencetext>It's probably just due to static electricity.</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494711</id>
	<title>What about the air?</title>
	<author>Anonymous</author>
	<datestamp>1246117680000</datestamp>
	<modclass>Redundant</modclass>
	<modscore>0</modscore>
	<htmltext><p>As sand falls, it would push air molecules around, causing minor pockets of slightly higher &amp; lower air pressure.  I have no clue what sort of contribution that would be, and expect to be schooled by people much more informed in this matter than myself in the subsequent replies.</p></htmltext>
<tokenext>As sand falls , it would push air molecules around , causing minor pockets of slightly higher &amp; lower air pressure .
I have no clue what sort of contribution that would be , and expect to be schooled by people much more informed in this matter than myself in the subsequent replies .</tokentext>
<sentencetext>As sand falls, it would push air molecules around, causing minor pockets of slightly higher &amp; lower air pressure.
I have no clue what sort of contribution that would be, and expect to be schooled by people much more informed in this matter than myself in the subsequent replies.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494283</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28495489</id>
	<title>Re:hmm...</title>
	<author>MouseR</author>
	<datestamp>1246123920000</datestamp>
	<modclass>Redundant</modclass>
	<modscore>0</modscore>
	<htmltext><p>I'd like to see that in a vacuum.</p></htmltext>
<tokenext>I 'd like to see that in a vacuum .</tokentext>
<sentencetext>I'd like to see that in a vacuum.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494283</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28495187</id>
	<title>Knudsden number</title>
	<author>Anonymous</author>
	<datestamp>1246121280000</datestamp>
	<modclass>Interestin</modclass>
	<modscore>3</modscore>
	<htmltext><p>
We see a stream of sand dividing up into 'drops'. It has been suggested that these 'drops' of sand are not being held together by internal forces, but by the air currents. The sand is arranging itself into shapes that can fall through the air, and horizontal oscillations of the air may be causing the column to break up into these 'drops'. I am not sure that is wholly the case - the video shows an intriguing 'satellite' droplet after a main one, a lot like you get with liquids.
</p><p>
So, could you get the same effect on Mars? You have less than 1/100th of the pressure, so we might expect the forces from the air to be proportionately weaker. There is also a characteristic length - the mean free path - which is the distance an atmospheric particle will travel before it hits another. If the geometry of what we are looking at - in this case, the sand - goes beneath the mean free path, then the flow changes. There is a dimensionless number called the Knudsden number which describes the point in which this change occurs. The man free path in the earth's atmosphere is about 0.1 micron, so on Mars it will be about 10 microns, which is probably still smaller than sand, so the Knudsden number is still below 1.0.  My guess is you may get these 'droplets' on mars, but the effect is a lot weaker ad you would need a much longer drop for the effect to show itself. I hope the people repeat the experiment under vacuum. If you still get the effect in vacuum, then it must be something else.
</p><p>
Powders can behave a lot like liquids provided they keep moving. They can leave tracks that look a lot like liquids. I suspect some of the things we see on Mars may have been formed by powders. However, most of these mechanisms are particles moving over each other under the influence of gravity, and don't really use the atmosphere as the sand may be doing here. However, I started off as a major sceptic on water on Mars, but the evidence of shorelines (which you wouldn't get with powders unless there was something to keep them moving) is beginning to win me over. We shall see.
</p><p>
Here's my usual pet peeve with journalism like this. The motion of powders is a fascinating topic, and it doesn't really need dressing up as the 5th state of matter that baffles scientists. It is not a forgotten topic in science. Fluidized beds are used in industrial chemistry. They tend to be a bit unpredictable, because when they slump, it can be very hard to get them going again, which is what makes them unpredictable.
</p></htmltext>
<tokenext>We see a stream of sand dividing up into 'drops' .
It has been suggested that these 'drops ' of sand are not being held together by internal forces , but by the air currents .
The sand is arranging itself into shapes that can fall through the air , and horizontal oscillations of the air may be causing the column to break up into these 'drops' .
I am not sure that is wholly the case - the video shows an intriguing 'satellite ' droplet after a main one , a lot like you get with liquids .
So , could you get the same effect on Mars ?
You have less than 1/100th of the pressure , so we might expect the forces from the air to be proportionately weaker .
There is also a characteristic length - the mean free path - which is the distance an atmospheric particle will travel before it hits another .
If the geometry of what we are looking at - in this case , the sand - goes beneath the mean free path , then the flow changes .
There is a dimensionless number called the Knudsden number which describes the point in which this change occurs .
The man free path in the earth 's atmosphere is about 0.1 micron , so on Mars it will be about 10 microns , which is probably still smaller than sand , so the Knudsden number is still below 1.0 .
My guess is you may get these 'droplets ' on mars , but the effect is a lot weaker ad you would need a much longer drop for the effect to show itself .
I hope the people repeat the experiment under vacuum .
If you still get the effect in vacuum , then it must be something else .
Powders can behave a lot like liquids provided they keep moving .
They can leave tracks that look a lot like liquids .
I suspect some of the things we see on Mars may have been formed by powders .
However , most of these mechanisms are particles moving over each other under the influence of gravity , and do n't really use the atmosphere as the sand may be doing here .
However , I started off as a major sceptic on water on Mars , but the evidence of shorelines ( which you would n't get with powders unless there was something to keep them moving ) is beginning to win me over .
We shall see .
Here 's my usual pet peeve with journalism like this .
The motion of powders is a fascinating topic , and it does n't really need dressing up as the 5th state of matter that baffles scientists .
It is not a forgotten topic in science .
Fluidized beds are used in industrial chemistry .
They tend to be a bit unpredictable , because when they slump , it can be very hard to get them going again , which is what makes them unpredictable .</tokentext>
<sentencetext>
We see a stream of sand dividing up into 'drops'.
It has been suggested that these 'drops' of sand are not being held together by internal forces, but by the air currents.
The sand is arranging itself into shapes that can fall through the air, and horizontal oscillations of the air may be causing the column to break up into these 'drops'.
I am not sure that is wholly the case - the video shows an intriguing 'satellite' droplet after a main one, a lot like you get with liquids.
So, could you get the same effect on Mars?
You have less than 1/100th of the pressure, so we might expect the forces from the air to be proportionately weaker.
There is also a characteristic length - the mean free path - which is the distance an atmospheric particle will travel before it hits another.
If the geometry of what we are looking at - in this case, the sand - goes beneath the mean free path, then the flow changes.
There is a dimensionless number called the Knudsden number which describes the point in which this change occurs.
The man free path in the earth's atmosphere is about 0.1 micron, so on Mars it will be about 10 microns, which is probably still smaller than sand, so the Knudsden number is still below 1.0.
My guess is you may get these 'droplets' on mars, but the effect is a lot weaker ad you would need a much longer drop for the effect to show itself.
I hope the people repeat the experiment under vacuum.
If you still get the effect in vacuum, then it must be something else.
Powders can behave a lot like liquids provided they keep moving.
They can leave tracks that look a lot like liquids.
I suspect some of the things we see on Mars may have been formed by powders.
However, most of these mechanisms are particles moving over each other under the influence of gravity, and don't really use the atmosphere as the sand may be doing here.
However, I started off as a major sceptic on water on Mars, but the evidence of shorelines (which you wouldn't get with powders unless there was something to keep them moving) is beginning to win me over.
We shall see.
Here's my usual pet peeve with journalism like this.
The motion of powders is a fascinating topic, and it doesn't really need dressing up as the 5th state of matter that baffles scientists.
It is not a forgotten topic in science.
Fluidized beds are used in industrial chemistry.
They tend to be a bit unpredictable, because when they slump, it can be very hard to get them going again, which is what makes them unpredictable.
</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494305</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28507699</id>
	<title>Re:Yawn</title>
	<author>A\_Non\_Moose</author>
	<datestamp>1246189500000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext><blockquote><div><p>Call me when they can run linux on sand.</p></div> </blockquote><p>Ugly bag of mostly water, stay out of our wet sand!</p></div>
	</htmltext>
<tokenext>Call me when they can run linux on sand .
Ugly bag of mostly water , stay out of our wet sand !</tokentext>
<sentencetext>Call me when they can run linux on sand.
Ugly bag of mostly water, stay out of our wet sand!
	</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494461</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28500901</id>
	<title>YouTube</title>
	<author>SheeEttin</author>
	<datestamp>1246123140000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext><a href="http://www.youtube.com/watch?v=X\_loG8AQKtY" title="youtube.com" rel="nofollow">YouTube link</a> [youtube.com] for illustration. (The hydrant failure occurs at 1:19 in the video.)

Are you SURE that's not water?</htmltext>
<tokenext>YouTube link [ youtube.com ] for illustration .
( The hydrant failure occurs at 1 : 19 in the video .
) Are you SURE that 's not water ?</tokentext>
<sentencetext>YouTube link [youtube.com] for illustration.
(The hydrant failure occurs at 1:19 in the video.
)

Are you SURE that's not water?</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494811</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494729</id>
	<title>Re:hmm...</title>
	<author>JustinOpinion</author>
	<datestamp>1246117860000</datestamp>
	<modclass>Informativ</modclass>
	<modscore>4</modscore>
	<htmltext>For those with access, the actual scientific article is:<br>
John R. Royer, Daniel J. Evans, Loreto Oyarte, Qiti Guo, Eliot Kapit, Matthias E. M&#195;bius, Scott R. Waitukaitis &amp;  Heinrich M. Jaeger "<a href="http://www.nature.com/nature/journal/v459/n7250/full/nature08115.html" title="nature.com">High-speed tracking of rupture and clustering in freely falling granular streams</a> [nature.com]" Nature, 459, 1110-1113 (25 June 2009) | <a href="http://dx.doi.org/10.1038/nature08115" title="doi.org">doi:10.1038/nature08115</a> [doi.org].<br> <br>

The associated "News and Views" (Summary) is:<br>
Detlef Lohse  &amp;  Devaraj van der Meer "<a href="http://www.nature.com/nature/journal/v459/n7250/full/4591064a.html" title="nature.com">Granular media: Structures in sand streams</a> [nature.com]" Nature, 459, 1064-1065 (25 June 2009) | <a href="http://dx.doi.org/10.1038/4591064a" title="doi.org">doi:10.1038/4591064a</a> [doi.org] <br> <br>

The previously-held belief in the field was that this breakup into droplets could be explained by inelastic collisions between the grains. That is, all the sand grains are bouncing off each other, but because these collisions are inelastic (the two particles slow down a bit relative to each other with the collision) the grains will, statistically, aggregate into larger structures.<br> <br>

However this new piece of work shows rather strikingly that the origin of the force is a very weak form of surface tension. In other words, the breakup into droplets occurs for the same reason as it does in water and other liquids... it's just the magnitude of the force that is much smaller. In addition to the high-speed photography the Slashdot summary mentions, they also used <a href="http://en.wikipedia.org/wiki/Atomic\_force\_microscope" title="wikipedia.org">atomic force microscopy</a> [wikipedia.org] to directly measure the nanometer-scale cohesive forces between particles. In water, surface tension arises from the (rather strong) cohesive forces between water molecules (each water molecule 'sticks' to its neighbors). In sand, it appears that a very weak nano-scale cohesive force is nevertheless enough to generate macro-scale droplets out of micro-scale particles. The cohesive forces in sand arise from the weak <a href="http://en.wikipedia.org/wiki/Van\_der\_Waals\_force" title="wikipedia.org">Van der Waals</a> [wikipedia.org] forces (weak, but universal, surface attraction), and due to capillary forces. That is, ambient water bridges the sand particles and causes what is effectively an attractive force, which leads to an effective surface tension.<br> <br>

In the paper, they describe how they vary the particle type and ambient conditions, to demonstrate that these two effects are important. For instance varying humidity alters the cohesion and thus droplet formation. Also, altering the sand particles has an effect: e.g. rougher particles cannot stick to each other as much, thereby reducing this effect.<br> <br>

This is a neat piece of work because it involves just "known" physics. It is demonstrating that well-established physical effects (surface forces and capillary forces) can explain phenomena where their effect was previously assumed to be negligible. The surface tension in these granular media are about 100,000 times smaller than water, yet the exact same effects are observed: the surface tension, weak as it is, tries to minimize surface area. Coupled with well-known <a href="http://en.wikipedia.org/wiki/Plateau-Rayleigh\_instability" title="wikipedia.org">instabilities</a> [wikipedia.org], this causes a breakup into droplets.</htmltext>
<tokenext>For those with access , the actual scientific article is : John R. Royer , Daniel J. Evans , Loreto Oyarte , Qiti Guo , Eliot Kapit , Matthias E. M   bius , Scott R. Waitukaitis &amp; Heinrich M. Jaeger " High-speed tracking of rupture and clustering in freely falling granular streams [ nature.com ] " Nature , 459 , 1110-1113 ( 25 June 2009 ) | doi : 10.1038/nature08115 [ doi.org ] .
The associated " News and Views " ( Summary ) is : Detlef Lohse &amp; Devaraj van der Meer " Granular media : Structures in sand streams [ nature.com ] " Nature , 459 , 1064-1065 ( 25 June 2009 ) | doi : 10.1038/4591064a [ doi.org ] The previously-held belief in the field was that this breakup into droplets could be explained by inelastic collisions between the grains .
That is , all the sand grains are bouncing off each other , but because these collisions are inelastic ( the two particles slow down a bit relative to each other with the collision ) the grains will , statistically , aggregate into larger structures .
However this new piece of work shows rather strikingly that the origin of the force is a very weak form of surface tension .
In other words , the breakup into droplets occurs for the same reason as it does in water and other liquids... it 's just the magnitude of the force that is much smaller .
In addition to the high-speed photography the Slashdot summary mentions , they also used atomic force microscopy [ wikipedia.org ] to directly measure the nanometer-scale cohesive forces between particles .
In water , surface tension arises from the ( rather strong ) cohesive forces between water molecules ( each water molecule 'sticks ' to its neighbors ) .
In sand , it appears that a very weak nano-scale cohesive force is nevertheless enough to generate macro-scale droplets out of micro-scale particles .
The cohesive forces in sand arise from the weak Van der Waals [ wikipedia.org ] forces ( weak , but universal , surface attraction ) , and due to capillary forces .
That is , ambient water bridges the sand particles and causes what is effectively an attractive force , which leads to an effective surface tension .
In the paper , they describe how they vary the particle type and ambient conditions , to demonstrate that these two effects are important .
For instance varying humidity alters the cohesion and thus droplet formation .
Also , altering the sand particles has an effect : e.g .
rougher particles can not stick to each other as much , thereby reducing this effect .
This is a neat piece of work because it involves just " known " physics .
It is demonstrating that well-established physical effects ( surface forces and capillary forces ) can explain phenomena where their effect was previously assumed to be negligible .
The surface tension in these granular media are about 100,000 times smaller than water , yet the exact same effects are observed : the surface tension , weak as it is , tries to minimize surface area .
Coupled with well-known instabilities [ wikipedia.org ] , this causes a breakup into droplets .</tokentext>
<sentencetext>For those with access, the actual scientific article is:
John R. Royer, Daniel J. Evans, Loreto Oyarte, Qiti Guo, Eliot Kapit, Matthias E. MÃbius, Scott R. Waitukaitis &amp;  Heinrich M. Jaeger "High-speed tracking of rupture and clustering in freely falling granular streams [nature.com]" Nature, 459, 1110-1113 (25 June 2009) | doi:10.1038/nature08115 [doi.org].
The associated "News and Views" (Summary) is:
Detlef Lohse  &amp;  Devaraj van der Meer "Granular media: Structures in sand streams [nature.com]" Nature, 459, 1064-1065 (25 June 2009) | doi:10.1038/4591064a [doi.org]  

The previously-held belief in the field was that this breakup into droplets could be explained by inelastic collisions between the grains.
That is, all the sand grains are bouncing off each other, but because these collisions are inelastic (the two particles slow down a bit relative to each other with the collision) the grains will, statistically, aggregate into larger structures.
However this new piece of work shows rather strikingly that the origin of the force is a very weak form of surface tension.
In other words, the breakup into droplets occurs for the same reason as it does in water and other liquids... it's just the magnitude of the force that is much smaller.
In addition to the high-speed photography the Slashdot summary mentions, they also used atomic force microscopy [wikipedia.org] to directly measure the nanometer-scale cohesive forces between particles.
In water, surface tension arises from the (rather strong) cohesive forces between water molecules (each water molecule 'sticks' to its neighbors).
In sand, it appears that a very weak nano-scale cohesive force is nevertheless enough to generate macro-scale droplets out of micro-scale particles.
The cohesive forces in sand arise from the weak Van der Waals [wikipedia.org] forces (weak, but universal, surface attraction), and due to capillary forces.
That is, ambient water bridges the sand particles and causes what is effectively an attractive force, which leads to an effective surface tension.
In the paper, they describe how they vary the particle type and ambient conditions, to demonstrate that these two effects are important.
For instance varying humidity alters the cohesion and thus droplet formation.
Also, altering the sand particles has an effect: e.g.
rougher particles cannot stick to each other as much, thereby reducing this effect.
This is a neat piece of work because it involves just "known" physics.
It is demonstrating that well-established physical effects (surface forces and capillary forces) can explain phenomena where their effect was previously assumed to be negligible.
The surface tension in these granular media are about 100,000 times smaller than water, yet the exact same effects are observed: the surface tension, weak as it is, tries to minimize surface area.
Coupled with well-known instabilities [wikipedia.org], this causes a breakup into droplets.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494283</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28495245</id>
	<title>Re:hmm...</title>
	<author>Daniel\_Staal</author>
	<datestamp>1246121760000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext><p>They did.</p></htmltext>
<tokenext>They did .</tokentext>
<sentencetext>They did.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494379</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494333</id>
	<title>It's the air.</title>
	<author>vettemph</author>
	<datestamp>1246114080000</datestamp>
	<modclass>Insightful</modclass>
	<modscore>3</modscore>
	<htmltext><p> Maybe this tells us more about what the air is doing than what the sand is doing. Chaotic particles spiraling down end up it in each others draft and stay there. (think nascar drafting)</p></htmltext>
<tokenext>Maybe this tells us more about what the air is doing than what the sand is doing .
Chaotic particles spiraling down end up it in each others draft and stay there .
( think nascar drafting )</tokentext>
<sentencetext> Maybe this tells us more about what the air is doing than what the sand is doing.
Chaotic particles spiraling down end up it in each others draft and stay there.
(think nascar drafting)</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28496169</id>
	<title>Re:hmm...</title>
	<author>OldSoldier</author>
	<datestamp>1246130220000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext><p>There was a recent impromptu experiment on the space station where an astronaut shook a bag of power... sugar, flour, I don't remember what and it clumped too. I'm guessing electrostatic... but more to the point... this solves a problem in the early planet formation... namely, gravity is a very weak force. Expecting dust grains to accumulate via gravity alone should a very long time, but having something to jump start the gravitational attraction like the mechanism behind this should speed up that process.<br>
&nbsp;</p></htmltext>
<tokenext>There was a recent impromptu experiment on the space station where an astronaut shook a bag of power... sugar , flour , I do n't remember what and it clumped too .
I 'm guessing electrostatic... but more to the point... this solves a problem in the early planet formation... namely , gravity is a very weak force .
Expecting dust grains to accumulate via gravity alone should a very long time , but having something to jump start the gravitational attraction like the mechanism behind this should speed up that process .
 </tokentext>
<sentencetext>There was a recent impromptu experiment on the space station where an astronaut shook a bag of power... sugar, flour, I don't remember what and it clumped too.
I'm guessing electrostatic... but more to the point... this solves a problem in the early planet formation... namely, gravity is a very weak force.
Expecting dust grains to accumulate via gravity alone should a very long time, but having something to jump start the gravitational attraction like the mechanism behind this should speed up that process.
 </sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494283</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28500109</id>
	<title>Re:Doh!</title>
	<author>alcmaeon</author>
	<datestamp>1246116360000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext>I was thinking the same thing.  After watching the video, I have observed this flowing-clumping behavior of sand many times on construction jobs when we are pouring sand into holes for backfill.  Maybe the physicists just need to get out more.</htmltext>
<tokenext>I was thinking the same thing .
After watching the video , I have observed this flowing-clumping behavior of sand many times on construction jobs when we are pouring sand into holes for backfill .
Maybe the physicists just need to get out more .</tokentext>
<sentencetext>I was thinking the same thing.
After watching the video, I have observed this flowing-clumping behavior of sand many times on construction jobs when we are pouring sand into holes for backfill.
Maybe the physicists just need to get out more.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494387</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28495993</id>
	<title>A strobe light wouldn't work for this.</title>
	<author>nuckfuts</author>
	<datestamp>1246128480000</datestamp>
	<modclass>Insightful</modclass>
	<modscore>2</modscore>
	<htmltext><p>The strobe light effect you mention appears to slow down, stop, or reverse falling droplets, but is merely an illusion. The individual droplets in each frame are actually replaced by successive droplets that are sufficiently similar-looking to give the illusion that you're seeing one individual droplet frozen in space.</p><p>With the sand example, the droplets are visibly different in size and shape. You don't want some sleight-of-hand trick with a strobe light, where you turn out the lights and quickly put a different droplet in place. You want to keep individual droplets in frame and follow them as they form and fall. Having the camera fall in unison with the sand seems like a pretty good way to do it.</p></htmltext>
<tokenext>The strobe light effect you mention appears to slow down , stop , or reverse falling droplets , but is merely an illusion .
The individual droplets in each frame are actually replaced by successive droplets that are sufficiently similar-looking to give the illusion that you 're seeing one individual droplet frozen in space.With the sand example , the droplets are visibly different in size and shape .
You do n't want some sleight-of-hand trick with a strobe light , where you turn out the lights and quickly put a different droplet in place .
You want to keep individual droplets in frame and follow them as they form and fall .
Having the camera fall in unison with the sand seems like a pretty good way to do it .</tokentext>
<sentencetext>The strobe light effect you mention appears to slow down, stop, or reverse falling droplets, but is merely an illusion.
The individual droplets in each frame are actually replaced by successive droplets that are sufficiently similar-looking to give the illusion that you're seeing one individual droplet frozen in space.With the sand example, the droplets are visibly different in size and shape.
You don't want some sleight-of-hand trick with a strobe light, where you turn out the lights and quickly put a different droplet in place.
You want to keep individual droplets in frame and follow them as they form and fall.
Having the camera fall in unison with the sand seems like a pretty good way to do it.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494297</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28502743</id>
	<title>Re:hmm...</title>
	<author>rhoder</author>
	<datestamp>1246194120000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext>Wind resistance.  Like a car riding behind a big rig.  There's not as much drag for the following particle.</htmltext>
<tokenext>Wind resistance .
Like a car riding behind a big rig .
There 's not as much drag for the following particle .</tokentext>
<sentencetext>Wind resistance.
Like a car riding behind a big rig.
There's not as much drag for the following particle.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494283</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494283</id>
	<title>hmm...</title>
	<author>Anonymous</author>
	<datestamp>1246113540000</datestamp>
	<modclass>Interestin</modclass>
	<modscore>5</modscore>
	<htmltext><p>That's peculiar.  What's binding the grains together to that extent?  Moisture?  Electrostatic charge?  Just chance mechanical interactions of surface asperities?  The first and last are already modelled in some engineering sand models, but I'm not sure they'd be powerful enough to cause droplet formation.</p></htmltext>
<tokenext>That 's peculiar .
What 's binding the grains together to that extent ?
Moisture ? Electrostatic charge ?
Just chance mechanical interactions of surface asperities ?
The first and last are already modelled in some engineering sand models , but I 'm not sure they 'd be powerful enough to cause droplet formation .</tokentext>
<sentencetext>That's peculiar.
What's binding the grains together to that extent?
Moisture?  Electrostatic charge?
Just chance mechanical interactions of surface asperities?
The first and last are already modelled in some engineering sand models, but I'm not sure they'd be powerful enough to cause droplet formation.</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494379</id>
	<title>Re:hmm...</title>
	<author>Anonymous</author>
	<datestamp>1246114500000</datestamp>
	<modclass>Interestin</modclass>
	<modscore>1</modscore>
	<htmltext><p>TFA says "The droplets formed because of instabilities in the subtle atomic forces that attract sand grains to each other."</p><p>Personally I'm thinking that the air flow around a falling object might have a concentrating effect. I hope they redo their experiments in vacuum to be sure.</p></htmltext>
<tokenext>TFA says " The droplets formed because of instabilities in the subtle atomic forces that attract sand grains to each other .
" Personally I 'm thinking that the air flow around a falling object might have a concentrating effect .
I hope they redo their experiments in vacuum to be sure .</tokentext>
<sentencetext>TFA says "The droplets formed because of instabilities in the subtle atomic forces that attract sand grains to each other.
"Personally I'm thinking that the air flow around a falling object might have a concentrating effect.
I hope they redo their experiments in vacuum to be sure.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494283</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28495035</id>
	<title>Re:Mars</title>
	<author>JustinOpinion</author>
	<datestamp>1246120260000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext>The effect as described in the scientific paper relies on van der Waals interaction and also capillary forces. In other words, a significant portion of the force/effect comes from ambient water that coats the particle surfaces, and creates adhesion by bridging between particles when they touch.<br> <br>

So this suggests that sand will act most "liquid-like" (breaking into droplets, flowing, etc.) when there is atmospheric water.<br> <br>

I agree that this kind of data on granular media will have an effect on the interpretation of Mars erosion patterns. But I think it would be simplistic to say that this offers a non-water explanation for the erosion patterns on Mars. In fact it may be further evidence of water and help determine exactly how much water Mars currently has, and previously had. (It's also worth noting that the erosion patterns are now just one of many pieces of evidence we have for there being water on Mars.)</htmltext>
<tokenext>The effect as described in the scientific paper relies on van der Waals interaction and also capillary forces .
In other words , a significant portion of the force/effect comes from ambient water that coats the particle surfaces , and creates adhesion by bridging between particles when they touch .
So this suggests that sand will act most " liquid-like " ( breaking into droplets , flowing , etc .
) when there is atmospheric water .
I agree that this kind of data on granular media will have an effect on the interpretation of Mars erosion patterns .
But I think it would be simplistic to say that this offers a non-water explanation for the erosion patterns on Mars .
In fact it may be further evidence of water and help determine exactly how much water Mars currently has , and previously had .
( It 's also worth noting that the erosion patterns are now just one of many pieces of evidence we have for there being water on Mars .
)</tokentext>
<sentencetext>The effect as described in the scientific paper relies on van der Waals interaction and also capillary forces.
In other words, a significant portion of the force/effect comes from ambient water that coats the particle surfaces, and creates adhesion by bridging between particles when they touch.
So this suggests that sand will act most "liquid-like" (breaking into droplets, flowing, etc.
) when there is atmospheric water.
I agree that this kind of data on granular media will have an effect on the interpretation of Mars erosion patterns.
But I think it would be simplistic to say that this offers a non-water explanation for the erosion patterns on Mars.
In fact it may be further evidence of water and help determine exactly how much water Mars currently has, and previously had.
(It's also worth noting that the erosion patterns are now just one of many pieces of evidence we have for there being water on Mars.
)</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494305</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494297</id>
	<title>They dropped their expensive camera?</title>
	<author>hey!</author>
	<datestamp>1246113780000</datestamp>
	<modclass>Insightful</modclass>
	<modscore>3</modscore>
	<htmltext><p>Haven't they heard of strobe lights?</p></htmltext>
<tokenext>Have n't they heard of strobe lights ?</tokentext>
<sentencetext>Haven't they heard of strobe lights?</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28497007</id>
	<title>Re:hmm...</title>
	<author>Nazlfrag</author>
	<datestamp>1246135800000</datestamp>
	<modclass>None</modclass>
	<modscore>0</modscore>
	<htmltext><p>So humidity is the confirmed lubricant and cause of surface tension, or is it that solids also possess surface tension of their own? I'd like to think there is no difference in the forces involved, no difference between solids, gasses and liquids, just a difference in the scale required for these forces to manifest.</p></htmltext>
<tokenext>So humidity is the confirmed lubricant and cause of surface tension , or is it that solids also possess surface tension of their own ?
I 'd like to think there is no difference in the forces involved , no difference between solids , gasses and liquids , just a difference in the scale required for these forces to manifest .</tokentext>
<sentencetext>So humidity is the confirmed lubricant and cause of surface tension, or is it that solids also possess surface tension of their own?
I'd like to think there is no difference in the forces involved, no difference between solids, gasses and liquids, just a difference in the scale required for these forces to manifest.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494729</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494727</id>
	<title>isn't that obvious...</title>
	<author>Anonymous</author>
	<datestamp>1246117860000</datestamp>
	<modclass>None</modclass>
	<modscore>0</modscore>
	<htmltext><p>...I thought of sand behaving like water when I first saw sand dunes and wavelike patterns in desert sand when I was a little kid.</p></htmltext>
<tokenext>...I thought of sand behaving like water when I first saw sand dunes and wavelike patterns in desert sand when I was a little kid .</tokentext>
<sentencetext>...I thought of sand behaving like water when I first saw sand dunes and wavelike patterns in desert sand when I was a little kid.</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494549</id>
	<title>FX guys have known this for decades.</title>
	<author>Anonymous</author>
	<datestamp>1246115880000</datestamp>
	<modclass>None</modclass>
	<modscore>0</modscore>
	<htmltext><p>They have used sand to mimic water in miniature, that is for sets built to scale (think Godzilla), since that 1960's at least. Good to know current American science is only 50 years behind the trades and craftsmen of Hollywood.</p></htmltext>
<tokenext>They have used sand to mimic water in miniature , that is for sets built to scale ( think Godzilla ) , since that 1960 's at least .
Good to know current American science is only 50 years behind the trades and craftsmen of Hollywood .</tokentext>
<sentencetext>They have used sand to mimic water in miniature, that is for sets built to scale (think Godzilla), since that 1960's at least.
Good to know current American science is only 50 years behind the trades and craftsmen of Hollywood.</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494321</id>
	<title>Water on Mars?</title>
	<author>koan</author>
	<datestamp>1246113960000</datestamp>
	<modclass>Funny</modclass>
	<modscore>2</modscore>
	<htmltext><p>The finer the sand the more it acts like this, that's your "water on mars" right there.</p></htmltext>
<tokenext>The finer the sand the more it acts like this , that 's your " water on mars " right there .</tokentext>
<sentencetext>The finer the sand the more it acts like this, that's your "water on mars" right there.</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28502699</id>
	<title>Re:hmm...  Gravity!!</title>
	<author>TapeCutter</author>
	<datestamp>1246193580000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext>Gravity is so weak that it is all but irrelevant at small scales. They have an interesting peer-reviewed publication in Nature, why do you doubt their explaination?</htmltext>
<tokenext>Gravity is so weak that it is all but irrelevant at small scales .
They have an interesting peer-reviewed publication in Nature , why do you doubt their explaination ?</tokentext>
<sentencetext>Gravity is so weak that it is all but irrelevant at small scales.
They have an interesting peer-reviewed publication in Nature, why do you doubt their explaination?</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494633</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28497113</id>
	<title>Re:hmm...</title>
	<author>MillionthMonkey</author>
	<datestamp>1246093440000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext>Yeah but Occam is always on that side so who cares what he says.</htmltext>
<tokenext>Yeah but Occam is always on that side so who cares what he says .</tokentext>
<sentencetext>Yeah but Occam is always on that side so who cares what he says.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494697</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28502651</id>
	<title>Re:hmm...</title>
	<author>TapeCutter</author>
	<datestamp>1246193100000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext>Better apply some lotion to that razor burn.<nobr> <wbr></nobr>/jk
<br> <br>
Seriuosly though I'm no physicist so purely based on their track record I give Nature the benifit of the doubt when it comes to thourough peer-review.</htmltext>
<tokenext>Better apply some lotion to that razor burn .
/jk Seriuosly though I 'm no physicist so purely based on their track record I give Nature the benifit of the doubt when it comes to thourough peer-review .</tokentext>
<sentencetext>Better apply some lotion to that razor burn.
/jk
 
Seriuosly though I'm no physicist so purely based on their track record I give Nature the benifit of the doubt when it comes to thourough peer-review.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494697</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28496275</id>
	<title>Re:hmm...</title>
	<author>Anonymous</author>
	<datestamp>1246131300000</datestamp>
	<modclass>Interestin</modclass>
	<modscore>2</modscore>
	<htmltext><p>Well the one thing that comes to mind for me is that sand when heated turns to glass; glass itself is a liquid in the sense that your regular table glass will change shape over time (e.g. start to sag) unlike other objects. Maybe we just miscategorized sand?</p></htmltext>
<tokenext>Well the one thing that comes to mind for me is that sand when heated turns to glass ; glass itself is a liquid in the sense that your regular table glass will change shape over time ( e.g .
start to sag ) unlike other objects .
Maybe we just miscategorized sand ?</tokentext>
<sentencetext>Well the one thing that comes to mind for me is that sand when heated turns to glass; glass itself is a liquid in the sense that your regular table glass will change shape over time (e.g.
start to sag) unlike other objects.
Maybe we just miscategorized sand?</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494283</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494259</id>
	<title>Lol</title>
	<author>Anonymous</author>
	<datestamp>1246113360000</datestamp>
	<modclass>Funny</modclass>
	<modscore>2</modscore>
	<htmltext><p>Quicksand discovered !!!</p></htmltext>
<tokenext>Quicksand discovered ! !
!</tokentext>
<sentencetext>Quicksand discovered !!
!</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494457</id>
	<title>more likely</title>
	<author>Anonymous</author>
	<datestamp>1246115220000</datestamp>
	<modclass>None</modclass>
	<modscore>0</modscore>
	<htmltext><p>They are making it up to explain to their boss why they need a new camera after accidently dropping it off of the roof.  No explanation given as to why they choose a roof that just happen to be facing to womens dormitory shower room....</p></htmltext>
<tokenext>They are making it up to explain to their boss why they need a new camera after accidently dropping it off of the roof .
No explanation given as to why they choose a roof that just happen to be facing to womens dormitory shower room... .</tokentext>
<sentencetext>They are making it up to explain to their boss why they need a new camera after accidently dropping it off of the roof.
No explanation given as to why they choose a roof that just happen to be facing to womens dormitory shower room....</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494399</id>
	<title>"Ugly bags of mostly water" are we?</title>
	<author>Anonymous</author>
	<datestamp>1246114620000</datestamp>
	<modclass>None</modclass>
	<modscore>0</modscore>
	<htmltext><p>The next time a crystalline life form <a href="http://en.wikipedia.org/wiki/Home\_Soil" title="wikipedia.org" rel="nofollow">insults me</a> [wikipedia.org] I'll play the kindergarten card and say "I know you are but what am I."</p></htmltext>
<tokenext>The next time a crystalline life form insults me [ wikipedia.org ] I 'll play the kindergarten card and say " I know you are but what am I .
"</tokentext>
<sentencetext>The next time a crystalline life form insults me [wikipedia.org] I'll play the kindergarten card and say "I know you are but what am I.
"</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494367</id>
	<title>News at 10</title>
	<author>auric\_dude</author>
	<datestamp>1246114440000</datestamp>
	<modclass>Funny</modclass>
	<modscore>2</modscore>
	<htmltext>Is a camel still the ship of the desert?</htmltext>
<tokenext>Is a camel still the ship of the desert ?</tokentext>
<sentencetext>Is a camel still the ship of the desert?</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494633</id>
	<title>Re:hmm...   Gravity!!</title>
	<author>Anonymous</author>
	<datestamp>1246116900000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext><p>Gravity!  It's working on a small scale, but that's why it would do that.  As a casual observer, i'm pretty sure i've noticed this type of behavior in sand before, it's surprising to me that others haven't.  I'm pretty sure that's the same reason why the last few cheerios stick together in the bowl of milk.</p></htmltext>
<tokenext>Gravity !
It 's working on a small scale , but that 's why it would do that .
As a casual observer , i 'm pretty sure i 've noticed this type of behavior in sand before , it 's surprising to me that others have n't .
I 'm pretty sure that 's the same reason why the last few cheerios stick together in the bowl of milk .</tokentext>
<sentencetext>Gravity!
It's working on a small scale, but that's why it would do that.
As a casual observer, i'm pretty sure i've noticed this type of behavior in sand before, it's surprising to me that others haven't.
I'm pretty sure that's the same reason why the last few cheerios stick together in the bowl of milk.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494283</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28497527</id>
	<title>Re:hmm...</title>
	<author>Anonymous</author>
	<datestamp>1246096020000</datestamp>
	<modclass>Informativ</modclass>
	<modscore>1</modscore>
	<htmltext><p>Air flow around a cluster of falling particles has a scattering effect, and they *did* redo their experiment in a vacuum to be sure.</p><p><div class="quote"><p>However, we still observe clustering in glass grains stored under vacuum (0.05 kPa) at low humidity (,1\%) and also in grains coated with hydrophobic silane.</p></div></div>
	</htmltext>
<tokenext>Air flow around a cluster of falling particles has a scattering effect , and they * did * redo their experiment in a vacuum to be sure.However , we still observe clustering in glass grains stored under vacuum ( 0.05 kPa ) at low humidity ( ,1 \ % ) and also in grains coated with hydrophobic silane .</tokentext>
<sentencetext>Air flow around a cluster of falling particles has a scattering effect, and they *did* redo their experiment in a vacuum to be sure.However, we still observe clustering in glass grains stored under vacuum (0.05 kPa) at low humidity (,1\%) and also in grains coated with hydrophobic silane.
	</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494379</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28502543</id>
	<title>Re:Yawn</title>
	<author>xSander</author>
	<datestamp>1246191480000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext>Congratulations, two whooshes!</htmltext>
<tokenext>Congratulations , two whooshes !</tokentext>
<sentencetext>Congratulations, two whooshes!</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494461</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28495371</id>
	<title>Re:hmm...</title>
	<author>eyepeepackets</author>
	<datestamp>1246122900000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext><p>"Go pound air!" doesn't have the same ummph to it.</p><p>"Go pound sand with air!" has promise.</p><p>"Go pound sand with water!" is kinda kinky.</p></htmltext>
<tokenext>" Go pound air !
" does n't have the same ummph to it .
" Go pound sand with air !
" has promise .
" Go pound sand with water !
" is kinda kinky .</tokentext>
<sentencetext>"Go pound air!
" doesn't have the same ummph to it.
"Go pound sand with air!
" has promise.
"Go pound sand with water!
" is kinda kinky.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494339</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28495821</id>
	<title>Re:hmm...</title>
	<author>SpectreBlofeld</author>
	<datestamp>1246126740000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext><p>I say they should ferry some sand up to the ISS and see what happens in null gravity.</p></htmltext>
<tokenext>I say they should ferry some sand up to the ISS and see what happens in null gravity .</tokentext>
<sentencetext>I say they should ferry some sand up to the ISS and see what happens in null gravity.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494283</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494553</id>
	<title>Pour sand in a vacuum</title>
	<author>Baldrson</author>
	<datestamp>1246115940000</datestamp>
	<modclass>Redundant</modclass>
	<modscore>1</modscore>
	<htmltext>The video shows sand droplets forming but some of the smaller droplets are falling more slowly than the larger droplets.  This indicates the drop column has air in it.
<p>
Evacuate and try it again...</p></htmltext>
<tokenext>The video shows sand droplets forming but some of the smaller droplets are falling more slowly than the larger droplets .
This indicates the drop column has air in it .
Evacuate and try it again.. .</tokentext>
<sentencetext>The video shows sand droplets forming but some of the smaller droplets are falling more slowly than the larger droplets.
This indicates the drop column has air in it.
Evacuate and try it again...</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494489</id>
	<title>Re:hmm...</title>
	<author>Anonymous</author>
	<datestamp>1246115400000</datestamp>
	<modclass>None</modclass>
	<modscore>0</modscore>
	<htmltext><p>The experiments were, in fact, performed under a reasonably strong vacuum.</p></htmltext>
<tokenext>The experiments were , in fact , performed under a reasonably strong vacuum .</tokentext>
<sentencetext>The experiments were, in fact, performed under a reasonably strong vacuum.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494283</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28496421</id>
	<title>Re:hmm...</title>
	<author>mosch</author>
	<datestamp>1246132200000</datestamp>
	<modclass>Informativ</modclass>
	<modscore>4</modscore>
	<htmltext><p>Had you read their research, you'd know that they tested this, and found it was not the case.</p><p>Sadly, it's a lot easier to post snarky comments than it is to do the 3 minutes of research required to determine that the snarky know-it-all was, in fact, wrong.</p></htmltext>
<tokenext>Had you read their research , you 'd know that they tested this , and found it was not the case.Sadly , it 's a lot easier to post snarky comments than it is to do the 3 minutes of research required to determine that the snarky know-it-all was , in fact , wrong .</tokentext>
<sentencetext>Had you read their research, you'd know that they tested this, and found it was not the case.Sadly, it's a lot easier to post snarky comments than it is to do the 3 minutes of research required to determine that the snarky know-it-all was, in fact, wrong.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494697</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494375</id>
	<title>This is called granular flows</title>
	<author>Saba</author>
	<datestamp>1246114440000</datestamp>
	<modclass>Interestin</modclass>
	<modscore>5</modscore>
	<htmltext>Sand belongs to a group of things called granular media. This includes things like pellets, ores, polymers, etc.<br> <br>

We typically regard the size of the particles to be larger than 1&#194;m. Any smaller and you have to start to take into account interparticle forces such as electrostatics and Van der Waals.<br> <br>

Trying to work out exactly how granular media behaves is tricky. Sometimes it behaves like a solid (sand on a beach, say -- you don't sink into it) and sometimes it behaves like a fluid (you can pour the grains of sand from a beach through your fingers). The example given here shows how it can behave inbetween solid objects (mechanics) and liquids (fluid dynamics). There's a large body of statistical and simulation results that try to understand what's going on, but nothing exists like Navier-Stokes does for liquids.<br> <br>

There's a lot of strange and unintuitive behaviour that arises out from studying these sorts of materials, and it's *extremely* important to industry. For example how granular media has a self-sorting behaviour when you subtly vary the size or mass of each particle. <br> <br>

The article shows another example of it.</htmltext>
<tokenext>Sand belongs to a group of things called granular media .
This includes things like pellets , ores , polymers , etc .
We typically regard the size of the particles to be larger than 1   m .
Any smaller and you have to start to take into account interparticle forces such as electrostatics and Van der Waals .
Trying to work out exactly how granular media behaves is tricky .
Sometimes it behaves like a solid ( sand on a beach , say -- you do n't sink into it ) and sometimes it behaves like a fluid ( you can pour the grains of sand from a beach through your fingers ) .
The example given here shows how it can behave inbetween solid objects ( mechanics ) and liquids ( fluid dynamics ) .
There 's a large body of statistical and simulation results that try to understand what 's going on , but nothing exists like Navier-Stokes does for liquids .
There 's a lot of strange and unintuitive behaviour that arises out from studying these sorts of materials , and it 's * extremely * important to industry .
For example how granular media has a self-sorting behaviour when you subtly vary the size or mass of each particle .
The article shows another example of it .</tokentext>
<sentencetext>Sand belongs to a group of things called granular media.
This includes things like pellets, ores, polymers, etc.
We typically regard the size of the particles to be larger than 1Âm.
Any smaller and you have to start to take into account interparticle forces such as electrostatics and Van der Waals.
Trying to work out exactly how granular media behaves is tricky.
Sometimes it behaves like a solid (sand on a beach, say -- you don't sink into it) and sometimes it behaves like a fluid (you can pour the grains of sand from a beach through your fingers).
The example given here shows how it can behave inbetween solid objects (mechanics) and liquids (fluid dynamics).
There's a large body of statistical and simulation results that try to understand what's going on, but nothing exists like Navier-Stokes does for liquids.
There's a lot of strange and unintuitive behaviour that arises out from studying these sorts of materials, and it's *extremely* important to industry.
For example how granular media has a self-sorting behaviour when you subtly vary the size or mass of each particle.
The article shows another example of it.</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28496739</id>
	<title>Re:hmm...</title>
	<author>Jurily</author>
	<datestamp>1246134300000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext><p>Can't the surface irregularities act like surface tension?</p></htmltext>
<tokenext>Ca n't the surface irregularities act like surface tension ?</tokentext>
<sentencetext>Can't the surface irregularities act like surface tension?</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494339</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494429</id>
	<title>5th State, Probably Not</title>
	<author>Anonymous</author>
	<datestamp>1246114920000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext><p>Water or anything flowing through air develops a charge. I'm sure sand does too Relative to each other there can be a some with more some with less that would have a tendency for them to group and form droplets</p></htmltext>
<tokenext>Water or anything flowing through air develops a charge .
I 'm sure sand does too Relative to each other there can be a some with more some with less that would have a tendency for them to group and form droplets</tokentext>
<sentencetext>Water or anything flowing through air develops a charge.
I'm sure sand does too Relative to each other there can be a some with more some with less that would have a tendency for them to group and form droplets</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28495293</id>
	<title>Re:It's the air.</title>
	<author>NuclearError</author>
	<datestamp>1246122180000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext>He made a car analogy. Big deal!</htmltext>
<tokenext>He made a car analogy .
Big deal !</tokentext>
<sentencetext>He made a car analogy.
Big deal!</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494615</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494419</id>
	<title>Gotta love it</title>
	<author>zoomshorts</author>
	<datestamp>1246114800000</datestamp>
	<modclass>None</modclass>
	<modscore>-1</modscore>
	<htmltext><p>My karma sucks, yet I got an early post in. Yes, quicksand has been re-discovered.<br>Wow, plus my karmic debt transcends almost anything. What goes around aggregates<br>around me, much like the sand described in the article.  Bonus!</p></htmltext>
<tokenext>My karma sucks , yet I got an early post in .
Yes , quicksand has been re-discovered.Wow , plus my karmic debt transcends almost anything .
What goes around aggregatesaround me , much like the sand described in the article .
Bonus !</tokentext>
<sentencetext>My karma sucks, yet I got an early post in.
Yes, quicksand has been re-discovered.Wow, plus my karmic debt transcends almost anything.
What goes around aggregatesaround me, much like the sand described in the article.
Bonus!</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28495007</id>
	<title>Re:They dropped their expensive camera?</title>
	<author>complete loony</author>
	<datestamp>1246120080000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext>Just send a small transparant container of sand on the vomit comit or a space shuttle...</htmltext>
<tokenext>Just send a small transparant container of sand on the vomit comit or a space shuttle.. .</tokentext>
<sentencetext>Just send a small transparant container of sand on the vomit comit or a space shuttle...</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494297</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494387</id>
	<title>Doh!</title>
	<author>Toad-san</author>
	<datestamp>1246114560000</datestamp>
	<modclass>Troll</modclass>
	<modscore>1</modscore>
	<htmltext><p>What?  Someone let the physicists out of their labs?</p><p>This has been intuitively obvious for \_my\_ entire life; and they just get around to noticing?</p><p>Sand hell.  Watch the films of some massive landslides (including boulders weighing hundreds of tons).  They're just as fluidic as they can be<nobr> <wbr></nobr>... and damn-all static attraction too.</p></htmltext>
<tokenext>What ?
Someone let the physicists out of their labs ? This has been intuitively obvious for \ _my \ _ entire life ; and they just get around to noticing ? Sand hell .
Watch the films of some massive landslides ( including boulders weighing hundreds of tons ) .
They 're just as fluidic as they can be ... and damn-all static attraction too .</tokentext>
<sentencetext>What?
Someone let the physicists out of their labs?This has been intuitively obvious for \_my\_ entire life; and they just get around to noticing?Sand hell.
Watch the films of some massive landslides (including boulders weighing hundreds of tons).
They're just as fluidic as they can be ... and damn-all static attraction too.</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28495783</id>
	<title>Re:hmm...</title>
	<author>CarpetShark</author>
	<datestamp>1246126260000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext><blockquote><div><p>That's peculiar. What's binding the grains together to that extent? Moisture? Electrostatic charge?</p></div></blockquote><p><a href="http://en.wikipedia.org/wiki/Sandman\_(Marvel\_Comics)" title="wikipedia.org">Stan Lee, clearly</a> [wikipedia.org]</p></div>
	</htmltext>
<tokenext>That 's peculiar .
What 's binding the grains together to that extent ?
Moisture ? Electrostatic charge ? Stan Lee , clearly [ wikipedia.org ]</tokentext>
<sentencetext>That's peculiar.
What's binding the grains together to that extent?
Moisture? Electrostatic charge?Stan Lee, clearly [wikipedia.org]
	</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494283</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494551</id>
	<title>Cool.</title>
	<author>Rik Rohl</author>
	<datestamp>1246115880000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext><p>Gotta say, the Vid is very cool - Especially if you're stoned<nobr> <wbr></nobr>:P</p></htmltext>
<tokenext>Got ta say , the Vid is very cool - Especially if you 're stoned : P</tokentext>
<sentencetext>Gotta say, the Vid is very cool - Especially if you're stoned :P</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494697</id>
	<title>Re:hmm...</title>
	<author>Anonymous</author>
	<datestamp>1246117620000</datestamp>
	<modclass>None</modclass>
	<modscore>0</modscore>
	<htmltext><p>I'm with you on this one.  Occam is too.</p><p>It seems like the researchers are overreaching a bit here for a complex explanation, when a simpler one will do nicely.</p></htmltext>
<tokenext>I 'm with you on this one .
Occam is too.It seems like the researchers are overreaching a bit here for a complex explanation , when a simpler one will do nicely .</tokentext>
<sentencetext>I'm with you on this one.
Occam is too.It seems like the researchers are overreaching a bit here for a complex explanation, when a simpler one will do nicely.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494339</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494615</id>
	<title>Re:It's the air.</title>
	<author>The Living Fractal</author>
	<datestamp>1246116600000</datestamp>
	<modclass>Funny</modclass>
	<modscore>2</modscore>
	<htmltext><p>That may have been the only time I've seen Nascar related to anything remotely intelligent.  I applaud you sir.</p></htmltext>
<tokenext>That may have been the only time I 've seen Nascar related to anything remotely intelligent .
I applaud you sir .</tokentext>
<sentencetext>That may have been the only time I've seen Nascar related to anything remotely intelligent.
I applaud you sir.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494333</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28496113</id>
	<title>that's not fair!</title>
	<author>commodoresloat</author>
	<datestamp>1246129620000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext><p>You read the article!</p></htmltext>
<tokenext>You read the article !</tokentext>
<sentencetext>You read the article!</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494835</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494845</id>
	<title>Re:It's the air.</title>
	<author>Anonymous</author>
	<datestamp>1246118940000</datestamp>
	<modclass>None</modclass>
	<modscore>0</modscore>
	<htmltext><p>According to the publication itself, they've done these experiments in pressures down to 0.03 kPa and have found that "grain-gas interactions" aren't a dominant factor.</p></htmltext>
<tokenext>According to the publication itself , they 've done these experiments in pressures down to 0.03 kPa and have found that " grain-gas interactions " are n't a dominant factor .</tokentext>
<sentencetext>According to the publication itself, they've done these experiments in pressures down to 0.03 kPa and have found that "grain-gas interactions" aren't a dominant factor.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494333</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494453</id>
	<title>So about those "rivers" and "lakes" on mars</title>
	<author>RichMan</author>
	<datestamp>1246115100000</datestamp>
	<modclass>Insightful</modclass>
	<modscore>2</modscore>
	<htmltext><p>If sand can flow like water then perhaps the lakes and rivers shown by "water" like flow on mars were just created by sand flow.</p></htmltext>
<tokenext>If sand can flow like water then perhaps the lakes and rivers shown by " water " like flow on mars were just created by sand flow .</tokentext>
<sentencetext>If sand can flow like water then perhaps the lakes and rivers shown by "water" like flow on mars were just created by sand flow.</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494835</id>
	<title>Re:hmm...</title>
	<author>Anonymous</author>
	<datestamp>1246118820000</datestamp>
	<modclass>Informativ</modclass>
	<modscore>5</modscore>
	<htmltext>The researchers did consider the effect of air. In fact, the ambient air has the opposite effect: the drag of the air as the droplets fall rips grains out of the droplets, thus working against whatever effect is aggregating them. In particular the authors say in <a href="http://dx.doi.org/10.1038/nature08115" title="doi.org">their article</a> [doi.org] (p. 1111):<blockquote><div><p>For a rough estimate of the cohesive strength we track clusters as they fall and accelerate to a speed at which Stokes drag pulls individual grains off cluster protrusions. Correcting for slight changes in the air viscosity at
reduced pressure, this gives values of a few nanoNewtons.</p></div></blockquote><p>
They then go on to measure more careful the strength of the clustering force, and ascribe it to both Van der Waals interaction and capillary forces. They did perform the experiment as a function of humidity to test the effect of water bridging (capillary forces) and found it to be significant. But they provide further data suggesting that Van der Waals forces also play a role. Again from the article (p. 1112):</p><blockquote><div><p>It is difficult to distinguish van der Waals from capillary forces because we cannot rule out molecularly thin absorbed films that create tiny bridges between individual asperities24,25. However, we still observe clustering in glass
grains stored under vacuum (0.05 kPa) at low humidity (,1\%) and also in grains coated with hydrophobic silane.</p></div></blockquote><p>
The fact that clustering still occurs in vacuum suggests air is not crucial to the effect. The precise scaling they observe (e.g. the size and separation of the clusters as a function of time) is not consistent with simple inelastic collisions, and the effect of air would actually be to breakup the droplets, absent any attractive force. What they instead measured was a weak (but sufficient!) interaction between grains, which they ascribe to surface forces and capillary action.</p></div>
	</htmltext>
<tokenext>The researchers did consider the effect of air .
In fact , the ambient air has the opposite effect : the drag of the air as the droplets fall rips grains out of the droplets , thus working against whatever effect is aggregating them .
In particular the authors say in their article [ doi.org ] ( p. 1111 ) : For a rough estimate of the cohesive strength we track clusters as they fall and accelerate to a speed at which Stokes drag pulls individual grains off cluster protrusions .
Correcting for slight changes in the air viscosity at reduced pressure , this gives values of a few nanoNewtons .
They then go on to measure more careful the strength of the clustering force , and ascribe it to both Van der Waals interaction and capillary forces .
They did perform the experiment as a function of humidity to test the effect of water bridging ( capillary forces ) and found it to be significant .
But they provide further data suggesting that Van der Waals forces also play a role .
Again from the article ( p. 1112 ) : It is difficult to distinguish van der Waals from capillary forces because we can not rule out molecularly thin absorbed films that create tiny bridges between individual asperities24,25 .
However , we still observe clustering in glass grains stored under vacuum ( 0.05 kPa ) at low humidity ( ,1 \ % ) and also in grains coated with hydrophobic silane .
The fact that clustering still occurs in vacuum suggests air is not crucial to the effect .
The precise scaling they observe ( e.g .
the size and separation of the clusters as a function of time ) is not consistent with simple inelastic collisions , and the effect of air would actually be to breakup the droplets , absent any attractive force .
What they instead measured was a weak ( but sufficient !
) interaction between grains , which they ascribe to surface forces and capillary action .</tokentext>
<sentencetext>The researchers did consider the effect of air.
In fact, the ambient air has the opposite effect: the drag of the air as the droplets fall rips grains out of the droplets, thus working against whatever effect is aggregating them.
In particular the authors say in their article [doi.org] (p. 1111):For a rough estimate of the cohesive strength we track clusters as they fall and accelerate to a speed at which Stokes drag pulls individual grains off cluster protrusions.
Correcting for slight changes in the air viscosity at
reduced pressure, this gives values of a few nanoNewtons.
They then go on to measure more careful the strength of the clustering force, and ascribe it to both Van der Waals interaction and capillary forces.
They did perform the experiment as a function of humidity to test the effect of water bridging (capillary forces) and found it to be significant.
But they provide further data suggesting that Van der Waals forces also play a role.
Again from the article (p. 1112):It is difficult to distinguish van der Waals from capillary forces because we cannot rule out molecularly thin absorbed films that create tiny bridges between individual asperities24,25.
However, we still observe clustering in glass
grains stored under vacuum (0.05 kPa) at low humidity (,1\%) and also in grains coated with hydrophobic silane.
The fact that clustering still occurs in vacuum suggests air is not crucial to the effect.
The precise scaling they observe (e.g.
the size and separation of the clusters as a function of time) is not consistent with simple inelastic collisions, and the effect of air would actually be to breakup the droplets, absent any attractive force.
What they instead measured was a weak (but sufficient!
) interaction between grains, which they ascribe to surface forces and capillary action.
	</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494339</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494403</id>
	<title>The Falling Sand Game</title>
	<author>Anonymous</author>
	<datestamp>1246114620000</datestamp>
	<modclass>Funny</modclass>
	<modscore>4</modscore>
	<htmltext><p>Huh.<nobr> <wbr></nobr>/Someone/ has been playing too much of that nifty little toy <a href="http://fallingsandgame.com/sand/" title="fallingsandgame.com" rel="nofollow">The Falling Sand Game</a> [fallingsandgame.com] and calling it research.</p></htmltext>
<tokenext>Huh .
/Someone/ has been playing too much of that nifty little toy The Falling Sand Game [ fallingsandgame.com ] and calling it research .</tokentext>
<sentencetext>Huh.
/Someone/ has been playing too much of that nifty little toy The Falling Sand Game [fallingsandgame.com] and calling it research.</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28495291</id>
	<title>Re:Yawn</title>
	<author>confused one</author>
	<datestamp>1246122180000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext>since microprocessors are made of silicon...  it already does.</htmltext>
<tokenext>since microprocessors are made of silicon... it already does .</tokentext>
<sentencetext>since microprocessors are made of silicon...  it already does.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494461</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28495851</id>
	<title>Agreed</title>
	<author>CarpetShark</author>
	<datestamp>1246127100000</datestamp>
	<modclass>None</modclass>
	<modscore>1</modscore>
	<htmltext><p>Agreed, maybe the sand most physicists tend to grow up with is much grainier or something, but any sand I ever played with as a kid has always behaved like a fluid.  Clearly this is more low-level particle interaction stuff, but I'm still a little shocked that no one's done the research before now, if there's anything practical to be gained from studying it in more detail.  There does seem to be a lot of research of the obvious these days, for the sake of every student being able to claim authorship of some paper or other, but hopefully there's a sensible reason for the study in this case.</p></htmltext>
<tokenext>Agreed , maybe the sand most physicists tend to grow up with is much grainier or something , but any sand I ever played with as a kid has always behaved like a fluid .
Clearly this is more low-level particle interaction stuff , but I 'm still a little shocked that no one 's done the research before now , if there 's anything practical to be gained from studying it in more detail .
There does seem to be a lot of research of the obvious these days , for the sake of every student being able to claim authorship of some paper or other , but hopefully there 's a sensible reason for the study in this case .</tokentext>
<sentencetext>Agreed, maybe the sand most physicists tend to grow up with is much grainier or something, but any sand I ever played with as a kid has always behaved like a fluid.
Clearly this is more low-level particle interaction stuff, but I'm still a little shocked that no one's done the research before now, if there's anything practical to be gained from studying it in more detail.
There does seem to be a lot of research of the obvious these days, for the sake of every student being able to claim authorship of some paper or other, but hopefully there's a sensible reason for the study in this case.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494387</parent>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494811</id>
	<title>who ya gonna call?</title>
	<author>Anonymous</author>
	<datestamp>1246118640000</datestamp>
	<modclass>Interestin</modclass>
	<modscore>5</modscore>
	<htmltext>physicists may have just figured this out but special effects guys have known about it for decades. 25 years ago in ghostbusters when the stay puft marshmallow man panic causes a fire hydrant to fail (in miniature), the fountain of "water" shooting out of it is actually diatomaceous earth. shot from above in high speed it looks amazingly real.</htmltext>
<tokenext>physicists may have just figured this out but special effects guys have known about it for decades .
25 years ago in ghostbusters when the stay puft marshmallow man panic causes a fire hydrant to fail ( in miniature ) , the fountain of " water " shooting out of it is actually diatomaceous earth .
shot from above in high speed it looks amazingly real .</tokentext>
<sentencetext>physicists may have just figured this out but special effects guys have known about it for decades.
25 years ago in ghostbusters when the stay puft marshmallow man panic causes a fire hydrant to fail (in miniature), the fountain of "water" shooting out of it is actually diatomaceous earth.
shot from above in high speed it looks amazingly real.</sentencetext>
</comment>
<comment>
	<id>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494339</id>
	<title>Re:hmm...</title>
	<author>Anonymous</author>
	<datestamp>1246114200000</datestamp>
	<modclass>Interestin</modclass>
	<modscore>2</modscore>
	<htmltext><p>I say it's air. In the places where the stream was thinnest, turbulence began to push the sand toward the thicker sections until it formed blobs. The water will stay in droplet form once it stops moving, but the sand will fall apart without moving air acting against it.</p></htmltext>
<tokenext>I say it 's air .
In the places where the stream was thinnest , turbulence began to push the sand toward the thicker sections until it formed blobs .
The water will stay in droplet form once it stops moving , but the sand will fall apart without moving air acting against it .</tokentext>
<sentencetext>I say it's air.
In the places where the stream was thinnest, turbulence began to push the sand toward the thicker sections until it formed blobs.
The water will stay in droplet form once it stops moving, but the sand will fall apart without moving air acting against it.</sentencetext>
	<parent>http://www.semanticweb.org/ontologies/ConversationInstances.owl#comment09_06_27_1141242.28494283</parent>
</comment>
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