## What is the mass of a feather?

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### Re: What is the mass of a feather?

Hmm, envelope made of feathers = save on postage!

Or you could:
Create balanced equation for chemical reaction of feather. React feather completely and determine how many moles of substance produced. Use to find how many moles of feather were initially reacted, and from molar mass of feather molecule, discover mass
brodieboy255

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### Re: What is the mass of a feather?

This is the easiest question ever asked on the forum, and you guys turn it into a two-page debate.

...Don't ever change.

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### Re: What is the mass of a feather?

brodieboy255 wrote:Or you could:
Create balanced equation for chemical reaction of feather. React feather completely and determine how many moles of substance produced. Use to find how many moles of feather were initially reacted, and from molar mass of feather molecule, discover mass

Well, if we're going to do that, you need to know the chemical composition of a feather:

http://www.ornithology.com/lectures/Feathers.html

Feathers are 91% protein, 1.3% fat and 7.9% water.

So we know the molar mass of the water, which is 18.02 g/mol. Now we just need to find what the protein and fat is:

http://www.geocities.com/felicitax/Birds.htm

Feathers are completely made up of the protein keratin.

http://www.geocities.com/felicitax/Birds.htm

According to Wikipedia, keratin has a high proportion of the amino acid glycine, with a molar mass of 75.07 g/mol. It also has a lower percentage of alanine, with a molar mass of 89.1 g/mol.

Now all we need to do is count how many molecules of keratin and water are in the feather, and we are done.
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### Re: What is the mass of a feather?

So to get around measuring the mass of a certain object, you want to react it with something (whose mass we'd have to measure) in a beaker (whose mass we'd also have to measure) so that we can measure the mass of a brand new object?

And then you're going to make the sloppy assumption that the reaction went to completion so that we can figure out the mass of our feather?
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### Re: What is the mass of a feather?

Hawknc wrote:This is the easiest question ever asked on the forum, and you guys turn it into a two-page debate.
...Don't ever change.

I think there was a discussion about this tendency awhile back. If someone's obviously asking for homework help, or it's a stupid (or at least stupidly worded) question, most of us feel pretty justified in horribly overcomplicating our responses, just to fuck with the original poster.

mathmagic wrote:numbers and stuff

Dude, that's way too much work. I don't know why you're bringing protein and water and stuff into it. Everyone knows feathers are made of feather molecules, like brodieboy said.

It's birds that are the difficult nuts to crack, so to speak. Since, like water, we just don't know what they are.
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### Re: What is the mass of a feather?

gmalivuk wrote:Dude, that's way too much work. I don't know why you're bringing protein and water and stuff into it. Everyone knows feathers are made of feather molecules, like brodieboy said.

It's birds that are the difficult nuts to crack, so to speak. Since, like water, we just don't know what they are.

So now the task is to... go back to the source! Of course! How do we go about unlocking the secrets of this feather molecule? This feather molecule obviously enables the birds to fly... therefore, the feather molecule is... less dense than air? Or is full of magic. One or the other.
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### Re: What is the mass of a feather?

mathmagic wrote:So now the task is to... go back to the source! Of course! How do we go about unlocking the secrets of this feather molecule? This feather molecule obviously enables the birds to fly... therefore, the feather molecule is... less dense than air? Or is full of magic. One or the other.

I'm gonna wrap myself in feathers and levitate. yay!

But seriously, I think he should weigth about a thousand feathers and divide. Or don't divide! Put them in some liquid and get the volume, then you get density, and then you can take the weight of one feather if you know it's volume.
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### Re: What is the mass of a feather?

"Tell you what, Bart, I'll trade you the weight of a bowling ball on the eighth moon of Jupiter from my lunch, for the weight of a feather on the second moon of Neptune from your lunch."
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### Re: What is the mass of a feather?

Get a bird, pull out all it's feathers, weigh them all that once, and divide it by the total number of feathers.

e946

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### Re: What is the mass of a feather?

Obviously you would place the standard feather and the standard kg exactly 1 standard meter apart in a gravitationally free vacuum, then measure the distance between them a standard unit of time later.
You're still limited by the precision of your measurement for G, but it's getting there.
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### Re: What is the mass of a feather?

Prepare a very large flask of pure feathers dissolved in some appropriate solvent. Compare its density with that of pure solvent to find the total mass of feathers. Then freeze the solution. Use the freezing point depression to find the total number of feathers. Divide for mass.

stockpot

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### Re: What is the mass of a feather?

Clearly the answer is to get someone to mail you a feather, and see how much they get charged for postage.

Kayamon

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### Re: What is the mass of a feather?

Kayamon wrote:Clearly the answer is to get someone to mail you a feather, and see how much they get charged for postage.

That would include the mass of the envelope. You would have to mail an empty envelope and check its postage first, then find the difference.
Sana

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### Re: What is the mass of a feather?

Can't you just find a large amount of average sized feathers?

Add a bowl to a sensitive electronic scale BEFORE switching it on, so when you do turn it on, the reading is set to 0.

Add any number of feathers it requires to get a reading on the scale and then divide the impending result by the number of feathers that you added into the bowl in the first place, thus producing an approximate weight of the feather.

The only issue there is finding a large amount of feathers o.O which I'm sure can't be TOO hard to find.

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### Re: What is the mass of a feather?

This thread reminds me of the riddle:

What weighs more; A pound of feathers or a pound of bricks?

You'd be surprised how many people choose the bricks.

With regards to weighing the bowl of feathers:

I think the buoyancy of air would have too much of an effect on that measurement, no? Unless you bounded all the feathers together...
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### Re: What is the mass of a feather?

mathmagic wrote:This thread reminds me of the riddle:

What weighs more; A pound of feathers or a pound of bricks?

You'd be surprised how many people choose the bricks.

With regards to weighing the bowl of feathers:

I think the buoyancy of air would have too much of an effect on that measurement, no? Unless you bounded all the feathers together...

That's the principle, in a sense. You weigh a larger amount of feathers then divide by the amount you put on the scale.

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### Re: What is the mass of a feather?

Xiphias wrote:
mathmagic wrote:I think the buoyancy of air would have too much of an effect on that measurement, no? Unless you bounded all the feathers together...

That's the principle, in a sense. You weigh a larger amount of feathers then divide by the amount you put on the scale.

That only makes the result more accurate by averaging, buoyancy still makes them push down on the scales less.

Also surely bounded isn't a word, (bound?).
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### Re: What is the mass of a feather?

zenten wrote:And generally feathers are always accelerating. Unless they're in free fall in a vacuum.

... no, just no. If it's in a free-fall state, then it is *by definition* accelerating, due to gravity.
Totally not a hypothetical...

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### Re: What is the mass of a feather?

Macbi wrote:
Xiphias wrote:
mathmagic wrote:I think the buoyancy of air would have too much of an effect on that measurement, no? Unless you bounded all the feathers together...

That's the principle, in a sense. You weigh a larger amount of feathers then divide by the amount you put on the scale.

That only makes the result more accurate by averaging, buoyancy still makes them push down on the scales less.

Also surely bounded isn't a word, (bound?).

Obviously, the solution is to do the experiment in a vacuum! But that would still only yield the weight of the feathers in whatever acceleration frame you happen to be in at the time. I suggest immersing a large number of feathers in a known quantity of pure, distilled water and then adding a solute of known density until the feathers are neutrally buoyant in the solution, then, simply calculate the density of the solution, measure the volume of displaced solution and multiply appropriately to get the mass of the feathers, divide by the number of feathers and you're done!

Alternatively, arbitrarily select a feather and declare it to be an 'ideal feather' and it's mass to be one feather mass unit (fmu)
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### Re: What is the mass of a feather?

Robin S wrote:
zenten wrote:
ArmonSore wrote:But once you accelerate it to a new velocity the mass changes

That depends on your reference frame.
Does it? I thought acceleration always affected mass, regardless of reference frame (unless the reference frame was accelerating with the feather, which I gathered it wasn't from the phrase "new velocity").

Velocity is relative. Say you have three objects, you, a feather, and a bowling ball. You and the feather are hanging out together, and the bowling ball is moving 0.99 c relative to you. The bowling ball is going to seem to be much more massive than it would be if it was moving the same speed as you. But you and the feather from the bowling ball's perspective are very massive, since from it's perspective you are the one moving at 0.99 c, even though the feather from your perspective is very light.

22/7 wrote:
zenten wrote:And generally feathers are always accelerating. Unless they're in free fall in a vacuum.

... no, just no. If it's in a free-fall state, then it is *by definition* accelerating, due to gravity.

No, it's not. It feels weightless, and thus is not accelerating. It's all about GR
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### Re: What is the mass of a feather?

e946 wrote:Get a bird, pull out all it's feathers, weigh them all that once, and divide it by the total number of feathers.

Way to copy my post....
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### Re: What is the mass of a feather?

Xiphias wrote:
mathmagic wrote:This thread reminds me of the riddle:

What weighs more; A pound of feathers or a pound of bricks?

You'd be surprised how many people choose the bricks.

With regards to weighing the bowl of feathers:

I think the buoyancy of air would have too much of an effect on that measurement, no? Unless you bounded all the feathers together...

That's the principle, in a sense. You weigh a larger amount of feathers then divide by the amount you put on the scale.

... what? That doesn't negate the fact that buoyancy affects the measurement. If you weight 100 feathers, but the weight is off by 10 grams, each feather will be off by 0.1 grams after averaging. That's a pretty large error for something with as little weight as is.
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### Re: What is the mass of a feather?

zenten wrote:
Robin S wrote:
zenten wrote:
ArmonSore wrote:But once you accelerate it to a new velocity the mass changes

That depends on your reference frame.
Does it? I thought acceleration always affected mass, regardless of reference frame (unless the reference frame was accelerating with the feather, which I gathered it wasn't from the phrase "new velocity").

Velocity is relative. Say you have three objects, you, a feather, and a bowling ball. You and the feather are hanging out together, and the bowling ball is moving 0.99 c relative to you. The bowling ball is going to seem to be much more massive than it would be if it was moving the same speed as you. But you and the feather from the bowling ball's perspective are very massive, since from it's perspective you are the one moving at 0.99 c, even though the feather from your perspective is very light.

22/7 wrote:
zenten wrote:And generally feathers are always accelerating. Unless they're in free fall in a vacuum.

... no, just no. If it's in a free-fall state, then it is *by definition* accelerating, due to gravity.

No, it's not. It feels weightless, and thus is not accelerating. It's all about GR

To the first point: when I made my original statement I was talking about an observer in an inertial reference frame observing the feather as it accelerated. Of course if you switch frames of reference then it doesn't really matter what happened.

To the second point: The equivalence principle states that you can't tell the difference between accelerating in a uniform gravitational field and not accelerating at all. It's not a statement that the feather isn't accelerating. It's a statement that it doesn't matter either way.
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### Re: What is the mass of a feather?

Citizen K wrote:
What is the mass of a feather?

In ancient Egypt...
One soul, more or less.

And I remember some reading about some scientist or another who once tried to weigh souls as they escaped dying people (don't remember all the details offhand). So find those numbers and use them. Or go collect your own data. "Now hold still. Remember, it's for science."

22-28 grams, but the science was pretty bad. kinda sad i told a lot of people it was true before i did research on it.
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### Re: What is the mass of a feather?

zenten wrote:
Robin S wrote:Does it? I thought acceleration always affected mass, regardless of reference frame (unless the reference frame was accelerating with the feather, which I gathered it wasn't from the phrase "new velocity").

Velocity is relative. Say you have three objects, you, a feather, and a bowling ball. You and the feather are hanging out together, and the bowling ball is moving 0.99 c relative to you. The bowling ball is going to seem to be much more massive than it would be if it was moving the same speed as you. But you and the feather from the bowling ball's perspective are very massive, since from it's perspective you are the one moving at 0.99 c, even though the feather from your perspective is very light.
I don't follow how that shows that acceleration doesn't always affect mass.

ArmonSore wrote:The equivalence principle states that you can't tell the difference between accelerating in a uniform gravitational field and not accelerating at all.
No, the equivalence principle states that you can't tell the difference between accelerating without a uniform gravitational field and being in a gravitational field without accelerating. In order for accelerating in a uniform gravitational field to be equivalent to not accelerating at all, the magnitude of the acceleration would have to balance the strength of the gravitational field exactly.
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### Re: What is the mass of a feather?

Ok, but Robin S and Armon Sore, do you both agree that, a feather in a freefall is still accelerating, regardless of whether or not it matters, or whether you can tell, if it's in a free fall (which, by definition, means it's in a vacuum and in a uniform gravitational field) it will be accelerating. Yes?
Totally not a hypothetical...

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### Re: What is the mass of a feather?

22/7 wrote:Ok, but Robin S and Armon Sore, do you both agree that, a feather in a freefall is still accelerating, regardless of whether or not it matters, or whether you can tell, if it's in a free fall (which, by definition, means it's in a vacuum and in a uniform gravitational field) it will be accelerating. Yes?

Regardless of their answers, I certainly don't agree. If it is impossible to tell that something is doing a particular thing, then it makes no sense to talk of it doing that thing.

Objects in free-fall act as if they're in an inertial frame; the simplest possible explanation for this is that this is because they are in an inertial frame, ergo, they are not accelerating.
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### Re: What is the mass of a feather?

Robin S wrote:
zenten wrote:
Robin S wrote:Does it? I thought acceleration always affected mass, regardless of reference frame (unless the reference frame was accelerating with the feather, which I gathered it wasn't from the phrase "new velocity").

Velocity is relative. Say you have three objects, you, a feather, and a bowling ball. You and the feather are hanging out together, and the bowling ball is moving 0.99 c relative to you. The bowling ball is going to seem to be much more massive than it would be if it was moving the same speed as you. But you and the feather from the bowling ball's perspective are very massive, since from it's perspective you are the one moving at 0.99 c, even though the feather from your perspective is very light.
I don't follow how that shows that acceleration doesn't always affect mass.

ArmonSore wrote:The equivalence principle states that you can't tell the difference between accelerating in a uniform gravitational field and not accelerating at all.
No, the equivalence principle states that you can't tell the difference between accelerating without a uniform gravitational field and being in a gravitational field without accelerating. In order for accelerating in a uniform gravitational field to be equivalent to not accelerating at all, the magnitude of the acceleration would have to balance the strength of the gravitational field exactly.

My mistake. My statement was, I suppose, the inverse of the equivalence principle. I meant to say that there's no difference between being in a uniform gravitational field with no other forces acting on you (in terms of the outcomes of experiments that you could perform), and not being in a gravitational field at all, still with no forces acting on you.

I think that I could also assert the stronger statement that being in a uniform gravitational field with any number of other forces acting on you is exactly the same as not being in a gravitational field with those same other forces acting on you. For example, any experiment that I perform on earth with only the normal force and gravity acting on me would look the same as being in a spaceship (where there is no gravitional field) with only a normal force of the same strength (and unchanging direction) acting on me.

And my above statement doesn't seem (to me) to be any different than the equivalence principle. And my original statement seems to me as a corollary to my above statement. If not then I have a fundamental misunderstanding. So feel free to present a phenomena that would be different when in a gravitational field with no outside forces acting on you, and not being in a gravitational field, still with no outside forces acting on you.

22/7 wrote:Ok, but Robin S and Armon Sore, do you both agree that, a feather in a freefall is still accelerating, regardless of whether or not it matters, or whether you can tell, if it's in a free fall (which, by definition, means it's in a vacuum and in a uniform gravitational field) it will be accelerating. Yes?

This echoes my response to the thread in serious business on "Non-falsifiable opinions". There I paraphrased Feynman, who said that if you can't test whether or not something is true then it's not that we shouldn't talk about the thing we can't test, but that we needn't talk about it.

I take the same stance here. It's not wrong to say that a feather is accelerating, but it's not right either. It's unprovable(which sounds to me to be a very godelian statement). So we needn't say that the feather is accelerating at all. For example, if we're in a spaceship that is accelerating upwards at 9.8 m/s^2, and we drop a feather, we can't tell the difference between doing the same experiment on earth. Which is to say, the feather does the same exact thing as it does in a vacuum near the earth's surface. So you can talk about either as being true, if you want to.

But this bothers me a little bit. My above argument seems to break down since we "know" that we're in a gravitational field, not free space. If it is impossible to tell the difference then how do we know this to be true? Does someone have an answer to this? Is there a completely consistent way to view our experience on earth as not being due to a gravitational field?
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### Re: What is the mass of a feather?

ArmonSore wrote:But this bothers me a little bit. My above argument seems to break down since we "know" that we're in a gravitational field, not free space. If it is impossible to tell the difference then how do we know this to be true? Does someone have an answer to this? Is there a completely consistent way to view our experience on earth as not being due to a gravitational field?

You have to be careful about what you're talking about. Things like velocity, acceleration, etc, are frame dependent quantities. Your thinking is mixing values from different frames together.
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### Re: What is the mass of a feather?

A feather's mass is 1 slug.

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### Re: What is the mass of a feather?

ArmonSore wrote:I take the same stance here. It's not wrong to say that a feather is accelerating, but it's not right either. It's unprovable(which sounds to me to be a very godelian statement). So we needn't say that the feather is accelerating at all. For example, if we're in a spaceship that is accelerating upwards at 9.8 m/s^2, and we drop a feather, we can't tell the difference between doing the same experiment on earth. Which is to say, the feather does the same exact thing as it does in a vacuum near the earth's surface. So you can talk about either as being true, if you want to.
To me, this is utter nonsense. Do you drive a car to work (school, the grocery store, whatever)? Can you prove to me that when you put your seat belt on, it'll actually do something, or that your brakes will work, or that when you put \$40 worth of gas in it you're actually getting \$40 worth of gas? No, you can't, especially with your above definition of proof. However, you still get in your car confident of what it will and won't do in a given situation. It's nice to pontificate about whether or not a feather is actually accelerating or not, but if I set my reference frame and the feather is in "free fall" relative to that reference frame, you're going to treat it as if it's accelerating, because if you don't, and you start applying that to other parts of your life, you're uber-fucked.

And if you're an engineer, so is everyone who buys the product you're working on.
Totally not a hypothetical...

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### Re: What is the mass of a feather?

I thought that acceleration wasn't symmetric and could only be measured from an inertial reference frame - that's how the twins paradox works.
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### Re: What is the mass of a feather?

1: Isolate the feather-growing gene sequence from bird DNA
2. Splice it into genome of E. Coli, and make them grow feathers In vitro
3. Measure the mass of the amino acids consumed in this process, comparing it to a control group.
4. Test to see if the bacteria can fly with these new modifications.

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### Re: What is the mass of a feather?

Robin S wrote:I thought that acceleration wasn't symmetric and could only be measured from an inertial reference frame - that's how the twins paradox works.

The twins experiment has to do with an object (or person) moving at nearly the speed of light and the effects that that difference in velocity will have on that object (or person). I don't believe that acceleration comes into play, but rather relative velocities.

Totally not a hypothetical...

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### Re: What is the mass of a feather?

22/7 wrote:The twins experiment has to do with an object (or person) moving at nearly the speed of light and the effects that that difference in velocity will have on that object (or person). I don't believe that acceleration comes into play, but rather relative velocities.

But the "paradox" comes from the fact that the now-younger (the one that left and came back) could claim by the equivalence principle that he was the one who stayed still, while everything else moved away from him and his ship and then came back. So, he asks, why is he younger while his brother has aged?

This is resolved by the fact that the travelling twin accelerated and decelerated. The reference frames are not always equivalent, and the travelling twin's frame isn't always inertial. Therefore he can't make such a claim.

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### Re: What is the mass of a feather?

Rather than attempt to discover the mass of 1 feather, which is open to much error both due to flexibility in possible results, and the small scale making measurement difficult, you should find the mass of several thousand feathers and divide. This has been left as an exercise to the reader.
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### Re: What is the mass of a feather?

No, you are all wrong.

The best way would be to measure the radius of the earth's orbit (major axis, obviously), and then accelerate the feather to escape velocity.

Wait for the feather to be far away, and then remeasure the radius. You can then figure out the change in mass of the Earth, which is equal to that of the feather.

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### Re: What is the mass of a feather?

but isn't earth losing air constantly (if slowly)? Even a minute loss would contaminate the results.
Roosevelt wrote:
I wrote:Does Space Teddy Roosevelt wrestle Space Bears and fight the Space Spanish-American War with his band of Space-volunteers the Space Rough Riders?

Yes.

-still unaware of the origin and meaning of his own user-title

EdgarJPublius
Official Propagandi.... Nifty Poster Guy

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Joined: Tue Oct 09, 2007 4:56 am UTC
Location: where the wind takes me

### Re: What is the mass of a feather?

EdgarJPublius wrote:but isn't earth losing air constantly (if slowly)? Even a minute loss would contaminate the results.

No, the atmosphere is stable. Hydrogen is light enough to escape, which is why we have almost none in the atmosphere. Helium too, but the other gases are heavy enough to stay.

BlackSails

Posts: 5128
Joined: Thu Dec 20, 2007 5:48 am UTC

### Re: What is the mass of a feather?

Someone said that you would have to remove the space by binding the feathers together to reduce displacement effects from gravity. Wouldn't it then make sense to break them into their components in a collider and have them packed together?

Obviously, this would approach the density of black hole material, so I'd guess that a teaspoon worth of feathers would weigh several thousand tons if not more.
fjman

Posts: 35
Joined: Sat Jan 26, 2008 1:58 pm UTC

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