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jrkeller
2002-May-25, 12:54 AM
We've all heard the HB's flag waving point; however, has anyone ever pointed out to these people that no dust is blowing and there are no wind erosion effects, such as sand dunes or soil deposits behind rocks.

Roy Batty
2002-May-25, 01:02 AM
Well I guess they'd argue that there would be none of those effects on the supposed stage in a hangar somewhere in Area 'insert no. here' /phpBB/images/smiles/icon_smile.gif

JayUtah
2002-May-25, 01:10 AM
Not everyone believes the flag is blowing in the wind because it's being filmed outside on earth. Bart Sibrel, for example, believes some super air conditioner is causing the motion of the flag. This allows for the terrain to be artificial.

When you ask why the wind doesn't stir up any dust, you usually get the answer that the wind is just strong enough to move the flag, but not strong enough to raise dust. Obviously these people have never been in a desert.

Oddly, some people point to still photos as evidence of flag motion. Some don't realize the horizontal curtain rod through the top hem. Others expect the flag to hang perfectly planar with no wrinkles.

The problem with pointing the scientific consequents to a windy antecedent is that these people are not scientific. So they'll just say, "Why should I expect to see what you say should be there?" Only hoax believers, apparently, are allowed to specify expectations for lunar surface documentation.

AstroMike
2002-May-25, 01:35 AM
Well, if you look at this video (http://www.hq.nasa.gov/office/pao/History/alsj/ktclips/ap17_flag.mpg), the flag suddenly stops waving as soon as Cernan lets go of the pole, and then waves as soon as he touches it. This is how we know it is not caused by wind or air conditioners.

Roy Batty
2002-May-25, 01:52 AM
Well just a v.small niggle /phpBB/images/smiles/icon_smile.gif it almost stops waving as soon he lets go, but there is some residual movement.. as you'd expect from the inertial forces propagated through the material.

JayUtah
2002-May-25, 02:15 AM
Sibrel introduced the notion that the flag moves when no one is touching the pole. Of course he neglected to mention (but Phil reminded him) that the astronaut had just let go of the pole a few seconds earlier.

What happens is that you have the horizontal rod attached to the pole, then a distributed load placed across it. Then the system is dyanamically agitated by means of the pole. Now to a structural engineer that has "resonance" written all over it.

The rod and its load will respond inertially to the moments and displacements introduced at the point of fixture. That response will be an elastic deformation of the rod and a rotation in the fixture according to its mechanical tolerances. The pole will also resonate. The fixture rotation doesn't concern me. The resonance of the pole and rod does.

In the video clips alleged to be of the flag moving with no apparent source of motion, the astronaut has just released the pole and the motion of the pole and rod is highly characteristic of resonance. The motion is regular, oscillatory, and decreases in amplitude over time. Motion induced by ongoing wind loads does not have these characteristics.

JayUtah
2002-May-25, 02:19 AM
as you'd expect from the inertial forces propagated through the material.

Yes, see above. Also note that while the flag's semi-rigid supports are moving, the flag itself isn't. Wind can't move the structure but fail to move the much lighter and much freer flag.


<font size=-1>[ This Message was edited by: JayUtah on 2002-05-24 22:19 ]</font>

Andrew
2002-May-25, 03:31 AM
Oops, wrong thread.

<font size=-1>[ This Message was edited by: Andrew on 2002-05-24 23:32 ]</font>

David Hall
2002-May-25, 10:51 AM
Love that video. The flag definitely isn't flapping around like in a wind. Instead, it seems to me to be swinging around more like a sheet of limp fettuccini. That's of course only when it's being directly handled. It just kind of spookily hangs there when nothing is moving it.

I also liked the little pirouette the astronaut made after he crossed behind the flag. I'd like to see anyone in a cumbersome, top-heavy full body suit do that maneuver in 1g!

DaveC
2002-May-25, 07:19 PM
What impresses me about this video is how clearly you can tell that the weight:inertia ratio is simply wrong for a 1g environment. The moving astronauts appear to slide a bit each time they hit the ground - and you can see the plume of dust that gets fired out ahead of their feet as they do so. When something like 360 pounds of mass is moving laterally where it weighs only 60 pounds, this is exactly what you'd expect to see. There isn't enough friction between the boots and the surface to stop the lateral movement as quickly as it would occur in 1g. To me, this plus the ballistic trajectories of the dust kicked up makes it absolutely clear that the video was taken in a reduced gravity vacuum.

Justincccc
2002-May-25, 07:46 PM
Here's a suggestion; If we can discuss the physics of the waving flag and the moon dust, then why can't we perform an actual experiment with a miniature flag on soil, and compare our results?

No one in this newsgroup I've seen has brought this up before, probably because most of us don't feel like geting up and performing an activity since most of us are eternally bonded to our computers at home or work. If anyone has actually done an experiment on this before, I'd like to know the results.

Either way, I think its pointless to discuss something like this, as NASA could have done a retake of the scene if it were faked.

Lisa
2002-May-25, 09:41 PM
Actually, when Megan asked me about this, I pointed out a little experiment she could do. It was a nice breeze-less day, so we could stick Ed's 2-iron in the ground and it wouldn't move unless we touched it. She confused the moon's airlessness with gravity. Okay, there's only 1/6, but there's gravity nonetheless. Inertia still applies.
Megan listens to her Aunt Lisa. Sensible girl. (And she eventually returns books too)
Lisa

The Bad Astronomer
2002-May-25, 09:51 PM
Last year, a guy who worked at Johnson Space Center and I were talking, and he looked into maybe doing a flag experiment in the big vacuum chamber. We never really pursued it, but I've been thinking about it again. Maybe I'll drop him a line... /phpBB/images/smiles/icon_wink.gif

JayUtah
2002-May-25, 11:01 PM
Experimentation is very useful for demonstrating principles, but empiricism is not an adequate substitute for correct understanding of the theoretical principles.

As the B.A. notes, it would take a large vacuum chamber to correctly simulate the behavior of the flag on the lunar surface. You can do it in miniature, but since fabric elasticity doesn't scale, you can't draw any conclusions from those tests that would apply to hoax believer arguments. Even with a full-sized flag in a large vacuum chamber, you still have the full effect of earth's gravity to contend with. This would also limit how far your results would generalize to the lunar environment.

Yeah, but close enough, right? Unfortunately we've all seen the tendency of hoax believers to grasp at any straw which gives them a reason to sidestep pertinent contrary evidence. If the flag were not full size, if the suspension system were not absolutely identical, if the vacuum were not total, if the gravity were not equivalent -- a hoax believer will likely use any of those points as an excuse to disregard the findings. This would likely happen even if significant portions of the hoax believer's expectations were proved untenable. The hoax believers have chosen this argument precisely because it cannot be accurately simulated on earth, in order to disprove them.

We can remove the effect of air, but we cannot simultaneously lessen the effect of gravity. It is possible to use a much lighter fabric than nylon, but then that fabric will have different mechanical properties.

If the hoax believer's premise is, "The flag motion is impossible in the absence of air," we can clearly dismiss this emprically. But it would be all too easy to change horses and say, "The flag motion is impossible in the absence of air and under the effect of lunar gravity," and we would be empirically stuck.

However, because negative propositions (e.g., that's impossible, doesn't exist, or can't happen) are impossible to prove, it is not wise to structure an investigation so as to rely upon proving one.

Thankfully the hoax believers provide a positive and testable proposition: "The flag motion is due to wind." I have performed experiments with 3x5 nylon flags in wind and in stationary air. I cannot duplicate the observed motion of the flag in earth atmosphere and gravity. This, of course, is inconclusive because the failure to prove the proposition does not equate to proof of its converse.

Nevertheless this is a more attractive procedure. It falls to the hoax believers to demonstrate by empirical means that their argument is plausible. Let them go buy 3x5 nylon flags and subject them to whatever air currents they can devise. Let them even wiggle the flagpoles themselves and try to duplicate the sort of pendulous motion that we observe in the Apollo photos. I have tried, and I can't do it.

Now if we wish to accept gravity as a confounding variable, we can partially test the effect of air using JSC's vacuum chamber. Gravity, in this case, is a continuous variable. We have a certain amount of gravity on earth, and a certain lesser amount on the moon. Air, on the other hand, is a categorical variable. It's either there, or it's not.

If we can note that the behavior of the flag is qualitatively similar to the Apollo footage in the vacuum chamber, and qualitatively dissimilar in plain air, we can attempt to generalize through the quantitative effects caused by the difference in gravity. This, of course, would amount to a certain degree of handwaving which is not, obviously, attractive.

But in that the hoax believers concentrate more on the presence or absence of air than on the relative difference in gravity, testing that particular variable -- even confounded with gravity -- is probably useful.

The Bad Astronomer
2002-May-25, 11:21 PM
On 2002-05-25 19:01, JayUtah wrote:
If the hoax believer's premise is, "The flag motion is impossible in the absence of air," we can clearly dismiss this emprically. But it would be all too easy to change horses and say, "The flag motion is impossible in the absence of air and under the effect of lunar gravity," and we would be empirically stuck.


Not necessarily. The motion on the Moon is interesting because the flag corner flaps much higher than it would with air. We all know the flag will flap in a vacuum, even on Earth. However, I just bet the corner won't flap as high on the Earth, due to the higher gravity.

Therefore, the video showing it flapping as high as it does shows that not only is there no air, but also lower gravity. Voila.

JayUtah
2002-May-26, 12:20 AM
Actually that's what I was getting at. It's easier to deal with a confounded continuous variable than a confounded categorical variable. The variable we can test is categorical, so if we see a qualitative change, that's a useful correlation. So you can make a case that testing in a vacuum chamber on earth is valid empiricism. But try telling that to a hoax believer!

johnwitts
2002-May-26, 12:36 AM
But try telling that to a hoax believer!

Try telling then anything and you'll wind up getting banned. The one notable exception to this rule is apollohoax.com, where the webmaster initially scoffed at our wayward ideas, but through patience and a willingness to listen and learn, he's now getting the right story.
He's also notably the only webmaster who doesn't ban people, no matter what. (OK, so he hit the 'panic button' and deleted 9/10ths of the forum, but his heart's usually in the right place).

<font size=-1>[ This Message was edited by: johnwitts on 2002-05-25 20:36 ]</font>

JimO
2002-Oct-31, 03:28 PM
In trying to mimic some of the Apollo flag dynamics on Earth, would it help to eliminate most air resistence by suspending a mesh/netting (or even light metal chain mail) drape from such a pole/rod, and shove and twist it? Would that sort of experiment be useful to suggest kids 'try at home'?

SpacedOut
2002-Oct-31, 03:57 PM
I would think a very flexible, open 1"x1" net made of rope or chain would probably work to help minimize the affects of air resistance, but I'm not sure how the additional weight would affect the experiment. My first thought is you would want something with 1/6 the weight of the flag, but then the object would be significantly more subject to the affects of the atmosphere, then again the weight of the object may not matter.

Probably something that will need to be refined by trial and error. Where best to find such a net?

heliopause
2002-Oct-31, 05:24 PM
On 2002-05-25 06:51, David Hall wrote:
I also liked the little pirouette the astronaut made after he crossed behind the flag. I'd like to see anyone in a cumbersome, top-heavy full body suit do that maneuver in 1g!


I liked that maneuver too. Take that, Michael Jackson!!!

The Bad Astronomer
2002-Oct-31, 05:34 PM
When I give my Moon Hoax talk, I take my belt off and use that. I let it hang down in front of my face and blow on it as hard as I can, showing that it doesn't respond to air movement much at all. Then I hold it at arm's length and move my arm back and forth. You get the wiggly wave going down the belt just like the flapping of the flag. It's not air blowing, it's inertia!

SeanF
2002-Oct-31, 07:27 PM
Better be careful, BA - I'd hate for your pants to fall down in the middle of a demonstration!

Jim
2002-Oct-31, 08:19 PM
On 2002-10-31 14:27, SeanF wrote:
Better be careful, BA - I'd hate for your pants to fall down in the middle of a demonstration!

Would that be considered ironic, or a visual pun? I mean, while debunking the Apollo hoax, mooning the audience.

heliopause
2002-Oct-31, 08:25 PM
On 2002-10-31 14:27, SeanF wrote:
Better be careful, BA - I'd hate for your pants to fall down in the middle of a demonstration!



Hmmm...if the BA was on the moon and his trousers fell, how fast/far down would they fall as compared to a similar embarassing situation on Earth?

JayUtah
2002-Oct-31, 09:20 PM
I use the belt method too, although I don't use the belt that is assigned to hold up my pants. I point out that the belt is not likely to be affected as much by air resistance as it is by inertia. Then I attach the belt to a stick representing the horizontal rod and perform some of the same maneuvers that happen to the Apollo flags. It's easy to produce something akin to the characteristic flip of the free corner.

Conversely I give kids a 3x5 nylon flag rigged Apollo-style and have them see if they can, by some combination of motion and air movement, to reproduce what they see in the Apollo EVA videos. They can't, and after they get frustrated I point out that the conspiracy theorists want you to believe that the phenomenon they can't reproduce is what happened every time to the astronauts.

cljohnston108
2005-Dec-23, 06:28 PM
Even though this thread has been dead for three years, I thought I'd post a thought.

It's been said here that one can't accurately simulate flag dynamics in a vacuum chamber because one can't decrease Earth's gravity, nor in a miniature VC because the fabric doesn't scale.

Two words: Dry Cleaning

That super-thin plastic that your local dry cleaner drapes over your garments, which takes on a life of it's own in the slightest breeze.

Demonstrate how that stuff reacts differently in vacuum.

Just my US$0.02.

jrkeller
2005-Dec-23, 07:42 PM
Thanks for resurrecting one of my first posts.

You do make a good point about thin plastic sheets.

It's too bad that NASA never filmed some liquid venting out of the LM. That would be very difficult to fake on the Earth.

Astronot
2005-Dec-24, 06:07 PM
But ** could find a way to claim it was!

jrkeller
2005-Dec-24, 07:05 PM
But ** could find a way to claim it was!

While I know he claim that, I can see no way to fake something like that. You've have projectile flow so gravity would be known. You've liquid flashing in a vacuum, which maybe possible to fake on Earth, but you would need a huge vacuum chamber. You couldn't fake both together.

Astronot
2005-Dec-27, 03:17 AM
While I know he claim that, I can see no way to fake something like that. You've have projectile flow so gravity would be known. You've liquid flashing in a vacuum, which maybe possible to fake on Earth, but you would need a huge vacuum chamber. You couldn't fake both together.
Agreed!