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Post by margamatix on Oct 1, 2005 18:32:39 GMT -4
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Post by lordoftherings on Oct 1, 2005 18:34:56 GMT -4
Uh, I can see an "arc" motion quite clearly, but only on my high-quality DVDs of the video. It's less apparent in these postage-stamp sized online clips. You are right, I misunderstood. the site I afterwards quoted said the same thing , that there are arc motion. In fact, you get a wonderful swirling rotation that is clearly purely ballistic. In air you get motion affected by fluid dynamics, which is wholly, totally absent in these videos. Consider a clot of dust ejected from a spinning wheel that has dug into a cohesive regolith. Consider a particle on the inside of the clot, directly adjacent to the wheel surface. Consider another particle on the outside of the clot, farthest from the wheel hub. As the clot separates from the wheel rim, it transitions to a purely linear velocity. It becomes ballistic at this point. But in transferring from angular to linear motion, the linear velocities do not equate. The outboard particle had a longer radius, and so now has greater linear velocity than the inboard particle. The clot will actually continue rotating in the same direction as the wheel as it follows a generally parabolic path. We consider that the cohesion of the clot is relatively weak, so the particles begin to pursue separate trajectories almost immediately. The faster particles move downrange (backwards, reckoned according to the direction of the vehicle) faster and may reach a higher apex. What if there were dryness in the place the shots were taken at? If you draw an imaginary line between these two particles and track it over the combined trajectories, you find that the line is initially vertical, but then rotates slowly in the same way that the wheel rotates. The particles also separate due to their slightly different ballstics, so the line lengthens. When you plot this sort of thing for all particles, you see a sort of pattern. And what's more, when you look at freeze-frame images of these disintegrating clots, they have a gorgeous geometrical shape deriving solely from the simple forces of angular momentum, linear momentum, and gravity. This simply doesn't happen on Earth. High-speed ejecta immediately meets with air resistance. This has two effects. First, it slows the particles. Second, it gives them chaotic paths. The mass of a particle increases roughly according to the cube of its size, but its surface area increases only according to the square of the size. Air resistance depends on surface area, but the force of gravity depends on mass. Thus ejecting a collection of variable sized particles into an ambient fluid is not a bad way of separating big and small particles. Air resistance also depends on speed. Very small particles, with a low surface area to mass ratio, are more susceptible per unit mass to air resistance. As they are ejected and meet with air, they slow immediately and become chaotic. Their interaction with fluid actually dominates, in which case we say that the particles have become aerosol. This is the way of the desert. You can't walk, drive, kick your feet, or do anything that sets dust in motion without a portion of that dust becoming suspended as aerosols that are very noticeable. There is no aerosol in any Apollo video. The heaviest particles have a smaller surface area to mass ratio and are thus proportionally less sensitive to air resistance. Their paths on Earth tend to remain ballistic regardless of how much air there is. The particles in between exhibit a smoothly varying response to air. You won't get good geometry in your rooster tail. You get this: a mixture of aerosolized clouds and particles being affected to varying degrees by the air. The fact that we can get any kind of pure geometry in a plume from the LRV tires suggests that there is no difference in the ballistics characteristics. Air simply isn't a factor in their shape -- otherwise you get chaos. ...very fast, dropBut the drop is consistent with the 1/6 acceleration. The reason it seems so fast is that all the dust falls to the ground. None of it hangs in the air, which is what you see on Earth. [/quote] But here it is not that fast, it doesn't behave like the rear weel (the video is not working so I am depending on the still shot). there is a cloud that is not like the "normal" rear weel dust. There is a space between the dust of the front weel and the ground, indicating there is air, even if few, holding it.
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Post by lordoftherings on Oct 1, 2005 18:40:44 GMT -4
besides, this is a racing car. I wonder if the LRV was racing at this same speed. I wonder about its environment if it was filmed on earth, (dry env.)
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Post by margamatix on Oct 1, 2005 18:42:41 GMT -4
There is dust, and there are clumps thrown up by the rally car. This is all to be expected on Earth, since there is moisture on Earth. Moisture causes soil to "clump"
Soil thrown up from the Lunar Rover also "clumped", although there is no moisture on the moon.
How could the soil from the Lunar Rover form clumps?
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Al Johnston
"Cheer up!" they said, "It could be worse!" So I did, and it was.
Posts: 1,453
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Post by Al Johnston on Oct 1, 2005 18:44:46 GMT -4
There is a space between the dust of the front weel and the ground, indicating there is air, even if few, holding it. No: if there is a space between the dust and the ground, ot just means that the dust hasn't hit the ground yet: just because there is no air, doesn't mean that dust falls instantly to the ground.
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Post by lordoftherings on Oct 1, 2005 18:48:13 GMT -4
the dust should instantly hit the ground, there are inches of space where the dust don't hit the ground, something must be carrying them
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Post by LunarOrbit on Oct 1, 2005 18:52:31 GMT -4
Soil thrown up from the Lunar Rover also "clumped", although there is no moisture on the moon. How could the soil from the Lunar Rover form clumps? What holds dust to the surface of your TV screen? What holds two pieces of velcro together? I just gave you two alternative ways that dust can clump that don't require water. And no, I'm not saying NASA used velcro to hold the dust together.
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Al Johnston
"Cheer up!" they said, "It could be worse!" So I did, and it was.
Posts: 1,453
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Post by Al Johnston on Oct 1, 2005 18:59:12 GMT -4
the dust should instantly hit the ground, there are inches of space where the dust don't hit the ground, something must be carrying them Rubbish: it's thrown up by the wheels and follows a ballistic trajectory to the ground exactly as expected for 1/6g in a vacuum
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Post by nomuse on Oct 1, 2005 19:28:04 GMT -4
Yeah...what holds up a baseball between the time it is thrown and the time it is used to strike out the batter? Air?
Whatever magical force is holding up the baseball, is holding up the dust dislodged by the right front wheel. Oh, yeah. I think they call it "inertia."
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Bob B.
Bob the Excel Guru?
Posts: 3,072
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Post by Bob B. on Oct 1, 2005 19:48:06 GMT -4
Margamatix is using another tried and true troll ploy. Make a claim, let his/her opponents expend their time and energy to refute the claim, and then post the claim again like nothing happened to bait the debunkers into repeating the refutations all over again. For anyone joining this thread a little late in the day, please go back and read from the beginning of the thread.
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Post by JayUtah on Oct 1, 2005 20:21:13 GMT -4
What if there were dryness in the place the shots were taken at?
Then moisture won't be the reason for clotting. Cohesive cementation occurs for lots of reasons. It the case of a tire digging up dust, it can just be temporary compression; the dust "sticks" together only as long as the tire is pressing it against the denser dust below.
There is a space between the dust of the front weel and the ground, indicating there is air, even if few, holding it.
No, it's just being flung upward.
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Post by JayUtah on Oct 1, 2005 20:31:17 GMT -4
Moisture causes soil to "clump"
Among other things.
How could the soil from the Lunar Rover form clumps?
The same way I can form clumps of portland cement on Earth even though there's no moisture in it. In fact, it doesn't work if there's moisture in it.
Any particulate is impressible at some scale, regardless of moisture. It's simple mechanical interlocking.
However, because particles on the moon have no oxide patina, the can cold-weld themselves together under nothing more than mechanical compression.
The clotting doesn't have to be extensive. It just has to be enough to create variance in the departure conditions of the dust.
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Post by PhantomWolf on Oct 1, 2005 23:04:06 GMT -4
OK, could you point me in the direction of any post where I have been rude? Well let's see. You have lied to us on a number of occasions that we know about. You have ignored responses, you have evaded questions, you have changed questions completely to avoid answering, them. You have quibled over the syntax of a question to avoid answering. You have complained and demanded that people stay on topic in your threads, but then turned around and happily totally change the subject whenever you feel like it or when your beliefs are getting to threated. You have yet to provide support for any claim, nor a retuation other then restating your intial claims. If I was link to every one of these, I'd end up linking to near enough to half your posts.
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Post by ouloncollouphid on Oct 1, 2005 23:05:04 GMT -4
I have been advocating your bannshment from this forum for weeks . Well thanks for that Bob, you're in the same box as Kiwi now. Bye! Unbelievable. Just put us all in the box, will you, for Christ's sake?
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Post by PhantomWolf on Oct 2, 2005 1:17:21 GMT -4
the dust should instantly hit the ground, there are inches of space where the dust don't hit the ground, something must be carrying them It takes time for gavity to counter the upward motion of the dust that the wheel has given it. There is a gap because the wheel has left the ground and so while not on the ground it isn't throwing up any more dust but the last amount of dust is still moving backwards due to the horizontal motion imparted to it, and the wheel is moving forward. Dust can't just fall straight down because the first thing the gravity has to do is stop it. It's like throwing a ball into the air. Gravity slows it down and reverses the motion, it just doesn't leave your hand, then instantly fall to the ground.
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