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19th April 2019, 07:29 AM | #441 |
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19th April 2019, 08:00 AM | #442 |
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Gingervytes, I repeat - again:
I’ve personally built (as part of a team), integrated, tested, observed the launch of, and operated spacecraft, including postflight testing. Your claim is observed to be wrong. Any response?. Or are you going to continue ignoring refutations like this one? Ya know, if it was me, and I was getting my head handed to me by people who actually do spaceflight for a living, as well as an assortment of educated laymen, I would stop and ask myself if maybe I was wrong, and investigate the criticisms of my claims, because it’s more important to me to get it right than to cling to my beliefs on an anonymous Internet forum. How about you? Would you like to learn something? |
19th April 2019, 08:25 AM | #443 |
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There has been no effort on his part to learn anything, just keep repeating the same nonsense adding a few other BS that knows he knows nothing of physics. All he wants is to continue the posting, so I'm done with this TROLL and I should have stopped several pages ago.
Have fun guys. |
19th April 2019, 08:38 AM | #444 |
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19th April 2019, 08:38 AM | #445 |
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/dann "Stupidity renders itself invisible by assuming very large proportions. Completely unreasonable claims are irrefutable. Ni-en-leh pointed out that a philosopher might get into trouble by claiming that two times two makes five, but he does not risk much by claiming that two times two makes shoe polish." B. Brecht "The abolition of religion as the illusory happiness of the people is required for their real happiness. The demand to give up the illusion about its condition is the demand to give up a condition which needs illusions." K. Marx |
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19th April 2019, 08:47 AM | #446 |
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Agreed. He's stumbling over basic first-year principles and completely unfamiliar with simple laws like PV/T = k. His arguments display a confusion between density and pressure, and just flatly deny Newton's third law. He seems to have it stuck in his head that the mechanics involved here work only with fluids. His model deals only with the special case of compressible fluids, which certainly can operate in a system that exhibits conservation of momentum. But he seems to think this now means a compressible fluid is required.
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19th April 2019, 09:24 AM | #447 |
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Better key words would be "letting go." Don't get me wrong; your analysis is correct. But if we choose our words carefully we can aid the analysis.
You let go of the weight. But for gravity, nothing would happen. Your fingers would release hold, but no significant motion would occur. Introduce gravity and the weight falls because it and the Earth attract each other. But for the floor, you would fall too -- attracted in the same way. In fact, you would fall at the same rate. Momentum would thereby be conserved between you and the weight. It is not in this case because the floor constitutes an external force. The momentum-conserving system defined by the Earth and the weight remains the same. The momentum-conserving system defined as the Earth and you remains the same.
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It's more applicable if you imagine this system sideways. The typical way to illustrate conservation of momentum in a classroom is with two students in office chairs who push off from each other. It's best if you choose two who have significantly different mass. Their final resting places obey the law of conservation of momentum, Newton's third law. And if you have students with advanced enough knowledge, you can show that their combined center of mass remains reasonably unchanged. This is about throwing mass, not "pushing against air" or moving toward zones of lower pressure. Another common apparatus is to sit on a skateboard and roll away a bowling ball. Both you and the ball move. This has nothing to do with the air in the room. Gingervytes doesn't seem to think throwing solid objects out the back of something would result in thrust. He is wrong. Rockets throw mass. The fact that the mass is in the form of a gas makes absolutely no difference. In engineering we have whole rooms that function like giant air-hockey tables. We use air cushion principles to "float" very large assemblies on a broad, flat surface and thereby and obtain at least two dimensions of relatively frictionless Newtonia. The measurements and calculations we make there involve only the masses and velocities of the objects, not whether there's air or how much the air affects the results. We're typically dealing there with objects with very high mass and very low velocity, so the effect of the ambient fluid is properly ignored. Yet Newton's third law holds. |
19th April 2019, 09:36 AM | #448 |
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I was just thinking (a dangerous thing to do at the best of times for me)- that 'technically' wouldn't dropping a weight actually lift you???
You are standing holding a weight, and release it Now (and this is just my musings) when you release the weight, it and the earth are mutually attracted, the weight will move (a lot) towards the earth, and the earth will move (microscopically) towards the weight You (standing on the earths surface) would also be 'lifted' by this movement of the earth So technically you would move (ever so incredibly tiny an amount) in the opposite direction to the direction of the weight's travel I think this is correct? |
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19th April 2019, 09:56 AM | #449 |
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I should emphasize that we all work in teams in this industry.
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The argument tries to rewrite our respective roles as just low-level flunkies who really don't have the knowledge that refutes his belief. Sure we did all that, but then some hidden, all-powerful entity took over and just magically gave us all we would need to observe indirectly (e.g., telemetry) in order to believe that what we did actually achieved the intended effect. When I pointed out pre-emptively that this is not how engineering works, he had nothing further to add. It's one thing to say in public, "Those people over there are lying." It's suitably impersonal and only mildly confrontational. It's another thing to say in public, "You, to whom I'm speaking, are lying." That's perhaps more aggressive than the typical claimant is willing to be. So it's safer just to pretend that people don't exist who are able to directly contradict you with direct observation. Or to pretend, by waving your hands vaguely at YouTube, that you've already "proven" whatever those experts are objecting to, and that they must be too ideologically compromised to acknowledge it. For conspiracy theorists it's always ultimately about which individuals have the least compromised ideology. |
19th April 2019, 10:43 AM | #450 |
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19th April 2019, 11:44 AM | #451 |
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Actually, he claimed that you can see them splash into the ocean, too.
The problem is, he doesn't provide us with HIS explanation of what it's doing between the time it disappears from sight and the time it reappears. As I've pointed out, the explanation for that without invoking space travel is a LOT harder than just simply conceding that it went into space. BTW, I've actually seen the ISS fly by. It was really cool to watch it pass over head. If that wasn't in outer space, where was it? Just like an airplane but really, really, really high up in the air? Instead of going at 30 000 feet, it is just 1.3 mil? |
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19th April 2019, 12:01 PM | #452 |
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19th April 2019, 12:04 PM | #453 |
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19th April 2019, 12:05 PM | #454 |
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Thank you; I missed where he claimed that.
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19th April 2019, 12:09 PM | #455 |
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19th April 2019, 12:10 PM | #456 |
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19th April 2019, 12:12 PM | #457 |
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Technically and ironically correct, a double-whammy. If the Earth and the weight move closer together, and the person who let loose the weight is standing on a scale, then the Earth and the person are inertially coupled and the lateral acceleration imposed by the Earth moving to meet the weight will result in a greater weight measured on the scale. It will be the sum of the gravitational attraction between the Earth and the person, and the reaction to the acceleration of the Earth toward the weight, as produced in the person.
A related problem occurs in actual rocketry when you model the spacecraft as a Newtonly-connected pile of components that comprises a system of inertially- and mechanically-coupled elements. The various submasses of a rocket are not rigid, but act like individual masses connected semirigidly. Then there is also fuel slosh, the effects of the mass of propellant wallowing around in the tanks. Elon Musk had some difficulty with this in the early Falcons. It's part of the overall problem of dynamic spacecraft control. |
19th April 2019, 12:13 PM | #458 |
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19th April 2019, 12:14 PM | #459 |
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19th April 2019, 12:26 PM | #460 |
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19th April 2019, 12:32 PM | #461 |
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19th April 2019, 12:53 PM | #462 |
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19th April 2019, 01:06 PM | #463 |
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Is it too late to point out that the reason why a gas wants to expand into a vacuum is because all of the particles of the gas are hitting each other and then bouncing further away from each other, and absolutely not because the vacuum is yoinking them in any way? It’s the same reason a gas wants to uniformly fill an enclosed space.
Even when talking about a leak rather than a rocket exhaust, the vacuum isn’t acting on the gas, the gas is escaping into the vacuum, by its particles bouncing off into it via millions of tiny bouncy collisions with other bits of gas and any container walls that are involved. It’s not like the gas particles queue up in an orderly way to leave into the vacuum making sure they are not jostling any other particles or solid surfaces on their way out, because they want to make sure they are not transferring any energy |
19th April 2019, 01:31 PM | #464 |
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/dann "Stupidity renders itself invisible by assuming very large proportions. Completely unreasonable claims are irrefutable. Ni-en-leh pointed out that a philosopher might get into trouble by claiming that two times two makes five, but he does not risk much by claiming that two times two makes shoe polish." B. Brecht "The abolition of religion as the illusory happiness of the people is required for their real happiness. The demand to give up the illusion about its condition is the demand to give up a condition which needs illusions." K. Marx |
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19th April 2019, 02:26 PM | #465 |
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19th April 2019, 02:36 PM | #466 |
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19th April 2019, 02:44 PM | #467 |
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Curious Cat:
"If he "pushed" the weight down while it was falling to accelerate its descent over 9.81m/s^2, he could achieve a point where he would lift himself from the ground. I don't think anybody is fit enough to achieve this though ;-)." I beg to differ. Why do you think it is not possible to to cause upward motion (you call it "levitation" if you wish ;-)) - while exerting a downward force on a falling object? I indicated I don't believe it is possible with human physical limitations, but in absolute terms it is perfectly possible. It is a simple maths, after all, but a little example may serve better: a falling bomb explodes in mid air. Do you seriously think you would be safe from its shrapnel if you are above it? I do not propose to try :-). |
19th April 2019, 02:54 PM | #468 |
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Reading a description of that whole "silly string" explanation, and about vacuums pulling things, I wondered if that is the source of the OP's confusion, and of whoever else might hold the same theories.
If you talk about our most familiar form of vacuum, which is a vacuum cleaner, a lot of people probably have an idea that the vacuum cleaner is exerting a force that lifts the dust or paper or whatever. I never thought about it before, but that's not really true is it? What's really happening is that the existence of the vacuum creates wind, and the wind blows things into the nozzle of the vacuum cleaner. If you thought that somehow the existence of a vacuum exerted a force on a gas, you could get some pretty messed up ideas about how things worked. |
19th April 2019, 02:55 PM | #469 |
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O.K., sorry if I ruffled your feathers. The first part was perfectly relevant to the topic, debunking the principle of rocket (gun) pushing itself from some outside object (bullet). In the rest of my incoherent blabbering I am trying to preempt possible objections by the OP.
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19th April 2019, 02:56 PM | #470 |
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No need to differ; we're in substantial agreement. I'm stating the equivalent case that would arise under normal human strength. If it were practicable for you to throw a solid mass downward with enough velocity, actual upward motion could be achieved. There is no theoretical problem with levitation according to that method. You'd just be a mechanical rocket. My case states that throwing a mass downward with ordinary human strength could result in a reactive force that lessens your weight momentarily, even if you didn't achieve liftoff. You'd be a mechanical rocket with an underpowered engine. Thrust is still generated, and that thrust could be measured by noting how it subtracts from gravity, by the scale. You just wouldn't fly.
Sorry for the confusion. |
19th April 2019, 03:17 PM | #471 |
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19th April 2019, 03:20 PM | #472 |
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19th April 2019, 03:26 PM | #473 |
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There is no Antimemetics Division. |
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19th April 2019, 03:31 PM | #474 |
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19th April 2019, 03:40 PM | #475 |
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Yup, science is theory explaining observation.
"A*scientific theory*is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment. Such fact-supported*theories*are not "guesses" but reliable accounts of the real world." |
19th April 2019, 03:47 PM | #476 |
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No problems. I was sure it wasn't a lack of knowledge on you part, but an obvious overlook of this part of my post:
"I don't think anybody is fit enough to achieve this though ;-)". BTW, it wasn't based only on my personal assessment, but also on an excellent Mythbusters' episode. They were trying to find out, if you can save yourself by jumping up from a collapsing bridge when it starts falling. The answer was a clear "NO". |
19th April 2019, 04:22 PM | #477 |
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19th April 2019, 04:40 PM | #478 |
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Neither. I read and agreed with your proviso. What I feared -- given the tendency in these threads to misunderstand accidentally or on purpose -- was that someone would think that no thrust would be produced in the practical case. Given the almost certain fact that no human can reach orbit by vigorously hurling cabbages, I felt it was still important to understand what the physics would be -- specifically that thrust will still be produced, just on a smaller scale. Then I thought about how one would measure that effect, and I hit upon the ... smaller scale.
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19th April 2019, 05:09 PM | #479 |
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19th April 2019, 11:59 PM | #480 |
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