John Cuthber

OK, to start with part 1 Firstly, we should ideally qualify "near free fall speed". There isn't one. If they were in free fall they would accelerate continuously on the way down. The collapse is difficult to see well on any video because it's dusty and the people often stop filming to run. As far as I can judge the floors fall as they would be expected to if the building pancaked. The delay between one floor and the rest is similar, but that delay doesn't get much shorter as the building falls. Each floor starts from rest as the floor above hits it. In free fall, each floor would fall at the same rate and the floors wouldn't get squashed together until they hit the ground. If they were in free fall because the girders were cut, then the first floor to break would be relatively slow, the second one would be faster the third faster still and so on. There's some evidence of that, but not as much as you would get with free fall. It's a bit of an oversimplification but the girders at the corners of the building have nothing to hold them out, but the impact of the debris pulling them in. That's why they get pulled down. They "roll up" into the building. Also you make an assertion that is unsupported and doesn't make much sense "and if it's from the falling inertia of the floors, then they wouldn't fall at free-fall speeds." What other speed would they fall at? Fundamentally, there isn't much difference between the two states. In one case you cut most of the supports with cutting charges and so the building falls- one layer lands on the one below it and that collapses. Those two land on the next one down and so on. In the case of the WTC, one floor was weakened by a massive fire. The weight of the floors above collapses that floor, and it lands on the one below. The impact smashes that and the whole lot carries on down pancaking the floors under it in turn. The failure modes are so similar it isn't possible to say clearly from the video which happened. Part 2 The simple answer is that normally, if there's a damn great fire in a skyscraper the whole fire service is mobilised to do something about it. In this case, they were busy. It's not realistic to compare that fire with an "ordinary" one. Apart from anything else, ordinary fires only have one "seat". The one in that building set lots of floors alight at the same time. There was not the usual supply of water or manpower to put it out, There's your assertion that "nor was its structure compromised by debris" which is odd. It was clearly hit by a lot of debris- there is no evidence that the debris didn't do any damage? part 3 " The Bush administration destroyed evidence and fought against independent investigation. This is not evidence of anything in particular" You said it. As I have pointed out there is a perfectly reasonable explanation for this. They wanted the mess tidied up so the city could recover quickly. There was no evidence at that time to suggest anything other than a terrorist outrage so there was no reason to look for clues about the cause of the collapse. They fell because the planes (or debris) hit them. Why make things worse by delaying the clear up? Also, re " I don't accept as fact any scientific conclusion where the evidence is kept secret, destroyed, or made unscrutinizable" Logically you don't believe in a lot of things then. Do you believe that men landed on the moon? If you do the you have contradicted yourself. If you don't then people will draw their own conclusions. Part 4 As I explained, there is, at best, evidence that if thermite was present, it didn't burn. Finding three of the commonest 5 elements on the planet is hardly evidence of anything. (oxygen, iron, aluminium) If it had been there and burned it wouldn't have done much, as shown by that video clip. In any event thermite isn't an explosive. What explosives? Is there actually any evidence of any? In particular is there evidence of the massive amounts that would have been needed? Part 5 5) Testimony of individuals having foreknowledge that the towers would be demolished. Testimony isn't evidence I'm afraid. People are prepared to lie for any number of reasons. The art of "prediction" has been with us for a long time, but it was never very credible. http://en.wikipedia.org/wiki/Nostradamus I agree that 5 points was arbitrary- but I only have so much time to spend on things like this. As you said, one point would be enough. Unfortunately all the points you raised were somewhere between dubious and wrong. Now, if the best 5 reasons to believe the conspiracy are not valid, there's no point whatsoever looking at numbers 5 to 10 or 10 to 1000000. So, we can stop now.

Can I just point out something really rather dull. I have still not seen any evidence, or even purported evidence, of explosives in the debris. Thermite is not an explosive. As a second, rather uninteresting point. They seem to have found iron oxide and aluminium. They seem not to have taken any notice of the fact that iron oxide is formed from steel in the presence of hot air. There were steel beams in the building. A fire was seen in the building. Fires create hot air (rather a lot in this case). There is a perfectly sensible explanation for the presence of iron oxide. The aircraft were largely made from aluminium. There is a perfectly sensible explanation for the presence of aluminium. Perhaps the real killer is that they found a mixture with the right components to make thermite (big deal- lots of kids make it so it's not difficult) What they didn't seem to find was the molten iron and alumina that you get after a thermite reaction. What they have found might be thermite- but if it is then it didn't work. Another dull fact is that people who know how to drop buildings use shaped charges. They don't use thermite to cut steel beams. There's a really good reason why not. Watch this vid and see if you can work out why. (You might want to turn the sound down). http://www.youtube.com/watch?v=7_-jVzYpQzc&feature=related The teeny weeny little problem is that thermite doesn't really cut through steel very well. Now, I wonder if you would be good enough to comment on my idea that you let me know your top 5 reasons. (Up to 10 or so won't kill me if you really can't tell the story in just 5)

MD65536, I have a suggestion. Rather than an endless back and to argument over this bit of data and that bit of data, can I ask you to provide your own personal "top 5" pieces of evidence for why you believe that the towers fell as anything other than a consequence of the impact from the planes and the subsequent fires? Just a list of 5 items - preferable with a link to put them in context but I can probably live without one in most cases. Also, can I ask for the rest of the contributors to the forum to hold fire for a few days or so in order to give him a chance to chose his "champions" and for me to offer a rebuttal.

Is there anyone here, apart from Vinko Rajic, who thinks that he shouldn't check into the local hospital and tell them what he believes has been happening so that they can provide him with the help he so clearly needs?

"Would you accept similar reasoning if there was a claim that cold fusion was real, but the experiment was kept secret and then destroyed before it could be analyzed by others (even if there was a video of it working)?" What the **** has that got to do with the issue? Are you claiming that the planes didn't hit the buildings? That's what happened. There's no question that we know what happened. Some people flew aircraft into the buildings. "Do you know of any scientific evidence that contradicts the controlled demolition theory?" As far as I'm aware no significant explosives residues were ever found. (And, I know 'cos it's part of my job, that you can find explosives residues years or decades later if you look, so the fact that they cleared up first and studied later doesn't affect that fact) The scientific conclusion from that is that no explosives were present. The scientific conclusion from that is that explosives were not used to destroy the building.

This "If gravity had an infinite range there would be no order in the universe" is a complete non-sequitur. It has and there is.

"Your first statement, that an object feeling no force will have constant velocity, and that an object feeling a force will change its velocity, now this is absolutely wrong. Because no object anywhere in the universe can have a constant velocity without a force acting upon it" Also wrong. Consider the monitor in front of me. In my frame of reference, it's not moving. It has a constant velocity of zero. Do you realise that you are saying "Newton's laws of motion are wrong, and so is the whole of physics. Simply making the assertion that something is "absolutely wrong" is absurd. It's certainly nothing to do with science. And you have not replied to my previous observation. You should do so.

Sorry, but that answer doesn't cut it. Who gets to decide what's ridiculous? If you can make that decision then you already have enough information about the set-up to know whether it is likely or not and, if you can already make that decision, the "rule" about absence... isn't telling you anything. The guy simply didn't get it right. Absence of evidence is not proof of absence, but whether it's evidence of absence or not depends on other factors.

"The orbital speed of the Moon being bound to the orbital force of the Earth is because Eaerth's gravitational field encompasses all around Moon's gravitational files, which extends to 52,000 km. while Earth's gravitational field extends to 685,400 km" Just plain wrong. Gravity has an infinite range.

" "Absence of evidence is not evidence of absence." - Sir Martin Rees " Is it just me who wonders how Sir Martin slept well with that rabid sabre-toothed tiger in his bedroom? I mean, I realise there's no evidence that it was there but, since absence of evidence isn't evidence of absence... Or, possibly, he was talking nonsense that he hadn't thought through. (and, in the words of the great philosopher Britney Spears "Oops! I did it again". I used ridicule to make a point). "we must not try to draw the line [between science and pseudo-science] too sharply. This becomes clear if we remember that most of our scientific theories originate in myths" That's an unevinced assertion and to rely on it is, at best, an example of this http://en.wikipedia.org/wiki/Appeal_to_Authority Unless someone can actually cite where Copernicus expressed this opinion "The Copernican system, for example, was inspired by a Neo-Platonic worship of the light of the Sun who had to occupy the ‘centre’ because of his nobility. " Copernicus looked at the numbers and found a system that fitted them. It's possible that he started by looking at the sun because it was big and flashy so it was obvious. It's also possible that he started by seeing how the maths would work for a system centred on the moon, of Venus. But neither of those would work so well. As far as I'm aware, there's no record of how Copernicus came to consider how the data would fit a heliocentric system. "This indicates how myths may develop testable components. " To be precise it indicates that one, and only one, might. "They may, in the course of discussion, become fruitful and important for science" They might, and so might dreams (Kekule's for example), but that doesn't mean we should seek to gain knowledge by eating lots of cheese before bedtime. There is a lot of difference between speculating wildly- which is sometimes a perfectly valid part of science- and pretending that those speculations are science. " In my Logic of Scientific Discovery I gave several examples of myths which have become most important for science, among them atomism and the corpuscular theory of light." Those were not myths in the usual sense of the word. They were speculations and, at the time, they were not amenable to verification or falsification. However, science has moved on. We now know that atoms exist (and the jury is still out on the corpuscular theory of light). "It would hardly contribute to clarity if we were to say that these theories are nonsensical gibberish in one stage of their development, and then suddenly become good sense in another." Which is why science didn't do that. That's a straw-man argument against science or a red herring.

OK, lets clarify something here. The validity of religion and the validity of "intelligent design" are not the same thing One is debatable (but not in this part of the forum). The other is just plain deceitful. Further, religion does not claim to be science, but ID does. I was talking about ridiculing pseudo-science in all it's forms. I note that I'm being accused of bringing religion into the thread. Actually as far as I can tell, no major religion thinks much of ID, but a lot of politicians do. Feel free to complain that I brought politics into the house of physics, but I didn't bring God into it. I still think that ridiculing pseudo-science is a valid way of teaching people that it is nonsense. So rather than telling me that "But there is nothing that proves a creator doesn't exist. Tainting a possible explanation with a biased opinion is illogical." which may be true, but is irrelevant since nobody had said there was (or was not) a Creator you might like to join me back at the topic and answer this. Perhaps someone would like to tell me what they could have made a practical steam engine from 2000 years ago? Without much better metallurgy that was available at the time, the idea was ridiculous.

What evidence? I looked and there's lots of adverts and a few things like some bloke saying "I had a full four-year scholarship to Cooper Union College in Manhattan, a small school with an acceptance rate of about 8% of those who take the application test," Which suggests that maybe he was clever once, but isn't evidence of his current ability. "Dusterwald remembered feeling that something was really odd about the way the WTC skyscrapers fell on September 11, 2001. “It did not fit what I know from my 37 years experience as a licensed structural engineer,” he said." Oh, so a bloke who "feels it's odd" is now evidence is it? No, just kidding. Of course it isn't. And as for "“It did not fit what I know from my 37 years experience as a licensed structural engineer,”" Of course it didn't. In those 37 years nobody deliberately flew two fully laden jets into a couple of skyscrapers. It was not, and could not be part of his experience. As for ". In his past experience, every event involving an aircraft crash or a building failure was investigated carefully with systems put into place developed to protect forensic evidence. “First they would cordon off the whole area, take pictures and carefully mark all material removed from the site, so that the forensic experts could determine how the failure happened,” he recalled. “After 9/11, they were just carting stuff away as fast as they could.”" Yeah well, that could be some weird conspiracy, but did anyone consider that 1 they wanted to get the city moving again and (perhaps more importantly) 2They knew what the failure was. Some bastards had flown aircraft into the buildings. You don't need a forensic investigation of the rubble to tell you that- it was on film. Seriously. If that's the sort of "evidence" that you can supply for the conspiracy then it's time you realised that nobody is ever going to believe you. In this context it is reasonable to examine the OP's contention and the fact is that the science doesn't support the idea of a demolishion (except in the bloody obvious sense that the terrorists wanted to bring the building down; which is demolishing it).

You can go quite a long way towards proving that the earth rotates with a tree, a rock and some string. What would you have made a practical stream engine from 2000 years ago? Unless there's a valid answer to that then you can't say we "lost" it. It is vital for the advancement of science that we ensure that people understand how to tell valid ideas from nonsense. Ridiculing the nonsense is a way to bring attention to the difference in a way that will attract people's attention and therefore encourage them to learn the difference. As an example I cite "intelligent design" as something that pretends to be science, but isn't and the Flying Spaghetti monster (BBHNA) as a way to ridicule it while exposing it's fraudulent nature.

"First of all, gravitation as a whole is composed of two forces; 1. Orbital force (Fo) 2. Centripetal force (Fc)" News to me. Unless there's some evidence I have missed, this should be in "speculations".

There are lots, room temperature, mains voltage...

Unless one wasn't. One might spot the joke and play along with it.

Actually, "If you don't round it off then there might be a significant energy loss there." is the right answer.

If you round off the "corner" at the bottom where the rams meet then F is 3 metres and C is 3/tan (42) I think i.e. about 3.33 m. If you don't round it off then there might be a significant energy loss there. Why do you want to know?

We are still waiting for the "science" from the last thread like this. http://www.scienceforums.net/topic/17133-is-this-thermite/page__st__40

Perhaps it's helpful to make the comparison with a unary function. Sin(x) only needs one operand: so do x^2 or 1/x. They are unary. On the other hand, addition (for example) needs two numbers. Another rather convoluted difference is that you don't (generally) need to push the "=" button on your calculator to calculate a unary function, but you do with binary functions.

I think the tooth fairy is made of the same stuff.

Can I just glue a steel washer to the back of it please? Seriously, do you have a magnet that would provide any significant force at that distance- say a couple of inches or more if the door is double glazed? I just love the idea of the sales pitch. "Hi, for a slightly higher price you can have the version that goes rusty." "Sounds good to me, but wait a minute: won't that leave it vulnerable to a man with a huge magnet?" "Damn!"

You must have really sophisticated thieves. Ours would just break the door.

Assuming that's right it rules out steel and a few other materials (really few, about 4 elements of which 2 are seriously impractical). So why isn't it glass or plastic or wood or ceramic or...? Incidentally, I strongly suspect the spring in it is steel.

"Okay, another clue: the makers of these handles also make them of bronze." Actually, I rather doubt that. I suspect they are bronze coloured. Bronze is rather expensive. However, I note that they all seem to be made from non magnetic, but electrically conductive metals. If it were not for the apparent "hinge pin", I'd wonder if they sensed touch electrically rather than mechanically.