9/11 Physics from Non-Experts

[Foolmewunz]

Why is it so hard to grasp that the towers were not solid objects?

But they were solid, I saw the sketch he drew and they sure looked solid to me.

I love that complete cut... just sliced the building stragiht through like a big block of Velveeta.

I'm glad I now know how to define a "force"..... gravity is a force..... and the uh, ground.... yeah, the ground holding....no, strike that... the ground pushing.... yeah that's it ..... The Ground Pushing Up is a force.

I missed that lecture in Physics - Groundpushingupital Forces and Their Relation to All Fall Down Go Boom

 

[gumboot]

"If you don't understand basic Newtonian physics and basic thermodynamics then you'll not understand this".

That's true. Of course, if you do understand basic Newtonian physics and basic thermodynamics you also won't understand it.

-Gumboot

 

[Zep]

I'm guessing he's an immigrant to Australia from elsewhere, as a child.

And I think it proves conclusively that we, too, have ignorant morons.

 

[gumboot]

I'm guessing he's an immigrant to Australia from elsewhere, as a child.

And I think it proves conclusively that we, too, have ignorant morons.

Upon additional viewings I am almost certain he is a South African immigrant to Australia.

-Gumboot

 

[Shrinker]

"The ground pushes up", wow that's just stupid.

I don't understand. In school I was taught that when an object is at rest, say on a table, the table is supplying the upward force necessary to keep it there.

Other than being a simplification of forces at the molecular level, is that wrong?

 

[Gravy]

Caffeine + stupidity = truther comedy gold.

 

[Zep]

He's completely misunderstanding the "equal and opposite reaction" thing. And he has no idea about momentum either. And his notion that the WTC towers were somehow "solid", and that they should have defied gravity and toppled over somehow, indicates he hasn't a frigging clue what he is waffling on about.

What I would have liked to have seen would be a skeptic asking him questions about his "explanation" at the end, just to see if he would actually froth up and explode.

 

[Shrinker]

Could somebody respond on Youtube to his "You coincidentalists can't win." post by pointing out that he seems to be 100% right, because his debate opponent "beefmadras" has been banned from posting.

 

[bje]

The poor chap may have attended Steven Jones's classes.

 

[Horatius]

He's completely misunderstanding the "equal and opposite reaction" thing.

That's just it. The "ground pushing up" line is his misunderstanding of the reaction force of the ground against the building. If the ground didn't equally and oppositely match the force of gravity in the building (when it was still sound), the building would still accelerate downwards. F_net must be zero for the building to remain motionless. What he doesn't understand is, if there's no connection between the ground and the object, the reaction force no longer exists.

And of course, once the structural connection betwen the lower building and the upper building is lost (say, by whacking a plane into it), then there's no longer a reaction force on the upper portion, so it starts to fall. He seems to think that, once the moving upper part hits the lower part, the exactly equal reaction force will magically re-appear and stop the movement.

But of course, designing a complex building structure that can transfer reaction forces from the ground upwards, is an involved and precise process, and the chances of this happening "accidentally" as the building falls is so small as to not matter.

That's where he falls down.

 

[Totovader]

I linked part 2, here is part 1:



It's really bad. He's trying to explain physics- which he clearly doesn't understand.

 

[T.A.M.]

example #1...

African woman holds water vase atop her head.

example #2...

Take said vase, lift it 8-12 feet up from her head, then drop it.

DO I have to say more...

TAM

 

[Totovader]

Could somebody respond on Youtube to his "You coincidentalists can't win." post by pointing out that he seems to be 100% right, because his debate opponent "beefmadras" has been banned from posting.

He's blocked everyone from posting who doesn't agree with him. I've had most of my comments removed even after I reposted them- and then he blocked me as well. All I did was ask for his calculations.

I notice that someone got a shot off- they asked him if he had shown this to his professor, he said that his high school teacher agreed with him...

...

I find it hard to believe that the kid explained it to his high school teacher like he did on YouTube- but even if he had, this just emphasizes my point: an incomplete education is a very dangerous thing. By shutting out any disagreement- by not even questioning your conclusions- and by looking for confirming evidence, even if it means bastardizing science itself- we arrive at the core of conspiracy theories.

Unfortunately- these types of conspiracy theory claims are going to be more popular: the kids with little or no education trying to prove "physics was violated" like their bigger- and just as ignorant- counter-parts are doing: Jones, et al. It appeals to people grasping at straws and in some of these cases it takes a greater education to defeat the argument.

Although- I always fall back on logic.

 

[~enigma~]

He's blocked everyone from posting who doesn't agree with him. I've had most of my comments removed even after I reposted them- and then he blocked me as well. All I did was ask for his calculations.

I notice that someone got a shot off- they asked him if he had shown this to his professor, he said that his high school teacher agreed with him...

...

I find it hard to believe that the kid explained it to his high school teacher like he did on YouTube- but even if he had, this just emphasizes my point: an incomplete education is a very dangerous thing. By shutting out any disagreement- by not even questioning your conclusions- and by looking for confirming evidence, even if it means bastardizing science itself- we arrive at the core of conspiracy theories.

Unfortunately- these types of conspiracy theory claims are going to be more popular: the kids with little or no education trying to prove "physics was violated" like their bigger- and just as ignorant- counter-parts are doing: Jones, et al. It appeals to people grasping at straws and in some of these cases it takes a greater education to defeat the argument.

Although- I always fall back on logic.

Uh...If you take a person and throuw them off a building the splatter when they hit the ground not because the ground is an orrosing force...well on the molecular level the electromagnetic force far outweighs gravity but that is NOT what the shyster means. He wouldn't know proper phydics if it bit him in the butt.

 

[gumboot]

example #1...

African woman holds water vase atop her head.

example #2...

Take said vase, lift it 8-12 feet up from her head, then drop it.

DO I have to say more...

TAM

Herein lies the single problem I have with the WTC collapse, and the only gap in my understanding.

I understand the above, which is an illustration of the difference between a dynamic load and a static load.

Let's modify your scenario a little, and make it a heavy solid bronze statue, sitting on a desk.

Just sitting there, obviously the force of gravity pushing the statue down matches the net force of the table resisting it.

Obviously if you lift the statue up and drop it, it will hit the table with more force than it has just sitting there. Much more. But it might crash into the desk and then stop, or it might hit the desk with enough force that the desk collapses.

My issue is, we know roughly how big the statue is and we know how high it fell from, and we know it made the desk collapse. Why can't we calculate the force involved in the impact collision?

We know NIST didn't present it, and we know CTers latch onto this like limpets onto a rock.

My question is, can we present it, even in simplified form? Wouldn't this be useful?

In the early days I was told NIST didn't present this calculation because it was very simple physics that the intact floors couldn't resist such an impact. I can accept that. But if it's simple, presenting a (simplified) calculation should be simple.

Alternatively, if it's actually highly complex (as some are now proposing here), shouldn't that be something NIST should have considered calculating? I would have thought it would be a useful thing to consider in building design and safety.

Or alternatively, is it a given in structural design that a total failure of 1 or 2 or 3 floors would always result in a global collapse?

Or finally another option, in the reality the initial impact event itself is so complex that NIST couldn't calculate it? (Even in simplistic form?).

Just to be clear, I am quite capable of accepting any of the above explanations, it's just right now this single part of the entire thing hasn't been explained to me. Hopefully someone can fill in the gap?

-Gumboot

 

[T.A.M.]

I hear ya...and agree. My understanding of mechanical physics is college 1st-2nd year level, but it is also over a decade since I had to use it.

If any of the mechanical engineers amongst us would care to show us, through simplified calculations, why the towers collapsed via the top portion coming atop the bottom, it would be most helpful.

TAM

 

[bje]

Herein lies the single problem I have with the WTC collapse, and the only gap in my understanding.

...

My issue is, we know roughly how big the statue is and we know how high it fell from, and we know it made the desk collapse. Why can't we calculate the force involved in the impact collision?

Isn't that what Frank Greening attempted to do?

 

[AZCat]

Herein lies the single problem I have with the WTC collapse, and the only gap in my understanding.

I understand the above, which is an illustration of the difference between a dynamic load and a static load.

Let's modify your scenario a little, and make it a heavy solid bronze statue, sitting on a desk.

Just sitting there, obviously the force of gravity pushing the statue down matches the net force of the table resisting it.

Obviously if you lift the statue up and drop it, it will hit the table with more force than it has just sitting there. Much more. But it might crash into the desk and then stop, or it might hit the desk with enough force that the desk collapses.

My issue is, we know roughly how big the statue is and we know how high it fell from, and we know it made the desk collapse. Why can't we calculate the force involved in the impact collision?

We know NIST didn't present it, and we know CTers latch onto this like limpets onto a rock.

My question is, can we present it, even in simplified form? Wouldn't this be useful?

In the early days I was told NIST didn't present this calculation because it was very simple physics that the intact floors couldn't resist such an impact. I can accept that. But if it's simple, presenting a (simplified) calculation should be simple.

Alternatively, if it's actually highly complex (as some are now proposing here), shouldn't that be something NIST should have considered calculating? I would have thought it would be a useful thing to consider in building design and safety.

Or alternatively, is it a given in structural design that a total failure of 1 or 2 or 3 floors would always result in a global collapse?

Or finally another option, in the reality the initial impact event itself is so complex that NIST couldn't calculate it? (Even in simplistic form?).

Just to be clear, I am quite capable of accepting any of the above explanations, it's just right now this single part of the entire thing hasn't been explained to me. Hopefully someone can fill in the gap?

-Gumboot

The problem is that impact dynamics is a particular kind of "complex". You may have heard of "chaotic systems" or "nonlinear systems" - systems where small changes in the initial conditions can cause wildly different results. Impact dynamics is like this. The collapse of the towers could have been modelled, although it would have taken quite some time (because of the numerical complexity) but it would not provide much of an answer about the probable behavior of the towers, because small differences in the initial assumptions of the NIST could cause drastically different collapse scenarios.

Sometimes when faced with this sort of problem, an analyst will do something called a "Monte Carlo method" (there are other techniques) whereas the initial conditions are tweaked randomly for each of a large set of simulation runs. This gives a distribution of the behavior of the system within a certain range of initial conditions, and can be more illuminating than a single run because it shows if the system behaves consistently or if it is particularly sensitive to changes in certain initial values. Unfortunately this means that the simulation must be run multiple times, which of course takes much longer than a single run. More importantly, even if the distribution shows that collapse is unlikely given those approximate initial conditions, we aren't trying to predict behavior - we are trying to analyze a single event, and probability has no real applicability in such an analysis.

 

[gumboot]

The problem is that impact dynamics is a particular kind of "complex". You may have heard of "chaotic systems" or "nonlinear systems" - systems where small changes in the initial conditions can cause wildly different results. Impact dynamics is like this. The collapse of the towers could have been modelled, although it would have taken quite some time (because of the numerical complexity) but it would not provide much of an answer about the probable behavior of the towers, because small differences in the initial assumptions of the NIST could cause drastically different collapse scenarios.

Sometimes when faced with this sort of problem, an analyst will do something called a "Monte Carlo method" (there are other techniques) whereas the initial conditions are tweaked randomly for each of a large set of simulation runs. This gives a distribution of the behavior of the system within a certain range of initial conditions, and can be more illuminating than a single run because it shows if the system behaves consistently or if it is particularly sensitive to changes in certain initial values. Unfortunately this means that the simulation must be run multiple times, which of course takes much longer than a single run. More importantly, even if the distribution shows that collapse is unlikely given those approximate initial conditions, we aren't trying to predict behavior - we are trying to analyze a single event, and probability has no real applicability in such an analysis.

I understand. I wasn't proposing the entire collapse - I imagine the variables in such a scenario would be literally billions, beyond the processing power of modern computers.

I'm simply talking the initial moment of impact, when the upper intact section of each tower came in contact with the first floor of the lower intact section of each tower.

Essentially, I suppose, what I'm referring to is the collapse of the first intact floor, rather than the collapse of the 92 (WTC1) or 76 (WTC2) floors below that.

-Gumboot

 

[AZCat]

I understand. I wasn't proposing the entire collapse - I imagine the variables in such a scenario would be literally billions, beyond the processing power of modern computers.

I'm simply talking the initial moment of impact, when the upper intact section of each tower came in contact with the first floor of the lower intact section of each tower.

Essentially, I suppose, what I'm referring to is the collapse of the first intact floor, rather than the collapse of the 92 (WTC1) or 76 (WTC2) floors below that.

-Gumboot

Modern computers are capable of handling quite impressive arrays (or rather matrices) of numbers, even in the billions. I'm not sure where the practical limits are - we'd have to find a compsci person to probably find that out.

The problem is this - if the assumption is that the upper intact section (UIS) essentially free-falls before striking the lower intact section (LIS) then the following are of concern:

1. What is the shape of the UIS after it breaks free from the supports? Has it deformed under loading?

2. What is the orientation of the UIS as it falls (probably dynamic, as the upper portion rotated)?

3. What is the shape of the LIS in our simplified model? Since we are trying to model free-fall for the UIS, what is left in the interstitial space between LIS and UIS?

We also have to look at how sensitive our model is to our answers to the three questions. Techniques such as Monte Carlo let you examine such sensitivity, so I don't think there's a way around it, but since this is a far less complex model (at least numerically) than the total collapse scenario it will therefore take much less time to run a block of simulations. It's still non-trivial, though, and will require a computer.