V
VonBonfire
Well-known member
That's cool but where does the 2" longer figure come from? I want to know how they arrived at that calculation.
Floyd Eye
Well-known member
Yeah wouldn't we all. They were world class engineers dude. The guy who invented pre-stressed concrete had a hand in that bridge. So I guess you would need to be an engineer to know how they came up with that number. The fact is it doesn't matter. 2" were added to it and they were able to know that in advance because they knew the rate of the curvature of the earth.
311boogieman
Well-known member
So what if there was no dust, fog or scattered light?
What if we went up the St. Louis Arch on a day when we knew there were was no dust or fag or any other obstruction between there and the Rocky Mountains do you think we could see them?
Floyd Eye
Well-known member
V
VonBonfire
Well-known member
I guess the point is you stating it as factual and then not being able to show how they arrived at the number and instead state "they were world class engineers dude" doesn't really do anything except present an argument from authority, which is a fallacy. It's just an arbitrary statement. If it fell down tomorrow then they are no longer world class engineers. Further if we are talking about curvature it would seem since the bridge sections are pre-fabbed and assembled on site the calculations would be in the pylon heights that actually support them off the water, not the bridge sections themselves. Why would they need to make the bridge 2" longer than the actual span? Sounds more like a cold weather contraction calculation than a curvature calculation to me.
Anyways, since you brought it up I was looking at some Verrazano-Narrows bridge tower data. They are said to be 1 5/8" further apart at the tops than at the bottom to account for earth's curvature but that number doesn't seem to square with the distance between them and earth's actual curvature numbers, it's much less. So are they really tilted apart from each other or do they actually lean towards one another?. Similarly they were not able to provide any data as to how they ended up at that final calculation.
Thumbpicker
Well-known member
It's the difference between the length of the arc at the base of bridge compared to the length of the arc of the suspended roadway.
Floyd Eye
Well-known member
So here we have two examples of completely different sets of engineers designing bridges around the curvature of the earth ( I'm sure there are many more examples) and you choose to believe they are lying since you can't understand their math ?
Come on dude.
Floyd Eye
Well-known member
I have to go back to the point I made months ago to either you or Acceptance. It's obvious, assuming you aren't just trolling, that you have made a conscious decision to simply not believe anything you don't see with your own eyes or can't prove yourself through your own knowledge. It seems to me though you are picking and choosing which things to disbelieve. I'll go back to my Jimi Hendrix analogy. You didn't see him burn his guitar at Monterray and considerably less people are alive who actually did see it than people who have been involved in putting people in space, yet you choose to believe he burned his guitar, but not that man has ever been in space or that space even exists.
Maybe not the best analogy but there are limitless analogies I could make.
Maybe not the best analogy but there are limitless analogies I could make.
V
VonBonfire
Well-known member
I'm asking "where's the math?". You stated it had to be made 2" longer (I would assume due to earth's curve) but that doesn't seem to square with any curvature math I've seen. 2" longer cause why? At least answer that. But you would've if you actually had that information but you're just repeating stuff you read and declaring it as truth and then come on dude-ing me when I make a further inquiry. I don't accept an appeal to authority, that's fallacious.
"Arc" meaning curve then?
Thumbpicker
Well-known member
The difference in distance due to the curve of the earth at the base vs the distance the roadway travels when it's a certain distance above the earth. Think of concentric circles which have different circumferences.
Floyd Eye
Well-known member
You are well read on curvature math are you ?
Draw a straight line on a piece of paper. Now draw a slightly arced line above it. The arced line will be longer.
Thumbpicker
Well-known member
This is from the wikipedia article on the bridge @Floyd Eye mentioned.
Each of the two suspension towers contains around 1 million bolts and 3 million rivets.[179] The towers contain a combined 1,265,000 short tons (1,129,000 long tons) of metal, more than three times the 365,000 short tons (326,000 long tons) of metal used in the Empire State Building.[2]: 141 Because of the height of the towers (693 ft or 211 m) and their distance from each other (4,260 ft or 1,298 m), the curvature of the Earth's surface had to be taken into account when designing the bridge. The towers are not parallel to each other, but are 1+5⁄8 in (41.275 mm) farther apart at their tops than at their bases.[2]: 138 [67]: 752 [179][182] When built, the bridge's suspension towers were the tallest structures in New York City outside of Manhattan.[112] The towers do not use cross-bracing, unlike similar suspension bridges; instead, there are arched struts near the top of each tower and below the lower deck. At the base of each tower is a concrete-and-granite pedestal, which rests on a caisson measuring 129 by 229 feet (39 by 70 m) across.[177]
Thumbpicker
Well-known member
You can ask AI a question like this as well:
what is the circumference of an arc 1 kilometer long with a radius of the earth vs the circumference of an arc 1 km long with a radius of the earth plus 100m
Last edited:
V
VonBonfire
Well-known member
The 23+ mile long ponchatrain bridge span has hundreds of feet of earth curvature to deal with and you're telling me it only needs to be built 2" longer to accommodate for it. I would like to know how they arrived at that 2" calculation. It doesn't seem like you really know.
Except it doesn't follow earth curvature formulas of 8" per mile squared. The towers are approaching 1 mile of distance between them, .8 miles actually, so how are they only 1 5/8" further apart at the top instead of like 6 or 7 inches? Doesn't that technically mean they are leaning towards each other? I could accept that but we are told they lean away from each other, due to earth's curve.
R
Robostyle
Well-known member
I was wondering if he meant 2 feet instead of 2 inches?
V
VonBonfire
Well-known member
On a flat earth I suppose you theoretically could.
On a globe earth the mountain would need be over 484467.3784 feet tall for you to see it's top because that is how much curvature blocks your view from the top of the 630 foot arch 888 miles away to the nearest of the rocky mountains per google and an earth curvature calculator. That's 91 miles of curvature, and that's with your vantage point at the top of the St. Louis arch. Standing with your eye 6 feet off the ground beneath the arch that's
515940.5896 of curve, or 97.7 miles of drop from your location.
V
VonBonfire
Well-known member
I don't really see the difference. The bridge is 23.8 miles long which means over 6,000 feet of curvature must be accounted for from the side you start building on. So why is it only two inches longer, or two feet longer, than the calculated span? And wouldn't the calculated span be a measurement that already was including the curve and additional resulting length?
R
Robostyle
Well-known member
Well, if it was measured, the measurement would include the curve too?
IDK much about the debate, to me the Earth is round.
V
VonBonfire
Well-known member
I would think so, but what's the extra 2" he's talking about for?
Don't worry, you're in good company cause not a single person in here knows what the hell they are talking about they are just repeating what they heard elsewhere. A few people are bothered cause I'm asking questions they can't provide adequate answers for. One or two others are pissed that I am asking questions at all.
Thumbpicker
Well-known member
You're misunderstanding what is going on. That's the wrong formula. You need to calculate the length of two arcs. The first arc follows the curvature of the earth according to the earth's radius. The second arc has a larger radius because it represent the height of the bridge deck up on the pillons. Having a larger radius means it has a longer length.
Think of it this way. The earth has a certain circumference according to its radius. If the earth's radius was 100m (or whatever) larger being the height of an imaginary bridge right around the earth then it's circumference would be bigger. A bridge however does not go right around the earth. It's just an arc however it's still longer over a given angular distance.