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Is it just me? Crossing the QE2 Bridge from north to south, the tall uprights appear to lean quite considerably to the left.
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Read somewhere the towers of the Humber Bridge lean towards each other to take account of the curvature of the earth.
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The earth is concave in Hull...?
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for every 5 miles you travel on "flat" water you would in fact be 16 feet and 8 inches higher than sea level ( from your start position) due to the curvature of the earth ...if that helps
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No the earth is round in hull, the people are flat.
All people up north are flat - I have seen Lowry pictures
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The earth is concave in Hull...?
If the requirement was to have them parallel to each other then surely they would need to lean in?
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The requirement is to have them vertical, relative to the surface of the earth, The bases are a certain distance apart and the tops are that distance apart, plus a bit more. Can't be bothered to do the maths and I don't have the distances and heights involved anyway!
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Basic geometry - make two rt angled triangles out of the isosceles triangle.
If the posts are 450m apart, 140m tall, then it is roughly 225 divided by 6,400,000 [radius of earth] times 6,400,137. Curiously my freebie calculator produces a number smaller, not larger, than 225.
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For one tower,
140*225/6.4e6
ans =
0.0049
Meaning that the distance between the 2 towers will be just less than 10mm more when measured at the top.
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Is it just me?
Its an optical illusion. The towers do lean at the top however towards each other during rush hour
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The leaning tower must be where they store all their toll money!
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Could it be that as the bridge isn't straight, they lean away from the curve?
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Nothing to do with it being a wide angle lens pointed upwards causing barrel distortion then?
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In several other photos they appear to lean too, but must be an optical illusion caused by the curvature of the bridge deck. I see no engineering reason why they would be designed to lean sideways? Looking on Google Maps, the bridge is straight. Designing something to lean when it does not need to creates problems and cost.
Just found out that the towers of the Humber bridge are 36mm further apart at the top than the bottom, I thought it would be a little bit more than that..
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Taking the curvature of the Earth into account when designing roads is quite normal. The design coordinate system is usually based on the Ordnance Survey National Grid, which also takes into account the curvature of the Earth.
It is easy to take into account and doesn't normally matter except on long structures, especially those that are made up of a number fixed length elements.
I remember that it was a particular problem when working on the design of the M62 Ouse River crossing in the early 70s. The design had been carried out on the OS National Grid; when the contractor arrived on site it was realised that the long viaduct wouldn't fit... Resulting in a few red faces and a quick coordinate recalculation. The difference was only millimetres but still significant.
Edited by RobertyBob on 03/12/2008 at 14:26
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Despite jokes made about very long corridors, the curvature of the earth is only clearly observable on a clear day at sea, only to a very limited extent on land owing to the confusing presence of relief.
Although the circularity, and relative closeness, of the horizon at sea confirms our established knowledge that we inhabit the surface of a very large ball, it seems not to have been intuitively obvious or even apparent to early mariners. Perhaps the ones who worked it out were thought mad and told to shut up, or else. That would be in keeping with the way our culture seems to proceed.
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An awful lot of history was "revised" during the period that all written work was in the hands of religious dictatorship. That's where the "flat earth" myth originated - and was challenged.
There seem to be many instances that show that the earth was considered a ball right back to pre-history. 10-12,000 years ago; man was almost as intelligent as we are - he just lacked the technology.
The mathematicians and astronomers of Egypt would have easily spotted the curvature of the earth - and, almost certainly it's rotation too. Stupid, they weren't.
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Hmm, you've prompted me to read Wikipedia on the subject. Fascinating. It appears that both ideas were entertained, unlike the idea of the earth being the centre of the universe, which could get you into a bit of bother.
Amongst other notes;
"The common misconception that people before the age of exploration believed that Earth was flat entered the popular imagination after Washington Irving's publication of The Life and Voyages of Christopher Columbus in 1828"
"It has been suggested that seafarers probably provided the first observational evidence that the Earth was not flat"
Meanwhile, back at the Dartford crossing toll booth...
JH
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Indeed Screwloose. It seems inconceivable that the shape of the earth wouldn't have been deduced by sailors once they started to cover real distances. I take your point too that religion has played an essentially reactionary role in science for long periods.
Real early navigators would have had an aura of mystery, almost witchcraft about them to most of the ordinary sailors though. As indeed scientists - people who could do the maths well enough and repeat their results - had for the hoi polloi until quite recently and still have up to a point in the Hollywood image mill...
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Lud,
you don't need to do any maths to see constellations rise up over the horizon as you travel and so deduce that we're all being carried along on the backs of 4 elephants astride a giant turtle... hang on, that's a third idea.
JH
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