Calling @swansonj ....

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Vapin' Joe

Formerly known as Smokin Joe
Catenaries look like heavy chains, and the equations have got coshes and sinhs in them somewhere.

I was quite please to discover catenaries, because it was the first bit of applied maths I learned where you didn't ignore an inconvenient but very real feature of the world. I'm now unreasonably disappointed to discover that in real life a parabola is an appropriate approximation.

(According to wikipedia....
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Ever wished you'd never opened a thread? :unsure:
 

TVC

Guest
Ever wished you'd never opened a thread? :unsure:
Research has recently pointed to the theory that the speed of light is not actually a constant. Data collected by watching deep space gamma bursts suggest that higher energy photons actually travel slower than low energy photons because they interact more with the ripples in space-time. The size of the speed difference; one light second in a billion light years. That's some interesting maths.
 
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Vapin' Joe

Formerly known as Smokin Joe
Research has recently pointed to the theory that the speed of light is not actually a constant. Data collected by watching deep space gamma bursts suggest that higher energy photos actually travel slower than low energy photons because they interact more with the ripples in space-time. The size of the speed difference; one light second in a billion light years. That's some interesting maths.
You took the words right out of my mouth :wacko:
 

Tim Hall

Guest
Location
Crawley
The universe is probably way more complicated than we currently understand.
There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another theory which states that this has already happened.
 

swansonj

Guru
Catenaries look like heavy chains, and the equations have got coshes and sinhs in them somewhere.

I was quite please to discover catenaries, because it was the first bit of applied maths I learned where you didn't ignore an inconvenient but very real feature of the world. I'm now unreasonably disappointed to discover that in real life a parabola is an appropriate approximation.

(According to wikipedia....
View attachment 146504 )
Wikipedia also tells me that Robert Hooke, after solving the equations for the application of catenaries to arches, published the solution as a Latin anagram. Now that's just taking the piss.
 

subaqua

What’s the point
Location
Leytonstone
I have been to Portland ,Dorset. The above statement at the end has signs of proof there !
 
U

User482

Guest
Yes.

Second tallest in the UK (as @subaqua says, the Dartford crossing is the tallest). The cables are basically a parabola (exactly so if you ignore self weight, if you want the exact solution it's a catenary*, but the parabola is a good enough approximation). y=x squared. So as you increase x, the span, y, the height, goes up much worse than linearly. Hence long spans end up with ridiculously tall towers. (Exception: valley crossings where the ends are on the raised land at the sides of the valley. Our line out to Dinorwic and Wylfa crosses the Aber Valley with one of our longer spans but it doesn't look so spectacular because the pylons are quite normal. ) Plus the clearance at the low point in the middle usually has to be higher for ships than the standard clearance for on-land which is based round combine harvesters.

That is our original 275kV line to Wales. When the time came to expand to a 400 kV crossing as well, we did that with a tunnel instead. They actually cross over each other in the no-mans-land of the Bristol Channel. We also tunneled under the Solent at Fawley and the Medway to avoid using these massive pylons, and there are tunnels under the Thames as well as the overhead line at Dartford.

Boy, those drinks at the drinks reception taste good :smile:

* I did catenaries from first principles in maths at school. 15 years later, having crossed a rope suspension bridge in Nepal, I lay awake in my sleeping bag that night trying to rederive the equations. And failed dismally. Now, another 15 years on, not only could I not derive them, I can't even remember what they look like...

See, that's the difference between you and me: I have also crossed a (particularly rickety) rope suspension bridge in Nepal. My thoughts were limited to i) Am I going to die right now? and ii) thank god that's over - where's the beer?

User's thread about a simultaneous equation got me thinking about maths: I distinctly remember doing a Laplace transform in one of my Finals papers (which I passed), but having just googled it, I don't even understand the explanation. I seem to have left an important part of my brain somewhere in a field in Hampshire.
 
There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another theory which states that this has already happened.

Interestingly, I read (I say read, I understood the words but not their meaning :wacko:) on the BBC website that the universe might be a 'simulation' as portrayed in the Matrix films. Hmmm...

http://www.bbc.com/earth/story/20160901-we-might-live-in-a-computer-program-but-it-may-not-matter
 

Tim Hall

Guest
Location
Crawley
But what of the graceful arc drawn by a precisely weighted cross? Does the equation to describe its path not excite you?
Sorry, I thought you were getting all ecclesiastical. Next week's lesson covers the trajectory of the thurible, and the shedding of incense vortices.
 
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