On Wednesday, August 13, 2014 12:48:24 PM UTC-4, Ed Huntress wrote:
On Wed, 13 Aug 2014 16:38:19 +0000 (UTC), Doug Miller

wrote:



rangerssuck wrote in

:



On Wednesday, August 13, 2014 6:43:55 AM UTC-4, Doug Miller

wrote: ...

Related thought experiment: suppose you have a string wrapped

tightly around the surface of the earth. How much longer does

that string need to be, if you want to put it on one-foot-high

standoffs all around the planet?

...

About 8" (two feet / pi).



Nope.



Correct answer is 2 pi feet.



Related thought experiment: Suppose you have a mile of railroad

track. Suppose it gets really hot and the track expands (in

length) by one inch. Suppose that, due to the expansion, the

track buckles in the middle, forming an isosceles triangle. How

high will the bump in the middle be?



Nearly fifteen feet.



Looking at it simplistically, it's around 17 feet (somebody did the

math; I checked it, and it was right).



However, in practice, what would it be? Probably less than a foot,

because of the compressive elastic modulus of the rails, lifted up,

and, once again, the catenary sag of the rails, which would consume

almost all of the linear expansion in the curve.



That's my story and I'm sticking with it. d8-)



--

Ed Huntress

Ed, in practice there'd be expansion joints or someone looking for a job. It would also probably make a hell of a noise.