Johnny B Good wrote:
On Tue, 20 Mar 2018 12:28:24 +0000, Tim+ wrote:

charles wrote:
In article , Max
Demian wrote:
On 19/03/2018 10:26, Brian Gaff wrote:
Well the earth is curved after all, so in reality nothing is flat or
level is it?

I wonder how big a thing (building? bridge?) has to be before
designers have to take into account the curvature of the earth?

It's certainly taken into account when predicting uhf tv coverage.


Humber bridge towers apparently diverge by 36mm due to curvature.

I tried to find out if they'd done something similar when building the
Severn suspension road bridge just over 50 years ago but the only
reference to 'tower divergence' was in relation to 388 millimetres[1] of
lean back to compensate for the weight of the suspension cables which has
nothing to do with the curvature of the earth over the one mile
separation distance.


I wonder what the *smallest* man made object is that has to take account
of the earths curvature?


I'd guess at something about a tenth of the size of the Humber Bridge
since the resulting 3.6mm 'curvature of the Earth allowance would likely
come within normal tolerances on a structure one tenth the size of the
Humber bridge but that's just a guess.


Thinking about it, you could argue that any structure built using plumb
bobs automatically compensates for earth curvature. I suppose the question
is, at what point does the discrepancy actively need to be compensated for?


Tim


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