Re: Longest single journey (was Distance from Waterloo International to Gare du Nord)

On Wed, 01 Aug 2007 11:56:42 +0100, "R.C. Payne" <rcp27@xxxxxxxxxxxx>
wrote:

The Good Doctor wrote:
feebo wrote:
A plumb line always points to the centre of gravity (earth's core to
all intents and purposes) andthing constructed would thus be built to
this datum and if you stood at any point and looked as far as you can
see - it would be flat - the curvature of the earth is only
perceptable at great altitude.


On the contrary, the curvature of the earth is clearly visible at
surprisingly low atitudes. If you are at the seaside on a clear day,
you can watch a ship come up over the horizon or disappear over it,
long before it is too far away for you to see. You don't even have to
be standing up to see it.

Indeed, it is better not to be. The higher your observation point is
above sea level, the further your horizon. If you're sitting on the
beach, your horizon will be of the order of 4 or 5 miles away (I can't
be bothered to do the calculations, it's relatively elementary
trigonometry, though).

Robin

gotta reply here coz tgd post lost (yay)

nope - you are seeing the effects to the curvature by using brain
power to explain what you see happening and thus deducing the earth
must be curved (assuming the ship is not sinking), but "seeing" the
curvature can only be done from great altitude - if you're at sea with
no sight of land, the horizon appears flat all around you - even when
you hold a straight edge to it the curvature cannot be seen. That
something can be demonstrated (i.e. percieved) does not get away from
the fact that observations will disagree. The key phrase being "as far
as you can see". Standing on the surface of the earth (or on a boat)
you will absolutely not be able to tell the earth is curving away from
you in all directions. Even from airliners at 35000 feet, there is no
perceptable curvature, you need to be nearly double the height at the
accepted level of 60000 feet (some say 50K).

this link covers nearly all points discussed here:

http://www.stratofox.org/twiki/bin/view/Stratofox/ViewingCurvatureOfTheEarth
.

Relevant Pages

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