NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Dip uncertainty
From: Bruce Stark
Date: 2004 Dec 6, 17:01 EST
From: Bruce Stark
Date: 2004 Dec 6, 17:01 EST
George and Alex,
I still think my simplistic logic is nearer the truth. Put normal refraction aside, as Alex does in his thought experiment, and suppose light should come straight from the horizon. Now put a bend in the light somewhere along its path. For simplicity, let's say the bend is caused by a prism planted on top of a five-foot tall buoy. Climb on the buoy and look at the horizon through the prism. The angle between the horizon and where you see it through the prism will be huge.
Now go twenty miles away, and from a height where you can see both the prism and the true horizon, look (you'll need a powerful telescope) at the prism. The horizon you see through the prism will be only slightly out of line with the true horizon.
That's because, from twenty miles away, the angle between top of the buoy and the horizon is small.
Bruce
I still think my simplistic logic is nearer the truth. Put normal refraction aside, as Alex does in his thought experiment, and suppose light should come straight from the horizon. Now put a bend in the light somewhere along its path. For simplicity, let's say the bend is caused by a prism planted on top of a five-foot tall buoy. Climb on the buoy and look at the horizon through the prism. The angle between the horizon and where you see it through the prism will be huge.
Now go twenty miles away, and from a height where you can see both the prism and the true horizon, look (you'll need a powerful telescope) at the prism. The horizon you see through the prism will be only slightly out of line with the true horizon.
That's because, from twenty miles away, the angle between top of the buoy and the horizon is small.
Bruce
