[Max_Almond]

Who volunteers to explain this to Tom?

Pretty straightforward:

- Experiments showed a range of k between −4 and +16 for sunny summer days
- Variations were larger just after sunset
- For mostly sunny days, there were wave-like and sawtooth-like fluctuations of the refraction coefficient with amplitudes of 1–1.5 at time scales of 10–30 min
- Results corroborate that the Gaussian refraction value of +0.13 is not suited for describing refraction effects in the lower atmosphere

Clear?

[edby]

Now wondering what this implies for the Bedford level!

Suppose the water really is flat, but that the light curves below the straight line joining the bridges. And suppose k = -1, so the curvature of the light is equal to the hypothetical radius of the earth r, 4000km. I think we can solve this by Pythagoras. Let m be the midpoint of about 1km. Finally let h be the apparent height of the midmarker over the line of sight.

       h  =  r - sqrt(r^2 - m^2)  =  7cm (or 2.7 inches)

So if the water was flat and there were negative refraction of 1, it would still not be enough to explain what they actually saw.