## Sunday 7 February 2016

68) “The Philadelphia skyline is clearly visible from Apple Pie Hill in the New Jersey Pine Barrens 40 miles away. If Earth were a ball 25,000 miles in circumference, factoring in the 205 foot elevation of Apple Pie Hill, the Philly skyline should remain well-hidden beyond 335 feet of curvature.

More refraction
This time, Dubay didn’t t even mention atmospheric conditions but simply put down an image. Well, that's cute. I look at that horizon and I see various discolourings. Since the refractive index depends on wavelength, that's a clear indication of refraction in the distance. To me, that's sufficient.

Note that the drop they discuss is only 100 m. We'll mention this point again, but it is called a skyline for a reason.

Phony numbers
Distance from Apple Pie Hill to the Philadelphia skyline is 52 km (32.3 and not 40 miles).
The highest point on Apple Pie Hill is the firetower. It stands 18m above Apple Pie Hill's elevation of 62m, making it 80m total (262 and not 205 feet).
https://en.wikipedia.org/wiki/Apple_Pie_Hill
Strangely enough, this 360° panoramic picture (available at the above Wikipedia link for higher res) around the tower neither shows the same features as Mr Dubays picture (river & open area in the foreground), nor can you "clearly" see the Philly skyline.

Let's do the math anyways: Comcast Tower in Philadelphia is 297m high, with ground level elevation of 12m thats 309m total.

That alone gives you a sea-level horizon at 62.8km.

That's it. You don't even need the firetower on Apple Pie Hill. You don't need refraction. No more math needed. The tallest buildings in Philadelphia must be visible from Apple Pie Hill under clear conditions. What happens is what we would expect in the real, spherical world.

#### 1 comment:

1. I have been interested in long distance views and refraction for a long time. I was wondering what the refraction coefficient would be to bring the Chicago skyline into view from near the Lake Michigan shoreline? Would it be around 0.20 or 0.21? I know that higher coefficients over such a large distance are rare.