Sunday 7 February 2016

71) ” It is often possible to see the Chicago skyline from sea-level 60 miles away across Lake Michigan. In 2015 after photographer Joshua Nowicki photographed this phenomenon several news channels quickly claimed his picture to be a “superior mirage,” an atmospheric anomaly caused by temperature inversion. While these certainly do occur, the skyline in question was facing right-side up and clearly seen unlike a hazy illusory mirage, and on a ball-Earth 25,000 miles in circumference should be 2,400 feet below the horizon.”

Phony numbers + refraction
On his facebook page, the photographer says that he's taking these pictures from the top of a dune at Warren Dunes State Park on the shore of Lake Michigan. The distance from there to the Chicago skyline is 53 miles (not 60), so roughly 85km. The highest dune in this park stands 73m above Lake Michigan, let's make it 75m from a photographers perspective:
Lake Point Tower is 197m high, less than half the size of Sears Tower. From what I can see in the pictures, we can add a few meters because it's ground level is slightly above the lake. Let's make it 200m.
85km distance accounts for a curvature drop (as seen from sealevel) of 570m. A standard and minimum refraction for this distance is this value multiplied with the refraction coefficient k=0.13. That gives you an extra 74m. Putting them on top of Lake Point Tower gives us 274m (still not even Sears Tower level).

Punch in the numbers (see sources at #69) and you get an added distance of 59.2+30.7= 89.9 km. Because the distance between the two points is 85km it means that the sight lines have to intersect. The tower must clearly be visible and for Sears Tower you wouldn't even have to factor in refraction in order to make this work.

There's also a time-lapse video available on the photographer's facebook page. At the end, you can clearly see refraction going on: 

Something about mirages not behaving like they do.

So, here they claim that mirages are 'hazy' and 'illusory'. Also, apparently they think mirages require the object to be upside down?

As we've discussed, mirages happen due to refraction bending the path of light rays. They do not require inversion. The haziness is mostly the different wavelengths, and is dependent on the background. The picture they show fits 'haziness' perfectly, or more properly, discolouration.

1 comment:

  1. The images of Chicago seen from Lake Michigan are fascinating. Do you know what kind of refraction coefficient would be needed to bring the Chicago skyline, would it be over 0.20? I am not 100% sure about the coefficients across water, but from hills mountains in the UK, long distance views rarely have a coefficient higher than 0.20.


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