Friday 5 February 2016

56) “The “Midnight Sun” is an Arctic phenomenon occurring annually during the summer solstice where for several days straight an observer significantly far enough north can watch the Sun traveling circles over-head, rising and falling in the sky throughout the day, but never fully setting for upwards of 72+ hours! If the Earth were actually a spinning globe revolving around the Sun, the only place such a phenomenon as the Midnight Sun could be observed would be at the poles. Any other vantage point from 89 degrees latitude downwards could never, regardless of any tilt or inclination, see the Sun for 24 hours straight. To see the Sun for an entire revolution on a spinning globe at a point other than the poles, you would have to be looking through miles and miles of land and sea for part of the revolution!”

Axial tilt doesn't exist, says Dubay.

The polar regions are interesting in two ways. First, we mentioned flattening. Second, there's axial tilt, which is explained quite clearly in the image below.  

Image displaying axial tilt and the Arctic and Antarctic circles.

Midnight sun can be explained by both of these. First, the phenomenon is possible because the axis is tilted with regards to the plane we move in. Second, the area is made larger than considered for a spherical earth because the poles are flattened.

Finally, one must remember that the sun is rather big - the approximation is a disc, not a point.

Taking all of these together, the phenomenon is completely explained [Wikipedia/midnight sun]. Why Dubay ignores axial tilt is beyond me. “ 

Incomprehension of the model.

Leaving out refraction (big factor, but not necessary here) and looking at geometry alone, the statement is just false. Let's say there was no axial tilt. Sun would never set at the poles and it would always move in a circle around the horizon. From any other vantage point we could not see the sun for 24 hours straight because of the rotation of the earth. The last observation is what should happen on earth according to Mr. Dubay's claim.

Now if we introduce an axial tilt of 23.5°, what happens?

Well, the north pole (90°N) would be exposed to the sun for 6 months and then the south pole (90°S) for 6 months. 

The altitude of the sun at each pole during summer solstice (day of maximum exposure) had to be equal to the value of the axial tilt (23.5°), with maximum and minumum altitude roughly the same as the sun describes almost a perfect circle around the pole during the day of midsummer, not dropping by even one degree. Let's look at the northern summer solstice.

What is the altitude of the sun at a proposed tropic of cancer (23.5°N) at this event?

The maximum altitude should be 90° at noon, minimum -66.5° at midnight.

What is it in, say, Toronto (44°N)?

The maximum altitude should be 69.5° at noon, minimum -22.5°.

Can we find formulas that correctly describe maximum and minimum solar altitudes for these three places during summer solstice? Yes, we can! Here they are:

MaxAltSuSo= 90°- Latitude + Axial Tilt (For places south of the tropic of cancer it's "- Axial Tilt")
MinAltSuSo= -90° + Latitude + Axial Tilt

Punch the numbers for any place within the polar circle into you calculator and it will make a happy face! ;-)”

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