Science of sunrises

The science of an amazing sunrise

This is something that I understand well but I'm not sure if I can explain it too well. What I can say for sure is that the sunrises here in New Zealand's Southland are more beautiful than the sunrises in South East Queensland. For no other reason than they last substantially longer.

There are two factors that go into a sunrise here. First is the colour wavelength and the second is the duration of the sunrise. I'm not going to explain why a sunrise, or sunset is the colour it is but I'll do my best to explain how the duration of a sunrise changes.

The closer you are to the equator, the more vertical the sun rises and sets. Conversely, the closer you are to the poles, the closer to horizontal the sun rises and sets. So much so that if you are close enough to the poles, there is a time in the year when the sun does not rise or set. Instead it circles the horizon.

This is an old time lapse of a summer day a very long way north.

Now I need to try and convert this into sunrises here in Southland. One caveat - the numbers and angles I'm going to use here aren't perfect but it's good enough to explain my point.

  • At the equator, the sun rises near enough to straight up - we'll call this 90 degrees.
  • At the south pole, the sun appears to travel almost horizontally - this we'll call 0 degrees.

So, the fastest sunrise is at the equator and the slowest sunrise is at the south and north poles. At the bottom of New Zealand, we are roughly 45 degrees (46.6deg) south of the equator. As such the sun rises a fair way off straight up - roughly at 45 degrees. Because of this, the sun takes longer to get from below to above the horizon.

All this put together means that when we have a beautiful sunrise, just like anywhere else in the world can and does, it lasts longer here than anywhere in Australia.

Another surprising thing I did not expect is stark contrast of where the sun rises between the peak of summer and winter. In summer, the sun rises almost directly south east and in winter, rises almost directly north east. This if very evident during the day too. In the depth of winter, the sun does not get much higher than about 35 to 40 degrees above the horizon. In summer, the days last so long and the sun rises and sets so far to the south that we get direct sun on the southern side of our house at sunrise and at sunset 10:30pm.

While I'm sure our family in Scotland experience this more so than us, it is still something that makes me marvel at how we experience the celestial bodies move in our solar system.

This is a time lapse video shot using my mobile phone. It is out the second floor east facing window. It was the last in a run of very beautiful sunrises.

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