One of the numerous peculiarities of the Arctic is, of course, the midnight sun and the phenomenon that, north to the Arctic Circle, sun does not rise in the winter, at least on the 21st of December. Living 400 km north of the Arctic Circle, the dark period here in North-Norway lasts almost two months. Fortunately, spectacular dawn/dusk colors can be seen around noon in the far south, and sometimes, northern lights are illuminating the sky.
Another phenomenon is not so well-known. During the two months when the sun is never rising, there are usually two full moons. And if the changeable weather allows it, it can be noticed that it circulates in huge waves around the sky, in fact, never setting. Thus, similarly to the common, or solar, Arctic Circle which marks the latitude when the sun is not setting for one day in June (and not rising for one day in December) there is also a lunar Arctic Circle, which is not fixed like the solar analog. Due to the moon’s precession (i.e., the change in the direction of its axis), there is an 18.6-year cycle when the moon is sometimes higher in the sky and sometimes lower. Tromsø lies way north to that band and a non-setting moon might be observed each winter twice, provided the skies are clear.