During the winter solstice, the day is at its shortest. In Utsjoki, Finland’s northernmost municipality, daylight, or at least blue twilight, lasts for about two hours.
Today, 21 December, is the winter solstice and the shortest day of the year. The sun has not been in the north for weeks. Even so, it is not completely dark around the clock in Utsjoki, Finland’s northernmost municipality.
In clear weather, there is some daylight between 10.30 and 13.30. In very cloudy weather, blue twilight lasts for about an hour or two.
Is the shortest day of the year also the darkest day? Not at all. It depends on the weather which day happens to be the darkest in winter. The thickness of the cloud cover, as well as the phase of the moon’s cycle, has a big influence.
Right now is the waning moon, and the New Moon is already on Friday this week. The moon does not have time to grow significantly on Christmas Day, and when viewed from the north, it is also below the horizon, so now might be a good time for the darkest day of the year.
The tilt of the axle matters
Due to the tilt of the Earth’s imaginary axis, the north polar region now points away from the sun, and there is a sunless period inside the polar circle. The closer the observer is to the polar circle, the shorter the shadow is.
So, in the northernmost municipality Utsjoki, the sunless kamos lasts a little over 50 days, but a little more than 300 kilometers further south in Sodankylä, only about five days. Similarly, in the Southern Hemisphere, Antarctica now has a nightless night.
If the length of the kaamos is calculated from, for example, Nuorgam, Finland’s northernmost village, i.e. around the 70th degree of latitude, and from the same readings to the southern latitude, it is found that the kaamos in the north is slightly shorter than in the southern hemisphere. It’s because the Earth is now closest to the Sun, and its orbital speed is the highest. In the summer, the track speed is at its lowest, and that’s why the nightless night lasts almost three weeks longer in Nuorgam than in the dark.
How dark is it then?
In order to be able to observe the dark and nighttime nature, it is necessary to get to an area without light pollution. In Northern Lapland, there are still light-polluted areas that can be reached by road, such as the big hills area of \u200b\u200bPetsiko on the border between the municipalities of Inari and Utsjoki.
The human eye is a special instrument because it adapts to dimness and darkness quite quickly. It’s never so dark in the north that you can’t distinguish the horizon, treetops against the sky or buildings, for example.
The reason is that even the smallest rays of light scatter on pure white snow. The stars and northern lights also illuminate, and even these tiny light sources help the observer standing in the dark to perceive his surroundings.
In the south, tall trees, dense undergrowth and fairly flat terrain add to the feeling of darkness. In the very north, the landscape opens up and the height differences are big, and the dark doesn’t seem so dark. It can be downright bright on a starry aurora night, not to mention a moonlit night.
In the north, the air quality is also more transparent than in the south, because there are not so many small particles in the atmosphere. That also affects how dark it really is.