CHAPTER I
ASTRONOMICAL FEATURES OF THE
POLAR REGIONS
From the earliest days of European civilisation it has been customary to define the direction of the sun at noon as well as the opposite direction. South and north are the terms that have been used by north-western Europe: hence North Pole for that end of the earth's axis towards which Europe stretches, and South Pole for the other end of the axis. Now there are very definite peculiarities of these two mathematical points, and I give a few of these to set the reader thinking.
1. The sun is continuously above the horizon for six months, from our spring to our autumn equinoxes, and continuously below the horizon for the other six months.
2. But there is only one time, namely noon, because all longitudes converge at the North Pole: whether it be light or dark it is always noon, because the sun is always due south.
3. Though there is only one time there are different seasons, because these depend on the position of the earth in its orbit and on the inclination of the polar axis to the plane of the ecliptic.
4. The apparent path of the sun is an ascending spiral from the vernal equinox till the summer solstice, and a descending spiral from the summer solstice till the autumnal equinox. Thus it is possible to take meridian altitude of the sun during the whole summer six months at the North Pole, at any moment, or at every moment, no matter where the sun is in the spiral. Exactly the same thing may be said of the moon when she is north of the Equator.
5. The greatest possible altitude of the sun above the horizon is about 23½ degrees (actually at Greenwich mean time, 1911, June 22nd, 2h p.m., 23° 27′ 9″.8). It reaches this altitude only at that date.
6. The constellations never set at the North Pole, their apparent paths (neglecting their own very tiny movements) being in circles, round the Pole; like the sun, they are always south of the North Pole.
7. When standing at the North Pole it is impossible to look in any other direction along the earth's surface but south. To the left or to the right, behind or in front of the person standing at the North Pole the direction is always south.
These conditions apply equally to the South Pole, except that the terms north and south have in every case to be reversed. It is very important to get a proper grip of these facts if one is to have a proper conception of where the Polar Regions are, and to account for various special phenomena peculiar to these two parts of the earth.
Theoretically it is convenient to define the Polar Regions as those areas that lie round about the North Pole and round about the South Pole, within the Arctic and Antarctic Circles, which are defined by being those circles of latitude where the sun on midwinter-day does not rise and where on midsummer-day it does not set.
In contrast to the tropical regions, where the sun is always vertically overhead at some place at noon on two days (at the north and south limits on one day) every year, and always reaches in every part an altitude exceeding about 43 degrees, in the Polar Regions the sun is never more than 23½ degrees above the horizon. On account of this great obliquity of the sun's rays in the Polar Regions the sun has less heating power and the regions are colder, while in winter intense cold prevails because of the entire absence of the sun.
Having now obtained a general idea of the position of the Polar Regions on the earth's surface let us pass on to consider their general features. And the Antarctic Regions are considered first, because it was there, about twenty years ago, that I first received my polar baptism and first learnt what the Polar Regions were.