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The expression the ends of the Earth is never better applied than to the poles. They are truly the least hospitable regions on the surface of the planet — beating out some pretty hot, arid or just simply starved and deserted places. Some parts of Earth's polar regions are so frigid and harsh, in fact, they resemble Mars more than Earth, which is why some Mars enthusiasts spend time there, practicing for a manned mission to the real Red Planet.
The deep chill is, of course, largely why the poles are the least populated regions of Earth. There are no permanent human residents of Antarctica, and about 3.7 million Arctic residents are spread out over eight countries. That's about the same population as Connecticut, Ireland or Lithuania. Not a lot as populations go by today's standards.
Geometry of Frigid
The frozen poles are no accident, of course. They are a product of our spherical planet. The cold is the fault of geometry: The sun is low in the sky at high latitudes, which means that even at noontime shadows are still long and sunlight is spread thinly over a lot of ground. In stark contrast, at the equator a person casts a shadow on little more than their own feet. Sunlight strikes the ground at the equator perpendicularly — delivering a lot of energy to a small patch of ground.
The low angle of the polar sun, combined with the tilt in Earth's spin axis, also give polar regions the greatest range of daylight hours through the year. At one extreme is midsummer when the sun never sets; at the other are midwinter nights when the sun never rises. Again, that's the exact opposite of the equator, where the sun is always high in the sky and days are all virtually the same: 12 hours of light and 12 hours of dark.
These extremes make for some very different creatures. It is eternal spring in the tropics. Seasons there revolve around wet and dry, not cold and hot. The excess of energy in the tropics creates layer upon layer of life, forests with multiple canopies and birds with spectacular plumage.
Meanwhile, winter never really leaves the poles. It's always either cold or very cold. To live here means either sleeping most of the year or piling on the blubber. There isn't a lot of time or energy to spare for bright colors or elaborate displays. Seals, penguins, polar bears, Arctic whales and tundra plants aren't particularly flashy. That's not what it takes to survive at the top and bottom of the world.
