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On our planet,

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we have two polar regions:

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the Arctic, whose name comes from

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the Greek Arktikos, of the North,

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and the Antarctic

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from Antarktikos,

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opposite of the North.

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But there's an easier way to remember them

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if you just remember what surrounds them.

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The Arctic, situated in the Northern hemisphere of our planet,

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is an ocean entirely surrounded by land.

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On the other side of the world,

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the Antarctic is a continent

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entirely surrounded by ocean.

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So, the Arctic has polar bears but no penguins,

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and the Antarctic has penguins but no polar bears.

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Let's talk about the Arctic first.

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The Arctic region consists of a vast, ice-covered ocean

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surrounded by treeless permafrost.

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The area can be defined

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as the region between the Arctic Circle

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and the North Pole.

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If you were to stand at the North Pole,

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everywhere you looked, in all directions,

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would be south.

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But standing at the North Pole

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is difficult to do for very long

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because it's in the middle of an ocean,

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covered by constantly shifting, frozen sea ice.

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If you were to fall into the water at the North Pole,

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you'd fall into water that's 13,980 feet deep.

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Above the water, average winter temperatures

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can be as low as -40 degrees Celsius,

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and the coldest recorded temperature

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is approximately -68 degrees Celsius.

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Despite these incredibly harsh conditions,

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humans have populated areas in the Arctic

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for thousands of years.

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Life in the Arctic includes organisms living in the ice,

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zooplankton and phytoplankton,

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fish and marine mammals,

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birds,

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land animals,

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plants,

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and human societies.

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Okay, what about Antarctica?

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Antarctica is Earth's southernmost continent,

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and it contains the geographic South Pole.

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It's the fifth largest continent on the planet

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at nearly twice the size of Australia.

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Almost 98% of Anarctica is covered by ice

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at least one mile in thickness.

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Conditions in Antarctica are some of the most extreme

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in the entire world.

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On average, it's the coldest,

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windiest,

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driest continent

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and has the highest average elevation

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of all the continents.

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You might think that it snows all the time at the Poles,

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but Antarctica is so dry,

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it's considered a desert

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with annual precipitation

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of only 200 millimeters along the coast

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and far less inland.

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The temperature in Antarctica

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has reached -89 degrees Celsius.

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Because it's so harsh and hard to get to,

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there are no permanent human residents on Antarctica,

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but anywhere from 1,000 to 5,000 people

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reside throughout the year

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at the research stations scattered across the continent.

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Even the most extreme animals fight for survival,

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and only cold-adapted organisms survive there,

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including many types of algae,

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animals,

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bacteria,

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fungi,

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plants,

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and protista.

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But why is Antarctica colder than its northern cousin?

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Well, first, much of the continent

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is more than three kilometers above sea level,

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and temperature decreases with elevation.

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That's why mountaintops have snow on them.

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Second, remember that the Arctic

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is really a frozen ocean.

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The water in the ocean beneath it

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is warmer than the frozen ground in the Antarctic,

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and that warmth is transferred through the ice pack.

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This prevents temperatures in the Arctic regions

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from reaching the extremes

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typical of the land surface of Antarctica.

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Third, the seasons are conspiring against the Antarctic.

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During the aphelion in July,

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when the Earth is the farthest away from the Sun,

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it also happens to be winter in the Antarctic,

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which creates a double-whammy of cold

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for the southern pole.

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But despite being inhospitable,

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the North and South Pole are a big reason

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why our planet is the way it is.

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Both of our polar regions

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are very important climate controllers.

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They help moderate the temperature

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in our temperate zones

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and give us stable weather.

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As sea ice in the Arctic declines

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due to climate change and global warming,

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weather around the globe

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becomes increasing more unstable.