How An Igloo Keeps You Warm

0:00 For thousands of years, humans, and plants and animals long before that, have been using

0:04 frozen “sky water” to keep warm.

0:08 Which sort of doesn’t make sense.

0:10 Because snow is cool.

0:12 You might even say it’s… ice cold.

0:16 YEEAAHHHHH!

0:18 No one knows for sure who built the first igloo, but with the right fit and the right

0:23 physics, snow can actually warm you better than the inside of a tauntaun.

0:27 "You'll be ok, Luke!"

0:29 So, how can something cold keep you cozy?

0:34 [MUSIC]

0:36 The vast, frozen Arctic is one of the most forbidding environments on our planet, yet,

0:42 the Inuit have managed to live there for about 5,000 years.

0:45 Out on the pack ice, winter temperatures reach 50 degrees below zero , and when it’s that

0:51 cold, surviving means finding shelter.

0:54 It’s not an area known for its forests, so nomadic hunters learned to build with the

0:58 only thing available: snow.

1:01 Eskimo languages really do have dozens and dozens of different words for snow, because

1:06 there are a lot of different types, and the type of snow you choose can dictate whether

1:11 your igloo keeps you warm, or turns you into a Homo sapiensicle.

1:15 To understand this, we need to know a little something about being cold.

1:20 When your body temperature starts to plummet – you’re feeling heat leave you.

1:24 Cold can’t move into your body – in fact, there is no such thing as cold.

1:29 Where have I heard that before?

1:31 Oh, right!

1:33 Think of heat as an actual quantity of stuff:.

1:36 The more you give away, the colder you feel.

1:38 This trading of heat can happen three different ways: by convection, conduction, and radiation.

1:45 All three are at play in an igloo.

1:47 A person inside will radiate body heat, which moves around the igloo by convection, and

1:52 is lost through the walls by conduction.

1:55 This is exactly what happens in your house.

1:58 Living insulation does the same thing.

2:00 Fatty tissues like blubber help stop heat transfer in whales and seals, but for animals

2:06 who don’t have as much junk in the trunk, they cover themselves in air.

2:10 Sea otter fur, for example, is about a thousand times denser than human hair.

2:14 It’s snuggly stuff "This is the softest thing I've ever felt

2:19 in my life.

2:20 You are adorable!" …but the secret to its insulation power

2:23 is in its texture.

2:24 Otter fur is spiky, so it traps insulating air molecules.

2:28 And that is exactly what snowflakes do.

2:32 Powdery, fresh snow can be up to 95% trapped air.

2:36 This makes it an excellent insulator, but the same way you have to pack it in your hands

2:41 to make a snowball, it isn’t dense enough to build with.

2:44 Solid ice, on the other hand, makes a good windbreaker, but it’s too heavy to lift.

2:48 Inuit hunters took the Goldilocks approach: the secret to good igloo snow is somewhere

2:54 in the middle.

2:55 Traditional igloo blocks aren’t molded, they’re cut out of the ground.

2:58 That tightly-packed ground snow is dense enough to hold up, but because it still has far more

3:03 air pockets than a block of ice, it’s light, and still a pretty good insulator.

3:08 As usual, animals figured this one out long before humans.

3:11 Polar bears, groundhogs, even birds like grouse all make snow burrows to stay warm.

3:16 And even before that, plants were tucking into snow to avoid death by freezing.

3:22 During the warm months, heat energy from the sun builds up in soil, and just like the the

3:26 roof above your head, a deep covering of snow prevents that heat from escaping onward and

3:32 upward.

3:33 This snowy blanket above stops ice crystals from forming inside plant roots, and shoots,

3:38 and seeds.

3:39 Not freezing to death is a pretty good motivator for any animal to get crafty, but our big

3:44 primate brains took it one step further with igloos.

3:48 Their engineering maximizes warmth and stability.

3:52 Cartoon igloos look like flat-bottomed half-spheres, but in reality, they’re neither of those

3:57 things!

3:58 If you were to slice a real igloo in half, you’d see a shape called a catenary.

4:03 This gradually sloping shape is the same one that would form if you held a chain from both

4:08 ends and let it droop.

4:09 A catenary arch distributes weight more evenly than a half circle, without bulging or buckling.

4:15 In fact it’s one of the most stable arches in nature, so sound that we still use it today.

4:21 Inside, snow houses are carved in different levels.

4:24 The hot air rises, and the cold air sinks down into the lower part, and away from where

4:29 you would eat, sleep, and chill.

4:32 To boot, body heat melts the innermost layer of the walls, strengthening the barrier between

4:37 you, your airy snow-block insulation, and the frigid great beyond.

4:42 When you live in an igloo, you act as a living furnace.

4:46 Over time, the temperature in your icy abode can hover some 40-60 degrees above the surrounding

4:52 air, but bring a friend to your igloo party, and you’ll get warmer, faster.

4:58 Stay cozy, and stay curious!

5:00 "Hey, you remember that thing I said about eskimos having all those different words for

5:05 snow?

5:06 Well our friends from Idea Channel made a video about that.

5:09 Here's an idea, you should go check it out.

5:11 It's pretty cool."