How An Igloo Keeps You Warm

[MUSIC] For thousands of years, humans, and plants
and animals long before that, have been using frozen “sky water” to keep warm. Which sort of doesn’t make sense. Because snow is cool. You might even say it’s… ice cold. YEEAAHHHHH! No one knows for sure who built the first
igloo, but with the right fit and the right physics, snow can actually warm you better
than the inside of a tauntaun. “You’ll be ok, Luke!” So, how can something cold keep you cozy? [MUSIC] The vast, frozen Arctic is one of the most
forbidding environments on our planet, yet, the Inuit have managed to live there for about
5,000 years. Out on the pack ice, winter temperatures reach
50 degrees below zero , and when it’s that cold, surviving means finding shelter. It’s not an area known for its forests,
so nomadic hunters learned to build with the only thing available: snow. Eskimo languages really do have dozens and
dozens of different words for snow, because there are a lot of different types, and the
type of snow you choose can dictate whether your igloo keeps you warm, or turns you into
a Homo sapiensicle. To understand this, we need to know a little
something about being cold. When your body temperature starts to plummet
– you’re feeling heat leave you. Cold can’t move into your body – in fact,
there is no such thing as cold. Where have I heard that before? Oh, right! Think of heat as an actual quantity of stuff:. The more you give away, the colder you feel. This trading of heat can happen three different
ways: by convection, conduction, and radiation. All three are at play in an igloo. A person inside will radiate body heat, which
moves around the igloo by convection, and is lost through the walls by conduction. This is exactly what happens in your house. Living insulation does the same thing. Fatty tissues like blubber help stop heat
transfer in whales and seals, but for animals who don’t have as much junk in the trunk,
they cover themselves in air. Sea otter fur, for example, is about a thousand
times denser than human hair. It’s snuggly stuff
“This is the softest thing I’ve ever felt in my life. You are adorable!”
…but the secret to its insulation power is in its texture. Otter fur is spiky, so it traps insulating
air molecules. And that is exactly what snowflakes do. Powdery, fresh snow can be up to 95% trapped
air. This makes it an excellent insulator, but
the same way you have to pack it in your hands to make a snowball, it isn’t dense enough
to build with. Solid ice, on the other hand, makes a good
windbreaker, but it’s too heavy to lift. Inuit hunters took the Goldilocks approach:
the secret to good igloo snow is somewhere in the middle. Traditional igloo blocks aren’t molded,
they’re cut out of the ground. That tightly-packed ground snow is dense enough
to hold up, but because it still has far more air pockets than a block of ice, it’s light,
and still a pretty good insulator. As usual, animals figured this one out long
before humans. Polar bears, groundhogs, even birds like grouse
all make snow burrows to stay warm. And even before that, plants were tucking
into snow to avoid death by freezing. During the warm months, heat energy from the
sun builds up in soil, and just like the the roof above your head, a deep covering of snow
prevents that heat from escaping onward and upward. This snowy blanket above stops ice crystals
from forming inside plant roots, and shoots, and seeds. Not freezing to death is a pretty good motivator
for any animal to get crafty, but our big primate brains took it one step further with
igloos. Their engineering maximizes warmth and stability. Cartoon igloos look like flat-bottomed half-spheres,
but in reality, they’re neither of those things! If you were to slice a real igloo in half,
you’d see a shape called a catenary. This gradually sloping shape is the same one
that would form if you held a chain from both ends and let it droop. A catenary arch distributes weight more evenly
than a half circle, without bulging or buckling. In fact it’s one of the most stable arches
in nature, so sound that we still use it today. Inside, snow houses are carved in different
levels. The hot air rises, and the cold air sinks
down into the lower part, and away from where you would eat, sleep, and chill. To boot, body heat melts the innermost layer
of the walls, strengthening the barrier between you, your airy snow-block insulation, and
the frigid great beyond. When you live in an igloo, you act as a living
furnace. Over time, the temperature in your icy abode
can hover some 40-60 degrees above the surrounding air, but bring a friend to your igloo party,
and you’ll get warmer, faster. Stay cozy, and stay curious! “Hey, you remember that thing I said about
eskimos having all those different words for snow? Well our friends from Idea Channel made a
video about that. Here’s an idea, you should go check it out. It’s pretty cool.”