At first glance, an igloo makes no sense.
It’s literally built from blocks of ice and snow — materials we associate with freezing temperatures.
So why are igloos surprisingly warm inside?
The secret lies in air.
Snow is actually an incredible insulator because it traps tiny pockets of air. These air pockets prevent heat from escaping quickly.
When people sit inside an igloo, their body heat slowly warms the air inside.
Even a small candle can raise the temperature noticeably.
Outside, temperatures might be –40°C (-40°F).
Inside an igloo, it can reach 0°C to 15°C (32–59°F).
Still cold — but dramatically warmer than outside.
Another clever design feature is the tunnel entrance.
Cold air sinks, so the entrance is built lower than the sleeping area. This keeps warmer air trapped above where people rest.
In a strange way, an igloo works like a natural thermos.
It doesn’t generate heat.
It simply refuses to let it escape.
Which makes you wonder:
How many other survival tricks has nature already figured out?