Why Does It Stay Light, 
So Late During Alaska’s Summers?
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Hiking at Midnight

The earth is tilted 23.5 degrees in from its orbital plane

Wow, we’ve been hiking for a long time.  It must be getting late but it’s not even close to being dark out.  

Why does it stay light out so late into the night? 

Ingrid, the park ranger, said that the earth is tilted 23.5 degrees in from its orbital plane. Remember, that picture she showed us?

Summer

On June 21st, the North Pole is tilted towards the sun. She told us how the as the earth rotates on it’s axis, the sun appears to move in a low circle in the sky. It only dips below the horizon for a few short hours. Although, the sun is never showing at midnight in Denali, you would have to go further north above the Arctic Circle for that, it does stay light out for 21 hours. When the sun sinks below the horizon, it does not get really dark but just stays a gray dusk called twilight.

The sun warms the tundra. Sometimes, the temperature can get into the upper 70’s.

In the Summer, the  North Pole is tilted towards the sun.

Winter

In the Winter, the  North Pole is tilted away from the sun.

On December 21, the North Pole is tilted away from the sun. Ingrid said that the sun just peeks above the horizon for just a few short hours. It stays dark out for most of the day but as the sun comes above the horizon, a twilight spreads across the land for a few short hours. 

This lack of sun makes the tundra cold, sometimes as a cold as –50 degrees.