Wednesday, May 7, 2008

Twilight

Pam and I went to bed at 11:30 pm last night. We hadn't intended to stay up so late, but it was still light out. We woke up at 3:00 am... it was still light.

The sun now sets at 10 pm and rises at 4:30, with civil twilight lasting until 11:15 and beginning at 3:19. Civil twilight is defined at the times which the sun less than 6° below the horizon. During this time, known to some as the "blue hour", the light has special romantic properties and it is a favorite time for painters. Another less precise definition of 'civil twilight' is the time after sunset and before sunrise where it is still possible to engage in outdoor activities without the need for artificial light.

The time when the sun is between 6° and 12° below the horizon is called 'nautical twilight'. During this time, if you're at sea you can still see just fine.

Right now in Trondheim, it is nautical twilight all through the midnight hours, which is a little bit strange. In a few weeks, it won't even be that dark: May 20th marks the day when it will get no darker than civil twilight, and these 'white nights' as they are called will last until July 20th.

It's time to find where we've put our heavy curtains, or they'll be little sleep around here!




Here's a cool graph of twilight times at various lattitudes and times of years.
Click for big version.

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