Tuesday, June 26, 2012

White Nights

We just passed through the longest day of year, here in the northern hemisphere, which means our days are really long, and the twilight is even longer.  This drove me crazy as a kid.  I hated going to bed when it was still light out!  But we get used to it.  Long summer days are just something I took for granted until I lived in Australia and (very briefly) Hawaii.  It had never occurred to me how different things are closer to the equator, where there's not much variation from summer to winter, and very little twilight.  And since I know that some of you bloggy friends don't experience this, I thought I'd show you.

In the winter, when we're tilted farther from the sun, we get barely eight hours of daylight.  The sun rises around 8am and sets just after 4pm.  People go off for a full day of work or school and they are leaving and coming home in darkness.  On the other hand...

Right now the sun is rising by 5am and doesn't set until almost 9:30 pm.  Well, that's if the world were a smooth, round ball, so the sun actually appears over the hills a little after 5, but you get the idea... lots of daylight!  And it's actually light much longer.

Do you have much twilight, where you live?  I just learned that there are three definitions of twilight - civilian, nautical, and astronomical.  Officially they're defined by how many degrees (of angle) the center of the sun is below the theoretical (smooth world) horizon, but defined more practically -

Civilian twilight means the sun is gone (or not up yet) but you can clearly distinguish things without needing artificial light.  During nautical twilight you can still see the horizon and outlines of landforms (and sailors would be able to take readings which require the horizon and a bright star to be visible).  Astronomical twilight has to do with their being enough light still refracted in the atmosphere to obscure sixth-magnitude stars (the dimmest ever visible to the naked eye) and isn't really very useful to most of us.

For our sake, I'm thinking of civilian twilight - which looks about like this to my eye, very blue

Just for fun, though, this is how the camera sees it.  Much brighter!  That was a really long exposure.

Looking to the west, I see a sliver of the moon, and a lot of brightness where the sun has already set.  You can see why, in Scandinavia and Russia, they call these white nights.

Looking down into a shaded corner of the yard, you can see white fever-few, my solar-powered garden lights, and light from my neighbor's house beyond the fence.

When the sky is clear and the sun goes down, the evening just gets bluer and bluer until it is finally dark.  But summer nights are never as dark as winter nights.

Here it has finally gotten dark enough to trigger the light sensor to turn on the street light.

Can you guess what time I took these photos?  Right around 10pm.  No kidding.  Twilight extends our day from about 4:30am to 10pm.

What is it like where you live?


RogersUIO said...

Here on the equator the sun is up at 6 and sets at 6, every day, all year long! I love visiting the US during the summer to enjoy those extra long evenings.

Choate Family said...

We were so used to living only eight degrees south of the equator with those twelve hours (or so) of sun. Now, we're having trouble adjusting to the light at nine o'clock at night! But I love the way the sunlight and the seasons change here :-)

sara said...

Even though I'm pretty sure we're only about 7 or so degrees south of you (opposite coast), it was still so wonderful to have you draw my attention to these things. I've got to savor more. Thanks.

The dB family said...

Our days are about the same length as yours. I adore civilian twilight!