Saturday, May 30, 2009

Sunrise and sunset

I have been amazed, lately, by how early it gets light, and how late it stays light. If we weren't training the cats not to wake us up for food (it's working, by the way), I wouldn't need to set an alarm in the mornings. I don't feel like drawing my curtains until after 9 pm at night. Wild.

So I thought I'd look up the actual sunrise and sunset times, and see if they're really all that different from when we lived in Philadelphia, or better yet, when we lived in Michigan -- because I know they were definitely different in Michigan compared to Philadelphia. We were much further north in the time zone, and almost as far west as you could be and still be in the same time zone. I'd have to see where we are comparatively, east-to-west, in the time zone here, but I do know we're much further north than we were in Ann Arbor (47th parallel here in Seattle; 44th parallel in Ann Arbor; 40th parallel in Philadelphia).

The US Naval Observatory has some very cool tools, including ones where you can get the sunrise and sunset data for a single day, or a whole year.

So I looked up May 29, 2009, for all three locations, and here's what I got:

  • Seattle: Sunrise, 5:17 am; Sunset, 8:57 pm
  • Ann Arbor: Sunrise, 6:02 am; Sunset, 8:32 pm (wow, they really are different...)
  • Philadelphia: Sunrise, 6:35 am; Sunset, 8:22 pm.

Now I'm curious... how about Summer Solstice?

According to the US Naval Observatory, Summer Solstice 2009 is on June 21st, at 5:45 am UT (Universal Time). In Seattle, we're in the Pacific Time Zone, UT-8, so Summer Solstice for us is at 9:45 pm the night before, June 20th. Ann Arbor and Philadelphia are in the Eastern Time Zone, UT-5, so Summer Solstice is at 12:45 am on June 21st.

Summer Solstice:
  • Seattle, June 20th: Sunrise, 5:11 am; Sunset, 9:11 pm
  • Ann Arbor, June 21st: Sunrise, 5:59 am; Sunset, 9:15 pm
  • Philadelphia, June 21st: Sunrise, 5:32 am; Sunset, 8:33 pm.

So on Summer Solstice, we have
  • 16 hours of daylight in Seattle;
  • 15 hours, 16 minutes of daylight in Ann Arbor; and
  • 15 hours, 1 minute of daylight in Philadelphia.

Very cool!

Today's post is brought to you by the joys of scientific geekdom in the service of spiritual mysticism. :)

Photo: sunset on Lake Michigan, August, 2006, (c) Stasa Morgan-Appel


Judielaine said...

I'm quite sensitive to these latitudinal variations. Visiting Vancouver over summer solstice a couple years ago was impressive, as the long light confused my inner clock, driving me towards some nearly sleepless nights.

staśa said...

I can totally see that. I spent one Summer Solstice in Grayling, MI, which is a few hours north and a little west of Ann Arbor, and was amazed by the difference. I was walking around one night at 10:30, and it still wasn't completely dark. The sky was an amazing, amazing shade of deep blue...

bnewman said...

I've been on coast to coast flights on both the winter and summer solstices where the time changes respectively made the longest night three hours longer and the shortest three hours shorter. That was downright odd.

staśa said...

Wow. I bet!

Nif said...

Awesome geekery.

I need to adjust my bedtime here in Philly, since the sun is definitely waking me. I don't mind getting up early if the sun is up -- but not if I haven't had enough sleep.

staśa said...

Thanks! I almost said, "I'm totally with you," and then I thought -- even with enough sleep, would I want to get up at 5 am? Hmmm.... :)

jlr said...


I did a math project in high school with the hours of daylight over the course of a year for various latitudes. It turns out when graphed, it creates a perfect sine wave. I figured out the formula to get the equation for the sine wave if only the latitude was known. I've forgotten a lot of the details in the intervening years, but it was really cool. I love math that actually has to do with real life!

Also, I lived in Northern Ireland for a year. Ballycatle is 55 degrees north, 6 degrees west, and on June 20th of this year, sunrise will be at 3:46 AM and sunset will be at 9:09 PM.

One summer night I was there I was walking home from the bar at about midnight. There was still just enough light in the sky to be able to see the outline of Scotland, 13 miles across the water. Mad!

staśa said...

Johanna - Wow! All three of those things are very cool.

Yes, that's the kind of math that I get excited about, too.

Sue's in Scotland right now, and we were talking about how long the days are there at the moment. :)