Oleg Zabluda's blog
Thursday, June 21, 2012
 
"Sunrise, Sunset" from "Fiddler On The Roof" [1] is a staple of our hiking repertoire.
"Sunrise, Sunset" from "Fiddler On The Roof" [1] is a staple of our hiking repertoire.

Let SF denote San Francisco, YO denote Yosemite.

Area of interest:
San Francisco CA to Yosemite National Park CA

Exact coordinates of YO and SF are as indicated by Google Maps (all hail). By an amazing coincidence, the two are almost precisely on the same latitude, 160 mi as crow flies, 200 mi as car drives. [3]

Tomorrow is Jul 9, 2011 [4]. All times are PDT.

SF sunrise is 5:55 am, sunset is 8:34 pm, day length: 14:40
YO sunrise is 5:44 am, sunset is 8:23 pm, day length: 14:40

SF Civil twilight 5:25 am - 9:05 pm Length: 15:40
YO Civil twilight 5:13 am - 8:53 pm Length: 15:40 

As you can see, in Yosemite, the Sun is 11 minutes earlier. so it must be (360/24)*(11/60) = 2.75 degrees to the east.

And indeed it pretty much is. Actually it's 2.85 deg. The difference is (2.85-2.75)*60 = 6 min. The Earth turns that much in 24 sec. 6 min of the great circle is 6 nmi = 6.7 mi. At our latitudes, 6.7*sin(37°)=4.0 mi. Negligible.

A very slight imprecision also comes from the fact that SF is actually 0.03°=1.7min=2 mi to the south of YO. .

Sunrise (actually civil twilight) is when we start hiking. Sunset (actually civil twilight) is when we try to come back. That's why it is called day hike. Tomorrow day is 15h 40min long.

Of course, during sunrise, we could have called back to SF on a cell phone to check on their sunrise 11 minutes later, Then reverse the calculations above (together with our odometer reading) to find out radius of Earth.

[3] When I drive to YO on CA-120 at night during summer, my course is exactly due East, straight to Pegasus/Taurus, and during winter, it's Hercules/Cygnus, so it's easy to navigate. And easy to imagine myself driving a spaceship, except I set my cruise control in mph instead of fractions of c, and odometer is not in ly.

SUNRISE SUNSET
Lyrics by Sheldon Harnick
http://www.stlyrics.com/lyrics/fiddlerontheroof/sunrisesunset.htm
music by Jerrold Lewis "Jerry" Bock.

[4] This is a repost of my Buzz (RIP) post Jul 8, 2011
https://profiles.google.com/112065430692128821190/buzz/FUxiFiXPkuE
http://www.youtube.com/watch?v=nLLEBAQLZ3Q

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