Since I live in a temperate climate, I think about seasons more than my friends who live in, say, San Jose, Calif. This becomes especially pronounced the closer we get to the equinoxes as the change in daylight hours peak then. On my walk with Cassie earlier today, I started thinking about how actually to quantify the lengthening shadows in autumn.
Here, then, is a chart of the position of the sun in Chicago for the first day of each month, along with its equivalent day on the other side of the equinox. For example, today the sun is about 63° above the southern horizon at solar noon—almost exactly the same as on May 1st. This means also that the day has about the same length (14 hours, 2 minutes), and the sun rises and sets in the same parts of the eastern and western skies, respectively.
Using the code I wrote for Weather Now, it took just a couple of minutes to generate the basic data for this chart. It should make sense right away, except for the column marked "Shadow." That's the length of the shadow cast per unit of hight at solar noon. So, for example, today's 63.3° sun angle gave a 10-meter building a shadow almost exactly 5 meters in length. The two days of the year (in Chicago, anyway) when the sun is 45° above the horizon—giving everything a shadow equal to its own height—are March 13th and September 30th.
Enjoy:
| Date |
Sunrise |
Sunset |
Daylight |
Rise |
Noon |
Set |
Shadows |
Same as |
| Jan 1 |
07:20 |
16:31 |
9:11 |
121° |
25° |
239° |
2.14 |
Dec 11 |
| Feb 1 |
06:35 |
17:07 |
10:02 |
112° |
31° |
248° |
1.67 |
Nov 10 |
| Mar 1 |
06:27 |
17:42 |
11:14 |
99° |
41° |
261° |
1.17 |
Oct 12 |
| Apr 1 |
06:35 |
19:17 |
12:42 |
83° |
53° |
277° |
0.76 |
Sep 11 |
| May 1 |
05:48 |
19:50 |
14:02 |
68° |
63° |
292° |
0.51 |
Aug 11 |
| Jun 1 |
05:19 |
20:21 |
15:01 |
59° |
70° |
301° |
0.36 |
Jul 11 |
| Jul 1 |
05:20 |
20:31 |
15:11 |
57° |
71° |
303° |
0.34 |
Jun 11 |
| Aug 1 |
05:45 |
20:10 |
14:25 |
65° |
66° |
295° |
0.45 |
May 11 |
| Sep 1 |
06:17 |
19:26 |
13:08 |
78° |
56° |
282° |
0.67 |
Apr 11 |
| Oct 1 |
06:48 |
18:34 |
11:45 |
94° |
45° |
266° |
1.01 |
Mar 12 |
| Nov 1 |
07:24 |
17:46 |
10:22 |
109° |
34° |
251° |
1.51 |
Feb 11 |
| Dec 1 |
07:00 |
16:21 |
9:21 |
119° |
26° |
241° |
2.03 |
Jan 11 |
Another thing I found interesting: notice how quickly shadows lengthen in the fall and shorten in the spring. That's what I noticed today, in fact: the east-west sidewalks were completely in shadow at noon today. They haven't been since, oh, the beginning of May.
Now, the date pairs should work for any point on earth, but all the other data will change. If you want to see your own location's sunrise and sunset times, go to Weather Now.