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Summer, bring it on! After the summer solstice (June 21), we start to lose daylight. How fast? Bob Berman talks solstices and sunsets—and you can find out how rapidly the times change where you live.
First a refresher: The summer solstice is the first day of summer, according to astronomy. The word solstice comes from the two Latin words “sun” and “stoppage.” Makes sense: The Sun stops moving North that day. The Sun’s most direct rays reach the maximum northernmost position.
The Sun stands directly over the Tropic of Cancer, the most northerly Earthly place that ever sees an overhead Sun. Interestingly, ‘Cancer’ isn’t really appropriate. True, it was the constellation the Sun hovered in front of on the day of the solstice, back when early observers started paying attention to such things, thousands of years ago. However, since then Earth’s axis has wobbled around like a slowing top, which made the place the Sun occupies on June 21 change first to Gemini, and then, in 1989, to Taurus the Bull, where it’ll remain for the next half millennium. Bottom line: Wednesday’s Sun should be labeled as hovering over the Tropic of Taurus!
No matter, the basic truth stands: Nowhere in the mainland US or Europe does anyone live on the tropic of whatever. So, no American except Hawaiians, who live south of that tropic line, can ever see the Sun straight overhead.
How Quickly We Lose Daylight
Ask friends what happens and they’re likely to get it right, mostly. Longest day of the year – check. Shortest night of the year – check.
On the solstice, sunrise in Seattle, Washington was at 5:09 a.m. and sunset was at 9:12 p.m. Daylight is 16 hours, 3 minutes!
After the solstice, the days will get progressively shorter throughout the summer into the fall. Yes, it starts to get dark earlier.
Take Seattle again. By the fall equinox, or the first day of fall, on Sept. 22, the sunrise is expected at 6:54 a.m. and sunset is expected to set at 7:09 p.m. Daylight is 12 hours, 14 minutes.
Take a southern city; notice the difference!
On the solstice, the sunrise in Miami, Florida was at 6:28 a.m. and the sunset was at 8:16 p.m. Daylight hours totaled 13 hours, 27 minutes.
On the fall equinox, sunrise is 7:08 and sunset is 7:18 p.m. Daylight is 12 hours, 10 minutes.
Here’s something else interesting: After the solstice, we’ll start losing daylight, but the pace will happen much more slowly in the summer and start to speed up as we reach the autumnal equinox.
Sunrise and sunset times hold fairly steady for the two weeks bookending the solstice. But after that, sunrise times start to get later in the morning again very subtly, by only one minute or so. And sunsets after the solstice slowly become earlier in the evening. As the summer marches on, you’ll notice the length of day starts to decrease more rapidly.
Take a Midwestern city this time. Chicago enjoys 15 hours, 16 minutes on the solstice (June 21). About 10 days later (July 1), daylight is 15 hours, 13 minutes (-3 minutes). Go another 10 days (July 11), and daylight is 15 hours, 4 minutes (-9 minutes more).
Why does the speed change? The Earth’s axis is tilted by about 23.5 degrees relative to its orbital plane, so the path of the Sun through the daytime sky goes from nearly perpendicular and directly overhead near the Equinoxes to far from perpendicular and far from overhead during the Solstices as the Earth orbits the Sun. You can see this effect by watching how much the angle of the sunrise changes during each period! Near the solstice, time seems to move more slowly than near the equinox.
One more Sun fact that few people know: As the sun is setting, does it drop straight down, down and to the left, or down to the right? Most get this wrong. A century ago, everyone would have correctly picked the latter choice (to the right) in a heartbeat.
Finally, the nicest fact may simply be that the Sun is now so wonderfully high. From a typical latitude, like that of Denver or Philadelphia, it stands 72° up at 1 PM and won’t change much in the next few weeks. Look how short your midday shadow is! You’ll be Punxsutawney Phil in reverse, marveling at your mostly-missing shadow.