Daylight Savings Ends This Weekend

Don't forget to turn your clocks back one hour this weekend!  Daylight Savings Time ends at 2:00 AM Sunday morning, October 29 here in the USA, and we "fall back" to Standard Time until we "spring forward" again next Spring.

Some may not see how this is an astronomy-related topic, but Daylight Savings is adopted because of the seasonal changes in the length of daylight.  This is a direct result of the Earth's revolution around the Sun, which we learn about from Classical Astronomy!

In recent years, Standard Time has been resuming later and later in the month of October.  Years ago, we fell back on the first or second Sunday of October, and sprang forward in about mid-April.  But according to this Yahoo story, this is the last time that we will fall back in October:

Thanks to a law passed last year, daylight-saving time will start earlier and end later beginning in 2007. It will last from the second Sunday in March to the first Sunday in November.

Many people think this is progress, and perhaps it is.  But with Daylight Savings, the Sun now longer reaches the middle of the sky at Noon.  It's just another way that our culture has become removed from the Two Great Lights that the LORD has placed in the sky for us to tell time (Gen. 1:14). 

The Summer Solstice

During June, the Sun appears to pass through the stars of Taurus the Bull, and this constellation is therefore not visible.  Toward month's end, the Sun enters the constellation Gemini the Twins.  The constellation Orion, prominent in the early evening skies of January and February, is invisible during June, hidden by the bright glare of the Sun in nearby Gemini.

On Wednesday, June 21, the Sun reaches the northernmost extent its annual cycle.  This day is the Summer Solstice for observers in the northern hemisphere and is traditionally regarded as the official First Day of Summer.  On the Solstice, the Sun is at its highest point of the year in the Noon sky, and the shadows at Noon are the shortest they can be.  Be sure to observe this in the coming months and notice how the Noon shadows get longer as the months go by.

On the Summer Solstice, the Sun rises very far to the north and later sets very far to the north.  The Sun is above the horizon for most of its 24 hour cycle and the length of daylight is greatest for people living north of the Equator.  For this reason, the Summer Solstice is also The Longest Day of the Year.

Here in Cleveland, the daylight on the longest day lasts about 15 hours.  Cleveland is near latitude 40 degrees North, along with many other large American cities, such as New York, Washington DC, Chicago, and San Francisco.  So the length of daylight is about the same for these cities as well. 

However, the length of summer daylight is even greater for places further north.  At the Arctic Circle, the Sun doesn't even set on the Summer Solstice!  Way up in Alaska or Iceland, one would see the solstice Sun rising on the northern horizon at midnight, wheeling a full circle all the way around the sky, and again touching the horizon in the north the next midnight!

In the southern hemisphere, in places like Australia, New Zealand and South Africa, the constellation Gemini lies very low in the sky.  So the solstice of June 21 is actually the Shortest Day of the Year in these southern lands.  Observers in these locations can see the longest Noon shadows of the year.  After this day, their shadows will get shorter as the shadows in the northern hemisphere grow longer.

Summer Twilight
Even though the Solstice is "the longest day" for North America, Europe and Asia, the daylight still lasts pretty long from about late May til late July.  During these long days, the period of twilight is the longest of the year.  This means that the sky still has a glow from the Sun for a long time after the Sun sets.  Also, in the morning before sunrise, the horizon starts to glow quite a while before the Sun actually rises.  This is because, during this season, the Sun appears to ride close below the horizon.  If you watch the twilight very closely, you can see the Sun's glow far to the north of the places of sunrise and sunset. 

In places to the north of the USA, like Canada and Europe, you can observe the "White Nights" during this season.  In these times, the sky never gets completely dark!  After sunset, the Sun scoots underneath the northern horizon, and a patch of twilight is always seen over the short summer night.  The sky never gets completely dark, so that evening twilight merges with morning twilight!  If anyone is planning a trip north this summer, to latitude 50 degrees or higher, try to notice this!