Why Days Get Shorter in Fall and Winter

Understanding the Shortening of Days in Fall and Winter

As summer transitions to fall, you may have noticed the days getting noticeably shorter. The gradual shortening of daylight hours continues throughout fall and winter until the winter solstice, which marks the shortest day of the year.

The changing lengths of days and nights is directly related to the earth's tilted axis and orbital revolution around the sun. This astronomical phenomenon causes seasonal variation in the amount of daylight across the globe.

Here's a deeper look at why days start getting shorter in fall and the science behind these seasonal daylight changes:

Earth's Tilt and Orbit Around the Sun

The earth is tilted at an axis of 23.5 degrees as it revolves around the sun. This tilt is what causes the seasons, as parts of the planet are angled towards and away from the sun at different times of the year. The Northern Hemisphere is tilted towards the sun in summer and away in winter. The opposite is true in the Southern Hemisphere.

In June, the Northern Hemisphere is tilted most directly towards the sun receiving longer days and more direct sunlight. In December, it tilts away resulting in shorter days and less intense sun exposure. The 23.5 degree tilt stays consistent throughout the orbit, causing this cycle of seasonal daylight variation.

Solstices and Equinoxes

On the June solstice each year, the Northern Hemisphere receives peak daylight hours marking the longest day of the year. The December solstice delivers the year's shortest day. Equinoxes in March and September mark days of equal daylight and darkness when the sun is centered above the equator.

The farther you live from the equator, the more pronounced the lengthening and shortening of days becomes between solstices. While daylight hours change more extremely, higher latitude locations experience more consistent 12 hour days during equinoxes.

Later Sunrises and Earlier Sunsets

As we progress into fall, you'll notice the sun rising later in the morning and setting earlier in the evening. The exact solar times will vary by location, but the pattern remains constant across the Northern Hemisphere.

Later sunrises are caused by the earth continuing to tilt further away from the sun. Earlier sunsets occur because the sun needs to travel a shorter path across the sky to reach its final setting position in the southwest.

Recurring Cycle

The routine shortening of days repeats every year for the Northern Hemisphere. Around September 21, days and night reach equal lengths during the Fall Equinox. Days continue getting shorter until the Winter Solstice in late December.

This marks the completion of the daylight cycle and signals that days will then start gradually lengthening again towards summer. After the Spring Equinox in March, daylight hours overtake nighttime until peaking again on the Summer Solstice.

How Equinoxes and Solstices Impact Daylight Hours

The daylight patterns of equinoxes and solstices provide insight into the changing lengths of days across the seasons:

Fall Equinox

The Fall Equinox occurring around September 21 is characterized by 12 hours of daylight and 12 hours of darkness. This "equal night and day" marks the turning point when days start becoming shorter than nights.

Winter Solstice

Around December 21, the Northern Hemisphere experiences the year's shortest day and longest night during the Winter Solstice. Daylight can be as little as 9 hours while darkness lasts 15 hours on this day.

Spring Equinox

At the Spring Equinox around March 20, days and nights reach equal 12 hour lengths again. However, days continue getting longer after this equinox leading into summer.

Summer Solstice

The Summer Solstice falling near June 21 brings the longest day and shortest night of the year. Peak daylight reaches up to 15 hours while darkness dips to just 9 hours on this solstice.

These seasonal changes showcase how the tilt of the earth on its axis creates our annual cycle of daylight variation.

Geographic Differences in Daylight

While the shortening of days happens across the Northern Hemisphere, the exact daylight hours vary by geographic location:

Closer to the Equator

Locations near the equator like Hawaii and Puerto Rico experience less drastic seasonal daylight changes. Year-round daylight stays relatively consistent in the 12 hour range without huge swings.

Farther from the Equator

Areas farther from the equator see more extreme daylight changes over the seasons. For example, Stockholm, Sweden has 18 hours of summer daylight but only 6 hours in the depths of winter.

Northernmost Locations

The closer you get to the North Pole, the more exaggerated the seasonal daylight variations become. Barrow, Alaska endures 67 days of total darkness in winter and over 80 days of perpetual sunlight in summer.

So latitude impacts how severely locations undergo daylight reduction in fall and early winter before the cycle reverses towards spring.

Human and Animal Impacts of Shorter Days

The transition to shorter fall and winter days can negatively impact health and behavior in humans and animals. Here are some of the effects:

Circadian Rhythm Disruption

Our body's circadian rhythm relies on exposure to daylight to stay synchronized. As days get shorter, circadian rhythms can become disrupted resulting in tiredness, insomnia, and mood changes.

Vitamin D Deficiency

Less sunlight in fall and winter means less ultraviolet radiation helping our bodies synthesize vitamin D. Deficiency in this key vitamin can weaken bones and the immune system.

Increased Melatonin Production

More darkness stimulates the brain's pineal gland to produce more melatonin making us sleepy. This typically leads to increased sleepiness and lethargy during the day.

Seasonal Affective Disorder

Some people suffer from seasonal depression as a result of reduced daylight. Known as SAD, symptoms include low mood, lack of motivation, fatigue, and carbohydrate cravings.

Animal Hibernation

Shorter days provide an environmental cue for some animals like bears to start hibernating. Reduced daylight triggers hormonal changes that make hibernation possible.

Animal Migration

Diminishing daylight is also an important factor in initiating animal migration. Shorter days prompt birds to start migrating to warmer climates.

Clearly, the natural shortening of days starting in fall and continuing into winter impacts numerous facets of human health, behavior and the natural world.

Coping With the Shorter Days of Winter

While you can't halt the earth's inevitable winter daylight reduction, here are some ways to cope:

Light Therapy

Daily use of light therapy lamps mimics sunshine to help maintain circadian rhythms and serotonin levels to combat seasonal depression and gloominess.

Take Vitamin D

Popping a vitamin D supplement makes up for reduced sunlight that triggers vitamin D production and prevents deficiency issues.

Morning Exercise

Exercising outdoors early in the day ensures you get some natural sunlight first thing to set your body clock and uplift mood.

Open Blinds

Make sure to open blinds and curtains during the day to allow ample ambient daylight indoors and maximize sun exposure.

Afternoon Walks

Take hourly movement breaks and get outside for a short afternoon walk to soak up whatever daylight remains in the early evening.

Implementing lifestyle adaptations enables you to thrive despite the prolonged darkness and daytime gloominess of winter.

Fun Facts About Shorter Days

Here are some interesting tidbits about the decreasing daylight happening in fall and winter:

Ancient Meaning

In ancient times, winter solstice marked the rebirth of the sun as days slowly began to lengthen again after the solstice.

Opposite Impact

While the Northern Hemisphere experiences shortening days starting in fall, the Southern Hemisphere sees days lengthening towards its summer.

Later Sunrises

At higher latitudes, the late sunrise during winter can occur after 9 AM due to how far the location has tilted away from direct sun exposure.

Temperature Impact

Due to the lower angle of the sun in winter, the same number of daylight hours in different seasons provide vastly different levels of warmth.

Polar Night

Within the polar circles, locations like Barrow, Alaska experience two months of "polar night" with zero sunlight around the winter solstice.

These fun facts showcase how radically daylight patterns can transform depending on location and time of year on our tilting, revolving planet.

The Opposite Phenomenon in Summer

The cycle comes full circle in summer when days reach their longest point on the summer solstice in June. Here's what happens:

Peak Daylight Hours

Instead of the 9 hours of daylight we see on the winter solstice, summertime sunlight peaks at the opposite extreme of 15-16 hours around June 21.

Highest Sun Angle

With the Northern Hemisphere tilted most directly towards the sun, the sun reaches its highest angle in the sky creating the greatest intensity of sunlight.

Earlier Sunrise and Later Sunset

Since the sun travels a longer path across the summer sky, it rises much earlier in the northeast and sets later in the northwest.

Long Twilight Periods

Surrounding summer solstice are prolonged dawn/dusk twilights expanding usable daylight for several weeks.

The lengthening days culminate on the summer solstice before the daylight reduction process starts again.

Celestial Reasons for Shortening Days

To summarize, here are the key astronomical phenomena causing days to shorten starting in fall:

• Northern Hemisphere tilting away from direct sun exposure
• Sun rising and setting further south along horizon
• Fewer daylight hours and longer nights
• Sun angle lower in sky, providing less intensity
• Changing equinoxes and solstices marking seasonal daylight variation

Understanding these celestial mechanics provides perspective on why daylight patterns transform throughout the year based on earth's position in space.

Embrace the Power of Winter Darkness

Although challenging, the increasing darkness of fall and winter is a necessary phase in the annual cycle. Here are powerful ways to embrace shorter days:

Reset Circadian Rhythms

Let the longer nights normalize your sleep-wake cycles and rebalance your body's 24-hour internal clock.

Stimulate Reflection

Use extra evening darkness for self-reflection, creative hobbies, or simply rest and relaxation.

Motivate Life Changes

Harness winter's introspective energy to fuel positive life changes and evolve your goals.

Practice Gratitude

Combat gloominess by appreciating things you overlook when busy in summer like family, health, warmth.

By changing perspective, you can discover deeper meaning in the recurring cycle of ever-shifting daylight and darkness.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.