But what does light have to do with sleep?

Airline pilots and travelers aren't the only ones to suffer sleep disruptions. They are also typical of migraineurs and persons with concussions and / or the fatigue and depression of Seasonal Affect Disorder (SAD). And even among the hale and hearty, who likes to get up in the black dark of a winter morning? — especially in areas that may not see actual sunshine for weeks or months at a time.

Light controls sleep cycles by its affect on the pituitary gland via the eyes. High energy "morning" light (towards the blue end of the spectrum) encourages production of serotonin (the "feel-good" hormone). Lower energy "evening" light (towards the red end of the spectrum) allows levels of melatonin (the sleep hormone) to rise.

Dark in the morning can lead to fatigue while exposure to blue light in the evening (whether on a computer screen or a phone charger) can lead to insomnia.

Two devices can help restore the natural balance: sunrise clocks and light boxes.

BioBrite was one of the first makers of the sunrise clock. This is a timed light (basically a bulb with a rheostat) that begins to glow and slowly brighten over a set period of time, emulating dawn. It wakens the sleeper gradually and naturally, without the heart-pounding blare of the standard alarm clock. Some models also emulate sunset, by darkening gradually. Others include features such as white noise or morning bird songs.

The GoLite, originally developed for relief of SAD, is more than a bright light. It is a panel of LEDs tuned to a specific frequency of morning blue. It is remarkably smaller and portable, and for many, more effective than the large bulky boxes traditionally used for light therapy. The light has several brightness settings; persons sensitive to light (typical of migraine and head injury) should use with caution.

If distressed by the price (you can also build your own), consider that several years ago these were over $300. Also cheaper than a trip to the lands of the Midnight summer Sun which endures the opposite phenomenon in winter — polar night. During this time, the sun does not rise for weeks or months. In Scandinavia, public light cafes are increasingly popular.

There are different versions of both these devices. Over years and months, popular models go out of production, designs and materials alter, manufacturerers and customer service personnel change for better or worse. Read the reviews for different models and years to find the best for you.

In the dark of winter, a sunrise clock and a dose of morning light can make your whole day amazingly better.