By Tyler Jackson
If you have ever been on a beach at sunset, you may have noticed that crowds gather with quiet reverence to watch the Sun lower in the distance. Interestingly, the quiet reverence may not simply be due to the beauty of the moment, but it might be because at sunset our eyes detect a specific type of sunlight which sets off an array of activity within our bodies that notify all the necessary systems that it is time to sleep. Likewise, at dawn as the Sun rises, this same light, blue light, reaches our eyes. Blue light is an integral part of maintaining our circadian rhythm, but too much of it at the wrong time can cause sleep problems.
According to health.ucdavis.edu, “Blue light is part of the visible light spectrum—what the human eye can see…it has the shortest wavelength and highest energy. About one-third of all visible light is considered high-energy visible, or ‘blue,’ light. Sunlight is the most significant source of blue light. Artificial sources of blue light include fluorescent light, compact fluorescent lightbulbs, LEDs, flat screen LED televisions, computer monitors, smart phones and tablet screens.” In 1981, Dr Charles Czeisler of Harvard Medical School showed that a person’s circadian rhythm is aligned with the environment specifically because of the blue light in daylight, but scientists are now discovering that an excessive amount of artificial sources of blue light contribute to sleep disturbances.
Blue light from the Sun is especially prevalent at dawn and dusk because it emerges when the Sun is 4-8 degrees below the horizon. Without a person knowing it, his or her retina detects these blue light rays, and by way of the optic nerve, it lets the body know that the blue light of dawn has arrived. This causes the production of melatonin to stop, and the body’s systems that were in sleep-mode begin to awaken. Later, as the Sun sets, our eyes take in the blue light again, but this time rather than stopping the production of melatonin, it encourages it, making us ready for sleep.
For centuries, our bodies and our melatonin flowed to the rhythm of the Sun, but the advent of the lightbulb and artificial light complicated our bodies’ relationship with the natural rhythms that regulated our sleep. Bright lights confuse our bodies into thinking it’s time to be awake and we often don’t get the rest our body needs. Researchers have found that bright overhead lights are especially disruptive to our sleep patterns. Lighting placed at a lower height tends to have less impact on our circadian rhythm, and one study showed that using candlelight causes no disruption to our melatonin production. Scientists are still researching and learning about how the blue light emitted from computer screens and smart phones affects our sleep patterns. The current findings suggest that screens are an intense form of blue light and are especially toxic to our circadian rhythm. Studies show that exposure to blue light from artificial light sometimes suppresses the release of melatonin for several hours.
Which ONE sentence below from Passage 2 BEST demonstrates the idea that artificial light may prevent the body’s natural sleep cycle?
“Without a person knowing it, his or her retina detects these blue light rays, and by way of the optic nerve, it lets the body know that the blue light of dawn has arrived.”
“Expose yourself to sunlight often during the day.”
“The current findings suggest that screens are an intense form of blue light and are especially toxic to our circadian rhythm.”
“Sunlight is the most significant source of blue light.”
choose the correct answer
1 answer
The correct answer is:
"The current findings suggest that screens are an intense form of blue light and are especially toxic to our circadian rhythm."
This sentence best demonstrates the idea that artificial light, particularly from screens, may prevent the body's natural sleep cycle.
