Lights Affecting SleepSleep has been connected to the grades of students. One in every four U.S. high school students admits to falling asleep in class at least once every week. As a result, research has shown that those that do poorly in class don’t have much sleep. Not having enough sleep is common within the United States for students, because almost all schools begin early in the morning and many of these students either due to the delayed sleep phase syndrome or choose to stay up all night. We generally need most light in the morning and during the day, less in the evening, and the least possible at night. Ideally, this implies getting outside as much as possible during the daytime, along with improved 24 hour control of indoor lighting systems, so that we sleep better and wake up refreshed. In our modern society, many of us are sleep deprived. Instead of the eight hours a night that a lot of us need, we now get an average of around six and a half. That is just not enough. Tiredness is linked to a huge number of psychological effects: stress and mistakes as well as poor judgment, memory, concentration, attention, and creativity. There are also links with medical effects: excessive use of drugs and stimulants, obesity, lower immunity and even increased rates of type-2 diabetes, cardiovascular disease, and cancer. Due to the invention of the electric lightbulb in the late 19th century, we are now exposed to much more light at night than we had been exposed to throughout our evolution. This relatively new pattern of light exposure is almost certain to have affected our patterns of sleep. Exposure to light in the late evening tends to delay the phase of our internal clock and lead us to prefer later sleep times. Exposure to light in the middle of the night can have more unpredictable effects, but can certainly be enough to cause our internal clock to be reset, and may make it difficult to return to sleep. People that have lived during the Industrial Age, before artificial lights, slept very differently from the way we sleep today. When artificial light is taken away, humans tend to revert back to this natural, two shift sleep pattern.Light is one of the most important external factors that can affect sleep. It does so both directly, by making it difficult for people to fall asleep, and indirectly, by influencing the timing of our internal clock and thereby affecting our preferred time to go to sleep. Light also has a profound effect on sleep, which the absence of light sends a signal to the body that it is time to sleep. Light exposure at the wrong times alters the body’s internal sleep clock in ways that interfere with both the quantity and quality of sleep. Light influences our internal clock through specialized light-sensitive cells in the retina of our eyes. These cells, which occupy the same space as the rods and cones that make vision possible, tell the brain whether it is daytime or nighttime, and our sleep patterns are set accordingly. Melatonin, a hormone produced in the brain’s pineal gland, influences sleep by sending a signal to the brain that it is time for rest. This signal helps initiate the body’s physiological preparations for sleep such as muscles begin to relax, increase of drowsiness, and temperature of body drops. Melatonin levels naturally rise during the early evening as darkness falls and continue to climb throughout most of the night, before peaking at approximately 3 a.m. Levels of melatonin then fall during the early morning and remain low during much of the day. Evening light exposure inhibits the naturally timed rise of melatonin, which delays the onset of the body’s transition to sleep and sleeps itself.Sunlight detected by cells in the retina of the eye sends messages to the brain that keep us in a roughly 24-hour pattern. These light cues trigger all kinds of chemical events in the body, causing changes in our physiology and behavior. For example, as evening approaches and the light in our environment dwindles, the hormone melatonin begins to rise and body temperature falls, both of which help us to become less alert and more likely to welcome sleep. With the help of morning light, melatonin levels are low, body temperature begins to rise, and other chemical shifts, such as a small increase in the activating hormone cortisol, occur to help us feel alert and ready for the day.Light particles strike when light enters the eye, which thereby stimulates the retinal cells, like cone cells, rods cell, and retinal ganglion cells. The cone cell is responsible for the color perception. The rod cell is responsible for the perception of motion and vision in dim light settings.Finally, the retinal ganglion cell receives signals from the cones and rods and then projects it into the brain.There are many colors that can affect sleep and some that don’t. Some colors like violet lights, around 380 nanometers to 400 nanometers, is not effective as much as blue light since it contains red in the mixture which will still make the body respond by being more alert and awake. Research has found that exposure to blue light suppresses the production of melatonin more than any other type of light. It is believed that the shorter wavelengths in blue light, around 400 nanometers (nm) to 500 nanometers, are what causes the body to produce less melatonin because the body is more sensitive to this type of light. Green light, around 500 nanometers to 530 nanometers, contains a lot of blue light which will have the body respond by producing more alert and awake feeling. Yellow light only produces long wavelength light around 530 nanometers to 600 nanometers, which shows that a study from the New York Times show that a parent replaces their regular light bulbs to yellow light bulbs, and has said, ” I transformed the bedrooms in my home into warm, cozy cocoons of yellow glowing light. Although the mood has done nothing to convince the children that their beds are not trampolines, they do seem to drift off to sleep faster.” Orange light only produces long wavelength light, around 600 nanometers to 640 nanometers, free from the blue wavelengths that can disrupt sleep. Studies suggest that the use of orange light can result in 90 minutes of increased melatonin production and up to an hour more sleep per night. While red is a long wavelength light that has been shown less disruptive to sleep than other light wavelengths, around 640 nanometers to 750 nanometers.