Category Archives: Science Communication

Wired and Tired: Detrimental Effects of Blue Light on Sleep

You have to wake up early tomorrow, however, you don’t feel tired, so you go on your phone to quickly check Instagram or Facebook and suddenly its 2 or 3 a.m. before you can finally fall asleep. According to the National Sleep Foundation, 95% of people in the U.S. admit to using an electronic device within the hour before slumber. This not only causes you to sleep later, but also substantially lowers the quality of sleep, leaving you feeling tired throughout the day. This can interfere with various aspects of your life including work, school, or driving. Poor sleep has also been linked to obesity, growth hormone imbalance, chronic illness… the list goes on and on.

Brain Activity Credit: Saad Faruque

Using your phone, watching television, or using any electronic device before bed delays the circadian rhythm, which is a 24-hour internal clock that cycles between sleepiness and alertness. Dr. Charles Czeisler from Harvard Medical School showed that daylight helps to keep your body’s circadian rhythm aligned with the environment. Therefore, when exposed to the blue light emitted from these electronic devices, your body perceives it as daylight, and as a result, your body will suppress the secretion of the sleep-inducing hormone melatonin and remain in a state of alertness. This shifts your circadian clock later and later, making it harder and harder for you to fall asleep.

Phone before Sleep Credit: Courtesy Photo

According to researchers at Harvard Medical School, blue light is the most effective at altering the body’s circadian rhythm. However, it was found that other sources of light, such as green light, can also alter the body’s circadian rhythm under certain conditions. This is because the photoreceptor system in the human eye is responsible for resetting the internal circadian body clock through the detection of light. These photoreceptors are very responsive to blue light; however, new research shows that the another set of photoreceptors in the human eye, which are sensitive to green light, also have an impact the internal circadian body clock. The researchers found that when exposed to dim light, green light is equally as effective as blue light in delaying circadian rhythm, however, the effects of green light die off more quickly and hence blue light suppresses melatonin for about twice as long as green light.

Morning Alarm Credit: Pixabay

To conclude, blue light exposure before bedtime can negatively harm your sleep and health by being physiologically and psychologically stimulating. So next time you are lying in bed and can’t fall asleep you should think twice about checking your phone.

-Jonathan Raj

The New and Improved Kilogram

How do we know how much anything weighs? Where does the measurement come from when you use the kitchen scale or the scale in your physics lab? Since 1879, the sole definition of the kilogram was carefully locked away in an underground vault in France, the International Prototype Kilogram (IPK). Starting May of 2019, this tightly stored piece  of platinum and iridium will no longer officially represent the mass of a kilogram. This renewed definition will be more accessible to everyone and remain accurate for the rest of time, demonstrating the importance of this change.The kilogram is one of the base units as part of the International System of Units (SI).

The International Prototype Kilogram, or Le Grand K informally, is the only physical artifact that determines the official mass of one kilogram. However, since it is stowed away under careful protection by the International Committee for Weights and Measures (ICWM). It is hardly accessible and any changes in mass due to scratches or dirt would change the official mass of the kilogram. Even copies made of Le Grand K may not always be exactly accurate.

This prompted the change by the ICWM to a much more accessible and unchanging value based on a fundamental constant, the Planck’s constant. Planck’s constant, or h, like all other fundamental constants of nature remain the same with time and throughout the universe. Planck’s constant relates the smallest energy packet possible to the frequency of that energy packet, and is defined to be 6.626176 x 10^(-34) kilogram meter squared per second. With the kilogram within this constant, the determination of the kilogram can be made much more precisely without needing to compare it with the actual IPK.

To determine the mass with the new definition, a Kibble balance can be used. The Kibble balance is able to weigh mass against an electromagnetic current, making it incredibly accurate and precise.

Shown below is a video from Veritasium working with NIST (National Institute of Standards and Technology) explaining the new changes for the kilogram and how a kibble balance is used to determine the mass:

For the common household scale, or even anything beyond advanced physics, the new definition of the kilogram will not cause any change in mass. However over time, the required precision for mass in all fields of science will benefit from this change. The importance for consistent and precise measurements in all of science and business are seen.

— Christy Lau