Think back to your last video conference. How many people looked unnatural or had weird lighting? With everyone in various circumstances at their home, there is a large variation of video quality. One common feature is the bluish tinge on people's faces. Without a sufficiently strong alternative light source, the light from your computer screen will make you look a little blue.
Science of colour
Let's examine how we see colour. Light from a source (newsflash - you cannot see in the dark) will hit an object and excite its electrons. These electrons can give off light, reflect it, or convert it to heat by knocking into an adjacent atom1. Depending on the atomic and molecular structure of the object, different wavelengths will get absorbed by the object. An apple will look red because its skin absorbs all frequencies of visible light except red. Light can also scatter within a material. If you shine a flashlight through your fingertip, it will look red because the blue lights tend to scatter more than red in your skin and fat tissues.
But your face is normally not blue (if it is, stop reading this and call a doctor). How is it reflecting the blue light from the screen? Looking at the RGB value of your skin in a picture, you will find that it is actually a combination of red, green, and blue – the red and green only have slightly higher values. Given the increased light from the source of shorter, blue wavelengths, the webcam will pick up more blue and reflect that in the video.
How to look human
So how can we avoid looking like our face is severely lacking oxygen2? One simple fix would be to use software like Windows' night light or f.lux to increase the red hue of your screen. A better solution would be to find a warm, diffused source of light and place it in front of you. A warm light source will complement the blue-heavy light from your monitors to get closer to your natural skin tone. If you have an old lamp lying around, placing a piece of paper as diffusion material can work quite well. As a bonus, having more light will improve your webcam quality as more photons will end up on the sensor, making it less grainy. The reason why low light videos and photographs tend to look grainy is that the sensitivity of the sensors or film need to increase to compensate for reduced light which increases noise.
Looking up
One thing you may see when buying light bulbs is its colour temperature3. It is denoted in Kelvin (K) and lights can be seen in warmer (2500~3000 K; incandescent) or cooler (5000+ K; fluorescent) temperatures. For the record, LCD screens are around 6500-9500 K. If you are confused because Kelvin – like Celsius or Fahrenheit – is a measurement of temperature and lower Kelvin is "warmer" light, then you are in good company.
Colour temperature is determined by the temperature of an ideal black-body radiator4 that is emitting that colour. A black body is an ideal object that absorbs all electromagnetic radiation and emits black-body radiation at a range of electromagnetic spectrum determined by only its temperature – think blacksmith working on glowing hot metal. Stars approximate a black-body radiator which gives us a convenient way to measure their temperature. Doing the math, our Sun's effective temperature is approximately 5780 K.
Missing spots
Now we know how hot the Sun is but how do we know what it's made of? In 1868, astronomers found a yellow line in the Sun's spectrum while studying a solar eclipse. Looking at the wavelength of the light, they realized it could not be produced by an element known at the time. They named it helium, after Helios, the Greek god of the Sun. Helium was the first element to be found outside Earth. Besides making your voice sound funny and balloons float, helium is the second most abundant element in the universe next to hydrogen and is chemically inert.
Today, astrophysicists study the night sky with powerful telescopes and look at the observed electromagnetic emission. Looking at any spikes or dips can provide information about the light source or perhaps what is in between us and the light. As mentioned, helium glows in the yellow range while mercury glows blue when excited. Elements also absorb a certain range of the electromagnetic spectrum. Different elements will absorb a different range, leading to a cosmic fingerprint of each star's composition. The Sun's spectrum has been studied in detail5, which provides information about its chemical make-up. This allows astrophysicists to estimate its origins and remaining life span. Luckily, you and I will be long dead before the Sun's nuclear fusion process runs out of steam, both literally and figuratively. It would be rather unpleasant to witness the Sun swell into a red giant and vaporize the Earth.
Conclusion
If this kind of science excites you, Neil deGrasse Tyson's book Astrophysics for People in a Hurry is a pocket-sized primer on various facets of astrophysics that you can read in a weekend. Beyond visible light discussed here, the universe is filled with wonder across the electromagnetic spectrum - from spectacular gamma-ray bursts that release as much energy in a few seconds as the Sun will in its entire 10-billion-year lifetime to the cosmic microwave background that permeates the universe and lets us peer into its origins6. Perhaps it is the hubris of humankind that declare a certain range of the electromagnetic spectrum as visible when other species on earth can see outside of this range – both below (infrared) and above (ultraviolet).
It took centuries for scientists to build a telescope outside the visible spectrum, and even that was accidental7. How many opportunities are staring at us in the face but we are simply blind to it? In the famous Müller-Lyer illusion, even if you know that the lines are the same length, your eyes still see them as different lengths. Simply knowing about infrared or radio waves wasn't enough for astronomers to look in the sky for them. In practice, it takes a concerted effort to break out of cognitive biases or blind spots. What opportunities are lurking in your blind spots? What will you do about it?
1Everyday Physics – Why do veins look blue?, March 15, 2015. https://osuwomeninphysics.wordpress.com/2015/03/11/everyday-physics-why-do-veins-look-blue/, accessed December 3, 2020
2What You Should Know About Discoloration of Skin, July 31, 2019. Healthline. https://www.healthline.com/health/skin-discoloration-bluish, accessed December 3, 2020
3Color temperature, (n.d.). In Wikipedia. https://en.wikipedia.org/wiki/Color_temperature, accessed December 3, 2020
4Blackbody radiators, (n.d.). http://dept.harpercollege.edu/chemistry/chm/100/dgodambe/thedisk/spec/blackbod.htm, accessed December 7, 2020
5Sun’s Spectrum, (n.d.). UCAR Center for Science Education. https://scied.ucar.edu/image/sun-spectrum, accessed December 3, 2020
6Although this only takes us to about 380 thousand years after the big bang because the universe was not sufficiently cool to form hydrogen atoms, which would allow photons to pass through without scattering. The reason why they are merely microwaves today is due to an effect called redshift
7Karl Jansky was building a radio receiver for Bell labs and found noise coming from the center of the Milky Way Galaxy