Visible light is peculiar. The human eye can distinguish between approximately one million unique colors, and yet none of these colors can be objectively distinguished with words. As English speakers we may treat green and blue and black as unique color concepts; but in Chinese the word 青 (qīng) can traditionally refer to hues falling under any of those three English categories, while in Irish there’s a distinction between dubh (“black”), glas (“light green, grey, or blue”), and gorm (“dark/deep blue, green, or grey”), and uaine (“bright/deep green”).
This means that from a scientific perspective, colors are best spoken of in terms of their electromagnetic frequencies or wavelengths. Red light has the lowest frequencies on the visible spectrum, and violet light has the highest. Scientists have been able to deduce that in clear air, higher-frequency light waves scatter more, so this is why the sky looks blue at most times of day or during twilight. It only takes on fiery colors during sunrise and sunset because the sun’s low angle sends its light through thicker atmospheric haze, altering the usual scattering effect.
Scattering is just one of light’s behaviors that we can measure, too. There are also behaviors like:
- Refraction – When light (or any waveform) passes between one material and another, this changes the angle of the light’s movement. A classic example of refraction is how objects placed in a glass of water, like a drinking straw, will appear oddly bent beneath the water’s surface. The degree of refractive “bendiness” in a material is known as the refractive index, and this can be calculated by dividing c (the speed of light in a vacuum, 299,792,458 m/s) by the light wave’s phase velocity. Refractive index actually underlies how scattering works, as well as the other two behaviors below.
- Reflection – When a ray of light hits the right material, generally something as smooth as a mirror, the light is bounced back at the same angle. If the material is too rough, the light won’t bounce as well, and some wavelengths may be absorbed by compounds in the given object’s surface; but other wavelengths will at least bounce back enough for you see the object in the first place. Those unabsorbed wavelengths will register in your own vision as the object’s color.
- Dispersion – Although the speed of light is a numerical constant in the vacuum of outer space, all bets are off under other circumstances! When light passes from one material to the next, its velocity changes. If it reverses direction entirely, that’s another way to understand why reflection happens; but the right material can also split a white light ray into separate colors by slowing down some frequencies more than others. This is the underlying principle behind prisms and the atmospheric moisture that causes rainbows. And frequency differences again explain why in a rainbow, red light is always on the “outer” bend and violet light is on the “inner” bend.
Now that you know some of the precise physics behind visible light, how precise are you feeling on Eyewire? It’s time for Accuracy Happy Hours! All times are EST:
Session 1 – 8:00 AM to 10:00 AM on 2/17
Session 2 – 2:00 PM to 4:00 PM on 2/18
Session 3 – 10:00 PM to midnight on 2/18
HQ will bestow typical Happy Hour bonuses for your work during each of those time frames, but there’s more than that to earn! Check your in-game notifications to see the full accuracy bonus breakdown.
Swag: Most accurate player completing at least 30 cubes wins a notebook, plus a sticker/magnet set! Second and third place will each also win a sticker/magnet set.
Mentors: You are still allowed to mentor people during these time windows. Please just use your best judgment as to whether someone is asking you for basic newbie help vs. trying to have you boost their accuracy on cube after cube.
Scythes: Please avoid scything during these time windows. Even though accuracy for this will be retroactively calculated, we would prefer to go with accuracy based on players’ raw tracing. By the time this challenge is scored, don’t worry, admins will have corrected consensus as needed.