OTHER CONCEPTS | SUNLIGHT

S U N L I G H T

Ever wondered if the distance between Earth and the Sun is the true cause of seasons?

Well, many may already know that the statement above is FALSE... Up to a point...

The cause of seasons big player is the Earth's axial tilt, however, it adds up that global temperature change is influenced by that 3.3% change in sunlight irradiation of our blue marble(+3,3% january / -3,3% july).

In terms of energy, sunlight at Earth's surface is around 52 to 55 percent infrared (above 700 nm), 42 to 43 percent visible (400 to 700 nm), and 3 to 5 percent ultraviolet (below 400 nm). At the top of the atmosphere, sunlight is about 30% more intense, having about 8% ultraviolet (UV), with most of the extra UV consisting of biologically damaging short-wave ultraviolet.

 This image is 1000px wide and ports the approximate proportion of sunlight output

Now, this can play a hella big role on starbuilding, here is why:

The peak emission our star is around green light, as far as we know our plants and other photo-synthetic life reflects those peak wavelengths for protection from overexposure to high-energy light.

Since humans and other species are quite more sensible to green tones, not only due to our environmental agents like camouflage of harmful snakes and insects, but due to a greater potential of acquiring visual data.

If your ambient light is reddish, it makes more sense that animals would learn to differ more shades of red than other non-existent colors like blue.

Now pack that to a larger scale, and we will see that almost all alien species with eyes that are similarly to ours, which developed within fairly different sunlight color and environmental biology, will have a certain degree of red/blue shifted Daltonism.

Picture a Kardashev II civilization arriving at a human settlement in huge dark ships with red lights all over its inferior hull, but despite that bad connotation red and black together have for the overall human population, their intent is purely pacific and their use of that look is just the way they were conceived to see near infrared light, making the ship visibly dark, makes it kind of gray-white to infrared light, which also explains the red lights under the hull, the same way it wouldn't make sense to use far UV in our car lights, aliens that see infrared wouldn't se any sense in using green or blues which are probably invisible to their biology born around a red dwarf/giant star emitting near infrared peaks.

It is also interesting to see how species born to see a certain degree of UV wouldn't be a good ground trooper in any interplanetary wars, since UV light scatter more in the atmosphere in ways that the air looks always foggy, reducing visibility down to a few hundred meters, their civilization might also use a lot of visible light in their communication technology, the same way we use Bluetooth and radio wavelengths.

We can define if our star emits decent amounts of ultraviolet and visible light and define its overall brightness.

Use a blackbody calculator to range your emission model.

Configurations:

Temperature = Temp. of your star, above choose Kelvin, Fahrenheit or Celsius scale.

Emissivity = Lum. of your star.

Wavelength = Insert a given wavelength and it outputs Spectral Radiance on the side box.

Lower Limit = 0,1 µm (shows most of ultraviolet)

Upper Limit = 3~5  µm (shows most of infrared)

Press CALCULATE.

For Vol, we have that the peak emission occurs at 493nm which is roughly this COLOR, while our Sun peaks at 500nm which is ~ this COLOR.

Sun model BLACK line; Vol model RED line

By tweaking the LOWER and UPPER LIMIT, we can isolate each band of the emission spectrum and calculate how much of each our star outputs.

For Ultraviolet we can plot from X-Ray (0.001µm) to Violet (0.385µm).

For Visible light, close in between 0.385µm and 0.750µm.

For Infrared, go from 0.750µm up to 50µm.

On the side where is written RESULTS, look for RADIANCE, thats the total output of the blackbody, now taking that as 100%, look down and compare with BAND RADIANCE.

The given value is your emission proportion. 

For Vol, we have:

UV = ~11,2%

VIS = ~43,7%

IR =  ~45%

This sum up to 99,2%, we can assume that its missing 0,8% are in the far radio and gamma-ray bands...

OKAY, guess it is up to you now what to do with this information, it literally is a building block for whatever biology you wanna build, if you star supposedly emits way more UV than our Sun in a way that colonists have to wear their vehicles with black-tinted windows and such or your small red dwarf outputs a microwave pulse as a lighthouse because someone had build a dyson sphere around it, ya already know what to look for here...

- M. O. Valent, 10/06/2019