107

One novel solution to this: make the planet infested with a mostly harmless microbe that either inhibits the production of, or simply eats, the specific photopsins (vision pigments) found in the cone cells of the human eye. Photopsins convert light into usable energy (similar to chlorophyll), so it is plausible that a microbe might be to acquire limited ...


89

Obviously, you don't literally mean "will they use the phonemes we put into the English word 'white' to describe the color they see?" Because not even terrestrial humans do that, apart from some of the minority who speak English. So I'm guessing you mean "will an alien that can see color always come to consider the light that they get from their sun to be ...


50

Building on L.Dutch's answer: Even if mirrors are very efficient and reflect 99.9% there still remains that residual .1% of energy they absorb. (almost) All energy is prevented from escaping and thus accumulates inside the sphere. Temperature inside the sphere will rise (quasi) linearly. Ditto for both radiation and solar wind. It is not said if the solar ...


45

While no one has ever turned off the sun, there are some historical reference points. Volcanic Eruption Data Following the May 20, 1883 eruption of the Krakatoa volcano which spewed ash into the air that slightly reduced the amount of sunlight reaching the Earth: Average global temperatures fell by as much as 1.2 degrees Celsius in the year following ...


39

Light emitted from the star would travel until the mirrors and then would be reflected back, bouncing back and forth. Due to enormous scale of the Dyson sphere, you can neglect cavity effects and related wavelenght selection. This would build up energy into the sphere, which can only dissipate through the mirrors. Basically such a configuration would act ...


38

You don't need high tech, or even glass, for light-reduction "glasses". In real life, there are places where bright light is a problem - in snowfields in the north. People find ways to cope. (Picture from a webpage about Inuits)


35

I imagine that army tactics in this world would evolve such that commanders would not put their troops in that situation in the first place - i.e. if they are expecting an attack in the open field from the direction of the rising sun, they have already made a gross tactical blunder. They would choose their time/place of battle such that this simply isn't an ...


32

With current aerial refueling technology, which is capable of refueling some aircraft in the air, one could "easily" keep the sun over the horizon, even near the equator, in a sufficiently fast aircraft. The circumference of the Earth is about 40000 km, so you'd need to go about $\frac{40\,000}{24} = 1667$ km/h to stay ahead of nightfall. That's just over ...


32

A burning Moon does not have enough fuel to sustain life on Earth for more than a few years, and it would have to be so hot it would instantly blow itself apart. Here's the rough calculations. Energy Density This is a problem of energy density, and an important historical one. Before nuclear fusion was discovered, the new science of geology was in ...


30

In one day you would see the full cycle (if you can see it) So if you stand a little distance from a lamp holding a ball at arms length, then turn around, you will see the phases on the ball. This is the same process, you are turning at the same rate as the ball, just as the planets surface and the moon would be. Your small not-too reflective moon might not ...


29

Photosynthesizing plants will have serious troubles and are already well covered by the other answers. But what about other kinds of plants? Life is not limited to using the sun as a power source (it just happens to be most abundant one on earth, so most organisms using it easily outcompete others in ecological niches where sunlight is available) - many ...


28

Others are estimating the results of the temperature change, but I wanted to point out another answer from humanity to the GGs: Do you good guys really need the entire output of the sun? Earth only occupies a circle 0.005 degrees in diameter from the sun. They could capture effectively all of the sun's energy, but leave a tiny pinhole aimed at our planet ...


27

Yes, it is possible, but for a normal travel airplane very hard to accomplish. In a former answer I errornously used an estimate of 24 hours, but as WhatRoughBeast pointed out, the real time is 12 hours (at equinox every latitude day and night are equally long). That is a real challenge. You start at the poles during the equinox in a plane, either with an ...


26

TL;DR you are looking for this image: As you can see, plants depend on those frequencies for photosynthesis. They can absorb some UV light (wavelengths close to 400nm), which we naturally can't see (except for some rare people who have no lens in their eyes), but that's not optimal. Plants living in such a world would evolve different pigments for ...


26

This actually is pretty easy using the similar methods to what you mention. The "sun" is rotating, meaning that if you look up at night when the shaded side is toward you, you can see the inside of the sphere where it is still daylight. You can figure out how long it takes for the sun to rotate once. Lets say 24 hours just for fun. Then you figure out ...


25

Have a companion star that orbits the same star The easiest way to accomplish something like this is to simply have a binary companion star. Here is an answer where I show a stable orbit for a binary companion inside the orbit of a habitable planet. In this scenario, there would be one main sun with a relatively fixed strength. However, there would be a ...


23

The definition of "white" is actually rather tricky. Obviously there is no "white light" in physics. All "white" light is made up of a distribution of photons in different wavelengths. The concept of white is something in the human mind, and as famously shown, its a complicated one: Our concept of white is actually adjusted in real time based on our ...


23

The name of what you and the first answer call "the (sunlight) Equator" is actually the terminator. The terminator is the line that separates the day and night sides of any astronomical body. On an airless place like the Moon the terminator is clear-cut, while on a body with an atmosphere, like Earth, it's fuzzy. Even on a tidally-locked planet the ...


23

Not all plants photosynthetise. About 1% of all angiosperms are freeloaders. Your plants might have evolved from regular photosynthetizing plants from back when the planet was not tidally locked. Millions of years in the eternal dark will have caused the ones on the dark side to evolve an absence of chlorophyll. Such plants may thrive by parasiting fungi ...


21

The sunlight equator, sort of First off, let be sure to distinguish between the sunlight equator that you are talking about, and the planetary equator that we have on our planet. The Earth is already at a distance that supports an optimum average temperature for life (~14 C). Therefore, if you keep the Earth the same distance from the sun, but make it ...


20

If the ambient light were to be a bright, bright yellow, it would wash everything out, and the human eye would quickly adjust to seeing it as black & white, or at least black & yellow. There's not much you could do about interior environments though if they were shaded from this yellow lighting, unless you found a way to get the light inside every ...


19

Physical health Sunlight is popularly regarded as beneficial due to the production of vitamin D, but also popularly regarded as non essential since vitamin D can also be gained from diet or supplements. However, the process of producing vitamin D uses up specific raw materials. Those materials, if not used up to make vitamin D, are instead used to make a ...


19

Give them a taste of their own medicine! Of course it is not the most proper answer to the OP, but it could be an interesting countermeasure. Attacked soldiers have a mirror (or a patch of very shiny metal) embedded on their helm, just above the forebrow and/or in their shield. By adequately shaping the mirror, it would reflect the light from the low sun ...


18

We could manage for a few days at least without too many bad effects. What we're dealing with here, essentially, is a planetwide long night; we don't get any direct energy from the sun at night and the amount of heat that bleeds over from the day side is basically insignificant. It would take about a week for the global average temperature to drop below ...


18

Well for starters there are diseases that get nick named 'Vampire Disease'. Porphyria being the most well known. The actual disease of allergy to Ultraviolet Radiation is called Solar Urticaria, and is pretty rare. I have this disease myself and while it is horrible, it's not life threatening. Most of the 'historical' reasons for why Vampires burst into ...


18

Rituals calling upon the hidden world. https://party.lovetoknow.com/party-supplies/how-should-i-decorate-my-backyard-black-light-rave-party Many naturally occurring minerals fluoresce in UV and these could be used to make pigments. Ultraviolet lighting without the rest of the spectrum shows things that cannot be seen otherwise - the unseen world that ...


17

Your world has a very long rotational cycle Consider our moon. It rotates about its axis remarkably slowly, taking around 28 days to complete one full day/night cycle. That means 336-hour days and 336-hour nights; dawn becomes a big event, a time of celebration and renewal, a time for weddings and preparations for the day ahead. Sunset becomes a dark and ...


17

UV light can be used to disinfect water, whether this is something a developing society would notice or not is questionable but if they noticed making their wells out of 'tan stone' stopped them getting cholera that would be good. they are actually explosive if I read you right? 'More surface area means more light' so grind them up into high surface area ...


16

They won't call it white, but they will likely see white, -ish. First, 'white' is just a word it has no intrinsic meaning. Second Our colors or lack thereof is an artifact of how we see light, which wavelength sensitivities we have. And more importantly how our brains interpret available light. Our star is a white star but through the atmosphere it has a ...


15

And now, to do away with pointless talk and actually do some science. Theoretical body which absorbs all the light is called black body, theoretical body which doesn't absorb all the light but absorption efficiency doesn't depend on wavelength is called grey body. Object for which absorption depends on wavelength is called coloured body. Curious property ...


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