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World's End

Discussion in 'World Building' started by v_legolas_gleaf, Sep 16, 2019.

  1. v_legolas_gleaf

    v_legolas_gleaf Scribe

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    I have a question for the community:

    Let's say that we have a planet, very much like the earth (tilted at 23.5 degrees) and its sun (a normal yellow star). The planet is populated by normal human beings or human-like beings who have been living on its surface for countless years (say 2-3 billions).

    Now let's suppose (by whatever magic mechanism) that a thin translucent and indestructible veil has suddenly started drawing over the sun. Since it is a big star, it will take time to cover the entire sun but let us suppose that the star is covered entirely in a 360 degrees direction in about 6 weeks' time. (The planet orbiting the star is untouched and unharmed and it continues to rotate and orbit the star.)

    Also, let us suppose that this veil lets out as much light as you would see on a cloudy day when the sun is directly overhead at 12 noon. But it also absorbs most of the heat of the sun and transmits to the planet only 25% of the normal heat received by it everyday.


    Now what would happen to the planet (that is very much like the earth) and its population?

    What will the sky look like?

    What will happen to the surface temperature? How long before cold bitter winds blow across all the surface of the planet freezing everything in sight?

    How long before mass extinctions start to happen?
     
  2. Yora

    Yora Sage

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    I think the easiest way to approach this is to treat the star as if its overall temperature went down. I believe various different gasses and dusts could have quite different effects on what frequencies of light get blocked and at what intensities.

    It should actually be quite easy to determine the temperature that would lead to only 25% of energy reaching the planet, and then finding the coresponding color and brightness of visible light. I could try to look into that later.

    My initial guess would be that daylight on a sunny day would look quite similar to late afternoon in summer.

    The temperature would fall massively, though I don't know how fast. Based on numbers I've seen for the sun completely disappearing, I would assume a global ice age in 2 or 3 years.

    I am not sure how much plant growth would be affected in the first year. I think sunlight is not usually the main bottleneck when it comes to growth, and with evaporation decreasing hugely almost instantly, the sky would be cloud free on most days. So getting full sunlight even at just 25% might be enough for plants. But decreased evaporation means massive draught. Depending on where the change falls in the growing season, the last harvest might still be pretty normal if it comes late, or fail completely if it comes very early.
    I would assume that within a year most rivers would dry up almost completely. There is barely any rain at all, and there won't be any snowmelt or glacier runoff in the mountains. Frozen lakes with no runoff would last basically forever, though.
     
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  3. v_legolas_gleaf

    v_legolas_gleaf Scribe

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    Thank you! Loved the answer! Just what I was looking for! :):happy::joyful:
     
  4. v_legolas_gleaf

    v_legolas_gleaf Scribe

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    Bump!

    Can anyone else reply to this thread? Open to more ideas!
     
  5. CupofJoe

    CupofJoe Myth Weaver

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    I would have thought that heat and light are the same thing. It is all radiation from the sun. Your star-veil would have to have a very specific wavelength gate to knock out non-visible light so completely but leave some visible light.
    I might stretch Yora's timeline a little but it would still be in the few years range.
    I'd look at impact or nuclear winters. Their source is terrestrial but the effects are global and along the lines of what you are asking about.
     
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  6. FifthView

    FifthView Istar

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    You can find videos on YouTube exploring what would happen if the sun completely disappeared. I was shocked when I first watched them. Turns out, we'd probably be fine for a few months—with no sun at all!—but by the end of the year, the surface of the planet would be frozen over. We'd need to live underground, nearer the Earth's core which would be providing heat. Amazingly, liquid water would continue to exist for billions of years at the bottom of the ocean, under a shell of ice, thanks to the heat the Earth's core produces. Very small organisms would also continue to exist, especially near thermal vents. But plant life and animal life would largely disappear everywhere else.

    But that's with no sun. Here's an interesting article comparing sunlight on Earth vs sunlight on Mars: Sunlight on Mars - Is There Enough Light on Mars to Grow Tomatoes? : Tomatosphere - First the Seed Foundation. At the surfaces, Mars receives slightly more than half the sun's energy that Earth receives. But lots of factors should be taken into account. Those measurements are for the surface of the planet when the sun is at high noon on either; if the light is coming in at an angle, for instance at different latitudes, it's going to be less. There are places on Earth that receive about as much direct energy from the sun as Mars receives at noon.

    Additionally, the planet's albedo and composition of the atmosphere make a huge difference. Here's another interesting article if you feel like using some math: Calculating Planetary Energy Balance & Temperature | UCAR Center for Science Education. The equations there can be used for any planet or moon anywhere in the universe. Using those equations, Earth's average temperature would be below the freezing point of water; Earth, right now, would be an ice world. But Earth's atmosphere traps a lot of the energy it receives from the sun. The actual average temperature is above the predicted temperature by about 34° C (60° F), thanks to our atmosphere.

    Now...how does all this help you? :sneaky:

    I think YoraYora gave a pretty good response already. I also think that the effects on our atmosphere and on the albedo of our planet in your scenario are a good place to begin.

    Any increase in surface ice would lead to a higher albedo for our planet, which in turn would mean more sunlight (energy) is reflected back into space, and this can be a reinforcing loop.

    You might also take a look at how the Little Ice Age occurred. I think there are two competing theories. Volcanic activity seems to be the dominant theory right now: increased particulates caused an initial cooldown, and sulphuric acids high in our atmosphere blocked more of the incoming solar radiation. Others think that a reduction in solar activity caused the Little Ice Age; however the drop in temperatures on Earth can't be explained entirely by the level of reduction in solar activity. Maybe it was a combination of these. Either way, the effects were rather quick, and in Europe there were droughts and famines and even destruction of farmland due to encroaching glaciers in the farthest north. But here's the kicker: the average global drop in temperature was only a couple or three degrees. Much less than in your scenario.
     
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  7. Darkfantasy

    Darkfantasy Sage

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    I am crap at this stuff because my simple brain can't grasp Science and Physics in a big no no.

    But something very similar happened after the asteroid hit that killed all the dinosaurs. A cloud of dust encircled the planet, blocking out the sun. There are a few documentaries and articles on it that I read years ago when I was writing something similar to what you've described above. Maybe look to real life events that mimic this for your answers?
     
  8. A. E. Lowan

    A. E. Lowan Staff Leadership

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    What you're describing sounds like much the same phenomenon that caused the Little Ice Age. Little Ice Age - Wikipedia It didn't cause a mass extinction, but it did cause crop failures and widespread famine and disease.
     
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  9. v_legolas_gleaf

    v_legolas_gleaf Scribe

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    I heard that scientists found evidence recently that there wasn't any asteroid impact that killed the dinosaurs but that there were multiple volcanoes and earthquakes which led to rapid climate change. Possibly the same thing you described happened, a cloud of dust encircled the planet blocking out the sun.

    What do you think?
     
  10. Yora

    Yora Sage

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    The idea has been around for a long time that it wasn't just any single event. The massed disappearance of species had already been going on for thousands of years. It's not something that happened in one or two years. There are many indications that the world had already been going through severe changes that many species were not able to adapt to, and that asteroid happened to come at a really bad moment when dinosaurs as a whole were already struggling.
    An asteroid impact on that scale probably wouldn't have been that devastating on a global scale, but when you're already struggling badly, it can be the final push to make the world uninhabitable for large reptiles.
     
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  11. Darkfantasy

    Darkfantasy Sage

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    Possible for the dinosaurs, but there was an asteroid impact because the found the crash site. It must have been a sudden event because of the KT Boundary showing it was a fast wipe out - but fast in Science terms can mean 10 millions years lol. There's aksi the theory of illnesses. I don't know if this would work for your book. As volcanoes give of toxic gases when they go "pop".
     
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  12. v_legolas_gleaf

    v_legolas_gleaf Scribe

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    Interesting....
     
  13. v_legolas_gleaf

    v_legolas_gleaf Scribe

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    Oh nothing soooo dramatic! :D

    I got lots of info that I could use so... great! :LOL:
     
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  14. Yora

    Yora Sage

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    The best idea is usually to decide what your end result should be and then not mentioning what specific circumstances caused it.

    Doing some basic research on what things are conected in which ways is always smart to make things seem somewhat plausible, but I think it's always best not to mention anything specific.

    The more specific you get, the greater audiences' expectations will be that it's scientifically sound. Be more vague and they are happy not to poke at it. It also gets you a setting that fits your story, and doesn't demand your story to bend over to fit the setting.
     
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