Slashdot Mirror

← Back to Stories (view on slashdot.org)

Nightfall: Can Kalgash Exist?

Posted by timothy on from the burning-questions dept.

First time accepted submitter jIyajbe (662197) writes Two researchers from the Indian Institute of Astrophysics investigate the imaginary world of Kalgash, a planetary system based on the novel 'Nightfall' (Asimov & Silverberg, 1991). From the arXiv paper: "The system consists of a planet, a moon and an astonishing six suns. The six stars cause the wider universe to be invisible to the inhabitants of the planet. The author explores the consequences of an eclipse and the resulting darkness which the Kalgash people experience for the first time. Our task is to verify if this system is feasible, from the duration of the eclipse, the 'invisibility' of the universe to the complex orbital dynamics." Their conclusion? "We have explored several aspects of Asimov's novel. We have found that the suns, especially Dovim are bright enough to blot out the stars. Kalgash 2 can eclipse Dovim for a period of 9 hours. We also tested one possible star configuration and after running some simulations, we found that the system is possible for short periods of time."

15 of 86 comments (clear)

  1. An excellent book... by poptix · · Score: 5, Interesting

    I would recommend this book to anyone, it's an easy read and thought provoking.

    --
    Just because you disagree doesn't mean it's not true.
    1. Re:An excellent book... by dreamchaser · · Score: 4, Insightful

      Anything by Asimov is recommendable.

    2. Re:An excellent book... by Jason+Levine · · Score: 5, Funny

      The short story ends as Nightfall is starting. The book extends past into the nightmare of the stars.

      I remember reading the book once and I was completely absorbed in the story. I finally looked up and noticed it was dusk. For a brief moment, I felt panic rising because the stars were going to come out soon. It took a moment to disentangle myself from the story.

      Being able to completely lose yourself in a book can be a good thing most times - other times, it can backfire.

      --
      My sci-fi novel, Ghost Thief, is now available from Amazon.com.
  2. Re:Beh by war4peace · · Score: 4, Insightful

    The words of a true fanatic.
    Nevermind the work, the science and the data. It's written in a format I dislike.
    *slowclap* well done, sir.

    --
    ...gis sdrawkcab (usually not responding to ACs; don't bother posting as AC)
  3. Stability by Livius · · Score: 5, Insightful

    Asimov's story only assumes that the suns' and planets' orbits are in that configuration for a few tens or maybe hundreds of thousands of years, not that they are stable for what astronomers would call the long term.

    1. Re:Stability by radarskiy · · Score: 3, Interesting

      The story depends on
      a) the cycle repeating enough times that people cans start to figure out that it is repeating
      b) sufficient conditions for life to evolve in the first place

      So if you do not require that the cycle be permanently stable, then you require two different life-supporting configurations and a transition that can also support life.

    2. Re:Stability by dryeo · · Score: 3, Interesting

      Actually the story assumes that Kalgash existed in a stable orbit long enough for technological life to evolve, something that likely takes billions of years with our one example needing a planet that was fairly stable for close to 4.5 billion years.

      --
      https://en.wikipedia.org/wiki/Inverted_totalitarianism
    3. Re:Stability by Artifakt · · Score: 3, Interesting

      That's not as challenging as you seem to think. For Nightfall, you could start with the assumption that there's at least one particularly massive star, not so big as a typical A or O that won't stay on the main sequence long enough for life to evolve, but bigger than our G 2 sun, say a G 4 or 5 or even something in the F series. The other five suns can be much lighter, all the way down to red dwarfs in some cases (and the story seems to describe at least one that is). Those small stars don't have nearly the light output of the bigger one - with the right options, The planet can orbit the main star at a distance quite a bit greater than Earth orbits our sun, and be close to the exact optimum of its "Goldylocks" zone or somewhere on the cool side. Then smaller stars could exist in various configurations, and their output is low enough that if they are at, say 5 x what that planet would call an AU, they would essentially just move the planet's climate a bit towards the inner edge of the "goldylocks" range. So long as they don't nudge it completely into the hot zone, why wouldn't life cope? (Note that we are talking about their light ouput raising the planet's temperature, not them gravitationally nudgeing the planet about - gravity and how stable the planet's orbit can be if the orbits of the suns themselves are changing, that's a seperate question) Fictional Kalgash would have to orbit the biggest sun of the group and it would have to count as being near the cooler edge of the life bearing zone before you figure in the other stars, but even before the lesser suns temporarily shift into a quasi-stable configuration that prevents night from occuring except once every several thousand years or whatever, there would be various configurations that would make night a very short lived or rare and irregular thing, and life would be used to that. There are other issues, such as how do plants dispose of waste products on Nightfall world, but those issues don't vary much if there's a short night every few months or only in a thousand years - plants would have to adapt for situations much less prolonged than the current one. If we call the Nightfall orbits "perfect", then even very imperfect multi-star systems would find life constantly facing this problem.I'm thinking that by your argument, it's all too easy to say things such as "Life in Binary systems? Impossible!," and even "Life when the day lasts more than 24 hours 17 minutes? Absurd!", and things like that. I'll refrain from quiting Jeff Goldblum at this point, but hope you will consider this.
              Then there's the question of how sensitive to light the natives eyes are. If nights have always been at least short and irregular for much longer than the perfect situation has existed, we should expect the natives to not have very good night vision, as there's less demand to evolve it, so talking about relative optical wavelength outputs and such is very hard to do meaningfully.I'm not sure how we could criticise the work as SF on that basis.

      --
      Who is John Cabal?
  4. Re:fundementally impossible by jeffb+(2.718) · · Score: 5, Interesting

    Epsilon Lyrae, and the vast number of amateur astronomers who've known about it for ages, would beg to differ. Two components that are naked-eye visible, one a double, one a triple. All gravitationally bound, and apparently quite dynamically stable. Five other nearby stars may be gravitationally bound to the system as well.

    Castor (Alpha Geminorum) is a sextuple system.

    But, of course:

    "It's simply not possible for a system like this to exist. If you point out that systems like this do exist, it doesn't mean that my statement is wrong, it means that you're a wack job, so just shut up."

    Bravo, good AC. Bravo.

  5. Re:As always, Asimov got it right way back then by I'm+New+Around+Here · · Score: 3, Informative

    And a physics professor. He knew how to plan the science in his science fiction.

    Also, he is one of my two favorite authors. It's him for science fiction, and Piers Anthony for fantasy.

    --
    If you think I voted for Trump because of this post, you're wrong. I voted for Dr. Jill Stein of the Green Party. Again.
  6. Re:fundementally impossible by meerling · · Score: 3, Interesting

    The article actually stated that it was only stable on the short term.
    It also seemed pretty obvious to me that the writer wasn't trying to "prove" that star system configuration existed, just that despite it being highly improbably, an approximation of it potentially could exist, at least for a little while. It's kind of like the idea that you could go buy one random lottery ticket and win the jackpot that drawing. It's possible, but it's a lot more likely that you won't, and there's a distinct chance that nobody will win this week, but that doesn't eliminate the possibility.

  7. Re:As always, Asimov got it right way back then by Anonymous Coward · · Score: 3, Informative

    He was NOT a physics professor at any time during his life -- unless you are trying to count his several nonfiction books on physics as "teaching". His doctorate was in biochemistry, and he served as a NONTEACHING associate professor (and later, a full professor) of biochemistry from 1958 onwards.

  8. Re:fundementally impossible by rpresser · · Score: 3, Insightful

    The problem is not the six suns but the constraints on the planet and moon:

    * that the planet's orbit be stable over thousands of years. Millions or billions, if you want life to evolve.
    * that the moon stay invisible at all times -- never be illuminated enough by any sun to be visible.
    * that the moon be wide enough in angular size to eclipse one sun for over a day!

    If you read this paper, you see they settled on a moon the same mass as Kalgash but with the density of Saturn! How could such a system possibly arise?

  9. Re:As always, Asimov got it right way back then by Culture20 · · Score: 4, Funny

    Biochem is just a specialty of chemistry which is in turn a specialty of physics.

  10. Re:As always, Asimov got it right way back then by AdamStarks · · Score: 4, Funny

    http://xkcd.com/435/