[HN Gopher] Apparent size of Andromeda galaxy compared to the Moon
       ___________________________________________________________________
        
       Apparent size of Andromeda galaxy compared to the Moon
        
       Author : sieste
       Score  : 321 points
       Date   : 2022-10-20 22:33 UTC (1 days ago)
        
 (HTM) web link (astronomy.stackexchange.com)
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       | possiblydrunk wrote:
       | Oh man, if only we could see the deep sky like the cameras do
       | (with long exposures/filters/etc). Space looks so underwhelming
       | in comparison with plain human eyesight -- though it's still cool
       | to see the stars from a dark site. Andromeda is a tiny fuzzy
       | smudge in our eyes.
        
         | specialist wrote:
         | I think humans would relate to each other very differently if
         | the stars (Milky Way) were normally visible.
        
         | ISL wrote:
         | _" I saw a star explode and send out the building blocks of the
         | Universe. Other stars, other planets and eventually other life.
         | A supernova! Creation itself! I was there. I wanted to see it
         | and be part of the moment. And you know how I perceived one of
         | the most glorious events in the universe? With these ridiculous
         | gelatinous orbs in my skull! With eyes designed to perceive
         | only a tiny fraction of the EM spectrum. With ears designed
         | only to hear vibrations in the air. ...
         | 
         | I don't want to be human! I want to see gamma rays! I want to
         | hear X-rays! And I want to - I want to smell dark matter! Do
         | you see the absurdity of what I am? I can't even express these
         | things properly because I have to - I have to conceptualize
         | complex ideas in this stupid limiting spoken language! But I
         | know I want to reach out with something other than these
         | prehensile paws! And feel the wind of a supernova flowing over
         | me!"_
        
           | wruza wrote:
           | I relate so much to every bit of it. Being a human is not a
           | blessing, but a curse truly absurd one for a conscious being.
        
           | possiblydrunk wrote:
           | That's beautiful. Forgive my ignorance -- what's that from?
        
             | loganwedwards wrote:
             | Ahh, great quote from Battlestar Galactica.
        
               | aaronbrethorst wrote:
               | Please no one offer any more context! Anything else might
               | end up being a spoiler for folks who haven't had the
               | chance to enjoy it yet :)
        
               | ISL wrote:
               | Precisely why I left it un-referenced :).
        
               | p1esk wrote:
               | Is it a book, or TV show, or?
        
               | simonh wrote:
               | It's from the reboot of the TV show in the early 2000s.
               | An incredible show.
        
               | p1esk wrote:
               | Thanks! Is it similar to Expanse?
        
               | ISL wrote:
               | If you like _anything_ in the spacefaring sci-fi genre
               | and haven 't yet watched the 2000's iteration of
               | Battlestar Galactica, you're in for one hell of a treat.
               | 
               | Be forewarned. It is very difficult to avoid binge-
               | watching the show.
        
               | aaronbrethorst wrote:
               | Looks like you can stream the whole series on Peacock.
               | 
               | Warning! Peacock bizarrely separates the 3 hour long
               | pilot episode (referred to as a 'mini series') from the
               | rest of the series.
               | 
               | Start here: https://www.peacocktv.com/watch-
               | online/tv/battlestar-galacti...
               | 
               | Then go here: https://www.peacocktv.com/watch-
               | online/tv/battlestar-galacti...
        
               | p1esk wrote:
               | I did like Expanse, but I tried to watch a few of the
               | older Star Trek and/or Star Wars movies (don't remember
               | the difference), and I didn't like them at all.
        
               | simonh wrote:
               | It's at the hard sci fi end of the spectrum, compared to
               | Star Trek and Star Wars, but not as hard edged as TE, but
               | get close. They have FTL and artificial gravity, but the
               | space combat portrays pretty decent zero-g manoeuvring
               | and combat tactics. Some of the space battles are among
               | the best ever committed to screen, and the most realistic
               | before TE anyway although some Babylon 5 fans might
               | argue. The CGI was a good generation or two better than
               | B5 though and still looks great.
               | 
               | There is some science fudging for sure, and I have to
               | warn you later on it gets more and more metaphysical and
               | ambiguous. The last season turned some fans off, but it
               | really didn't bother me. I'd have rather is stayed more
               | grounded, but even right to the end the characters and
               | the storytelling carried me through. Some of it's tough
               | watching, a few of the characters really go through the
               | grinder.
               | 
               | I'd highly advise checking some clips on Youtube, and
               | maybe check out the Spacedock channel's analysis of some
               | of the battles.
        
               | andrewprock wrote:
               | Arc fleet ship b
        
               | chrononaut wrote:
               | The first series or the remake?
        
           | RcouF1uZ4gsC wrote:
           | > And feel the wind of a supernova flowing over me!"
           | 
           | The wind of a supernova flowing over you would be the end of
           | you and everything around you.
        
             | simonh wrote:
             | It depends on your physical form and how close you got.
             | With forms like ours yes that's the point he's making. In
             | context it makes sense he's pissed off.
        
             | shagie wrote:
             | Even the neutrinos from a supernova would be enough.
             | https://what-if.xkcd.com/73/
             | 
             | > How close would you have to be to a supernova to get a
             | lethal dose of neutrino radiation?
             | 
             | > The phrase "lethal dose of neutrino radiation" is a weird
             | one. I had to turn it over in my head a few times after I
             | heard it.
        
               | raydiatian wrote:
               | > Only one neutrino will hit you every few years
               | 
               | Ah, the excuse I've been looking for.
               | 
               | "Can't come into work today, was hit by a neutrino this
               | morning. Need to rest up."
        
               | somat wrote:
               | An even better one is proton decay.
               | 
               | Proton decay is theoretically possible but has never been
               | observed. and perhaps somewhere in the vast universe one
               | might have done so... maybe.
               | 
               | So I like to blame it on many of life's unexpected
               | events.
               | 
               | https://en.wikipedia.org/wiki/Proton_decay
        
               | d0mine wrote:
               | "there are about a trillion neutrinos from the Sun
               | passing through it every second."
        
             | ISL wrote:
             | The wind you feel today probably has a meaningful supernova
             | component.
        
             | PhasmaFelis wrote:
             | That's exactly the point, isn't it?
        
         | dreamcompiler wrote:
         | Likewise magnification for bright objects like Saturn. Saturn
         | is usually one of the brightest "stars" in the sky, but it's
         | just a point of light without magnification. Once you add some
         | magnification, it looks like all those photos you've seen of
         | Saturn with the rings. It blows your mind the first time you
         | see it.
        
       | jader201 wrote:
       | It may be obvious and this may be a bit pedantic, but the "actual
       | size" and "size compared to the moon" part is confusing, as
       | comparing the size of two objects is usually comparing two
       | objects at the same scale.
       | 
       | If someone was completely clueless, they would think Andromeda is
       | a teeny tiny galaxy. But it's actually 110,000 light years wide
       | -- quite a bit bigger than the moon. :)
       | 
       | The title show just be something along the lines of "Andromeda in
       | the sky if it were brighter, next to the moon". Or just
       | "Andromeda if it were brighter".
       | 
       | I say this because I've seen other "X compared to Y" articles on
       | HN (one compared planets and the sun to the moon, where the moon
       | was a pixel), and these are all at-scale comparisons. So I was
       | expecting something similar here from the title.
        
         | dylan604 wrote:
         | > as comparing the size of two objects is usually comparing two
         | objects at the same scale.
         | 
         | It is actually quite common to hear that something in the night
         | sky is xFullMoons distant/apart. Of course, that is a relative
         | measurement of area of sky covered from a human's viewpoint
         | while standing on terra firma. It's just a size/distance that
         | is understandable by most people. Telling someone that one
         | object is 3deg from another object means nothing. Knowing that
         | the width of the moon is roughly 0.5deg means that it is the
         | distance of 6 full moons is more relatable. So in this case,
         | the width of the full moon is the scale
         | 
         | Slight tangent, there are other measurements that make things
         | easier to navigate[0]. The width of your index finger ~1deg,
         | the width of 3 fingers ~5deg, the full fist ~10deg, the width
         | of thumb/pinky fully extended ~25deg. Knowing these helps find
         | other objects.
         | 
         | [0]https://www.timeanddate.com/astronomy/measuring-the-sky-
         | by-h...
        
         | unnah wrote:
         | It's even bigger than that: the diameter of the main galactic
         | disk of Andromeda is 152 000 light years. There are additional
         | stars orbiting the galaxy in a halo with a total diameter 220
         | 000 light years.
         | 
         | In comparison, Earth's moon is very much smaller, with a
         | diameter of less than 1 light year.
        
           | jader201 wrote:
           | Yeah, I realized that after it was too late to edit. I posted
           | that after a quick Google search -- I originally had no idea
           | how big it was, but new it was more the 2x the moon :) -- and
           | of course the big "110,000 light years" it returned at the
           | top was the radius, not the diameter.
        
           | santoshalper wrote:
           | For some reason I really enjoy the way you describe the moon
           | as having "a diameter of less than 1 light year.", which is
           | also true of my cat and the shoe I am wearing. And everything
           | else I have ever seen or will experience in my life.
        
         | ronnirradd wrote:
        
         | usrusr wrote:
         | You'd have no trouble understanding that andromeda is a large
         | number of magnitudes bigger than the moon even if your entire
         | astronomical education was from that Star Wars intro scroller.
         | It's a total non-issue.
         | 
         | What I find surprising ( _really_ unexpected!) is how close
         | this  "appears bigger than the moon" observation makes our
         | neighbor galaxy: considerably less than 100 "galaxy diameters"!
         | My intuitive understanding of the vastness of space would have
         | expected far more emptiness. (objectively, that's certainly
         | more than made up by the insane amounts of emptiness we already
         | have within each galaxy, but still, so close!)
        
         | thfuran wrote:
         | Andromeda Galaxy is visible at its actual brightness, but it
         | appears much smaller than in that image because only the
         | central area is bright enough to be seen. Thus the "actual
         | size" part. I don't think anyone was going to demand a 100,000
         | light-year wide image based on that phrasing.
        
         | dang wrote:
         | Ok, we've consed "apparent" onto the title above.
        
           | haimez wrote:
           | Thank you for your cons-cientious moderation!
        
       | bumbledraven wrote:
       | The apparent size of the Andromeda galaxy (M31) is 3.167 square
       | degrees [1], and the angular diameter of Moon ranges from 29.3 to
       | 34.1 arcminutes [2]. Using area = pr2, the apparent size of Moon
       | ranges from 0.1873 to 0.2537 square degrees. Hence M31 should
       | appear to be roughly 12.5 to 16.9 times the size of Moon.
       | 
       | [1] https://en.wikipedia.org/wiki/Andromeda_Galaxy
       | 
       | [2] https://en.wikipedia.org/wiki/Moon
        
         | bumbledraven wrote:
         | I should have mentioned that area = p r2 is only an
         | approximation for the moon's apparent size in square degrees.
         | What we really want to calculate is the surface area of the
         | spherical cap (on a unit sphere) with the same angular diameter
         | as the moon. A formula for that is 2p(1 - cos r) [1], where r
         | again is the radius of the moon in degrees. In this case, the
         | two formulas give the same result to four significant digits
         | (e.g. [2]).
         | 
         | [1] https://en.m.wikipedia.org/wiki/Spherical_cap
         | 
         | [2]
         | http://www.wolframalpha.com/input/?i=2pi%281-cos%5B%2834.1%2...
        
         | [deleted]
        
         | rendall wrote:
         | > _Hence M31 should appear..._
         | 
         | I don't think square degrees should be used here. People don't
         | visually approximate that way when fitting round objects into a
         | space.
         | 
         | Andromeda 3.167deg across its longest length. Moon 0.518deg.
         | That's about 6 moons across the longest length.
         | 
         | Andromeda is 1deg across the shorter axis. Approximately 2
         | moons.
         | 
         | So, _appearing_ about 10-12 moons in area maximum, shaving some
         | off at the corners.
        
       | 8bitsrule wrote:
       | It's too bad it isn't brighter. I managed to see _most_ of it one
       | time when I was in an place with  'good seeing' and a _very_ dark
       | sky (150 miles from the nearest city).
       | 
       | I'd been looking at that part of the sky for a long time, and was
       | astonished that something that big had always been there!
       | 
       | These maps may help you to find the nearest dark spots.
       | 
       | US: https://www.go-astronomy.com/dark-sky-sites.php
       | 
       | World: https://blue-marble.de/nightlights/2019
        
         | ByThyGrace wrote:
         | I would like to know if there's estimates for how long it
         | should be before Andromeda gets near enough to be as visible as
         | the moon in plain daylight. (All else being equal.)
        
       | superposeur wrote:
       | I've heard it said that the angular size of many astronomical
       | targets is not so small -- that the real limit to seeing them is
       | the overall amount of light collected.
       | 
       | But then some basic sense of scale eludes me: 1) isn't most
       | astronomical stuff insanely far away, to the point that it would
       | have to be cosmically large to take up a medium angular size? 2)
       | the angular "real estate" in the sky is severely limited (4pi
       | solid angle) so wouldn't this get quickly used up such that we
       | could only see a small collection of such objects? (Andromeda is
       | already taking up a huge patch of the night sky!)
       | 
       | Of course these are quantitative questions that can be settled by
       | calculation, but does anyone have relevant intuition to offer?
        
       | mandmandam wrote:
       | Aahh, it's coming right at us!!
        
       | ggm wrote:
       | ignoring actual size, what is the APPARENT size of the object
       | from the same observers point of view, if they could "see" all
       | the fainter magnitude stars which make it up?
       | 
       | thats what this shows. the arc of vision the moon covers, against
       | the arc of vision the galaxy covers, for the same observer, if
       | they are drawn "together"
       | 
       | its right there in the title. Apparent size, is about what things
       | "appear" to be to you, the observer.
        
       | javajosh wrote:
       | Just want to point out that it was only about 100 years ago
       | humans discovered that galaxies exist. Good old Edwin Hubble
       | doing observations from Palomar in a Southern California sky that
       | was still good for seeing.
        
         | exitb wrote:
         | To be clear, people have discovered galaxies earlier, but
         | didn't understand their true nature. Hence, the discussed
         | galaxy was first known as "Andromeda Nebula".
        
           | mnw21cam wrote:
           | And anyone to anyone sailing on one of those first ships to
           | Australia, the SMC and LMC would have been _really_ obvious
           | in the sky. Sure, they 're only dwarf galaxies, but still.
        
         | spindle wrote:
         | I believe it was Lemaitre who first discovered that! Just in
         | case it matters.
        
           | djmips wrote:
           | Apparently, there was lively debate prior to it being settle
           | by Lemaitre and Hubble. I like the original name of 'island
           | universes'
           | 
           | https://physicsworld.com/a/shapley-curtis-and-the-island-
           | uni...
        
       | anandrmedia wrote:
       | I got confused with the term "size compared to moon".
        
       | ReptileMan wrote:
       | Begs the question - if everything was brighter what would be the
       | biggest object - excluding solar system and milky way.
       | 
       | Quasar, Pulsars, Filaments...
        
       | tombh wrote:
       | I made that image![1]. And this is not the first time it's been
       | on the front page of HN either[2]. So I'd like to share some
       | context that I've not mentioned elsewhere before.
       | 
       | My father died from alcoholism in 2004. He made his living
       | writing software (hence why I do too, and why I enjoy HN). But he
       | also, for a short time, taught Astronomy evening classes. I've
       | always felt short-changed by the emotional absence and traumatic
       | passing of my male parent. But the continued virality of this
       | image has been some sort of magical glimmer from the depths of
       | the universe that it was still his shoulders that I stood on in
       | order to reach where I am today. Maybe it was the glint in his
       | eyes every time he showed me the latest APOD image[3], and the
       | deep love with which he would explain their contexts. I made this
       | composite image of Andromeda and the moon precisely because of
       | that extra commentary, or rather I should say, extra love, of the
       | night sky that my father gave me. Seeing it here, sparkling in
       | the "night sky" of the HN front page stirs the same kind of
       | wonder I sometimes feel catching those million year old specks of
       | light above my head. Reminding me that though the universe is
       | mostly cold and dark that doesn't diminish its warmth and
       | brightness.
       | 
       | 1.
       | https://www.reddit.com/r/spaceporn/comments/1u0dxs/andromeda...
       | 
       | 2. https://news.ycombinator.com/item?id=22992384
       | 
       | 3. https://apod.nasa.gov/apod/astropix.html
        
         | mythz wrote:
         | touching back story, thanks for sharing.
        
         | [deleted]
        
         | sph wrote:
         | Beautiful (and well written) story, thanks for sharing.
        
         | got2surf wrote:
         | Thank you! For making the image, and sharing story behind it
        
         | dmix wrote:
         | > You should read Nightfall by Isaac Asimov. It's a short story
         | about a planet that has four suns so it is always daytime,
         | except for one night every thousand years.
         | 
         | >> If the stars should appear one night in a thousand years,
         | how would men believe and adore, and preserve for many
         | generations the remembrance of the city of God!
         | 
         | Love that Reddit comment.
         | 
         | https://old.reddit.com/r/spaceporn/comments/1u0dxs/andromeda...
        
           | credit_guy wrote:
           | A bit tangential, but here we go.
           | 
           | A place where there's daytime all the time, except every once
           | in a while is quite close to us. It's the Moon.
           | 
           | If you live on the near side of the Moon, then you always see
           | the Earth hanging there in the sky in the same spot every
           | day. It does not rise and it does not set, it just stays in
           | place. But it goes through phases. New Earth, Crescent Earth,
           | Half Earth, etc.
           | 
           | The Sun does rise and set. A "day" on the moon is half a
           | month long. When the Sun is in the sky, the Earth is at most
           | in "half Earth" phase. When it's nighttime though, the Earth
           | is at least "half Earth".
           | 
           | And seen from the Moon, the Earth is big. Very big. Just take
           | the Andromeda in the picture, and make it a disk. That's how
           | big. (Actually about 15% bigger).
           | 
           | The Earth is also bright. Much brighter than we see the Moon
           | on a bright night. Earth's albedo is about 3 times higher
           | than Moon's. All in all, at "full Earth", you would receive
           | about 40 times more light that we get here from the Moon when
           | it's full.
           | 
           | In other words, when the Sun is not in the sky, you get
           | enough light from the Earth to see around. The closer to
           | "midnight" the more light you get, because the Earth is
           | closer to "full Earth" phase.
           | 
           | Of course, when you have a solar eclipse, you stop seeing
           | light from either the Sun or the Earth. Here on Earth, solar
           | eclipses are quite short. The moment of full eclipse is
           | fleeting, generally it's 3 minutes or less. On the Moon,
           | because the Earth is so much bigger in the sky, the eclipse
           | is long. Of course, we knew that from here: when it's a solar
           | eclipse on the Moon, it's a lunar eclipse on Earth, and that
           | takes hours.
           | 
           | It's not completely dark on the Moon when there's a solar
           | eclipse.
           | 
           | It's not completely dark here either. Because of the Sun's
           | corona. The apparent diameter of the sun is virtually
           | identical with the diameter of the Moon as seen from the
           | Earth, but the Sun's corona extends a bit further, so we get
           | to see it during total eclipse.
           | 
           | But on the Moon, the Earth is so large that the Sun and the
           | corona are fully obscured during total solar eclipse. What
           | you will see instead is the Earth atmosphere. Very thin,
           | impossibly thin, you will not be able to perceive its
           | thikness. It will just look like a one-dimensional line. A
           | part of it will be very, very bright. And very red. It will
           | be a very bright, very large and very red circle in the sky.
           | 
           | You will also see the inner planets, Mercury and Venus.
           | Normally you can't see them on the Moon, but during a full
           | solar eclipse they'll be quite close to that bright circle,
           | and they'll be very bright themselves.
           | 
           | And what a glory the Milky Way will be at that time. And if
           | you are lucky, you'll see that very oblong shape that's the
           | Andromeda. Somewhat faint, but still, much brighter than any
           | of us here on Earth would perceive it.
        
           | Someone wrote:
           | > a planet that has four suns
           | 
           | I remembered five; Wikipedia says six, two of which form a
           | binary star system (https://en.wikipedia.org/wiki/Nightfall_(
           | Asimov_novelette_an...)
           | 
           | I also remember reading that such a system can exist, but
           | can't find a reference. It's probably not that surprising,
           | though, given that the proposed system has one large star and
           | five minor ones, making it similar to a system with one star
           | and five giant planets. Putting a planet in in such a way
           | that it only has a night every 2000 years may be the only
           | tricky part (giving it a much smaller orbit than the minor
           | stars would help avoiding nights, but giving it a single moon
           | that can cause nights once every 2000 years?)
        
           | btilly wrote:
           | And sadly with 4 suns the orbit would be chaotic and no
           | periodic pattern would exist to be found. Which ruins the
           | premise of the story.
           | 
           | Foundation also fails because human society is chaotic so his
           | psychohistory would never work.
        
             | adrianN wrote:
             | It's called science _fiction_ for a reason ;)
        
               | polycaster wrote:
               | Sure, but the _science_ is also there for a reason
        
             | AnIdiotOnTheNet wrote:
             | This is lampshaded a bit in the novel length version of the
             | story, where the theory of universal gravitation was
             | invented only recently because the complexity of motion of
             | the bodies involved made it incredibly non-obvious.
             | 
             | Also, there are _six_ suns.
        
             | xupybd wrote:
             | Sometimes it's best just to enjoy the fiction and not over
             | think it too much. I think you have to give them some
             | artistic license.
        
               | btilly wrote:
               | He wrote both before there was general public awareness
               | that a thing called chaos existed.
               | 
               | True, Poincare had already worked out that gravity was
               | chaotic. But Asimov was a chemist and so was unlikely to
               | be familiar with that work.
        
               | Gordonjcp wrote:
               | I suspect that Asimov was a better physicist than you.
        
               | loonster wrote:
               | Someone can be both a better physicist and have a poorer
               | understanding of physics. We have the luxury of time. We
               | can learn about the great discoveries that the great
               | physicist developed from scratch. Just imagine the type
               | of discoveries he would have made if he was born in the
               | late 20th century.
        
               | Gordonjcp wrote:
               | Probably less than he did in this reality.
               | 
               | We haven't discovered much, really.
        
               | btilly wrote:
               | Relevant to this discussion is that between then and now
               | we have discovered a lot about the ubiquity of chaotic
               | systems, and their practical consequences for
               | forecasting.
        
               | Gordonjcp wrote:
               | Chaotic systems were well-known and had been studied in
               | great detail before Asimov was born. He knew about
               | chaotic systems, as anyone with a high-school level
               | mathematics or physics education would have.
        
               | kwhitefoot wrote:
               | > Asimov was a chemist and so was unlikely to be familiar
               | with that work.
               | 
               | The premise is true but the conclusion does not follow.
               | Asimov was one of the most prolific authors of popular
               | science books including astronomy, cosmology, physics,
               | etc. It's entirely plausible that he was familiar with
               | chaos.
        
               | btilly wrote:
               | When the book was written in 1941, he was a graduate
               | student. His attempts to popularize science were many
               | years in the future. Lorenz's work with chaos and
               | powerful enough computers to enable it were still 20
               | years in the future. Terms such as "the butterfly effect"
               | did not get introduced for another decade.
               | 
               | It was unlikely that he was unfamiliar with chaos. Doubly
               | so given that the first prediction of what we now call
               | chaos theory is that we won't see the periodic behavior
               | that is a fundamental premise of the story.
        
             | Gordonjcp wrote:
             | Don't worry, XKCD has you covered!
             | 
             | https://xkcd.com/2623/
        
             | biggc wrote:
             | Akshually...
        
             | dmurray wrote:
             | A few details might need to be tweaked, but neither the
             | story nor chaos theory is fundamentally incompatible with a
             | solar system where night happens every few thousand years
             | _on average_ , is unpredictable over long timescales but
             | can be predicted years or decades in advance using 20th
             | century technology.
        
               | btilly wrote:
               | The idea of the story? Of course.
               | 
               | But the actual story as told? The regularity of
               | civilization collapse was rather central to the people in
               | the story.
        
             | camillomiller wrote:
             | You must be fun at sci-fi conventions afterparties
        
             | eesmith wrote:
             | > Foundation also fails because ...
             | 
             | The Mule shows Asimov knew psychohistory would never work
             | on its own.
             | 
             | The recorded prediction of the crisis with the independent
             | traders didn't happen, because of The Mule. This was the
             | Era of Deviations, and it took centuries for the Second
             | Foundation to manipulate things back to the Sheldon Plan.
             | 
             | And of course, the influence of R. Daneel Olivaw across
             | nearly 20,000 years, guided by the Zeroth Law of Robotics.
        
             | marginalia_nu wrote:
             | > with 4 suns the orbit would be chaotic and no periodic
             | pattern would exist to be found
             | 
             | This is only true for certain configurations of N-body
             | systems. The solar system is an N-body system with periodic
             | patterns, at least at a human timescale.
        
               | btilly wrote:
               | This is true as long as at least 3 of the bodies have
               | comparable masses, or the timescale is long enough.
               | 
               | The periodic behavior of the Solar System is because
               | 99.86% of its mass is in the Sun. So every other
               | interaction is a small rounding error. And therefore the
               | Solar System is chaotic but with a long Lyapunov time -
               | estimated at about 5 million years.
        
             | feral wrote:
             | The Wikipedia page on three body problem shows many
             | periodic patterns.
             | 
             | There appear to be stable configurations for the 4 body
             | problem too, even if the 4 masses are similar.
             | 
             | Its not fair to say there's no periodic pattern possible
             | with 4 suns, then, even though most initial configurations
             | might lead to chaotic behavior.
        
             | tetris11 wrote:
             | > Foundation also fails because human society is chaotic so
             | his psychohistory would never work.
             | 
             | Ant's are also chaotic as individuals, but if you get
             | enough of them you can model them easily. We can already
             | semi-predict global human behaviour; population graphs,
             | economic charts, actions of specific demographics. When
             | enough humans walk down a street, you can model their flow
             | with fluid dynamics.
             | 
             | Psychohistory wasn't a study of the intricacies of the
             | human condition, it was an iterative model that follows
             | general trends. It just happened to be sophisticated enough
             | to predict thousands of years into the future _and_ to
             | allow for outliers.
        
               | btilly wrote:
               | The whole weather vs climate argument.
               | 
               | However when you look back over the last 200 years, one
               | of the striking features is that every 10 years or so
               | people are concerned about something very different than
               | they were before, and which was often a result of a
               | crisis that few were ready for. For example nobody in the
               | Clinton era would have predicted 9/11. The 2008 financial
               | crisis caught most of us by surprise. COVID was on
               | nobody's radar. Nor did we expect Russia to launch a
               | full-scale invasion of Ukraine (nor to lose if they did).
               | And so on.
               | 
               | I can't tell you what we'll all be worried about in 2030.
               | It won't be COVID or Ukraine. My guesses include
               | financial collapse, climate change, the collapse of
               | Russia, the invasion of Taiwan, and so on. But odds are
               | that it will be none of those things.
        
             | tempestn wrote:
             | Sounds like you would enjoy the Three Body Problem, if you
             | haven't already read it (which I expect you have).
        
               | raydiatian wrote:
               | First book was great. Lost my ability to keep track of
               | names as a non-Chinese speaker on the second one, for
               | some reason.
        
               | siquick wrote:
               | Glad I'm not alone. I really want to love this series of
               | books but I'm never excited about reading it because i
               | find it too hard to follow.
        
               | MezzoDelCammin wrote:
               | same here. Not just the names, but IMO even the
               | storylines get pretty convoluted by the second book. Game
               | of thrones number of story branches, but French New Wave
               | thickness of plots.
        
               | [deleted]
        
               | [deleted]
        
               | saiya-jin wrote:
               | For me its even the plot. I mean scientific parts are
               | very fine, but human parts are meh at best.
               | 
               | [minor spoilers below] It is practically a racist book
               | where everybody non-chinese is evil, conspires to harm
               | chinese in a comical villain fashion, should be killed,
               | and is killed eventually. I get that 100 years ago
               | similar literature was OK in the west too, but we moved
               | our societies quite a bit since then.
        
               | lgl wrote:
               | > I get that 100 years ago similar literature was OK in
               | the west too, but we moved our societies quite a bit
               | since then.
               | 
               | 100 years ago? Today, the ratio of militaristic "America
               | F** Yeah!" sci-fi vs every other language is probably
               | 100/1 and the amount of times the Chinese and Russian are
               | the ones portrayed as evil in that literature is
               | literally orders of magnitude greater. Are those also
               | racist books?
        
               | zasdffaa wrote:
               | > Chinese and Russian are the ones portrayed as evil in
               | that literature
               | 
               | I've not noticed that. OTOH as a brit, the number of
               | times I see us portrayed in American films as cold,
               | unemotion, untrustworthy, manipulative, I could go on...
               | 
               | Edit: on reflection that does seem to have died down a
               | bit in recent years.
        
               | Aeolun wrote:
               | I don't think this is true at all. Especially the parts
               | about the cultural revolution made me wonder how this was
               | ever published in China at all.
               | 
               | It was kind of refreshing to have someone else be the
               | villain for once.
        
           | pks016 wrote:
           | What a coincidence! I'm currently reading Nightfall.
        
         | zasdffaa wrote:
         | A small counterpoint. The pain of losing someone is the cost of
         | having someone decent and good, for the time you had with them.
         | Some of us have never felt that because we've never had someone
         | decent to lose (though I will be glad; feel the world a better
         | place; when one of my parents dies, and mainly indifferent when
         | the other goes, reflecting his apparent indifference to me.
         | Sometimes being left alone is the better option).
         | 
         | To all those with normal lives, make sure you count your
         | blessings now, now when it's too late.
         | 
         | Sorry for weird post, but I had to say it.
         | 
         | Perhaps though, people should not go through life always
         | acutely aware of what they've got. Perhaps in some ways it's
         | better to feel your loved ones' presence but not think about
         | it, sort of take it for granted, feel the warmth of their
         | presence but not think about it. I don't know. Anyway, I'm glad
         | you had him.
         | 
         | BTW absolutely love the pic! I just wish I had the eyesight to
         | see it. In fact In london, I wish I could just see the stars at
         | all...
        
           | TaupeRanger wrote:
           | Saying "enjoy it while it lasts" serves no purpose other than
           | to blunt a person's enjoyment of the the thing. They will
           | already suffer when the the thing goes away...why remind them
           | of their future suffering, causing double the suffering? If
           | one person has a pleasant 15 minute call with their father as
           | a result of reading this thread, but 30 people get depressed
           | or anxious about not having visited their parents for too
           | long due to the normal circumstances of life, there is a net
           | loss.
        
             | zasdffaa wrote:
             | > Saying "enjoy it while it lasts" serves no purpose other
             | than to blunt a person's enjoyment of the the thing
             | 
             | Does it blunt it, or make you realise what you have while
             | you have it, and value it the more? Or are you right and I
             | acknowledged that possibility in my pentultimate paragraph?
             | 
             | I hear a lot of regrets about people no longer there, I
             | hear very little of people saying how lucky they are with
             | their partner/parents/others. I just don't know.
        
         | squeaky-clean wrote:
         | I've used this photo to show friends the size comparison at
         | star-parties! It's a great educational photo but also just
         | beautiful.
        
         | quickthrower2 wrote:
         | Very good image, thanks for sharing it out there. Not even JWST
         | could do that ha ha :-)
         | 
         | Do you mind if I ask: is that image CC licensed at all?
        
           | tombh wrote:
           | Thank you :-)
           | 
           | The base image is indeed public domain:
           | https://www.flickr.com/photos/srahn/9013096528 But I don't
           | remember where I got the image of Andromeda from. Not that I
           | believe I have any power to claim rights over it, but I've
           | always considered it to be affectively CC licensed.
        
       | dirtyid wrote:
       | Which animal has eyes best biologically tuned to star gaze? And
       | when cam I get that transplant.
        
       | somat wrote:
       | This (or some sort of very similar comparison) prompted me to
       | figure out how to locate Andromeda. And I could not see anything,
       | So I bought a nice pair of binoculars, and perhaps I could see
       | something, but it was impossible to tell for sure. until I went
       | camping in Arizona, I was looking at the stars, I remembered how
       | to find Andromeda, remembered my binoculars. everything had came
       | together and there it was! it looked like a blue mist.
       | 
       | But really it was a nearly spiritual experience. Out in the cold
       | Arizona desert, more stars than I have ever seen in my life and
       | you bring up a pair of binoculars to what looks like an empty
       | area of sky and it too is full of stars, And there is this blue
       | mist, the furthest thing you can see with the naked eye(at least
       | with better eyes than mine) with billions and billions of stars
       | contained within. I don't know, but you feel stuff under those
       | circumstances.
        
         | tempestn wrote:
         | How amazing would it be if it were as bright as in the photo
         | though? We'd probably take it for granted, but at the same
         | time, maybe not always. I'll sometimes marvel at the moon when
         | you can really see its details and three-dimensionality, and
         | that's just a moon. I expect being able to look up and see a
         | whole galaxy with your naked eyes like that would be a pretty
         | incredible experience.
        
         | theandrewbailey wrote:
         | If you have good eyesight (or good glasses/contacts
         | prescription), you can see it without binoculars (at least the
         | brighter core of the galaxy). Just don't look directly at it or
         | it disappears, because you don't have rod cells in the middle
         | of your field of view.
        
         | ISL wrote:
         | I often recommend to beginning sky-watchers that they try
         | looking at the night sky with a large pair of binoculars (look
         | for large objective-lenses and not too much magnification)
         | rather than a telescope.
         | 
         | The nebulae and larger Messier objects are beautiful and
         | approachable with bright handheld optics.
        
           | pophenat wrote:
           | A small bit of advice from me: consider the weight of the
           | binoculars when buying them. They can be too heavy to hold
           | for more than a minute - especially large ones made for
           | astronomy. You will either want a tripod (which is
           | inconvenient to carry around and set up), or you'd want the
           | binoculars to be smaller in size.
        
             | vl wrote:
             | For any practical viewing with binoculars you do need a
             | good tripod - otherwise instead of stars you'll see shaky
             | lines. Unlike daytime viewing your eye/brain doesn't
             | eliminate small shakes, or maybe it's just harder to
             | stabilize binoculars when looking up.
        
             | bumbledraven wrote:
             | Or you can buy image stabilizing binoculars which
             | mechanically keep the image steady in your view despite the
             | slight motion of your hands.
        
               | sph wrote:
               | I didn't know this was a thing.
               | 
               | https://en.m.wikipedia.org/wiki/Image-
               | stabilized_binoculars
        
         | lightbulbjim wrote:
         | There's something special about the actual photons hitting your
         | eyeball, instead of just looking at a picture.
        
           | Gordonjcp wrote:
           | I just about fell on my arse the first time I saw Saturn
           | through my telescope, actually looking at it and seeing the
           | rings. Rings, right around a planet, right there. I couldn't
           | see a lot of of detail because it's a fairly small refractor
           | but there it was, a planet with rings.
           | 
           | Rings. Right around a whole fucking planet. Right there for
           | everyone with a couple of hundred quid's worth of glass and
           | aluminium and a reasonable view of the night sky to see.
           | Just, right there in the sky, bright and clear.
        
             | dm319 wrote:
             | I know exactly what you mean. I saw it with a PS40 amazon
             | telescope.
             | 
             | You know that weird feeling when you, for whatever reason,
             | take another route from somewhere you know well, find
             | you've arrived at an unusual end of another place you know
             | well. The moment of connection, realisation that these two
             | places are linked in this way.
             | 
             | I felt that, but on a huge level seeing Saturn's rings for
             | the first time. For years outerspace, without me realising,
             | occupied a place in my encyclopedias, books, internet
             | images from NASA. Maybe subconscious me didn't really
             | 'believe' it was actually just above my head this whole
             | time.
        
               | Hallucinaut wrote:
               | Great analogy. Lovely way of thinking about it.
        
         | saiya-jin wrote:
         | I mean, in Southern Hemisphere you can see ie Large Magellanic
         | Cloud with naked eye, and its by definition another (albeit
         | smaller) galaxy.
         | 
         | I do _love_ astronomy and can stare at starry skies on top of
         | mountains for half a night, but you don 't need to buy some
         | crazy equipment to see similar things, just travel a bit (or
         | not if you live there).
         | 
         | I believe mankind would be mentally in a bit better place of
         | all folks that want enjoyed starry nights more often, and maybe
         | grokked a bit what they actually see. Humility and all.
        
         | Medox wrote:
         | > billions and billions of stars contained within. I don't
         | know, but you feel stuff under those circumstances.
         | 
         | Obligatory link to Gigapixels of Andromeda[1]. There are other
         | Gigapixels of Andromeda videos out there but this one also has
         | the perfect background music.
         | 
         | Crazy how "billions and billions" might be an understatement,
         | looking at how many stars appear after the 2min mark alone. And
         | Andromeda is not even a huge galaxy[2].
         | 
         | 1. https://www.youtube.com/watch?v=udAL48P5NJU
         | 
         | 2. https://en.wikipedia.org/wiki/List_of_largest_galaxies
        
       | em-bee wrote:
       | i saw a similar image in a documentary video. i was so impressed
       | by it that i took a screenshot, intending to look up more about
       | that some time. looks like i don't have to do that anymore
       | because HN brought it to me.
        
       | Archelaos wrote:
       | I once tried to observe Andromeda on a clear night with simple
       | binoculars. The hardest thing was not to shake too much, to get a
       | good view. In the binoculars it was clearly larger than the moon.
       | It appeared like a smudge with a very soft eliptic halo. I was
       | surprised by its size.
        
       | zoomablemind wrote:
       | The image of M31 in the sky reminded me of that StarTrek DS9
       | wormwhole. How's going there, Cmdr Sisko?
       | 
       | I do agree that without the myriad of stars from our Milky Way
       | the M31 looks very much pasted in.
        
       | 5mv2 wrote:
       | Fun classics for star lovers:
       | 
       | - The three body problem
       | 
       | - The hitchhiker's guide to the galaxy
        
       | lopuhin wrote:
       | A nitpick on the image Andromeda image: when viewed with
       | telescope and in most images you can find online, the core of the
       | galaxy and the region around the core is much brighter than the
       | outer branches, while on the composite image it looks like the
       | core is dimmed to make the outer branches stand out more.
       | 
       | So the actual bright part of the Andromeda, seen with naked eye
       | under dark skies, is much smaller.
        
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