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.
> 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!
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.
I am personally convinced that the close correlation of the perceived sizes of the Sun and Moon, and the spectacularity of eclipses, drove mankind to study them and thence to measure intangible things. Next step: progress!
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?)
> 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.
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.
> 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.
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.
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.
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.
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.
Reference needed supporting your claim that it was so widely understood.
My strong impression is that it wasn't until James Gleick published Chaos: Making a New Science in the 1980s that there was a popular treatment available to the lay public. And that book lays out many examples from the early 1960s at people like Edward Lorenz and Yoshisuke Ueda being surprised at extreme sensitivity to initial conditions, and having their discoveries met by doubt and disbelief. Which indicates pre-1960, only a fairly niche audience was strongly aware of chaos theory among either the lay public or scientists.
Okay, have you heard of Henri Poincaré? Because he studied chaos in the 1880s, and anyone with a high-school level grasp of mathematics would know that.
Hinged pendulums which exhibit chaotic behaviour have been a popular demonstration for about 100 years.
Just because the first pop-sci glossy coffee table book to mention chaos wasn't published until the 1980s, it doesn't mean that anyone who studied maths or physics - particularly at a level that would allow them to teach at a university - would not have even heard of chaos theory.
The double pendulum actually goes back further. It was studied in the 1700s. But what could be done with them was limited until computer simulations were available - in the 1960s. The same time that chaos as a subject became a thing.
And your claim that chaos was something that anyone with a high-school grasp of mathematics would have known about in the 1940s is supported on nothing more than your say-so. And directly contradicts multiple reports of working scientists in the 1960s. For example from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3202497/ you find:
Lorenz considered, as did many mathematicians of his time, that a small variation at the start of a calculation would Induce a small difference In the result, of the order of magnitude of the initial variation. This was obviously not the case, and all scientists are now familiar with this fact.
In other words people with PhD in directly relevant fields in the 1960s actually were ignorant of basic facts about chaos theory that are now known to every high school student. Even the phrase we all have heard to capture it, namely "the butterfly effect", dates from the 1970s.
And with that, I'm done. You're providing assertions that run counter to my citations, and are refusing to accept information that I cited about what was and was not general knowledge. There is no point in continuing.
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.
> 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.
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.
Pandemics have absolutely been on the radar. We already had plenty of hints: SARS, swine flu, heck the great influenza pandemics of the past. Increasing total population, increasing population density, and increased travel have been obvious risk factors for as long as anybody has talked about this stuff.
one of the striking features is that every 10 years or so
There are multiple things every decade. In the past 10 years we've had the pandemic, something resembling a coup in America, war in Europe, a nuclear disaster, accelerated global warming, and so on.
Trying to fit it into a shallow truism like "every 10 years, it's something!" is some kind of magical lazy thinking, right up with "it takes 10,000 hours to master a thing!" and "celebrities always die in threes!"
It wasn't stated as a truism. It was stated as a practical limit to our ability to naively project the future forward. And therefore the centuries long sweep of Foundation fails.
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.
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.
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.
> 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?
> 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.
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.
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...
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.
> 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.
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.
Your awesome, thank you for sharing this comment and the image you created with the world. As someone who has struggled with a similar family history with my own father, I appreciate and am thankful for the humanity you have shared. We are all better for it. Thank you.
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