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“The moon blew up without warning and for no apparent reason” (jasmcole.com)
710 points by mhb on Sept 21, 2017 | hide | past | favorite | 270 comments

Hey, author here. As several of you have noted, there are a lot of tweaks to speed this simulation up - making it 2D increases (unphysically) the collision rate, the particles have overly large collision radii, and the fragmentation threshold is quite soft initially but then quite high for small masses.

Regardless, I hope the video is fun - the sudden burst of fragmentation makes for quite the sight.

Thought you meant you were Neal Stephenson for a second!

Quick question: If I haven't read the book, but want to, are there any spoilers in the article?

You should definitely read the book, however. Hell, his entire corpus is one “whoa” after another.

Still, Seveneves < Anathem, in my jumped up not so humble opinion!

Anathem is probably Stephenson's best novel, and I say that as a huge fan of Cryptonomicon and Snow Crash. I've actually found his last few novels lacking, still struggling to finish The Rise and Fall of D.O.D.O. and REAMDE. I do wish he'd stop trying to reverse-engineer RPG settings and got back to his post-cyberpunk roots.

REAMDE - don't take it seriously. The author basically just took a vacation and wrote a mindlessly fun action book. If you read it as such, it's pretty good. It's definitely written from a Western perspective, but it does have some pretty astute insights about East European mentalities and culture (I say this as someone straddling the fence between West and East culturally).

DODO is not pure Stephenson. The personality of the other writer (Nicole Galland) quite clearly changes the atmosphere. It's the first NS book where characters' emotions are actually given some attention, and the first where female characters are described from a first-person perspective (in a way that's convincing).

REAMDE was surprisingly good and I learned a lot about gold farming in the process.

As a fun adventure novel I loved REAMDE. It very much improved the experience that I had just spent a week in Xiamen before I started reading it!

Funnily enough, one of my big gripes with REAMDE so far has been that Neal doesn't seem to get the Russian mentality at all. I'm not familiar enough with the Hungarian culture to judge Csongor, tho.

Anathem > Cryptonomicon > Snow Crash > all the rest

I have read through Anathem at least three times and still enjoy it with each reading.

I love the Baroque Trilogy. It's such a different universe than his other work, and I'm a history buff so it's fascinating to read and try to figure out what is accurate, and what is his imagination.

Please stop trying to get me to commit to reading this series. My expected lifespan is already too short to complete my queue. Thanks.

Don't fear. The inertia from all the over the top action sequences where the reading marker drops through the stack of pages like through vacuum keeps you going through the heavier parts in no time.

Ps: Anathem > Seveneves, unless you ignore the last third. Stephenson is usually weak at the end, when all the pieces are put in place and there is no room left for brilliant tangents. Anathem suffered surprisingly little, Seveneves more than usual.

I think the issue I had with the last "section" of Seveneves was it felt more like a prologue. The pacing was entirely different. I didn't hate it or anything, but going from the previous two parts to the last one was jolting.

I'm really not sure how I feel about Quicksilver. I read it when it came out, and I remember loving it, but when the second book arrived I thought "dang, I don't remember what was happening, I should reread Quicksilver first," and suddenly realized that I really, really don't want to do that ever. I suspect that my conscious mind is only remembering the thrilling action bits, but my subconscious remembers the miles of slog in between and cringes away.

Come to think, I have the same issue with Snow Crash and Heinlein's Starship Troopers. I remember both of them as nonstop action thrillrides and suppress the endless bloviating over linguistics and ethics, respectively.

I had the opposite experience—the first time I read it, I barely made it through. The second time, before reading The Confusion, I re-read it, and fell in love with it. It gets better each time I read it.

I don't think there's much slog---but I do love the bits about history and economy.

I try to re-read the trilogy every couple of years since it's so deeply constructed. Plus the main characters are fascinating. Life is short, bump this to the top of your queue!

I've read it five times. It gets better every reading.

I made the conscious decision to just skip any plot lines where I wasn't interested. I left over half the writing on the shelf, but I think I enjoyed it more than most people who've read the whole thing.

Well, if you don't want to read it I can strongly recommend the unabridged version they have on Audible....

Read Quicksilver until you are bored. You should already know most of the characters anyway. Then skip ahead to the Confusion and don't look back.

I'm enjoying The Diamond Age more than Snow Crash.

I started in Cryptonomicon, I just doesn't catch me, I'm about 20% in but nothing happens. I like descriptive, setting an atmosphere, but Stephenson goes to far I feel. The world is different ok, fun, but it just moves so slowly. Shaftoe goes everywhere and nowhere, I get it, he saw some dragon, yes third time you mention it... I put it away. Perhaps I'll pick it up later.

I also disliked REAMDE and am struggling to get into D.O.D.O. Cryptonomicon, Diamond Age, and Seveneves were great. Have't read Anathem.

> The Rise and Fall of D.O.D.O.

Thanks; I'm a little surprised I missed that!

I loved Snow Crash (top 5 personal favourite book) and Cryptonomicon (I haven't read Seveneves yet), but I didn't like Anathem that much?


Especially the sort of quantum-ex-machina "twist" near the end was kind of off-putting to me. Everything so far was very well crafted and researched, but this part was a lot like "yeah multiple universes or something", but I'm not sure if it even works that way, if true.

Also I found the constant back-translating of scientific discoveries and theorems with-a-different-name kind of tedious. I caught a lot of them, but many also not and I kept feeling like I was missing out on some cool references. Even though (IMHO) I have a pretty broad general knowledge of most important scientific/math theorems.

There were some other bits I didn't like but that's personal taste. I loved the humour in Snow Crash (so much better reading than Neuromancer) and the hi-tech thriller action stuff in Cryptonomicon. Anathem seemed kind of slow, building a whole world and such (as I said, matter of taste, I don't get quite as excited about world-building in fiction/fantasy books, unlike many people).

If you're interested in knowledge (broadly defined) then Anathem must be near the top of the list of your reads.

Anathem is the last book of his I read, and my favorite so far, partly because he suddenly remembered how to write endings. Does his later stuff continue that trend, or does he return to the "just sort of stops" style of Snow Crash, Diamond Age, and Cryptonomicon?

Seveneves is in two distinct parts (near future and far future). Let's just say the last part is ... different than the first part.

The characters in Seveneves feel like an afterthought that Stephenson needed to fill out a book about a cool idea he had. I personally found it uninteresting.

Cryptonomicon is my favorite work of his.

The first phrase in the book is a massive "spoiler".

Well, kidding, sort of.

But no, there are no major spoilers in the article. A few very minor ones. Go ahead and read the book.

Yes. The moon blows up in the book. Sorry to ruin it for you.

IMHO it's a pretty fun book, great for a long train ride.

However it's a little problematic in places, with some weirdness with eugenics and the role of women's reproduction. Trying to be vague to prevent spoilers.

Yeah, that part seemed a little forced, as if he was working backwards from the title, to accidentally arrive at the good stuff that comes before that in the book. Which makes it a good read nonetheless.

There are spoilers for like the first few chapters, that's it.

There's one bit that could be a pretty big spoiler for the last book too.

Unless the relative velocity's are extreme they would merge on the first collision. So you get millions of small fragments from the first collision and one much larger one.

On the other hand if it's got high relative velocity's they would both end up destroyed into millions of fragments. Picture firing balls of sand at each other.

Moon even has a molten interior these fragments would be mostly liquid.

The relative velocity's what?

Super fun thought experiment and project! Did you simulate n-body gravity, or just the Earth's? I couldn't tell from the project page or comments.

My son just asked me yesterday what would happen if the moon went away, and he hasn't even read any Stephenson yet.

Good question - another side to this though experiment! What happens if tides cease to exist? Could that cause enough change in the oceans or weather to pose a threat to life on earth? What if animals can't hunt at night anymore? What else do we rely on the moon for?

>Gravitational interactions between all bodies. I use an extraordinarily naive direct summation approach, which scales as O(N^2) and is horrible. A huge improvement would be to approximate forces from distant bodies with some kind of multipole expansion, and store masses in a balanced tree – this is known as a Barnes-Hut simulation.

Thank you for this and previous articles, your blog is my favorite technical blog online. It's a great mix of technical detail and entertainment, and it's always impressive.

Thank you, that's very kind. I'd like to post more often, but real life does tend to throw a spanner in the works!

Does a ring develop if the simulation runs long enough?

I'd love to see your writing become a book! Four color, nicely bound. I'd love to read that.

Thanks! I am in the process of writing a wordpress to LaTeX converter, so watch this space...

Can you post the source code?

I will do after I've cleaned it up, it will appear at the blog repository at:


Very nifty, but the fragmentation of bodies wouldn't look anything like in Seveneves or this sim in real life.


Agreed. In all likelihood, the seven parts would collide a bit, heat up a lot, and generally lump back together into a new moon. On that scale, the moon is really soft. So much so that each of the seven individual lumps would probably flow into a roughly spherical shape before colliding with anything.

Right. What most people don't realize is that at planetary scale (or even at Moon scale) things are fluid. There are no solids at that scale. Gravity dominates all other interactions except gas pressure - and that only for things made mostly of gas.

That being said, I would love to see an accurate, 3D, high resolution simulation of the scenario described in Seveneves.

It's not exactly what you wanted but this is pretty close. If I'd run into it earlier I'd have put it in the blog post.


Yep. In fact, this is how it formed in the first place.

Because the new body will heat up a lot due to collisions, how bright do you think will this new body be, for people on Earth?

Wouldn't that, in turn, depend on how much energy was put into the system by the original blast/splitting?

Indeed, and it would be interesting to take a fuller numerical simulation that takes https://en.wikipedia.org/wiki/Hydrostatic_equilibrium into account.

Absent enough input energy to push one or more of the fragments onto a new geodesic, to zeroth-order the moon would very quickly recollapse into a hot spherical droplet (likely by way of seven increasingly droplet-like components), and it would take an enormous amount of time for surface features -- like seas and so forth -- and lunar mascons[1] to appear.

There's some brief discussion of this sort of thing at https://gizmodo.com/what-if-the-earth-suddenly-turned-flat-1... which while it's Gizmodo, is one of the better "What If?"s. Dave Stevenson (Caltech)'s answer is short and sweet.

The undistorted body in the Earth-moon pair under either scenario is distant enough that the squashed Earth or the fragmented moon would still source a close approximation of the Schwarzschild metric[2], with an interface between the two as part of the boundary condition of each. Usually for simplicity we'd just describe the motion of the lighter body in the geodesics of the Schwarzschild solution of the heavier body, and the whole moon, its seven fragments, and the fragments' successor arrangements are very likely amenable to that.

One could always kick part of the mass of the moon such that it escapes "to infinity" from the Earth-moon system. Unfortunately one would have to recalculate the stress-energy tensor around the residual moon (and around the Earth, and around the sun) and then work out the geodesics. This would make for an entertaining project in numerical relativity.

- --

[1] https://www.nasa.gov/mission_pages/grail/news/grail20121205.... from https://www.nasa.gov/mission_pages/grail/main/index.html

[2] The Schwarzschild solution is after all an exterior solution, and is fine for approximately spherically symmetric bodies with approximately zero angular momentum. Moreover, if we don't care about ~ microsecond accuracies (and we almost certainly don't, because the conditions at lunar fragmentation are not that finely specified), we can do everything with small corrections to Newtonian gravity (cf. sec 6.4 of http://onlinelibrary.wiley.com/doi/10.1002/9783527634569.ch6... for the post-Newtonian Kepler solution and ch 8 on relativistic geodesy).

> Galileo observed that small animals like cats can survive falls much better than large animals like horses even over a couple of meters. The thing is that a things strength increases in proportion to its cross section but its weight increases as its volume

Does the principle have a name? I always felt this in the back of my had but never formulated it, I find it extremely interesting that Galileo wrote about it.

Turok already answered, but you might enjoy this classic "On being the right size."

Money quote: "A horse splashes."


This is fantastic.


I think this is what you are referring to, the square cube law.

This book [0] was quite enjoyable to read.

I realize the article is about far beyond the book, but in case anyone has not read it yet, I highly recommend it as some good grade Sci-Fi.

[0] https://www.amazon.com/Seveneves-Neal-Stephenson/dp/00623345...

Oh, Seveneves! I once listed it as the book that disappointed me the most [1] and seeing cool stuff like this simulation reminded me why again.

I think my explanation still reflects my opinions on the book and might be relevant here:

> I didn't know it before I started reading it, but the book plot is divided in 2 (very different) acts.

> The first one just captivates you in a way that makes it very hard to stop reading or even thinking about it when you are reading.

> Little did I know when the second act started and oh man, it was a complete struggle. It seems that the pace changes completely to an almost stall and the book just became complete unreadable for me.

> While the first act took me days, the second took me weeks and weeks to go further in the book and even with my kindle saying I still had 15% to finish, I got so frustrated that I just quit and never even had the curiosity to know how it ends.

[1] https://www.reddit.com/r/books/comments/65z04t/what_book_dis...

Many of Stephenson's books, particularly Seveneves and Diamond Age, have amazing worldbuilding, but simply fall apart from a plot coherence perspective about 2/3 of the way through. We on this thread aren't the first to notice this: https://www.google.com/search?q="neal+stephenson"+ending

It's not easy: when you build "mysteries" into a well-built self-consistent world (and Stephenson's worlds are excellent in this regard), it becomes increasingly hard to reconcile them all. As soon as you allow yourself to explore emergent phenomena during a creative process, you run the risk of writing yourself into a corner. I tend to read most fiction with an approach of "imagine the stories you wish happened in this well-thought-out universe" rather than worrying too much about the way an author actually writes a plot.

I found Seveneves felt quite different to his other work in that it seemed that the first 2/3 was setup for the last third which was the story he really wanted to tell. Unfortunately I enjoyed the setup much more than the payoff - didn't help that it had a much more powerful climax.

Conversely in many of his other books he's having fun describing the world early on but drawing it back together at the end doesn't work as well - Diamond Age is probably the clearest example. In the end the experience is very broadly similar but it seems to come from different causes.

I don’t think it has anything to do with writing himself into a corner. I think he’s just an insanely ambitious author and I’ll pretty much always give mad props to any author that is that skilled and ambitious, even when things don’t quite work out (like the last act of Seveneves). I also found the last act jarring and weaker than the rest of the book, but I still came away thinking “woah, an individual human not only set out to write this whole book, but then actually WROTE it.”

It's my theory that he tends to get bored, or runs out of time. I love Seveneves, but the last part seems rushed. And cries out for a sequel. Diamond Age too, but less so. And I found its ending to be quite satisfying. Ditto for Anathem.

The Baroque Cycle trilogy is actually a counterexample, being an extended followup and backstory to Cryptonomicon. That's also one aspect of the Mongoliad trilogy. And even D.O.D.O., in a way. But I can't say how, without major spoilers.

I have loved Stephenson's work in the past, up until about Cryptonomicon. Everything I've read since has been a great short read, bundled up in a thousand pages.

Seveneves started off strong, but then turned into a real slog. It could have been a great 200 page book, but at 600 pages I was just glad to be done with it and expect it to be the last thing of his I read. The Baroque Cycle felt similar, even though it contained many of the characters I loved from Cryptonomicon, but I just couldn't make it through it.

I see there are people here who like or love it, which is great. I am not surprised to see others here echoing my feeling that it was quite a slog to get through.

Stopping at Act 2 is probably not a bad idea, though I feel like Act 1 is a lot of setup that pays off in Act 2 so I wonder what the point would be.

I never finished the Baroque cycle, and never will, but enjoyed Anathem tremendously, and thought Reamde was a fun adventure novel.

But Anathem is his best work!

If the thing that most deeply interests you is Knowledge (with capital initial, and understood in the broadest sense possible), then Anathem is like catnip for your brain.

It's the book that shows how deeply the author understands what motivates knowledge geeks - be they active in science, technology, or any other field.

Reading it, nearly at every page I was like "wow, this guy gets it!"

It's funny how personal all of these preferences are. I, personally, thought that "Diamond Age" was tepid, and "Zodiac" pretty stupid (but an early work, so forgiveable), but I've pretty well loved everything else that Stephenson wrote by himself. On the shared-author side of things, the DODO book is terrible - dropped after about 2 pages - and the Mongoliad stuff looks tripe too.

Anathem and Seveneves are among my favorites. And I really liked the entire Baroque Cycle! (after consciously avoiding it for years).

> the Mongoliad stuff looks tripe too

It's not like Stephenson's other works but I found it to be perfectly competent historical-ish fiction.

I’m curious what parts you thought were a slog other than the last act? I presume you disliked other parts as well, because from my memory there was a lot more to the first two acts than 200 pages.

I recall a lot of really deep dives into details that I don't feel moved the story along. In my mind, the wing suit, her trip back up in the wing suit, the ring world, a lot of these things were described in excruciating detail.

Maybe there is more to the book than could be fit into 200 pages, but I also don't feel like there was enough to it to fit into 600 pages.

I ended up skimming. A lot. I just didn't have the patience for pretty much everything post-white-sky until the leap forward in time.

Not OP, but the chapter Ymir, near the end of the first act I'd waaaay too long.

I enjoyed Seveneves, but found it to be the one of the most depressing books I've ever read, right up to the final act. Not only because of the dark underlying theme, but also because you get invested in so many characters who then end up dying in a myriad of ways. The ending feels like the setup of a sequel book which I doubt will follow.

You should try Liu Cixin's Remembrances of Earth's Past trilogy[1]. Fantastic sci-fi. Utterly depressing.

[1] https://en.wikipedia.org/wiki/Remembrance_of_Earth%27s_Past

I read The Three Body Problem by the same author. I wish I didn't. By the third volume I was reading more like the way you keep watching a slow catastrophe unfold.

Not only does it paint an utterly depressing picture of the future and the Universe in general, but worse, the assumptions it makes about human nature basically imply this is a failed species.

Dune is often described as being about oil [1]. Similarly, TBP is mostly about Chinese nationalism and the politics involved with being economically intertwined with the United States while retaining an opportunistic military posture.

The message of TBP is hopeful in that the US and China are ultimately locked together against a universe of unknowns.

It totally goes off the deep end there at the end though, but this would be a hard book to write while living in China. The CPC wouldn't allow this kind of propaganda to be sold to the West if it didn't basically follow their party line. I mean, the author basically telegraphs this situation with the subplot about how the Terrans learn how FTL travel works.

[1] https://futurism.media/dune-and-oil-the-real-world-influence...

Ok, seen in that light it makes a bit more sense.

The chapters where people are treated basically like grass, letting them dry out when conditions are unfavorable, and just hydrating them back to life when things get better - that's some seriously puke-inducing allegory. That's a world I would absolutely refuse to live in. Something is seriously wrong with a universe that produces that kind of outcome.

The Trisolarian world was definitely shitty, and it's pretty improbable that life would manage to thrive there, but I thought it was still interesting.

My problem with those novels shows up anywhere someone uses "pure logic" to solve some problem, but the logic is totally insane and nobody ever calls them on it. In fact the entire universe follows the same insane logic for some reason, and it dooms the whole place.

It does get kind of funny near the end when the author decides that the big crunch is going to happen after all. But then all of the alien races have stolen too much of the mass of the universe to hide in their own little pocket universes so it won't happen. The protagonists at that point return their mass to the universe, but given the logic of the rest of the series there is no chance that the alien races will do that, the universe remains doomed.

Well, you know, they're aliens. The books never describe what they actually look like but you can well imagine that they are some kind of insect like creatures which would be horrifying to us.

For many life forms even on Earth, going into stasis during difficult times is a completely normal occurence.

The books actually do describe the aliens. They look like the aliens from "Mars Attacks" [1], except their brains are bioluminescent and the patterns displayed involuntarily reveal their thoughts.

[1] http://cdn3.bigcommerce.com/s-sby4jv/product_images/uploaded...

The thing that kept bothering me about that novel is that it treated the entire human race as if they had the emotional maturity and stubbornness of a toddler.

I was also a bit annoyed that the Trisolarians could mass produce these godlike sophons and never thought to use them to find non-inhabited solar systems to colonize. The third book did slightly explain this by having regions of space that broke their connection to home, but if you can produce thousands or millions of these things it doesn't matter so much if you lose some.

The logic of "in order to prevent other species from using up the resources in our universe we have to destroy the universe" never really worked for me either. The third book had a low level flunkie in an alien race launch an attack that would doom the entire universe at the speed of light with only the approval of a low level middle-manager. I'd almost say it was a parody except that the books took themselves so seriously.

I saw it as a uniquely Chinese perspective on humanity. As the series helpfully reminds you, barely 40 years ago, China was in the midst of the Cultural Revolution, a collective self-inflicted madness which we would find difficult to imagine.

With that as your history and living memory, it's not surprising if your opinion of humanity's emotional maturity isn't as high as it could be.

> As the series helpfully reminds you, barely 40 years ago, China was in the midst of the Cultural Revolution, a collective self-inflicted madness which we would find difficult to imagine.

I grew up in the "communist" Eastern Bloc. I can easily visualize that type of event.

I still don't buy it - neither the premises of that trilogy, nor its conclusions.

At the end I was like - there's got to be a better way, or else this is a pointless Universe.

The books had a few points to make, even if it cut some corners to make them.

1. Humans are bad at real long term (generations or more) planning.

2. Humans have been successful because of their ability to trust each other. This works okay on Earth, but if they live in a universe that is actively hostile towards this, it could turn us into a doomed species.

3. Conversely, an entire universe of species that go around destroying each other on a whim is also doomed for everyone.

The only resolution seems to be that maybe if groups of both species that want to peacefully coexist can find a third place to inhabit together, they may be able to find a compromise even if their original races end up wiped out completely.

My take on the "why are we behaving this way" was that, if you find intelligent life:

a) Its probably either very far behind or very far ahead of you.

b) Civilizations that are very far behind you can jump to being very far ahead of you "overnight"

c) Civilizations that are very far ahead of you can launch a preemptive strike that is guaranteed to destroy you.

d) Civilizations can modify local space to put themselves in a "stone-age" from which they cannot escape, thereby proving "we are not a threat".

Rationally, the only thing to do is destroy any civ you can, or preemptively take yourself out of the game.

An example of (c) was that Civilizations living in a n-dimensional universe could, if advanced enough, figure out how to modify themselves to live in an (n-1)-dimensional universe and then convert the n-d universe into an (n-1)-d universe that only they (and a few other clever civs) could survive in. Harsh. But rational.

Except of course you can escape from the Light Tombs using the pocket dimention door thing from the end of the book. That's another thing I found insane, in order to prove to the universe that you are not a threat you alter the speed of light in a solar system sized area in a way that the entire universe can easily see. If that isn't threatening I don't know what is. It doesn't even protect you from attacks!

The logic that "if you see someone, you must kill them" is kind of like "the first country that develops nuclear weapons must immediately deploy them against every other country, even thought that dooms the world to a nuclear winter." It's super-villain logic that ignores all of the other potential solutions--like diplomac--and ignores the MAD component of being able to easily destroy solar systems.

The entire reason given that alien species can't coexist is due to limited resources, but the Dark Forest mindset means they'll never be able to use those resources in the first place and at the end of the day they end up destroying all of them anyway. It's self defeating, and logically they should be able to figure that out.

The book feels like it's written by some game theory nerd who can't look past the first order equations.

>The logic that "if you see someone, you must kill them" is kind of like "the first country that develops nuclear weapons must immediately deploy them against every other country, even thought that dooms the world to a nuclear winter."

Except that they don't live on a planet, the weapons aren't nuclear, and they don't have spies or reconnaissance planes and satellites that can determine whether the other side really has them or not in near real time.

When we were looking at the SDI, some people argued that SDI was bad because it would allow us to launch a preemptive first strike without any consequences, while other argued that that was a good reason to build it, and then use it immediately. So even in the case where we actually all live on the same planet and share the risk, some in the USA argued for what you claim is super-villain logic. That's what I though the books got dead right: humans are fucking stupid.

The alien weapons also destroy the universe, although in some cases they are able to escape before the destruction is complete. This was in fact the endgame strategy for alien races in the novels: Figure out a way to reform yourself in a lower dimension then destroy the dimension you are in, except that ended up being a completely retarded idea because there are already races in the lower dimensions and far far fewer resources for your race to exploit. They're jumping out of the fire and into a much smaller and still crowded fire.

The whole trilogy is built on a solid foundation of complete paranoia.

Yep. It's a zero trust universe. Luckily the real world doesn't work that way because that would suck.

If self-replicating automated interstellar probes are possible, then given the size and age of the galaxy, they're inevitable -- and then so is a galaxy that's rife with them.

So where are they? Either self-replicating interstellar probes are impossible, or we're the first or only civilization to approach the ability to launch them.

The Fermi paradox.

IMHO the answer is: Once you have the technology necessary to travel interstellar distances, you no longer need to. Species are stuck in their own solar systems because leaving doesn't make much sense. The resources (including available space) in our solar system are nearly unlimited at the human scale, why take a staggeringly expensive and hazardous trip to some distant solar system for just more of the same?

That would mean conscious beings are stuck forever to their systems of origin.

I really, really want to revolt against this law, if it's really a law. Not sure why. I just do.

IMHO it is one of the best possibilities for the Fermi Paradox. Way better than the Dark Forest, we're alone, or all intelligent species destroy themselves alternatives. At least with this there is the possibility for our long range probes to make contact and exchange culture/technology.

Imagine there was one, or even a dozen such probes in our solar system right now.

Would we notice?

Briefly, until the Earth was gobbled up for material to make new self-replicating interstellar probes. Evolution would ensure that the probes would be voraciously reproducing as quickly as physically possible.

The numerical argument that the age of the galaxy gives sufficient time that it should be well-covered with probes seems reasonable.

However, extending that argument to "...and the various probes will have then competed in a Darwinian struggle leaving only a few voracious survivors causing a galactic-scale grey-goo scenario." does not seem especially well supported.

Book one: lots and lots of scientists committing suicide out of despair that science is a lie (reader demographic will relate to this how?).

End of book one: yay!

Beginning of book two: oh we're totally fucked.

End of book two: yay?

Beginning of book three: yeah, we're totally fucked.

End of book three: the universe and all possible future universes are totally fucked.

It was epic. Highly recommended. So good to read sci-fi without a happy ending. Liked Horizon: Zero Dawn for same reason.

Science wasn't a lie, there was just an artificial cap on it, one that those scientists wouldn't even hit in their lifetime.

And honestly, the cap seemed a bit contrived to me. I read it more that the Trisolarians headfaked all of humanity and three books later Humanity never realized it. There's more to science than smashing subatomic particles together. It would be quite the subversion of "Trisolarians suck at lying" meme that emerged later.

>> You should try Liu Cixin's Remembrances of Earth's Past trilogy

> I read The Three Body Problem by the same author.

Information for future readers of this thread: those are the same books.

(Also, 11/10 great sci-fi; highly recommended.)

Or on the fantasy front, Joe Abercrombie's First Law trilogy.

Everybody seems to love those books, and I can recognize their high quality - but they're so depressing. God, the ending just gutted me.

Yeah, I read through that trilogy, and the third book in particular really took it to a point of "flawed people fail to rise above their flaws; the future of the human race is wizards eating each other forever". Which, okay, is a valid story. Tragedy is a genre. It's just not really where I hoped the story was going.

I really enjoyed the first book, liked the second one, and wish I could unread the third one.

The problem with the third book was that it rapidly expanded in scope and grandeur but was the same number of pages as the previous books, so concepts and scope and scale which had enough exposition in the previous books simply fell short in the third.

Kind of, but I think even so, it just wasn't consistent enough. It felt like his publisher demanded, "Ok, you owe us a third book. Let's go for Stephen Baxter's scale, with Greg Egan's mathematical prowess." That's not a reasonable goal to shoot for, unless you're Baxter or Egan.

That’s an interesting take. I found it one of the most optimistic books I’ve ever read, so much so that given how I see real humans behave I find the optimism perhaps the most unbelievable aspect of the book.

I initially felt similar. But once I realized that Seveneves is actually two RPG novels [1] it gets much better.

Part 1 & 2 are universe backstory. Like the Horus Heresy in 40k or the story of Lilith in Vampire.

Part 3 is just to advance the plot of the univers. Like the Dragonheart Trilogy in Shadowrun or when the clans get introduced in Battletech.

[1] http://arthur-johnston.com/essay/2015/10/03/seveneves.html

The first parts (and also Anathem a bit) reminded me a bit of Isaac Asimov... in the sense that his sci-fi is often more about exploring society and human plight over long time periods, rather than focusing on laser beams and teleportation devices and specific characters who die off in a short galactic timeframe.

Yes, totally! Never thought about it on this terms, but totally agree and I guess that similarity was what made me like the first parts so much

I had the exact same experience. I absolutely chewed up the first act (or two depending on how you look at it) in the matter of a few days, and it was awesome. But I never finished the final act. It was just not interesting enough for me to finish it.

> I still had 15% to finish, I got so frustrated that I just quit and never even had the curiosity to know how it ends.

I hope you will finish. I understand the gap was both abrupt and left quite a bit to be desired. I was shocked and disappointed as well, felt like it was the easy way out of telling a storyline that was becoming increasingly complex.

In the end I very much enjoyed the great parts of the book and thought provoking dialogue between characters. That being said, I could nitpick on the parts I do not like but I prefer to celebrate the parts that were incredibly enjoyable.

I agree - I recommend Seveneves to anyone, but I say stop as soon as Act 1 ends. I think Act 2 spoils the ending of Act 1 by undermining the high stakes that made it impactful.

I can tell Stephenson enjoyed writing Act 2 as an act of fun semi-hard sci-fi, but I think it should have been in its own setting, not tacked on to a dark hard sci-fi survival novel.

That's funny I liked the second act much better. I found the study of human nature in the first act too depressing.

> I got so frustrated that I just quit and never even had the curiosity to know how it ends.

lol, then you missed the brief Act 3!

What was so different between the two acts?

The first act is about how the present day human race survives the moon being destroyed. The second takes place 5000 years in the future and is essentially about the return to earth.

I don’t share GP’s opinion, I quite enjoyed both acts. I do agree that the pace of the two is quite different - the first being a bit more sci-fi thriller pace and the second is a bit more contemplative.

There's actually three acts: Earth, Space, Moon. It's really a trilogy smushed up into one book.

I agree, though. The first two acts were great, and the third fell flatter than the earlier two. But I enjoyed it nonetheless. It's nice to imagine what would happen, and it's pretty hard scifi throughout, albeit greatly accelerated.

Yeah, though I tend to like breaking it into 'the end of Earth and our efforts to survive that end' and 'what happens to a society that's been through that trauma and their return home' split. The time jump really makes the jump feel more solid between book/acts 2 and 3 to me.

Fair enough, but I lump the first two together in my head simply because they occurred in the same time frame, at least compared to the third act

It's two separate books that were put under the hydraulic press and smashed into one tome. Keep that in mind when reading it, otherwise the second act is jarring.

Yes, well said. Honestly it's kind of like reading "The Diamond Age" immediately after reading "Snow Crash" and expecting them to be similar since they're set in the same universe.

Act 2 is Neal Stephenson's re-imagining of the Fellowship of the Ring - complete with the cast that makes up the fellowship, and roughly 500 pages of walking to places, so that they can walk to other places, so that they could walk to other places, without doing much of anything.

Beautiful worldbuilding, but very much not like the rest of the book.

I said very much the same thing in my review:

“[The characters] spend most of the third part literally doing nothing. They are assembled into a team of seven by a nebulous authority for some secret purpose; neither they nor we are told what it is. They go from place to place to investigate something or other, making several pointless stops and excursions and wondering, as I did, what was going on and when something was actually going to happen.”


Literally doing nothing seems to be a valid literary technique. The part I remember most from Cryptonomicon is about some guy eating cereal.

I have no problem with that in general. The cereal-eating was focused and vivid (it was Cap'n Crunch), and anyway it was over in a couple of pages. Nicholson Baker's entire novel The Mezzanine is like that, and it's just fine.

But so much of my time was spent reading about those people going from A to B to C on their way to D, and for what?

There was a similar episode in _Anathem_, which I generally liked. But for some reason the characters had to go from A to B and the best way to get there was to go over the North Pole, and the book stopped for fifty pages until they got over the Pole and everything could continue.

In a different world some editor would have persuaded Stephenson to cut the whole thing out, and I used to hope he would one day meet that editor and we would live in that world, but by now I've given up.

I remember there's an episode in The Princess Bride where Goldman interrupts Morgenstern and says “At this point there's a long section about [I forget what] that I cut out because it isn't important to the plot, except that along the way Fezzik obtains a Holocaust Cloak, and I'm only mentioning it because I don't want you to wonder where the Holocaust Cloak came from.”

I would have liked to have seen something like that in Anathem: two sentences along the lines of “Then we had to get to Siberia by driving an APC over the North Pole, but the less said about that the better” and then the book moves on.

Since the Alaska trip to find POTUS in Snow Crash, it's rare to see a Stephenson novel without some variant of The Nordic Voyage. Hackworth traveling to meet the drummers, Waterhouse inheritance dealings in the cold northern Midwest, Root in Boston, maker-kids driving up into the hills to their falcon9 knockoff. The Anthem north pole crossing fits right in, almost to the point of parody.

Interesting pattern - Reamde also provides an example. Of course, in Cryptonomicon there is also a literal Nordic Voyage, from the coast of Norway to the Swedish coast, but he skips over it entirely, only giving the highlights retrospectively from the perspective of his least reliable narrator.

The pole expedition is one of the parts of Anathem I consistently skip, sometimes opting to read the part where The Protagonist deals with The Obstacle.

As pointless as those travels were, there was plenty of showing off of hypothetical travel tech; I really appreciated that.

Funny, that scene stuck with me too. With UHT milk. Extra cold.

You are talking about the third act.

Although in fairness, the person you're replying to is probably doing the same.

The first part is "real time" and very intense and nerve-wracking. Then in Act 2 it skips forward 5000 years and tries to tell you what happened later. It feels like an extended epilogue and none of the original characters are alive for you to care about.

I liked it, but I can totally see the criticism.

Myself, I enjoyed the entire book, but I understand the let down feeling some here are expressing. The first part is immediate, gripping, intense, and hard to go through it (but you don't want to stop, because it is so good).

After all of that resolves, it's pretty hard to emotionally connect with the rest of the story, since you are exhausted from all that came before. The final act is worthwhile and interesting, it's just a pretty big change in direction.

The first part is a race against time to survive.

The second part is a war between humans for scarce resources in space.

The third part is about humans, who are largely doing fine, finding out stuff about the past and themselves.

There are some deadlines & urgency in the last part, but I think it's a tall task to try and create urgency when the previous sections were about the entire human races being extinguished.

I really liked the book, probably my favourite from Neal Stephenson. Great hard scifi, fantastic solutions to problems without any deus ex machina (of course the agent that splits the moon can be thought as one) - will definitely make you think and satisfy your hunger for this kind of thing.

The book can be thought of two big parts (the first is about 3/4 of the book), I don't really want to spoil, but the second part is much inferior to the first one and you won't miss much if you skip it. I know you won't but in any case...

The 2nd part is terrible. Should have been cut by an editor. Or the editor should have made him rewrite that whole 2nd part, perhaps make it into Book 2.

> The good news: Stephenson has learned how to write a good 600-page book. The bad news: Seveneves is 900 pages long.


The second part is weird. First he spends a lot of time on describing that world in very little detail but then he rushes through the story without giving much background. And the end just comes out of nowhere without closing the story,

I thought the first 2/3's of it were too depressing, and thought the last bit was decent sci-fi, which is what I actually like to read.

There is a good story in the last bit, but it's horribly written and deserves to be better. Despite there being some interesting elements, it is still pretty much unpublishable (in terms of coherence in characterization and setting, plot, etc - basic elements of good writing). I think a fanfic writer can come up with something better given the same material.

I think Stephenson could also do that material justice, IF he rewrote it.

It did feel like the last part was Stephenson deciding that he had far too many ideas about how this would all turn out in the end to leave it that way, or even with a short epilogue, so he expanded it into an extended epilogue, which is what it feels like in the end. Add in him wanting to throw in what he thinks are some cool technologies, or how weapons would develop when carried through an arc that largely bypasses gunpowder, or when satellites are ubiquitous, and you get the filler segments we ended up with.

I largely enjoyed that part, but not as much as the first two parts. I would have been supremely annoyed if he didn't give some explanation of what happened after the first two parts, since he didn't really resolve humanity's problems as much as trade one problem for another. Some sort of extended epilogue was warranted, and I can see how deciding just the right length for it could be hard to get right when it needs to relay a lot of information to satisfy the readers. What we got was the third act which doled out the history sparingly but consistently over its length, but the story was lacking.

Yeah, it's not great, but it's at least back to being kind of uplifting sci-fi. I would have been happier with a book that was a more developed 'future world' with a few flashbacks to the big disaster, rather than dwelling on it. If I want to contemplate death and destruction, there's plenty of that in the real world.

I love the first half but the second half is predictable and formulaic with stock characters that annoy you more than inform you. And then the sea people come back? Jesus.

<Former Spoiler regarding my frustration with some DNA stuff here>

Still, i'll probably read it a third time one of these days.

Gosh, the whole DNS stuff was a constant WTF for me.

DNS is often like that for me as well :-) But, yes, the DNA in Seveneves involved a huge amount of handwaving to arrive at the story that Stephenson apparently wanted to close on.

That. Right at the end of the first part of the book - when some of the DNA Stuff (put that way to avoid spoiling) is when I sort of mentally check out. It was especially annoying because it could have gone somewhere more fun if less... I don't know what the term would be, mythic, maybe? I think he was going for some giant over arching plot that spanned the book and that desire created the need for a bit more hand waving then I could handle.

He should have made at least 2 or 3 books out of Seveneves. The last quarter of the book feels so rushed and it left me quite disappointed.

This is every Stephenson book. Snowcrash, Cryptonomicon, Anathem, and The Diamond Age also fall victim to similar problems. He is a fantastic world-builder, but eventually he runs out of paper and needs to make things resolve, and the pacing falls apart.

Incidentally, GoT is suffering badly from the same problem.

I think this would have "fixed" this book. I actually liked the major concept shift for the second half. It was totally different and unexpected. But it also felt rushed and really heavy on some of the "sciencey" type descriptions of how various things were possible.

If it had been split into two releases, both would probably have done better, but I bet they would have sold less as well. :)

I love Stephenson as a storyteller, but hate him as a writer, if that makes any sense.

There were parts of Seveneves that I thought were spectacular, and a lot that I thought was silly, and most of which I hated reading. ;-)

Stephenson is my absolute favorite living author (RIP, DFW) when he's good (Anathem, Cryptonomicon, Snow Crash), but appallingly bad when he's bad (The Rise and Fall of DODO, REAMDE). You can safely give Seveneves a miss, and should go read the really good stuff first in any case.

Oh man, I loved REAMDE. It was just a fun book to read. It was absolutely absurd with how much was going on, but I loved reading it.

So, in the first part, I was able to identify characters that are thinly veiled allusions to famous people in the real world. Elon Musk, and Neil deGrasse Tyson, were the ones I've found. Anyone else missing from the list?

This is definitely controversial, but Julia Bliss Flaherty / Hilary Rodham Clinton

With the little knowledge of US politics that I have, I imagined the JBF as Sarah Palin.

It did cross my mind, but it doesn't seem to rhyme with what I (think I) know about the author.

I really hope Stephenson writes a sequel. He left it open for one but he tends to do that.

Nice simulation.

But I think that the assumption that all the collisions are elastic is too unrealistic. I expect that adding the inelastic collisions, where two fragments can merge in a bigger fragment, would produce a very different result, where a big chunk (50%?) of the moon is reconstructed and get to a stable almost circular orbit.

For comparison: "What Made the Moon? New Ideas Try to Rescue a Troubled Theory" https://www.quantamagazine.org/what-made-the-moon-new-ideas-... HN discussion: https://news.ycombinator.com/item?id=15094302 (59 points, 27 days ago, 18 comments)

This was my first beef with the book. It seems to me that

1) the forces involved in smashing the big chunks into smaller pieces make the inelastic-ness of this significant, and because of this

2) there would not be the accelerating self-destruction that eventually turns into the white rain.

Physics aside, the idea that multiple non-communicating groups, separated for 5000 years, would be able to communicate, is unrealistic. Two friends who are linguistic professors tell me that the idea is preposterous.

For anyone interesting in toying with a Barnes-Hut gravity simulator that can handle lots of particles and produce pretty pictures, here's one I made last year for fun. https://github.com/PWhiddy/Nbody-Gravity Takes about a minute to set up and start generating images and video (mac/linux only, sorry)

"(mac/linux only, sorry)"

Don't be sorry. There's lots of software out there that I am interested in from a quick read of its description, but I have to pass on it because it's either Mac-only, or Windows-only.

(And, yes, I am aware of Wine and the existence of some emulators for older versions of the Mac OS.)

Also, the AWS free tier lets you get a windows VM for 750 hrs/month for absolutely $0.

I have actually tested this nbody sim on the aws linux free tier :)

> mac/linux only, sorry

Don't be. Perfect use case for the Windows Linux Subsystem: https://i.imgur.com/v0b9Nmh.png

I love this post so much ... as a fan of Kerbal Space Program, the sentence, "as long as you can deal with hundreds of pages of orbital mechanics" is super interesting :P

I'm not even exaggerating. If you're into KSP, I think you'll like the book!

Elon Musk and Neil deGrasse Tyson also appear in the book as pretty important characters, just under different names. ;)

As a huge fan of Neal Stephenson I found Seveneves to be one of his worst books. Cryptonomicon, Diamond Age, Snow Crash; some of my favorite books so the length of the book has nothing to do with it. The characters were flat, unbelievable and unlikable. The dialogue was weak and awkward. The scenario felt contrived and uninspired (the moon blew up, earth had to evacuate; yep, Cowboy Bebop already set a high bar for this story).

I listened to this one in the car (10+ hours for books a week thanks to my drive). Maybe it was a rough week but I had to stop halfway through because it completely lost me. Maybe it gets better but having read the spoilers I really can't imagine how.

But hey, your mileage may vary.

With you on this one -- I've got all of his major works in first editions -- Seveneves is the only one I actively disliked. It's probably the only one I'll never read again. Beyond being intensely depressing (near future enough that everyone you know and love dies on the page... horribly), the plot felt about as strongly held together as an average episode of network television, and the characters managed to be both boring and unlikable.

Agreed. To me, it felt like three good books squashed awkwardly into one with jarring leaps forward in time, and entire viewpoints cut out. I also found the third act entirely unsatisfying.

I really struggled with it. Over a year I’ve been stalled at the start of the third act.

Hearing that others had similar experiences motivates me to give his other novels a chance.

If you liked this, you should read the Broken Earth series:


They're pretty different. By the way, the connection to Seveneves is kind of a spoiler for the first two books of Broken Earth.

Your post was more of a spoiler !

Has anyone considered that the witches from "The Rise and Fall of D.O.D.O." are responsible for the moon's destruction?

That's a hell of an ODEC.

They could be on a strand where they figured out how to stop the need for ODECs :)



A fictional device in the DODO book. Describing it would be a spoiler.


I wonder how it would go in 3D. In 3D the relatively tiny Moon pieces have much smaller rate of hitting each other and fragment into smaller pieces.

Very different.

The three main problems is space is 3d, moon fragments are going to be very soft, the sun is going to impact these orbits.

The likely result is the earth ends up with a huge amount of dust, but not many large impacts.

Isn't the whole process pseudo-2D even in a 3D simulation? The moon initially moves on a plane around the and I guess most of it's broken pieces would stay in that plane?

I think in a 3D simulation, the initial fragments would have various trajectories in 3D space, and their orbits would intersect back in the original plane as they pass through it in different directions. (Unless you meant unrolling the center-of-the-orbit as a line, then the fragmentation expands that as a plane? Not sure on the implications of that.)

this might be true, but i don't see why it should be. if two pieces collide at a high speed and shatter explosively, why would they stay confined to a single plane?

I think the plane change would be small, since the velocity change experienced by the fragments would be small compared to the orbital speed. For empirical support of this idea, consider Saturn.

Ring formation has an intermediate dust phase. http://curious.astro.cornell.edu/about-us/66-our-solar-syste...

Another consideration the moon does not orbit the earths equator but Uranus, Saturn, and Jupiter's rings do. This suggest tidal forces play a major role and you would not end up with a ring in the same inclination as the Moon's orbit.

The plane change would be just as small or large as the change in orbit, the directions are the same. If a collision is not likely to produce significant plane change, it's also not likely to produce fragments that go to significantly lower orbit to hit Earth; and if a collision is sending some fragments towards earth, then it's sending as many fragments significantly sideways to a different orbit inclination.

To quote another Stephenson novel, "plane changes are expensive."

they are - an explosive collision provides a lot of financing though.

This is tangential to the article, but one of the more interesting and less-discussed aspects of Seveneves is the ubiquitous surveillance that everyone is living under. Most characters hardly give it a thought most of the time. The way that this later becomes essentially an epic myth composed of original footage, and how it has tangible effects on subsequent cultures, is kind of fascinating.

On barely related note, I immediately thought about Three Moons Over Milford, in which the moon breaks into three chunks and rains meteorites down on the surface. As it turns out the tile comes from Seveneves, which has a similar concept. The TV show focuses on the life of the townspeople, while Seveneves focuses on the science and drama of the exploded moon. Stephenson started working on his book in 2004, completing it in 2013. TMOM came out in 2006.

Again, these are two completely different stories with only a common catalyst, but I wonder if the idea for TMOM may have come from someone that knows Stephenson (ie, he mentioned the idea in 2004/5 to someone that ran with it), or if the creators are even aware of the other.



Check out https://en.wikipedia.org/wiki/Kessler_syndrome

Similar but with low earth orbit

Last I read, Ron Howard was involved in producing the movie adaptation. Anyone seen any update on this project recently?

I haven't heard anything since the announcement. IMDB's last update was in January. It's not just Ron Howard though--it's also a bunch of the people who worked on the Apollo 13 film, which seems like a very good fit.

Unlike a lot of folks, I liked the second part of Seveneves, but I won't miss it if they cut it from the film. I don't even know how they'll fit the whole first part in without a 3.5 hour running time.

I absolutely loved this blog post. This, incidentally, is the perfect thing to blog about if you're looking for ideas. Just read books and things outside what is normally part of the engineering culture, in the meanwhile keeping all the things you're good at (e.g. mathematical modelling) or interested in in the back of your mind. When you stumble upon the intersection of things you're technically good at and things you read about, do some cool research or write some code and then post it on HN and there you go.

I agree, but I don't think Neal Stephenson is outside of engineering culture. :)

I was frankly surprised seeing this thread just how popular Stephenson is here. It makes sense though.

First, spoilers for the first few chapters below, if you care about such things.

This (neat!) article and the comments here (so far) miss/skip a few details (or my mind is making fake memories again).

1. Regarding the destruction of Earth - IIRC, while the pounding (and subsequent geological and atmospheric responses) the Earth was to receive was an ELE, the real kick in the teeth was the cumulative heat generated as much of a moon's worth of mass burned up in the atmosphere.

2. Regarding whether the moon would just sit there fragmented or mirror the descriptions of the book - IIRC, the moon didn't just break, it was _broken_ (by what is never known). So whatever thing wielding a massive physics bat did that, it can also impart all sorts of momentum. Pretty easy to say that if you can get the end result from SOME starting conditions, that those starting conditions could have been created by the Deus Ex Machina.

I know no orbital physics, but isn't the solar system is a great example of showing how big rocks in orbit become fewer, smaller rocks given enough iterations? So far as I know, asteroids occasionally manage to strike one another (defying the vastness of space by their numbers and persistence) and asteroids can capture smaller bits, but on the whole asteroids are getting smaller, not larger (albeit at a cosmically slow pace).

'Course, I could be wrong. Had an hour long argument with a friend who said that there was no angle that would allow one mass to capture another approaching mass approaching into orbit, while I was relying on my experience of reading of various suspected "captures". After much googling, we decided he was right from a two-body position, but that the Sun ( or other mass) can provide the necessary nudge to turn a swingby into a lasting orbit, so I could be right too.

> I thoroughly recommend it, as long as you can deal with hundreds of pages of orbital mechanics.

You say that as if it's a bad thing.

This is the warning I got when I borrowed someone’s three volumes of Feynman’s lectures in physics except with pages of calculus. It was a wise warning.

Wow, this is perfectly timed for me. I just read Seveneves last week. Interesting that this simulation results in a "white sky" event half a year after the moon explodes -- in the book this takes a few years.

The article mentions that he chose to use a larger than accurate size for the simulated earth to speed up the simulation. That suggests that "in real life" it would in fact take longer.

You should have used Parambulator to create a more precise model :) Awesome job.

So... one big thing I recall from the book is the collective collisions turn the world into an enormous ball of fire for decades. If (according to the simulation) the number of collisions tapers off after a couple years, does that mean the world would be habitable again in short order? I understand that, for the purposes of the book's arc, the planet needed to be rendered a literal hell for as long a time as possible... but perpetual burning seemed a bit far-fetched.

Aw! I thought Seveneves was amazing and the orbital mechs made it even better. (Author sounded like it was tedious in the opener)

I absolutely LOVE it when a scifi author gets that stuff right and it's great working it through in your head as you absorb the story they're weaving. Really added something to the book. Very much like Arthur C. Clarke's work - stuff that would work that way in real life.

Does this account for the size of the pieces? Every time they fragment, the pieces would get smaller making it less likely to hit another.

While the simulation is really cool, I doubt it represents the reality (assuming the Moon blew up).

Why I think so: the planets have formed out of space debris, they didn't all fall into the star.

> Pairwise collisions between bodies – most of the collisions are approximated as elastic.

Yeah, that's one reason why.

> A static mass at the origin of a 2D co-ordinate system – this is Earth

Why not simulate the Earth too?

> Why I think so: the planets have formed out of space debris, they didn't all fall into the star.

Nearly all of them did, there is way more mass on the Sun than orbiting it.

Just to put a number on "way more": the Sun contains 99.86% of all known mass in the solar system.

Of the 0.14% of the solar system that isn't the Sun, Jupiter accounts for roughly two thirds of it.

Only 25% of the mass ends up on earth.

And a point mass at the center of a sphere produces the same gravitational pull.

But a different collision probability.

The earth is being given a size for collision purposes. But possibly much too large of one?

With that and it being 2d it's nearly useless for figuring out the actual collision rates, or how long it takes things to settle. But it is useful in some respects.

I would also guess a full 3D simulation would give slightly different results.

Neat! But wouldn't Earth's gravity be affected by all the additional mass from moon-meteorites hitting it? It probably wouldn't be by much, but possibly enough to have an effect on how long it would take before the number of collisions leveled off.

More support for the exploding planets hypothesis! https://www.bibliotecapleyades.net/sumer_anunnaki/esp_sumer_...

Is the second paragraph of TFA spoiling the whole book, or is that just part of the premise that is set up during the first chapter or so? Because it just sounds like a massive spoiler.

The latter. I don't even know if I'd consider it a spoiler at all. Kind of like saying Harry Potter is a wizard.

The moon breaks up in the opening sentences of the book. But the realization that it'll destroy the planet doesn't come for some time later. That part is a bit of a spoiler. But the moon blowing up just can't be good for the planet long term, so maybe it's not too big of a spoiler.

Earth is the Ned Stark of Seveneves.

I checked it out on Amazon, and the threat to the Earth is out in the open by the 27th page of the story in the hardcover edition. It's also literally the first sentence in the blurb on the back cover.

I am not really sure where this idea of "Spoiler alert" needed when discussing stuff in text is coming from. Maybe it makes sense when people are beginning to talk about a book, movie, etc. It gives someone else that is listening the time to say, "Hey I have not read/watched that yet, let me have time to get out of ear shot before you guys start discussing it." But if one is discussing a creative work and there is nothing "spoiled" then really there is nothing of interest said. Spoilers aplenty in any essay worth reading. As long as the author states what he/she is writing about before writing any "spoilers", and this writer does that in the second sentence, you should just stop reading at that point if you don't want to have the work "spoiled" for you.

The title: "The moon blew up without warning and for no apparent reason" could be a legitimate cause for complaint as one reads it before knowing what the topic is, but in this case it is not as it is the first sentence in the novel. This fact is conveyed to the reader in the second sentence in the essay.

It's pretty common to discuss creative works in a useful and productive way without spoilers. Just about any worthwhile movie or book review pulls it off.

In fact, you are commenting on an article discussing a work which has no spoilers for that work, so case in point right there.

I guess I don't have a fine tuned sense of what is a spoiler and what is not. If I know I am going to see a movie based on say, an actor I like being in it, I don't want to know anything about the movie ahead of time. Everything is a spoiler. If I start to see a preview of that movie, I'll close my eyes and try not to concentrate on the sound. If I don't know if I want to watch a movie and start reading a review about it to see I should go, I stop reading as soon as I decide I'm going to go and don't finish reading the review. Same sort of situation with books. If the thing you are reading is not meant to be a review to help you decide to go and read/watch, then writing/talking about a work of art without discussing details seems pointless. Why mention the work in the first place. This article is not a book review.

If you consider the standard three-act structure (setup, confrontation, resolution), a spoiler is typically any important plot point from acts 2 or 3. Information about act 1 is much less important, because expectations are still being created at that point, so there isn't much room for twists yet.

For example, the fact that The Tortoise and the Hare involves a race between the two animals isn't a spoiler, because that's part of the setup. The fact that the tortoise wins because the hare is overconfident is. (Or it would be if the tale wasn't thousands of years old and familiar to essentially everybody already.)

In this particular case, the plot point in question is revealed less than 30 pages into the book and can comfortably be considered part of act 1. It's even described on the cover blurb. So, not a spoiler.

You can discuss quite a lot only using details from act 1, and being more vague (or ignoring) acts 2 and 3. In this particular article, everything is from very early in the book, so no spoilers are present.

Ok. That makes some sense. I'll keep it in mind.

Not only is it just the premise but it's basically treated as this event that just happened for an unknowable reason. The rest of the article discusses events that take a few more pages to get to but still aren't really spoilers. A few pages in a Stephenson book don't amount to much :-)

That's just the premise.

Nope, just part of the premise - you're good to go!

Bill Gates loves this book: https://www.gatesnotes.com/Books/Seveneves

If you don’t get the reference and you like scifi Seveneves is awesome. It’s not hard scifi.

I managed to finish it in two days. Super entertaining.

Anywho, this visualization is cool to see after reading the book.

> It’s not hard scifi.

I'd say it's pretty hard sci-fi. What's harder?

There are fish people. So...?

There are currently mammals living in the water, some people already have webbed feet, the "fish people" had evolved over 5,000 years, and their ancestors may have had access to advanced genetic tech. The book also references epigenetics pretty heavily in that part of the book; presumably that's involved in the evolution of all of the different surviving human groups.

It certainly wasn't the hardest science element of the book, but it seems pretty well supported for scifi.

That was also one pretty minor element of the book as a whole.

I still can't think of another book that's 'harder' scifi (and not also like really-close-near-future).

so how much does this contribute to global warming? no, seriously, how much does temp actually rise and can an equilibrium temp be predicted? Roughly how much of the energy can be accommodated by phase change of the oceans into gas? Once the increased vapor content in the air is calculated, then a predicted greenhouse event can be calculated.

I'd love to see the source code for this.

Am I the only one who gave up reading Seveneves because of pages and pages of complicated orbital mechanics?

No, I know of other people who did. I was personally bored by those sections, since I already have a good understanding of them - so I skimmed through parts.

This article should come with more of a SPOILER ALERT for a book I would like to read at some point.

It's not a spoiler by any meaningful definition of the word.

Isn't just the title of this Hacker News entry and the connection with the book a massive spoiler? Could argue it got me intrigued, but wondering what Stephenson intended. (I always wonder about not putting spoilers in movie trailers for instance)

The title of this post, "The moon blew up without warning and for no apparent reason", is the very first sentence in the book [0]. It's not a spoiler for any meaningful definition of the word, the word spoiler should be reserved for things that spoil the enjoyment of a work, like a surprise ending.

[0] http://www.nealstephenson.com/news/2015/04/13/seveneves-exce...

For what it's worth, when Stephenson does readings he always reads passages of the book that won't give spoilers. He made a statement when reading seven eves "let me tell you now. The moon blows up. That's not a spoiler, it's the first sentence. And no, I won't tell you why. It blows it in the first sentences so I don't have to come up with a reason." (My paraphrasing)

Everything in the title and the linked article happens or is described in the first chapter of the book. It's effectively the premise of the book. No reading experience of the book should be disturbed by this.

The linked post literally talks about what happens in the book and says that it's half about orbital-mechanics so not sure how that's not a spoiler

Where do you think the book is going to go from "the moon blew up?" Orbital mechanics follows logically from the premise. Again, people who have read the book, myself included, are telling you: this is not a spoiler.

As one who has not read the book, but very well might, it’s not a spoiler at all. The blurb (and first sentence of the book) says the moon blows up. Well, by golly if there isn’t some discussion of pieces of moon and orbital mechanics, and if those pieces just sit up there and inertly do nothing, that is going to be one hell of a boring book.

The title of the article is actually the very first sentence in the book.

It's not a spoiler to say the Avengers movie is about a bunch of superheroes fighting evil.

If you think that’s a spoiler, then for $DEITY’s sake don’t read the dust cover before starting it.

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