Hacker News Reader

Comment by jasmcole | Hacker News Reader

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.

View on HN

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?

(POSSIBLE SPOILERS FOLLOW)

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:

https://github.com/jasmcole/Blog

Reply on news.ycombinator.com