Comets Are More Dangerous Than We Thought | Hacker News Reader

Comets Are More Dangerous Than We Thought

nautil.us

83 pointsdnetesn47 comments

I read "Comments are more dangerous than we thought" and was expecting a discussion about comments in source code.

A comet will kill you instantly and painlessly. A misleading and outdated comment however can make your life miserable for a while.

might not be so instant if a planetary killer hits on the far side and the acid rain / global winter / famine is what does you in. in such a case it would almost match my feelings about outdated comments...

The number of times I was misguided by an outdated comment: 0

The number of times a comment saved my ass, despite being slightly inaccurate: 435

The number of times I struggled to understand what the authors thought when writing "self-documenting" code, because they left no comments: 249579

The number of times I’ve been obliterated by a comet: 0.

Draw your own conclusions.

Level of risk = probability of the harmful event occurring, multiplied the severity of the harm.

granted, the probability of comet-strike in your lifetime is low, but the severity is off the charts high.

This definition of level of risk is relevant only when you have a von Neumann-Morgenstern utility function though.

We should totally act as if we had a von Neumann-Morgenstern utility function though

    // Do not remove.
    // This comment repels comets.

Survivor's bias.

W.r.t. "self-documenting" code: at best, clear code tells you what it does. What it's supposed to do and why will always be left to comments.

I can't count the number of times I've read some code that was very clear that it generally did the correct thing, but clearly wasn't handling some corner case, and it wasn't clear if I had missed something that obviously made the corner case impossible, the author had missed the corner case, or something else was going on.

And how should someone write a comment about that they intentionally forgot about some corner-cases?

Or if they did add a similar comment and in the meantime someone implemented it, but didn't remove the comments, how many people will only read the comment and not look at the code?

If the explanation of intended behavior left out the corner case, then it would be much more likely that the author hadn't considered the corner case. More insight into the author's thought process gives you more confidence in your assessment.

corner-cases should either be mentioned in the comments or be handled in the code. if they are neither, then the author missed them.

a future developer potentially forgetting to update a comment is not an excuse to avoid commenting.

In a perfect world... You'd find that in the commit log for the code. Comments aren't the right place for things you forgot to do, or things that occur to you after the code sort of works.

The commit message, and unit tests, are where those ideas can be best captured.

I tend to point my team at this as a practice: https://chris.beams.io/posts/git-commit/

> at best, clear code tells you what it does.

This depends a lot on what you mean by "clear" code! You can write higher-level code with abstractions that emphasize the what rather than the how and you can write code that explicitly captures important additional information like invariants. Personally, I've found aiming for that works better than writing code where the "how" is clear at the expense of the "what" so that readers don't lose the forest for the trees.

I am not sure I'm explaining the difference well—it would benefit from examples that I am too tired to provide right now—and documentation is still useful even with higher-level code, but my point is that code absolutely can and should clearly reflect many of the things you would also cover in documentation.

> but my point is that code absolutely can and should clearly reflect many of the things you would also cover in documentation.

I absolutely agree, but my point was very specific about the "what should" and "why". At best, one could infer some intent from invariants, and hopefully the mapping between the invariants and the requirements document is pretty clear, but comments are still better at explicitly referencing requirements documentation and explaining why the chosen solution is preferable to alternatives.

Wait till you're outdated by a misguided comet.

I read "Camels are more dangerous than we thought" and expected no discussion beyond "of course camels are scary dangerous,wth?"

There is another reasons comets might be more dangerous than we think. There are rare meteor outbursts that are associated with long period comets whose earlier appearance has never been recorded in human history. Any of these might reappear at any moment. https://www.sciencedirect.com/science/article/abs/pii/S00191...

> Would a comet contain enough [Iridium]? It depends on what the comet was made of. There aren’t a lot of pieces of comets to test, but the samples returned from Comet Wild-2, courtesy of NASA’s Stardust mission, found that they were very similar to carbonaceous chondrite meteorites, which are known to contain iridium (although somewhat less than ordinary chondrites). Presumably the iridium level of a cometary object wouldn’t be that far off, but it remains to be seen.

So, the theory proposed doesn't account for existing observations? Keen to see what kind of comet would be needed, theoretically, to create the K-Pg Boundary.

That said, I find the timing of the Deccan Traps and the (alleged) Shiva Crater to be reasonably compelling for the "something broke up and hit the Earth bad"

I thought the Oort cloud is a (sound) hypothesis, not a confirmed thing?

> [long-period comets] originate in the Oort cloud, which extends several light-years from the sun [...] to the edge of the solar system

Yes that's correct, it's not possible to directly observe these objects at the moment.

I also thought the cloud wasn't that big.

200,000 AUs is 3 and a bit LY. Alpha Centauri is 4 and a bit LY away. When does our cloud stop and theirs begin?

The extent of the Oort cloud is basically defined by the point where Galactic tides start to overwhelm the gravitational attraction to the Sun. But objects in the outer Oort cloud are very loosely bound and can easily be expelled or exchanged by interactions from passing stars.

I suppose Alpha Centauri is only in one specific direction, so it distorts the cloud in that region.

There’s also other “clouds”, with smaller radii. Kuiper Belt is roughly where Pluto is. There is the Scattered Disc (probably) beyond that. Only then, a long way away, maybe, the Oort Cloud. So there is a lot of cloudy stuff closer in too.

<<It’s now “indisputable” that an asteroid killed the dinosaurs.>>

But actually, it is.

This time it looks like it will be Global Warming that kill the dinosaurs.

Only the poor dinosaurs, not the rich ones.

That remains to be seen. With some major crash and money not being worth anything anymore - it will be more about claws, fangs and numbers.

How are birds faring with climate change, actually?

It'd impact migration patterns first I suspect. Well, unless migration is a circadian mediated behavior rather than a climatologically mediated one. Anyone know which it is?

There'd be a certain irony if burning dino juice (I know, I know) killed off all of the dino-descendants' competitors.

My understanding is that it may have finished them off quite decidedly, at least those that were not on their way to becoming birds & others, but evidence suggests many of the large species were already in significant decline due to other pressures (there are various theories about what the main cause(s) of that was, including changes in atmosphere balance, changes in temperature, changes in food supply due to evolution elsewhere in the chain, etc.)

I recently did a review of just what happened during the asteroid/comet impact and afterward, and it was insanely bad. And not limited to near the impact site, either, as ejecta shot back into space and rained down on the whole planet. The atmospheric temperature was well above boiling, rain of fiery stones starting literally all the world’s forests on fire, earthquakes of 11 on the Richter scale. For those within visual distance of the impactor, flesh would turn to flame due to the intensity of the light. Massive inland tsunamis. Followed by years and decades of dark winter (50 degrees below average) and then 5 deg C global warming for thousands of years.

Almost everything would’ve been dead on land within hours. That species survived means a few individuals survived. Something like 99% of everything living on land would’ve been killed early on. No exclusively land-based tetrapods over 25 kilograms survived.

I would like to learn more about these 11-on-the-Richter-scale earthquakes.

Here’s a dramatization of the Earthquakes (etc) from when the impactor hit: https://youtu.be/vq3nWnTkFbk

Thank you for the link. I haven't felt this bad for dinosaurs since the death of Littlefoot's mother.

Look at the data around the late Cretaceous Deccan Traps eruptions. It's pretty clear that large scale volcanic activity is the real culprit, just as it's been with nearly every mass extinction event.

The impact event had a big effect too but the end was already written before the cosmic gun went off.

There's also emerging evidence that dinosaurs survived in pockets for a few hundred thousand years after the impact. Most of this comes out of New Mexico and is based on radiometric sequences that have yet to be accepted on a wide scale, but it is there.

Dinosaurs are so easily hoaxed.

I hear the tyrannosaurs were up in arms over the hoax but it did little good. The brontosaurs were sticking their necks out but it never came to a head. The triceratops kept trying to put a fine point on the argument but alas, it came to naught.

I thought it was strange that they highlighted that sentence as well since the rest of the article goes on to dispute that. I'm guessing whoever made the excepts didn't read the rest very well.

I thought it made sense. They were quoting a scientist from one study, and then showed how the next study disputes this. They were highlighting the scientific argument.

I guess if you think of pull-quotes as the take-away points of the article it's confusing, but I don't usually read them that way.

Very nice article. A bit of a lame start though, talking about a particular TV show and brand of chocolate on the sidewalk. I guess such things are taught, that you should start off with something familiar to the reader.

Indeed, one measly comet crash-landing on my desk would ruin my whole compile.

Tl;dr, anyone?

It was indeed a comet, not an asteroid, that Bruce Willis had to blow up in Armageddon (1998).

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